Final Regulatory Impact Analysis 

Corporate Average Fuel Economy 

for MY 2011 

Passenger Cars and 

Light Trucks 

Office of Regulatory Analysis and Evaluation 

National Center for Statistics and Analysis 

March 2009 
TABLE OF CONTENTS 

EXECUTIVE SUMMARY ............................................................................................................. i 

I. INTRODUCTION ................................................................................................................I-1 

II. NEED OF THE NATION TO CONSERVE ENERGY..................................................... II-1 

III. ALTERNATIVES..........................................................................................................III-1 

IV. IMPACT OF OTHER FEDERAL MOTOR VEHICLE STANDARDS ON FUEL 

ECONOMY ...............................................................................................................................IV-1 

V. FUEL ECONOMY ENHANCING TECHNOLOGIES AND THE VOLPE MODEL..... V-1 

VI. MANUFACTURER SPECIFIC CAFE CAPABILITIES .............................................VI-1 

VII. COST IMPACTS......................................................................................................... VII-1 

VIII. BENEFITS.................................................................................................................. VIII-1 

IX. NET BENEFITS AND SENSITIVITY ANALYSES ...................................................IX-1 

X. PROBABILISTIC UNCERTAINTY ANALYSIS............................................................. X-1 

XI. REGULATORY FLEXIBILITY ACT AND UNFUNDED MANDATES REFORM ACT 

ANALYSIS................................................................................................................................XI-1 
i

EXECUTIVE SUMMARY 

This assessment examines the costs and benefits of improving the fuel economy of passenger 

cars and light trucks for model year (MY) 2011. It includes a discussion of the technologies that 

can improve fuel economy, analysis of the potential impact on retail prices, safety, lifetime fuel 

savings and their value to consumers, and other societal benefits such as improved energy 

security and reduced emissions of pollutants and greenhouse gases1

. 

In the previous rulemaking, the agency reformed the corporate average fuel economy (CAFE) 

standards for light trucks with a size-based standard based on footprint2

. This rulemaking 

continues this approach for both passenger cars and light trucks. A continuous mathematical 

function provides a separate fuel economy target for each footprint. Different parameters for the 

continuous mathematical function are derived. Individual manufacturers will be required to 

comply with a single fuel economy level that is based on the distribution of its production among 

the footprints of its vehicles. Although the same reformed CAFE scheme is required for both 

passenger cars and light trucks, they are established with different continuous mathematical 

functions specific to their design capabilities. 

The final rule is the “Optimized (7%)” alternative. In this alternative the agency uses a 7 percent 

discount rate to value intra-generational future benefits and costs and sets the required mpg 

levels where marginal costs equal marginal benefits. It is one of eight alternatives examined in 

the analysis. We also examined an optimized scenario when discounting intra-generational 

future benefits and costs at 3 percent “Optimized (3%)”. In all of the alternatives, intergenerational3

 benefits from future carbon dioxide reductions are discounted at 3 percent. When 

discussing an alternative we provide the discount rate in parenthesis afterwards to keep track of 

which alternative we are discussing. In general order of increasing stringency (see Table 1), the 

seven scenarios examined are: 

1: “25% Below Optimized (7%)”: This alternative mirrors the absolute difference in mpg 

derived from the 25% Above Optimized scenario in going the same mpg amount below the 

Optimized 7% alternative 

2: “Optimized (7%)”: An increase in the standard based upon availability of technologies and a 

marginal cost/benefit analysis. The mpg levels are set using a 7 percent discount rate for 

benefits. 

3: “25% Above Optimized (7%)”: This alternative looks at the mpg levels of the Optimized 

(7%) and the Total Cost Equals Total Benefit (7%) alternative and picks mpg levels that are 25 

percent of that difference. 

 

1

 This analysis does not contain NHTSA’s assessment of the potential environmental impacts of the final rule for 

purposes of the National Environmental Policy Act (NEPA), 42 U.S.C. 4321-4347. 

2

 Vehicle Footprint is defined as the wheelbase (the distance from the center of the front axle to the center of the 

rear axle) times the average track width (the distance between the centerline of the tires) of the vehicle (in square 

feet). 

3

 Inter-generational benefits, which include reductions in the expected future economic damages caused by increased 

global temperatures, a rise in sea levels, and other projected impacts of climate change, are anticipated to extend 

over a period from approximately fifty to two hundred or more years in the future, and will thus be experienced 

primarily by generations that are not now living. 
ii

4: “50% Above Optimized (7%)”: This alternative looks at the mpg levels of the Optimized 

(7%) and the Total Cost Equals Total Benefit (7%) alternative and picks mpg levels that are 50 

percent of that difference. 

5: “Optimized (3%)”: An increase in the standard based upon availability of technologies and a 

marginal cost/benefit analysis, except that the mpg levels are set using a 3 percent discount rate 

for benefits. 

6: “Total Costs Equal Total Benefits (7%)”: An increase in the standard to a point where 

essentially total costs of the technologies added equals total benefits. In this analysis, for brevity, 

at times it is labeled “TC = TB (7%)”. 

7: “Technology Exhaustion (7%)”: An increase in the standard based upon the maximum usage 

(based on NHTSA’s perspective) of available technologies, disregarding the cost impacts. 

 Table 1 shows the agency’s projection of the actual harmonic average that would be achieved by 

the manufacturers, assuming those manufacturers whose plans were above the requirements 

would achieve those higher levels. Table 1 also shows the estimated required levels. All of the 

tables in this analysis compare an adjusted baseline to the projected achieved harmonic average. 

Benefits: Benefits are determined mainly from fuel savings over the lifetime of the vehicle, but 

also include externalities such as reductions in criteria pollutants. Table 3 provides those 

estimates on an industry-wide basis. 

Costs: Costs were estimated based on the specific technologies that were applied to improve 

each manufacturer’s fuel economy up to the level required under each alternative. Table 2 

provides those cost estimates on an average per-vehicle basis, and Table 3 provides those 

estimates on a fleet-wide basis in millions of dollars. Most costs are not discounted because they 

occur at the time of purchase. 

Net Benefits: Table 3 compares societal costs and societal benefits of each alternative. 

Fuel Savings: Table 4 shows the lifetime fuel savings in millions of gallons. 

Total Benefits are significantly affected by the decision to discount future fuel savings by a 7 

percent or 3 percent discount rate. Based on a marginal cost/marginal benefit analysis, the 

projected achieved levels in Table 1 are 0.3 mpg higher for the Optimized (3%) scenario than the 

Optimized (7%) scenario for passenger cars and essentially the same mpg level for light trucks. 
iii

Table 1 

Alternative CAFE Levels 

MY 2011 

(in mpg) 

 Projected Harmonic Average 

for the Fleet4

Estimated Required Average 

for the Fleet 

Passenger Cars 

25% Below Optimized (7%) 30.7 29.9 

Optimized (7%) 30.7 30.2 

25% Above Optimized (7%) 30.8 30.5 

50% Above Optimized (7%) 31.0 30.9 

Optimized (3%) 31.0 31.2 

TC = TB (7%) 31.2 31.5 

Technology Exhaustion (7%) 32.4 35.5 

 

Light Trucks 

25% Below Optimized (7%) 23.2 24.1 

Optimized (7%) 23.2 24.1 

25% Above Optimized (7%) 23.2 24.2 

50% Above Optimized (7%) 23.2 24.2 

Optimized (3%) 23.2 24.1 

TC = TB (7%) 23.2 24.3 

Technology Exhaustion (7%) 23.7 29.0 

 

 

 

 

4

 The values represent weighted mpg values that we predict will be achieved by the fleet. For most manufacturers, 

the mpg values represent the higher of the manufacturer’s plans and the alternative level of the standard. Some 

manufacturers are assumed to pay fines in lieu of achieving compliance with their required level. 
iv

Table 2 

Average Incremental Cost 

Per Vehicle 

MY 2011 

(2007 Dollars) 

Passenger Cars Cost per vehicle 

25% Below Optimized (7%) 40 

Optimized (7%) 64 

25% Above Optimized (7%) 120 

50% Above Optimized (7%) 193 

Optimized (3%) 220 

TC = TB (7%) 310 

Technology Exhaustion (7%) 1,445 

 

Light Trucks 

25% Below Optimized (7%) 126 

Optimized (7%) 126 

25% Above Optimized (7%) 169 

50% Above Optimized (7%) 169 

Optimized (3%) 126 

TC = TB (7%) 242 

Technology Exhaustion (7%) 1,177 
v

Table 3 

Present Value of Lifetime Societal Benefits5

, 

Incremental Total Costs by Societal Perspective, and 

Net Total Benefits by Alternative 

(Millions of 2007 Dollars) 

Passenger Cars Societal Benefits Societal Costs Net Total Benefits 

25% Below Optimized (7%) 786 291 496 

Optimized (7%) 1,027 496 531 

25% Above Optimized (7%) 1,332 1,003 329 

50% Above Optimized (7%) 1,773 1,630 143 

Optimized (3%) 2,647 1,820 828 

TC = TB (7%) 2,487 2,619 (132) 

Technology Exhaustion (7%) 6,406 11,907 (5,501) 

 

Light Trucks 

25% Below Optimized (7%) 921 649 272 

Optimized (7%) 921 649 272 

25% Above Optimized (7%) 989 915 75 

50% Above Optimized (7%) 989 915 75 

Optimized (3%) 1,176 649 527 

TC = TB (7%) 1,189 1,391 (202) 

Technology Exhaustion (7%) 2,950 6,214 (3,264) 

 

Passenger Cars and Light Trucks Combined 

25% Below Optimized (7%) 1,707 940 767 

Optimized (7%) 1,948 1,145 802 

25% Above Optimized (7%) 2,321 1,918 403 

50% Above Optimized (7%) 2,763 2,545 218 

Optimized (3%) 3,824 2,469 1,355 

TC = TB (7%) 3,676 4,009 (334) 

Technology Exhaustion (7%) 9,356 18,120 (8,765) 

 

5

 These benefits are considered from a “societal perspective” because they include externalities. They are 

distinguished from a consumer perspective, because consumers generally would not think about the value of carbon 

dioxide, etc. 
vi

 Table 4 

Savings in Millions of Gallons of Fuel 

Undiscounted Over the Lifetime of the Model Year 

MY 2011 

 Passenger Cars Light Trucks Passenger Cars and 

Light Trucks 

Combined 

25% Below Optimized (7%) 352 424 776 

Optimized (7%) 463 424 887 

25% Above Optimized (7%) 598 456 1,054 

50% Above Optimized (7%) 794 456 1,250 

Optimized (3%) 946 424 1,371 

TC = TB (7%) 1,121 567 1,687 

Technology Exhaustion (7%) 2,982 1,420 4,402 
I-1

I. INTRODUCTION 

The purpose of this study is to analyze the effects of changes in the fuel economy standards for 

passenger cars and for light trucks for MY 2011. It includes a discussion of the technologies that 

can improve fuel economy, the potential impacts on retail prices, safety, the discounted lifetime 

net benefits of fuel savings, and the potential gallons of fuel saved. 

The agency issued a final rule on April 7, 2003 (68 FR 16868), setting the CAFE standard 

applicable to light trucks for MY 2005 at 21.0 mpg, for MY 2006 at 21.6 mpg, and for MY 2007 

at 22.2 mpg. On April 6, 2006 (71 FR 17566), the agency issued a final rule for MYs 2008 to 

2011 under a new “CAFE Reform” structure. Similar to this report, a Final Regulatory Impact 

Analysis accompanied that final rule.6 Much of the technical and cost information used in the 

2006 analysis was taken from the findings in the National Academy of Sciences study7

 published 

in January 2002. 

The new attribute-based Reformed CAFE system is based on the vehicle footprint (wheel base8

 x 

average wheel track width9). The anticipated advantages of the new reformed CAFE system are: 

First, the energy-saving potential of the CAFE program was hampered by the original regulatory 

structure. Manufacturers who offer predominately small vehicles had little or no regulatory 

incentive to enhance fuel economy, because their vehicles tend to be more fuel efficient than the 

CAFE level. Moreover, the difference between the fuel economy standards for passenger cars 

and light trucks (27.5 mpg and 20.7 mpg, respectively, for MY 2004) encouraged vehicle 

manufacturers to offer vehicles classified as light trucks for purposes of CAFE, possibly 

inducing design changes that hurt overall fuel economy. A CAFE system that more closely links 

fuel economy standards to the various market segments and their fuel economy performance may 

reduce the incentive to design vehicles which are functionally similar to passenger cars but are 

classified as light trucks. 

Second, we were concerned that the original light truck CAFE standards could create safety 

risks. Vehicle manufacturers are encouraged to achieve greater fuel economy by downsizing and 

downweighting. Alternatively, manufacturers may offer small vehicles to offset their offerings 

of large vehicles. The resulting increase in the disparity between the smallest and largest vehicle 

sizes and weights in the on-road vehicle fleet is widely believed to have increased the number of 

fatalities in crashes involving passenger cars and light-duty trucks. The National Academy of 

Sciences (NAS) report and a NHTSA study10 have suggested that if downweighting were 

concentrated on the heaviest vehicles in the fleet, there could be a small fleetwide safety benefit, 

but downweighting of passenger cars and the lighter light trucks would increase fatalities. 

 

6

 “Final Regulatory Impact Analysis, Corporate Average Fuel Economy and CAFE Reform for MY 2008-2011 

Light Trucks”, March 2006, Docket No. 24309-5. 

7

 “Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards”, National Research Council, 

2002. The link for the NAS report is http://www.nap.edu/books/0309076013/html/ 8

 “Wheel base” is essentially the distance between the centers of the axles. 9

 “Track width” is the lateral distance between the centerline of the tires. 10 “Vehicle Weight, Fatality Risk and Crash Compatibility of Model Year 1991-99 Passenger Cars and Light 

Trucks”, Charles J. Kahane, Ph.D., NHTSA, October 2003, DOT HS 809-662. 
I-2

A third reason for considering CAFE reform relates to the adverse economic impacts that may 

result from such future increases in the stringency of CAFE standards. Rapid increases in the 

level of the CAFE standard could have substantial economic consequences on manufacturers, 

especially those full-line manufacturers with product mixes dominated by large heavier vehicles. 

For example, full-line manufacturers – especially those with substantial sales in the heavier end 

of the light truck market – may generate fewer CAFE credits and incur larger compliance costs 

than vehicle manufacturers who focus their sales in the smaller, lighter end of the light truck 

market. As CAFE standards become more stringent under the original structure, the full-line 

manufacturers may experience adverse financial consequences, with resulting disruptions for 

employees in these firms and their suppliers. 

EPCA also gives NHTSA authority to set passenger car CAFE standards for each model year, 

but sets a default standard of 27.5 mpg. NHTSA has not raised the passenger car CAFE standard 

from 27.5 mpg since Congress lifted the ban on CAFE rulemakings in 2002 because it did not 

believe that it had authority to reform passenger car CAFE as it had for light trucks. Reforming 

the CAFE program achieves larger fuel savings while enhancing safety and preventing adverse 

economic consequences—objectives which apply equally to passenger cars as to light trucks. 

NHTSA was unwilling to raise the passenger car CAFE standard without also reforming it, 

because of the same fuel savings, safety, and economic concerns that led it to reform the light 

truck CAFE standards. 

In December 2007, Congress passed the Energy Independence and Security Act (EISA). EISA 

mandates the setting of separate standards for passenger cars and for light trucks at levels 

sufficient to ensure that the average fuel economy of the combined fleet of all passenger cars and 

light trucks sold by all manufacturers in the U.S. in model year 2020 equals or exceeds 35 miles 

per gallon. That is a 40 percent increase above the average of approximately 25 miles per gallon 

for the current combined fleet. EISA additionally gives NHTSA authority to reform passenger 

car CAFE, allowing the agency to set standards for those vehicles according to an attribute-based 

mathematical function as it currently does for light trucks. 

On May 2, 2008, NHTSA published a notice of proposed rulemaking (NPRM) in the Federal 

Register (73 FR 24352) proposing standards for model years (MY) 2011-2015, the maximum 

number of model years under EISA for which NHTSA can establish standards in a single 

rulemaking. A Preliminary Regulatory Impact Analysis (PRIA) accompanied the NPRM.11 

While a large number of alternatives were examined, the proposed required mpg levels 

(comparable to Table 1) for the proposed alternative (labeled as Optimized 7%) were: 

 

11 “Preliminary Regulatory Impact Analysis, Corporate Average Fuel Economy for MY 2011-2015 Passenger Cars 

and Light Trucks” April 2008, NHTSA, (Docket No. 2008-0089-3.1) 
I-3

Table I-1 

Proposed Required Levels 

 MY 2011 MY 2012 MY 2013 MY 2014 MY 2015 

Passenger Cars 31.2 32.8 34 34.8 35.7 

Light Trucks 25.0 26.4 27.8 28.2 28.6 

These proposed required levels were higher than the agency estimated the harmonic level of the 

fleet would be in those years, since some manufacturers would not be able to achieve those 

levels or would choose to not meet those levels and would pay a penalty for not complying. The 

lower achievable levels served as the basis for many of the analyses in the PRIA. New vehicle 

price increases included technology costs and penalties for consumers, but benefits only included 

fuel savings up to the achieved levels. 

The dual fuel incentive program, through which manufacturers may improve their calculated fuel 

economies by producing vehicles capable of operating on alternative fuels, is not considered in 

this analysis. By law, the agency has always analyzed fuel economy without considering the 

dual fuel credits, since it is an incentive program designed to increase the availability of 

alternative fuel vehicles. 

Throughout this analysis, unless otherwise noted, the agency has not considered the ability of 

manufacturers to use credits or credit trading in achieving the alternative fuel economy levels. 

Throughout this document, confidential information is presented in brackets [ ]. 

Additionally, by way of background, the agency notes that in mid-October 2008, the agency 

completed and released a final environmental impact statement in anticipation of issuing 

standards for those years. Based on its consideration of the public comments and other available 

information, including information on the financial condition of the automotive industry, the 

agency adjusted its analysis and the standards and prepared a final rule and Final Regulatory 

Impact Analysis (FRIA) for MYs 2011-2015. On November 14, the Office of Information and 

Regulatory Affairs (OIRA) of the Office of Management and Budget cleared the rule and FRIA 

as consistent with the Order.12 However, issuance of the final rule was held in abeyance. On 

January 7, 2009, the Department of Transportation announced that the final rule would not be 

issued, saying: 

The Bush Administration will not finalize its rulemaking on Corporate Fuel 

Economy Standards. The recent financial difficulties of the automobile industry 

will require the next administration to conduct a thorough review of matters 

affecting the industry, including how to effectively implement the Energy 

Independence and Security Act of 2007 (EISA). The National Highway Traffic 

 

12 Record of OIRA’s action can be found at http://www.reginfo.gov/public/do/eoHistReviewSearch (last visited 

March 8, 2009). To find the report on the clearance of the draft final rule, select “Department of Transportation” 

under “Economically Significant Reviews Completed” and select “2008” under “Select Calendar Year.” 
I-4

Safety Administration has done significant work that will position the next 

Transportation Secretary to finalize a rule before the April 1, 2009 deadline.13

In light of the requirement to prescribe standards for MY 2011 by March 30, 2009 and in order 

to provide additional time to consider issues concerning the analysis used to determine the 

appropriate level of standards for MYs 2012 and beyond, the President issued a memorandum on 

January 26, 2009, requesting the Secretary of Transportation and Administrator14 of the National 

Highway Traffic Safety Administration NHTSA to divide the rulemaking into two parts: (1) MY 

2011 standards, and (2) standards for MY 2012 and beyond. 

The request that the final rule establishing CAFE standards for MY 2011 passenger cars and 

light trucks be prescribed by March 30, 2009 was based on several factors. One was the 

requirement that the final rule regarding fuel economy standards for a given model year must be 

adopted at least 18 months before the beginning of that model year (49 U.S.C. 32902(g)(2)). The 

other was that the beginning of MY 2011 is considered for the purposes of CAFE standard 

setting to be October 1, 2010. As part of that final rule, the President requested that NHTSA 

consider whether any provisions regarding preemption are consistent with the EISA, the 

Supreme Court's decision in Massachusetts v. EPA and other relevant provisions of law and the 

policies underlying them. 

The President requested that, before promulgating a final rule concerning the model years after 

model year 2011, NHTSA

[C]onsider the appropriate legal factors under the EISA, the comments filed in 

response to the Notice of Proposed Rulemaking, the relevant technological and 

scientific considerations, and to the extent feasible, the forthcoming report by the 

National Academy of Sciences mandated under section 107 of EISA. 

In addition, the President requested that NHTSA further consider whether any provisions 

regarding preemption are appropriate under applicable law and policy. 

In keeping with the President’s remarks on January 26 for new national policies to address the 

closely intertwined issues of energy independence, energy security and climate change, and for 

the initiation of serious and sustained domestic and international action to address them, NHTSA 

will develop CAFE standards for MY 2012 and beyond only after collecting new information, 

conducting a careful review of technical and economic inputs and assumptions, and standard 

setting methodology, and completing new analyses. 

For MY 2011, however, time limitations precluded the adoption of this approach. As noted 

above, EPCA requires that standards for that model year be established by the end of March of 

this year. Thus, immediate decisions had to be made about the establishment of the MY 2011 

standards. There was insufficient time between the issuance of the President’s memorandum in 

late January and the end of March to revisit and, if and as appropriate, revise the extensive and 

 

13 The statement can be found at http://www.dot.gov/affairs/dot0109.htm (last accessed February 11, 2009). 14 Currently, the National Highway Traffic Safety Administration does not have an Administrator. Ronald L. 

Medford is the Acting Deputy Administrator. 
I-5

complex analysis in any substantively significant way. This is particularly so given the 

requirement under EPCA to consult with the Environmental Protection Agency and the 

Department of Energy on these complicated and important technical matters. Decisions 

regarding those matters potentially affect not just NHTSA’s CAFE rulemaking, but also 

programs of other departments and agencies. Accordingly, the methodologies, economic and 

technological inputs and decision-making criteria used in this rule are necessarily largely those 

developed by NHTSA in the fall of 2008. 

In looking ahead to the next CAFE rulemaking, the agency emphasizes that while the 

methodologies, economic and technological inputs and decision-making criteria used in this rule 

were well-supported choices for the purposes of the MY 2011 rulemaking, they were not the 

only reasonable choices that the agency could have made for that purpose. Many of the key 

aspects of this rulemaking reflect decisions among several reasonable alternatives. The choices 

made in the context of last fall may or may not be the choices that will be made in the context of 

the follow-on rulemaking. 

The deferral of action on the CAFE standards for the years after MY 2011 provides the agency 

with an opportunity to review its approach to CAFE standard setting, including its 

methodologies, economic and technological inputs, and decision-making criteria. It is 

reasonable to anticipate that this process may lead to changes, given the further review and 

analysis that will be conducted pursuant to the President’s request, and given the steady and 

potentially substantial evolution in technical and policy factors relevant to the next CAFE 

rulemaking. These factors include, but are not limited to, energy and climate change needs and 

policy choices regarding goals and approaches to achieving them, developments in domestic 

legislation and international negotiations regarding those goals and approaches, the financial 

health of the industry, technologies for reducing fuel consumption, fuel prices, and climate 

change science and damage valuation. 

The goal of the review and re-evaluation will be to ensure that the approach used for MY 2012 

and thereafter produces standards that contribute, to the maximum extent possible under 

EPCA/EISA, to meeting the energy and environmental challenges and goals outlined by the 

President. We will seek to craft our program with the goal of creating the maximum incentives 

for innovation, providing flexibility to the regulated parties, and meeting the goal of making 

substantial and continuing reductions in the consumption of fuel. To that end, we are committed 

to ensuring that the CAFE program for beyond MY 2011 is based on the best scientific, 

technical, and economic information available, and that such information is developed in close 

coordination with other federal agencies and our stakeholders, including the states and the 

vehicle manufacturers. 

We will also re-examine EPCA, as amended by EISA, to consider whether additional 

opportunities exist for achieving the President’s goals. For example, EPCA authorizes, within 

relatively narrow limits and subject to making specified findings, for increasing the amount of 

civil penalties for violating the CAFE standards.15 Further, while EPCA prohibits updating the 

 

15 Under 49 USC 32904(c), EPA must “use the same procedures for passenger automobiles the Administrator used 

for model year 1975 (weighted 55 percent urban cycle and 45 percent highway cycle), or procedures that give 

comparable results.” 
I-6

test procedures used for measuring passenger car fuel economy, it places no such limitation on 

the test procedures for light trucks.16 If the test procedures used for light trucks were revised to 

provide for the operation of air conditioning during fuel economy testing, vehicle manufacturers 

would have a regulatory incentive to increase the efficiency and reduce the weight of air 

conditioning systems, thereby reducing fuel consumption and tailpipe emissions of CO2. 

In response to the President’s request that NHTSA consider whether any provisions regarding 

preemption are consistent with EISA, the Supreme Court’s decision in Massachusetts v. EPA 

and other relevant provisions of law and the policies underlying them, NHTSA has decided not 

to include any provisions addressing preemption in the Code of Federal Regulations at this time. 

The agency will re-examine the issue of preemption in the content of its forthcoming rulemaking 

to establish Corporate Average Fuel Economy standards for 2012 and later model years. 

 

16 49 USC 32912(c). 
I-7

Response to Docket Comments 

Comments to the NPRM were submitted to www.regulations.gov to NHTSA docket 2008-0089. 

This section summarizes those comments by issue and provides NHTSA’s response to them. 

The issues are listed in alphabetical order (by our reference method) and the table of contents 

helps the reader find issues. 

Table I-2 

Docket Issues and Page Numbers 

Docket Issue Page # Docket Issue Page # 

Baseline I-4 Learning Curve I-32 

Congestion, Crashes and Noise 

Costs 

I-6 Marginal Cost/Marginal Benefit I-32 

Consumer Benefits from Additional 

Driving 

I-8 Market Failure I-33 

Cost and Effectiveness of 

Technologies 

I-9 On-road Fuel Economy 

Adjustment 

I-34 

Discount Rates I-10 Payback Period I-34 

Emissions savings per ton – Value 

of Carbon 

I-19 Price of Gasoline I-36 

Emissions Worldwide vs. U.S. I-21 Product Restrictions I-44 

Emissions Growth Rate over Time I-22 Rebound Effect I-44 

Emissions Values for Criteria 

Pollutants 

I-22 Regulatory Flexibility Analysis I-46 

Externalities – Monopsony I-25 Restrict Product Offerings I-46 

Externalities – Supply Disruption I-25 Retail Price Equivalent 

Multiplier 

I-47 

Externalities – Military Costs I-26 Sales Impact and Related 

Employment Impact 

I-50 

Financial Impact I-27 Safety Standards Impact on 

Weight 

See 

Chapter IV 

Inequality of Impacts on Smaller 

Manufacturers 

I-29 Size/Safety Impacts See 

Chapter IV 

Leadtime I-31 Uncertainty Analysis I-52 

Baseline 

In the NPRM, the agency used an “adjusted” manufacturer’s product plans as a baseline. If a 

manufacturer’s product plans were equal to or above the MY 2010 CAFE requirements, then the 

manufacturer’s product plans were their baseline and costs and benefits were estimated as an 

increment above that level. However, if the manufacturer’s product plans were below the level 

of the MY 2010 standard, then technologies were added to their plans to bring them up to the 

level of the MY 2010 standard and this “adjusted” baseline became their baseline for the 

analysis. 

Comment: Alliance, 2008-0089-0179.1, P7 
I-8

NHTSA should use as a current baseline MY 2006 used by Sierra Research Inc., not a projected 

baseline. The current baseline has complete data. Manufacturers who planned for new 

government mandates are penalized and their costs are underestimated. NHTSA has 

underestimated the increase in vehicle prices by $260 per car and $920 per truck. 

Agency response: NHTSA develops an adjusted baseline because the costs and benefits of 

reaching the MY 2010 standards were already accounted for in prior rulemakings, just as the 

costs and benefits of reaching the MY 2011 standards are accounted for in the current 

rulemaking. To avoid double-counting the costs to manufacturers (and the benefits to society) 

required to meet the MY 2010 standards, NHTSA develops this adjusted baseline, which the 

agency then uses in analyzing the MY 2011 standards. 

Comment: Alliance, 2008-0089-0179.1, Attachment 2 P4-5 

NHTSA should consider a constant model mix, rather than the projected changing model mix 

from the manufacturers. Model mix creates significant uncertainty. Consumer preference 

ultimately determines model mix, and since forecasts made 8 years before are inherently 

unreliable, there is significant uncertainty in the use of manufacturers plans and model mix 

estimates. 

Agency response: We agree there is uncertainty in the future model mix, but we are trying to 

estimate the incremental impact of the fuel economy standards, not the future of the automobile 

industry sales. The format of the standards, with target goals based on footprint, allows the 

manufacturer’s standard to float with their sales mix and makes model mix less of an issue. 

Comment: Union of Concerned Scientists, 2008-0089-0201.13, P3 

The Union of Concerned Scientists uses a baseline scenario corresponding to laws on the books 

at the time. 

Agency response: Without the manufacturers’ confidential plans, this might be the most 

reasonable assumption. However, we have the manufacturers’ confidential plans and we prefer 

our approach for purposes of this rulemaking. 

Comment: Mercatus Center, George Mason University, 2008-0089-216.1 

Raise the baseline forecast of fuel economy of the vehicle fleet to reflect the recent increase in 

fuel economy in response to higher fuel prices. The Mercatus Center discusses whether the fuel 

savings calculated in the CAFÉ model correctly reflect the gains that would come from the 

proposed regulation. Noting current market forces are driving fuel economy higher, the 

comment argues that NHTSA’s analysis underestimates the baseline level of future fuel 

efficiency, and consequently overestimates the amount of fuel saved by raising CAFE standards. 

Agency response: The approach suggested by the Mercatus Center could lead to significant 

speculation and it would be very hard to justify any particular baseline for the future. 

Congestion, Crashes and Noise Costs – 
I-9

In the NPRM the agency stated that increased vehicle use associated with the fuel economy 

rebound effect can also contribute to increased traffic congestion, motor vehicle crashes, and 

highway noise. In the NPRM, NHTSA relied on estimates developed by the Federal Highway 

Administration (FHWA) of the increased external costs of congestion, accidents (property 

damage and injuries), and noise costs caused by added driving due to the rebound effect.17 

NHTSA translated these marginal estimates in the tables and then the marginal costs were 

multiplied by the expected annual increases in automobile and light truck use from the rebound 

effect to yield the estimated increases in congestion, accident, and noise externality costs during 

each future year. These estimates are intended to measure the increases in costs due to these 

externalities caused by automobiles and light trucks that are borne by persons other than their 

drivers, or “marginal” external costs. The only new comments were on congestion. 

Comment: Alliance, 2008-0089-179.1 

The Alliance submitted an analysis by NERA Economic Consulting that essentially argued that 

NHTSA had underestimated the increased costs from congestion, crashes, and noise. The NERA 

analysis argued that FHWA’s estimate was “based on a value of $12.38 per vehicle hour (in 

1994 dollars),” while NHTSA used a value of $24 per vehicle hour “to value time savings it 

estimates would result from fewer fill-ups as a result of higher MPG and increased range for a 

tank of fuel.” Thus, the NERA analysis concluded that NHTSA had overvalued the time 

savings, which NERA seemed to attribute to its belief that NHTSA does not value time spent in 

traffic congestion “at least as highly as time spent in service stations while filling up.”18 Thus, 

the NERA analysis argued that congestion costs per mile would increase by about 68 percent if 

NHTSA had updated FHWA’s estimates in a “consistent” manner with “NHTSA’s valuation of 

time savings for vehicle occupants in another part of its analysis.” 

Agency response: The agency does not intend to imply that time spent during one activity is 

more valuable than time spent during another activity. What has occurred is that in 2003 the 

Department of Transportation updated its estimate of the value of time. The 1997 FHWA report 

does not include the more recent update. However, the agency cannot go back to every reference 

it relies on and redo those analyses. This is not the only area that the Department or others have 

updated their estimates. For example, DOT has updated its estimate of the value of a statistical 

life, which affects crash costs. The agency does not have the wherewithal to accomplish such a 

time consuming task. The typical method is to update the dollars estimates to $2007 by using the 

Gross Domestic Product price index. 

Comment: The NERA analysis also argued that the baseline 1997 congestion values “should be 

adjusted upward even more to reflect increasing levels of congestion between then and now and 

the further increases likely” within the lifetimes of the vehicles, the basis for NHTSA’s cost 

analysis. The analysis stated that this was because “With higher baseline congestion, the 

marginal impact of additional VMT will increase because congestion, like other queuing 

phenomena, increases at an increasing rate as capacity utilization grows.” 

 

17 These estimates were developed by FHWA for use in its 1997 Federal Highway Cost Allocation Study. See

http://www.fhwa.dot.gov/policy/hcas/final/index.htm (last accessed April 20, 2008). 18 NERA appears to suggest that time spent in service stations while filling up includes the fact that “stops at service 

stations often serve multiple purposes, not just refueling.” NERA then appears to suggest that people feel similarly 

about time spent in traffic congestion. 
I-10

Comment: The Mercatus Center (2008-0089-216.1) focused only on congestion costs, and 

commented that NHTSA should consider “The possibility that the cost of increased congestion, a 

product of the ‘rebound effect,’ does not take into account likely increasing marginal costs as 

considered in NHTSA’s model.” The commenter stated that NHTSA’s estimates “implicitly 

assume a constant marginal cost of congestion across all possible total quantities of vehicle miles 

driven for each vehicle category.” However, it cited the FHWA study as stating that congestion 

cost impacts are “extremely sensitive” to peak versus off-peak traffic periods. Thus, the 

commenter argued, if the costs can vary within a day (as during peak and off-peak periods), they 

must certainly vary across years, if the total amount of traffic varies across years as well. In 

essence, if VMT increases, total congestion and the marginal cost of congestion must also 

increase, all other things held constant. 

However, if all other things are not held constant, e.g. if new roads are built to handle increasing 

traffic, the commenter argued that “total congestion does not necessarily increase with increases 

in total vehicle miles driven.” The commenter argued that NHTSA should include an estimate of 

the costs of building additional roads or altering existing ones to mitigate congestion due to the 

rebound effect. That estimate should include accounting for “the increasing difficulty of 

building a new road in an urbanized area,” which the commenter stated is “probably one of the 

best examples of an activity that has rapidly increasing marginal costs,” as well as the 

environmental costs of building new roads, i.e. costs due to sprawl. The commenter asserted that 

“It is incumbent upon NHTSA and the Environmental Protection Agency to produce an inclusive 

estimate of the costs of the rebound effect—one that either includes both increasing marginal 

cost of congestion and the cost of the new roads that will lead to increased congestion.” 

Agency response: The agency does not know the relationship between potential increases in 

VMT and congestion. The FHWA marginal costs were projected for future requirements of 

highways up through year 2000 using the base period of 1993-1995 and a national value of 

VMT. There is no other known similar estimate of highway costs beyond 2000. Neither is there 

an estimate of the relationship between the rebound effect and the amount of congestion for 

years beyond 2000, i.e. congestion is not assumed to be linear with VMT. Similarly, it is not 

clear how the additional roads, if built after 2000, would offset congestion and future year costs. 

Once again, the agency simply does not have the resources or time to redo and update these very 

complicated analyses that could make very minor differences in the level of the standard. 

NHTSA believes it is reasonable to assume that additional vehicle use due to the fuel economy 

rebound effect will be distributed over the day and among locations in much the same way as 

current travel is distributed. As a consequence, the FHWA estimates of congestion costs from 

increased vehicle use are likely to provide more accurate estimates of the increased congestion 

costs caused by added rebound-effect driving than are the estimates submitted by commenters, 

which apply to peak travel periods and locations that experience high traffic volumes. Thus, 

NHTSA has continued to rely upon the FHWA values to estimate the increase in congestion 

costs likely to result from added rebound-effect driving.

Updated to 2007 dollars, FHWA’s “Middle” estimates for marginal congestion, accident, and 

noise costs caused by automobile use amount to 5.4 cents, 2.3 cents, and 0.1 cents per vehiclemile (or 7.8 cents per vehicle-mile in total), while costs for light trucks are 4.8 cents, 2.6 cents, 
I-11

and 0.1 cents per vehicle-mile (7.5 cents per vehicle-mile in total).19 These costs are multiplied 

by the annual increases in automobile and light truck use from the rebound effect to yield the 

estimated increases in congestion, accident, and noise externality costs during each future year. 

Consumer Benefits from additional driving 

In addition to the benefits that drivers receive from increased vehicle use due to the rebound 

effect, the agency argued in the NPRM that improving the fuel economy of passenger cars and 

light-duty trucks may also increase their driving range before they require refueling. By 

reducing the frequency with which drivers typically refuel their vehicles, and by extending the 

upper limit of the range they can travel before requiring refueling, improving fuel economy thus 

provides some additional benefits to their owners. 

Comment: The Alliance 2008-0089-0179.1, P8, P36, Attachment 2 P5, P103-107, stated that 

“NHTSA incorrectly assumes that its new fuel economy standards will improve vehicle range 

and thus reduce the number of times a vehicle owner would have to refill the tank (creating 

consumer benefits).” The Alliance comments focused on two points: one, that analysis by 

Sierra Research demonstrates “the complete absence of any relationship between fuel economy 

and range in the light truck fleet,” and two, that manufacturers “design fuel-storage capacity to 

achieve the basic range requirements consumers demand,” and will reduce the space necessary 

for fuel tanks to keep vehicle ranges to 300-400 miles in order to devote it to other uses (such as 

increasing cargo space) if fuel economy levels rise. 

Agency response: As discussed in the PRIA, “...if manufacturers respond to improved fuel 

economy by reducing the size of fuel tanks to maintain a constant driving range, the resulting 

cost saving will presumably be reflected in lower vehicle sales prices.” Or if a manufacturer 

decides to increase trunk space, they have implicitly assumed that trunk space is of more value to 

their consumers than fewer refills. Either way, the benefit or the opportunity for benefit is there. 

This implies that NHTSA’s estimate of the value of increased refueling range will underestimate 

the true benefits from the resulting changes in vehicle attributes or prices. 

Additionally, there is a relationship between typical gasoline engines and hybrids in terms of 

vehicles with better fuel economy having more range. It was intuitively believed that the market 

condition was such that drivers would indeed very much like to have a much lower frequency of 

visits to fuel stations than every 300-400 miles. A review of current hybrid specifications in 

Table I-3 shows that higher ranges are provided in these vehicles. 

Table I-3 

 Hybrid Vehicle Range Specifications 

Vehicle 

Specified Range

(miles) 

Rated Fuel 

Economy (mpg) 

2008 Honda Civic Hybrid 650 47/48 

2007 Honda Accord Hybrid 600 29/37 

 

19 Id., at Tables V-22, V-23, and V-24 (last accessed October 5, 2008). 
I-12

2008 Nissan Altima Hybrid 720 42/36 

2008 Toyota Prius 547 46 

2008 Toyota Camry Hybrid 585 33/34 

2008 Ford Escape Hybrid 510 34/30 

2007 Lexus RX Hybrid 530 32/27 

2008 Mazda Tribute 544 29/34 

Cost and effectiveness of technologies 

NHTSA developed detailed estimates for the NPRM of the costs and effectiveness of applying 

fuel economy-improving technologies to vehicle models for use in analyzing the impacts of the 

alternative standards considered in this rulemaking. NHTSA explained that the NPRM estimates 

were based on those reported by the 2002 NAS Report analyzing costs and effectiveness for 

increasing fuel economy, but NHTSA modified those costs and effectiveness estimates for 

purposes of the PRIA as a result of extensive consultations among engineers from NHTSA, EPA, 

and the Volpe Center. As part of this process, NHTSA also developed varying cost and 

effectiveness estimates for applying certain fuel economy technologies to vehicles of different 

sizes and body styles. NHTSA stated that it may adjust these estimates based on comments 

received to the NPRM. 

NHTSA explained that the technology cost estimates used in the agency’s analysis are intended 

to represent manufacturers’ direct costs for high-volume production of vehicles with these 

technologies and sufficient experience with their application so that all cost reductions due to 

“learning curve” effects were fully realized. 

Comments: Almost every manufacturer commented that NHTSA had overestimated the benefits 

of certain technologies or had underestimated the costs of technologies. Several provided 

confidential information of their estimates. Other commenters indicated that NHTSA had 

underestimated the benefits of certain technologies. The comments are too numerous to include 

in this document. 

Agency response: The agency hired a contractor (Ricardo) to go through all of the technologies 

and all of the comments and provide their expert opinion on the appropriate usage of 

technologies and their costs and benefits. The agency worked in consultation with Ricardo to 

develop the agency’s estimates of technology costs and effectiveness. Costs do change over time 

and the cost estimates were based on the prices in effect at the time the estimates were made. 

The agency intends to monitor commodity prices carefully and will adjust affected technology 

costs as necessary in future rulemakings. 

Because costs change over time, the agency re-examines costs for each rulemaking. See Chapter 

V for more information. 

Discount rates 

Most of the commenters realized that the discount rate has a significant impact on the level of the 

standard. The discount rate is used to determine the present value of future benefits (e.g. fuel 
I-13

saved over the lifetime of the vehicle). The agency used a 7 percent discount rate to determine 

the proposed CAFE levels, and asked for comments about whether a 3 percent discount rate 

should be used for standard setting purposes. Based on our marginal cost = marginal benefit 

methodology, discounting by a lower rate results in higher benefits, which allows more 

countermeasures to be cost effective and the standard to be higher. 

Almost every commenter expressed an opinion about the discount rate. Some argued that there 

is an intergenerational discount rate that should be applied to benefits like carbon emission 

reductions that occur over long time frames, like 100 to 150 years. The intergenerational 

discount rate could be different than the conventional discount rate applied to fuel savings (that 

occur over the next 36 years in the case of light trucks). We will always use the term 

intergenerational to distinguish this long term discount rate from the conventional discount rate 

we normally use. 

Those favoring a 7 percent discount rate include: 

Comment: AIAM, 2008-0089-0205.1, Pg. 6 supports the discount rates used by NHTSA. The 

NAS report assumed discount rates that bracket those considered by NHTSA. 

Comment: National Automobile Dealers Association, 2008-0089-223.1, Pg 6-7 stated that a 

discount rate of at least seven percent (or higher) should be used to estimate the future costs and 

benefits of the proposed standards. NHTSA should not use the OMB default calculation of the 

economy-wide opportunity cost of capital. As NHTSA correctly notes, financing rates on motor 

vehicle loans are indicative of appropriate discount rates since they reflect the real-world 

opportunity costs faced by consumers when buying vehicles having greater fuel economy costs 

associated with them. 

Those favoring a 5 percent discount rate include: 

Comment: Consumer Federation of America, 2008-0089-0183, Pg. 52-53 stated that NHTSA 

should have used 5% (the average of 3% and 7%). The rate NHTSA uses fails to reflect the 

importance of fuel savings. 

Those favoring the 3 percent discount rate, saying that the discount rate should be based on the 

social rate of time preference, include: 

Attorney General of the States, 2008-0089-0199.1, Pg 11 

Union of Concerned Scientists, 2008-0089-201.1 

Air Resources Board, 2008-0089-0173, Pg. 11 

Natural Resources Defense Council, 2008-0089 225.1, Pg. 2 and following 

Those discussing a lower rate, but not identifying that rate included: 

Comment: Yohe, 2008-0089-139.1 disagrees with NHTSA’s rationale for relying primarily on a 

7% discount rate. Commenter argues that public investment should be based on a low discount 

rate if it complements private investment, since by doing so public investment raises the rate of 

return to private investment, thereby partly offsetting the effect of reduced returns to private 

investment caused by the corporate profits tax. Commenter contends that mitigating greenhouse 

gas emissions complements private investment more broadly, while at the same time making 

adaptation to climate change more productive. Commenter observes that the higher average fuel 
I-14

economy resulting from applying a lower discount rate indicates that the analysis captures some 

of the value of this complementarity. Commenter acknowledges that taxes that support public 

investment generally affect consumption, but argues that this effect is captured in the cost 

calculation, and states that mitigation offers a co-benefit because it improves the marginal 

productivity of other private investments. Commenter also believes the definition of the social 

rate of time preference to be stated incorrectly and believes “utility” should be substituted for 

“consumption.” 

Comment: Another discount rate was proposed by Sierra Research, 2008-0089-0046, Page 74, 

based on an analysis by NERA they use a 12.4% discount rate for future fuel savings. 

NERA National Economic Research Association, 2008-0089-050, Page 1-7 uses a 12.4% 

discount rate based on a range of plausible discount rates to be used in an analysis of the 

operating cost savings from improvements in automotive fuel economy improvements. 

When purchasing a car, a rational consumer will consider future operating costs and will 

discount them to present value using a discount rate that will reflect the risk or uncertainty in the 

value or future operating costs. Consumers will perform this discounting using his or her own 

private discount rate. Consumers will not use a social discount rate that a government agency 

might use in doing a cost benefit analysis. Nor will consumers use the rate of a new car loan, 

which is a known certain rate. The operating costs of a vehicle vary with fuel prices and driving 

patterns, which are much more uncertain. As such, they would consider consumers private 

discount rate to be higher than the rate of a new car loan. Empirical economic research has 

consistently demonstrated that consumers use high discount rates when calculating the present 

value of future cash flows associated with operating costs of durable equipment. One study 

addressed the discount rate used by consumer with respect to automobile in particular. The 

appropriate discount rate is the rate that consumers actually use when deciding on vehicle 

purchases. While the discount rate consumers actually use can not be observed, it can be 

inferred from consumer behavior. Dreyfus and Viscusi (1995) use a hedonic regression model to 

estimate consumer value for fuel economy improvements and the associated discount rate. 

Dreyfus, M. and Viscusi, W., (1995) Rates of Time Preference and Consumer Valuations of 

Automobile Safety and Fuel Efficiency, Journal of Law and Economics. Their estimates of the 

discount rate range from 10.7 to 17.4 percent, depending upon the specification selected. The 

study was based on 1988 data when interest rates were higher and should be adjusted to today’s 

economic conditions. The nominal yield on Treasury bonds in 1988 is 8.9 percent. After 

adjusting for inflation (4.3%) the real rate of growth in treasury bonds was 4.6 percent. 

Subtracting 4.6 percent from 10.7 – 17.4 percent leaves 6.1 to 12.8%. And after adjusting for 

interest rates, adding the 10 year Treasury bond yield of 2.9 percent, the rates are 9.0 to 15.7%, 

the average is 12.4%. 

Comment: The Alliance, 2008-0089-0179.1, Pg. 9, 31 supports the 12.4 percent discount rate. 

Those discussing the intergenerational discount rate commented: 

Comment: Yohe, 2008-0089-139.1 recommends that NHTSA apply a lower discount rate to 

benefits from future reductions in CO2. 

Comment: Mark Eads, 2008-0089-0165.1
I-15

Mr. Eads disagrees with NHTSA choice of 7 percent discount, both in terms of the magnitude of 

the discount rate and in NHTSA’ rationale. He argues that the choices made primarily involve 

long-term inter-generational environmental benefits and costs rather than intra-generational 

benefits and costs. He advocates that NHTSA apply a non-constant declining discount rate that 

begins at 2.6 percent in year one, declining to 0.6 percent in year 300. 

 

Comment: Prof. Michael Hanemann, Dept. of Agricultural and Resource Economics, University 

of California, Berkeley, 2008-0089-0188, recommends using a discount rate no higher than 4%, 

and a rate as low as 2% for sensitivity analysis. It is not clear whether these rates are to be 

applied to benefits from future reductions in CO2 emissions only or to all future benefits from 

lower fuel consumption (presumably the former). Commenter criticizes 7% and 4% discount 

rates used by NHTSA and by Nordhaus and Boyer as unjustified for use in assessing benefits 

from reducing threat or severity of climate change, and briefly cites some research suggesting 

that discount rates below 3% are appropriate for discounting future climate-related damages. 

Comment: Attorney General of the State of California, 2008-0089-0199.4 provides no clear 

recommendation for action by NHTSA; but provides a detailed presentation from Hanemann to 

an unidentified audience. 

Comment: Center for Biological Diversity, 2008-0089-222.1, Pg. 5, 8 stated that NHTSA’s 

discount rate value is too high, and NHTSA didn’t use a reasonable range of values in the 

sensitivity analysis. 

Stern (2007) estimates the discount rate at lower than 1%. Any calculations performed under a 

selected discount rate for societal benefits must be compared to the same calculations under 

standard inflationary discount, but without discounting societal benefits to future generations. 

Stern (2006) notes the discount rate can be negative (in the context of discounting CO2 

emissions). 

Comment: Environmental Defense Fund, 2008-0089-224.1, Pg. 1 recommends use of a 3 

percent discount rate for standard setting, with a sensitivity analysis using a 0.5 and 1 percent 

rate. Use of a high discount rate does not reflect the intergenerational impacts of CAFE 

implementation. One of the major benefits of the CAFE standards, in addition to increasing 

energy security and energy efficiency, is significantly reducing global warming pollution from 

automobiles. Because the benefits of reducing climate change will occur over multiple 

generations, we recommend that the Agency use a 3 percent discount rate for standard setting, 

with a sensitivity analysis using a 0.5 and 1 percent rate. This practice would follow EPA and 

OMB guidelines for estimating costs or benefits that affect multiple generations. 

Comment: Attorneys General, 2008-0089-0495, Pg. 67-89 

Provides a paper by Frank Verboven, “Implicit Interest Rates in Consumer Durables Purchasing 

Decisions – Evidence from Automobiles”, March 1999. The paper examines consumer decisions 

to purchase 41 pairs of identical cars with the exception being whether they are equipped with 

diesel or gasoline engines in different European countries. Diesel engines have a higher initial 

purchase price but provide future savings in operating costs. He infers implicit interest rates 

given the purchases of gasoline and diesel variants, the differences in initial purchase price, price 
I-16

of gasoline and diesel fuel costs per mile and other characteristics. The implicit interest rate that 

consumers use in making this decision is estimated to range from 5 to 13 percent. 

 

Agency response: Discounting represents the conversion of the economic values of benefits and 

costs that are expected to occur in the future to their equivalent values today, or present values. 

It is intended to account for the fact that most individuals attach lower values to economic 

outcomes that are not expected to occur until some future date than to equivalent outcomes that 

are expected to occur sooner. It is particularly important to discount the future values of benefits 

or costs when they are expected to vary from year to year, or when the time profiles of benefits 

and costs are not expected to be similar. Discounting enables a consistent comparison of benefits 

to costs across time periods, and also enables consistent comparison of costs or benefits that are 

expected to occur in the future to those that occur in the present.

In establishing the proposed CAFE standards for MYs 2011-2015 that were presented in the 

NPRM, and whose environmental impacts were evaluated in the Draft EIS, NHTSA employed a 

discount rate of 7% to discount future benefits and costs resulting from increased fuel economy 

to their present values. Discounting the value of future fuel savings and other benefits that result 

from higher fuel economy, as well future costs resulting from added driving caused by the fuel 

economy rebound effect, accounts for the fact that they will occur over the future lifetimes of the 

MY 2011-15 vehicles. The discount rate expresses the rate at which the value of these future 

benefits and costs – as viewed from today’s perspective – declines for each year they are 

deferred into the future. 

In response to the extensive comments it received to the NPRM and the DEIS on this issue, 

NHTSA has carefully reviewed published research and OMB guidance on appropriate discount 

rates, including discount rates that should be applied to benefits that are expected to occur in the 

distant future and thus be experienced mainly by future generations, and discount rates that 

buyers of new vehicles apply to savings in fuel costs from higher fuel economy. For purposes of 

this final rule, the agency has elected to apply separate discount rates to the benefits resulting 

from reduced CO2 emissions, which are expected to reduce the rate or intensity of climate 

change that will occur in the distant future, and the economic value of fuel savings and other 

benefits resulting from lower fuel consumption, which will be experienced over the limited 

lifetimes of newly-purchased vehicles. Specifically, NHTSA has decided to discount future 

benefits from reducing CO2 emissions using a 3 percent rate, but to discount all other benefits 

resulting from higher CAFE standards for MY 2011 cars and light trucks at 7 percent. 

As some commenters pointed out, OMB guidance on discounting permits the use of lower rates 

to discount benefits that are expected to occur in the distant future, and will thus be experienced 

by future generations.20 The main rationale for doing so is that although most individuals 

demonstrate a strong preference for current consumption over consumption they expect to occur 

later within their own lifetimes, it may not be appropriate for society to exercise a similarly 

strong preference for consumption by current generations over consumption opportunities for 

future generations, particularly when it is contemplating actions that affect the relative income 

levels of current and future generations. In addition, while market interest rates provide useful 

guidance about the rates that should be used to discount future benefits that will be experienced 

 

20 White House Office of Management and Budget, Circular A-4, September 17, 2003, pp. 35-36. 
I-17

by current generations, no comparable market rates are available to guide the choice of rates for 

discounting benefits that will be received by future generations. 

For this final rule, NHTSA has elected to use a rate of 3 percent to discount the future economic 

benefits from reduced emissions of CO2 that are projected to result from decreased fuel 

production and consumption. These benefits, which include reductions in the expected future 

economic damages caused by increased global temperatures, a rise in sea levels, and other 

projected impacts of climate change, are anticipated to extend over a period from approximately 

fifty to two hundred or more years after the impact of this rule on emissions by MY 2011 cars 

and light trucks occurs, and will thus be experienced primarily by generations that are not now 

living. As indicated previously, studies of the economic cost of GHG emissions select a rate to 

discount economic damages from increased emissions. These damages are typically projected to 

occur over an extended time span beginning many years after the future date when emissions 

increase, and the chosen rate is used to discount these distant future damages to their present 

values as of the date when the increased emissions that cause them were assumed to occur. 

This procedure yields estimates of the damage costs from increased GHG emissions during 

specific future years, which NHTSA uses to value the reductions in emissions that would occur 

each year over the lifetimes of vehicles affected by higher CAFE standards. For example, higher 

CAFE standards for MY 2011 cars and light trucks would reduce GHG emissions each year from 

2011 through approximately 2047, and the estimated value of avoiding each ton of emissions 

rises each year over that span. In turn, the estimated economic values of the reductions in GHG 

emissions during each of those future years must be discounted to their present values as of 

today, so that they can be compared with the present values of other benefits from higher CAFE 

standards, and with vehicle manufacturers’ costs for meeting higher CAFE standards. 

The 3 percent rate is consistent with OMB guidance on appropriate discount rates for benefits 

experienced by future generations, as well as with those used to develop many of the estimates of 

the economic costs of future climate change that form the basis for NHTSA’s estimate of 

economic value of reducing CO2 emissions.21 Of the 125 peer-reviewed estimates of the social 

cost of carbon included in Tol’s 2008 survey, which provides the basis for NHTSA’s estimated 

value of reducing CO2 emissions, 83 used assumptions that imply discount rates of 3 percent or 

higher. 

Moreover, the 3 percent rate is consistent with widely-used estimates in economic analysis of 

climate change of the appropriate rate of time preference for current versus distant future 

consumption, expected future growth in real incomes, and the rate at which the additional utility 

provided by increased consumption declines as income increases.22 The Ramsey discounting 

rule is widely employed in studies of potential economic damages from climate changes in the 

distant future. The Ramsey rule states that -r = δ + ηg, where r is the consumption discount rate, 

 

21 Richard S.J. Tol, The social cost of carbon: trends, outliers, and catastrophes, Economics Discussion Papers, July 

23, 2008. 

22 EPA notes that “In this inter-generational context, a three percent discount rate is consistent with observed interest 

rates from long-term intra-generational investments (net of risk premiums) as well as interest rates relevant for 

monetary estimates of the impacts of climate change that are primarily consumption effects.” See U.S. EPA, 

Technical Support Document on Benefits of Reducing GHG Emissions, June 12, 2008, p. 9. 
I-18

δ is the pure rate of time preference (or the marginal rate of substitution between current and 

future consumption under the assumption that they are initially equal), g is the expected 

(percentage) rate of growth in future consumption, and η is the elasticity of the marginal utility 

of consumption with respect to changes in the level of consumption itself. Commonly used 

values of these parameters in climate studies are δ = -1 percent per year, η= −1, and g = 2 

percent per year, which yield a value for r of 3 percent per year.23

The remaining future benefits and costs anticipated to result from higher fuel economy are 

projected to occur within the lifetimes of vehicles affected by the CAFE standards for MY 2011, 

which extend up to a maximum of 35 years from the dates those vehicles that are produced and 

sold. Because the vehicles originally produced during this model year will gradually be retired 

from service as they age, and those that remain in service will be driven progressively less, most 

of these benefits will occur over the period from 2011 through approximately 2025. Thus, a 

conventional or “intra-generational” discount rate is appropriate to use in discounting these 

benefits and costs to their present value when analyzing the economic impacts of establishing 

higher CAFE standards.24 

The correct discount rate to apply to these nearer-term benefits and costs depends partly on how 

costs to vehicle manufacturers for improving fuel economy to comply with higher CAFE 

standards will ultimately be distributed. If manufacturers are unable to recover their costs for 

increasing fuel economy in the form of higher selling prices for new vehicles, those outlays will 

displace or alter other productive investments that manufacturers could make, and the 

appropriate discount rate is their opportunity cost of capital investment. In contrast, if 

manufacturers are able to raise selling prices for new vehicles sufficiently to recover all their 

costs for improving fuel economy, those costs will ultimately affect private consumption 

decisions rather than capital investment opportunities. Under this second assumption, economic 

theory and OMB guidance suggest that a consumption discount rate, which reflects the time 

preferences of consumers rather than those of lenders or investors, is appropriate for discounting 

future benefits. Since the time preferences of savers and investors are probably similar, financial 

intermediation would be expected to equalize investment and consumption discount rates. In the 

presence of corporate income taxation, however, consumption discount rates are generally 

thought to be lower than the opportunity cost of investment capital. Finally, if competitive 

conditions in the new vehicle market manufacturers and potential buyers’ valuation of higher 

fuel economy permit manufacturers to recover only part of their costs for meeting higher CAFE 

standards through higher prices for new vehicles, a rate between an investment discount rate and 

the lower consumption discount rate may be appropriate, with the exact rate depending on the 

distribution of compliance costs between vehicle manufacturers and buyers. 

 

23 See Tol (2008), p. 3. 

24 NHTSA acknowledges that using different rates to discount the distant and nearer-term future benefits from 

higher CFAE standards presents a potential problem of time inconsistency, which arises from the much greater 

uncertainty that surrounds long-term future rates of growth in investment, economic output, and consumption than is 

associated with near-term estimates of these variables. However, the agency believes that this problem is less 

serious than those that would result from using a single rate to discount benefits that occur over the next 25-35 year 

sand those that are likely to occur over a 100-200 year time frame. 
I-19

OMB estimates that the real before-tax rate of return on private capital investment in the U.S. 

economy averages approximately 7 percent per year, and generally recommends this figure for 

use as a real discount rate in cases where the primary effect of a regulation is to displace private 

capital investment.25 However, this figure represents an economy-wide average estimate of the 

return on private investment, which incorporates no risk premium other than that associated with 

uncertainty about future growth in total economic output. As a consequence, it may understate 

the opportunity cost of capital for corporations facing firm- or market-specific risks on future 

investment returns. In addition, domestic motor vehicle manufacturers currently have little or no 

accumulated earnings available to re-invest, and may be required to enter private capital markets 

to finance the investments necessary to allow them to comply with higher CAFE standards. In 

doing so they are likely to face real interest rates well above the 7 percent opportunity cost of 

capital estimated by OMB, which may provide a more accurate estimate of the appropriate 

investment rate for discounting future benefits resulting from increased fuel economy. 

OMB guidance estimates that an appropriate current value for the consumer rate of time 

preference – and thus the discount rate that should be used if the costs of complying with a 

regulation are borne by consumers – is approximately 3 percent. However, this estimate is 

derived from rates of return demanded by consumers on highly liquid investments, and is 

intended to apply to situations where there is little or no risk that consumers will actually realize 

the future benefits resulting from a proposed regulation. In the case of CAFE standards, buyers 

face considerable uncertainty about future fuel prices, and thus about the value of fuel savings 

resulting from higher fuel economy. Uncertainty about their future levels of vehicle use and the 

actual lifetimes of new vehicles also contribute to buyers’ uncertainty about the value of future 

fuel savings that is likely to result from purchasing a vehicle with higher fuel economy. In 

addition, buyers’ initial investments in higher fuel economy are illiquid, and the extent to which 

they will be able recover the remaining value of an initial investment in a new vehicle that 

achieves higher fuel economy in the used vehicle market is uncertain. Finally, unlike most of the 

regulations that OMB Circular A-4 is intended to address, most (75-80 percent) of the benefits 

from higher CAFE standards accrue directly to the parties they affect – vehicle buyers – rather 

than to society at large. Taken together, these circumstances may make the use of a riskless 

consumption discount rate, which is intended for use in discounting the economy-wide effects of 

a proposed regulation on consumption, inappropriate for discounting the future benefits that 

result from requiring higher fuel economy. 

Empirical studies of the discount rates that new vehicle buyers reveal by trading off the higher 

purchase prices for more fuel-efficient vehicles against future savings in fuel costs resulting from 

higher fuel economy, which capture the effects of these uncertainties, conclude that buyers apply 

real discount rates well above the 3 percent rate recommended by OMB for riskless situations. 

Dreyfus and Viscusi estimate that, when adjusted to reflect differences between the current 

interest rate environment and rates at the time the data for their study were drawn, U.S. buyers 

apply real discount rates in the range of 12 percent when weighing expected future fuel savings 

against higher purchase prices.26 Verboven estimates that European buyers’ nominal discount 

 

25 White House Office of Management and Budget, Circular A-4, September 17, 2003, p. 33. 

26 See Dreyfus, Mark K. and W. Kip Viscusi. 1995. “Rates of Time Preference and Consumer 

Valuations of Automobile Safety and Fuel Efficiency.” Journal of Law and Economics. 38: 79 – 
I-20

rates for fuel savings resulting from buying more fuel-efficient new vehicle models range from 5 

to 13 percent, with an average estimate of slightly above 10 percent. Verboven’s estimate 

corresponds to a real discount rate of approximately 7 percent when adjusted to reflect current 

and recent U.S. inflation rates.27 These studies may provide more reliable estimates of the 

appropriate consumption rate for discounting benefits from higher fuel economy than the 3 

percent figure recommended in OMB guidance. 

Uncertainty about future developments in the international oil market, the U.S. economy, and the 

U.S. market for new cars and light trucks make it extremely difficult to anticipate the extent to 

which vehicle manufacturers will be able to recover costs for complying with higher CAFE 

standards in the form of higher selling prices for new vehicles. If new vehicle buyers expect fuel 

prices to remain higher than those used by NHTSA to establish CAFE standards for MY 2011, 

they may be willing to pay the higher prices necessary for manufacturers to recover their costs 

for complying with those standards.28 However, potential buyers who expect future fuel prices 

to be lower than the forecast NHTSA relies upon are likely to resist manufacturers’ efforts to 

raise new vehicle prices sufficiently to recover all of their CAFE compliance costs, since those 

buyers’ assessment of the value of higher fuel economy will be lower than that reflected in the 

CAFE standards NHTSA establishes. 

From the manufacturer perspective, the current financial condition of some car and light truck 

producers suggests that they are likely to find it difficult to absorb the full cost of complying 

with higher CAFE standards. Because CAFE standards apply to all manufacturers, establishing 

higher standards may provide a ready opportunity for all producers to raise car and light truck 

prices. However, this opportunity may be restricted if producers that face very low incremental 

costs for complying with higher CAFE standards because of higher fuel economy levels in their 

planned model offerings compete aggressively with others that face significant costs for 

increasing fuel economy levels in their product plans to comply with higher CAFE standards. 

After considering the comments received and various arguments about the ultimate incidence of 

manufacturers’ costs for complying with higher CAFE standards, NHTSA has concluded that the 

costs for complying with higher MY 2011 CAFE standards are likely to be shared by 

manufacturers and purchasers of new vehicles, but that the exact distribution fraction of these 

costs between manufacturers and buyers is extremely difficult to anticipate. Generally, NHTSA 

believes that manufacturers are likely to be able to raise prices only to the extent justified by 

potential buyers’ assessments of the value of future fuel savings that will result from higher fuel 

economy, but the agency recognizes that buyers’ valuations of fuel savings are inherently 

 98; and the adjustment of discount rates reported in that source discussed in NERA, “Discount Rates for Private 

Costs,” pp. 4-5, attachment to Alliance of Automobile Manufacturers comment on NPRM, Docket Item NHTSA2008-0089-50. 

27 See Verboven, Frank, “Implicit Interest Rates in Consumer Durables Purchasing Decisions – Evidence for 

Automobiles,” p. 22, attachment to California Department of Justice, comment on NPRM, Docket Item NHTSA2008-0089-0495. 

28 Whether they will be willing to do so, however, depends partly on how the combined value of the economic and 

environmental externalities used to determine CAFE standards compares to current fuel taxes. It also depends on 

whether new vehicle buyers take account of the value of fuel savings resulting from higher fuel economy over the 

entire expected lifetimes of the vehicles they purchase, or over only some part of that lifetime (such as the period 

they expect to own new vehicles). 
I-21

uncertain, and undoubtedly vary widely among individual buyers. As a consequence, price 

increases for new cars and light trucks are likely to allow manufacturers to recoup some fraction 

of their costs for complying with higher CAFE standards, while the remainder of those costs are 

likely to displace other investment opportunities that would otherwise be available to them. 

Regardless of the ultimate incidence of costs for complying with higher CAFE standards, 

however, both manufacturers’ opportunity costs for capital investment and empirical estimates of 

the discount rates that buyers of new vehicles apply to future fuel savings suggest that a rate in 

the range of 7 percent is an appropriate rate for discounting the nearer-term benefits from 

increased fuel economy that will occur over the lifetimes of MY 2011 cars and light trucks. Thus 

for purposes of establishing the CAFE standards adopted in this final rule and estimating their 

economic benefits, NHTSA has continued to employ a 7 percent rate to discount future benefits 

from higher CAFE standards other than those resulting from reduced CO2 emissions. 

Recognizing the uncertainty surrounding this assumption, NHTSA has also tested the sensitivity 

of the level of the optimized CAFE standards and their resulting economic benefits to the use of 

a 3 percent discount rate for all categories of benefits. 

NHTSA will consider whether to revise the discount rates used in this analysis when it analyzes 

the consequences of future CAFE standards. At that time, the agency will consider whether to 

apply a lower discount rate than 3 percent to the benefits from reducing future emissions of CO2

and other greenhouse gases, as well as whether to use a rate different from 7 percent to discount 

the nearer-term benefits from raising CAFE standards. In making these decisions, the agency 

will consider guidance on discounting future benefits – particularly those from reducing the 

threat of climate-related economic damages – issued by OMB, EPA, and other government 

agencies, and will also consider the discount rates used by other federal agencies in similar 

regulatory proceedings. NHTSA will also consider recent research on appropriate rates for 

discounting future benefits from reducing the threat of climate-related economic damages, as 

well as on the discount rates that buyers of new vehicles apply to the fuel savings they obtain 

from purchasing models with higher fuel economy, since such research is particularly relevant to 

its choice of discount rates. Finally, the agency will consider the financial situations of vehicle 

manufacturers and the competitive state of the new vehicle market at the time it considers new 

CAFE standards, as well as their implications for the choice of an appropriate discount rate for 

near-term (or “intra-generational”) economic benefits that result from higher CAFE standards. 

Emissions savings per ton – Value of Carbon 

Comment: Air Resources Board, 2008-0089-0173, Pg.3 believes we should use the Phase II 

European Union Allowances – tradable right to emit one ton of carbon dioxide- market value. 

They are currently trading at $42 per ton, and the benchmark contracts have fluctuated between 

$18 and $42 this year, with Germany Deutsche Bank forecasting EUA prices of $60 for 2008 

and EUA prices as high as $100 by 2020

Comment: Prof. Michael Hanemann, 2008-0089-0188 recommends that NHTSA use a value of 

$25 per metric ton of CO2 emissions reduced, growing at 2.4% annually beginning in 2005. 

Commenter disagrees with NHTSA’s rationale for selecting CO2 damage cost, and argues that 

there is no credible evidence to support a lower bound of zero on range of possible damage costs. 

Commenter identifies Nordhaus and Boyer’s DICE model as a source that NHTSA could instead 
I-22

have relied upon for estimates of climate damages to the U.S. economy, but identifies several 

key assumptions and parameters that commenter believes cause its estimates of U.S. climate 

damages to be understated by a factor of two to four. Comment includes a detailed discussion of 

these key assumptions and parameter values, identifies why the values employed in the DICE 

model may be incorrect, and recommends values that he views as more defensible on the basis of 

recent empirical research. 

Comment: Union of Concerned Scientists, 2008-0089-201.1 states that NHTSA undervalues the 

cost of global warming and should employ a value of at least $45 per metric ton CO2, the value 

at which CO2 emission permits are currently trading on the European Climate Exchange. The 

recommended value represents a predicted marginal cost of achieving the required level of 

emissions reduction for the EU, and is likely to be a conservative estimate of mitigation benefits. 

It is consistent with other recent estimates such as the EPA’s assessment of GHG allowance 

prices under Lieberman-Warner: $22-40 in 2015 and $28-$51 in 2020. 

Comment: American Council for an Energy-Efficient Economy (ACEEE), 2008-0089-211.1 

argues that the “NHTSA decision to use Tol’s estimate of $14 as the upper bound based on the 

argument that this value includes the worldwide costs CO2 is flawed and the low estimate of the 

marginal damage cost of carbon emissions also discounts the high risk associated with climate 

change.” 

Martin Weitzman says accounting for risk of catastrophe raises marginal damage value further 

“legislative efforts to implement a carbon regime in which the projected market cost of CO2 is 

expected to lie between $20 and $30 – significantly higher than the average damage cost 

assumed by NHTSA – serves as evidence that the U.S. is now beginning to contemplate the high 

risk of rising greenhouse gas emissions.”

Comment: Center for Biological Diversity, 2008-0089-0222.1, Pg. 6-10 states that NHTSA’s 

value is too low. NHTSA must consider the high premium associated with achieving dramatic 

reductions in CO2 emissions in the near term. The sensitivity analysis must include the range of 

values in Stern (2007). (Hansen, 2008) says CO2 will need to be reduced from its current 385 

ppm to at most 350 ppm soon to avoid seeding irreversible catastrophic effects. The Volpe 

model only calculates the marginal costs and benefits provided to consumers and automakers, 

not society as a whole. NHTSA doesn’t take into account the loss of biodiversity and complex 

and large-scale ecosystem services. The range of estimates of CO2 $/ton extends much higher 

than $14; there is no justification for a value of $0; and simply splitting the difference between 

two points is not a defensible methodology. Tol (2005) estimates $95/ton. IPCC estimates at 

$5-125/ton. The Tol studies date back as much as 18 years, with 25 of them more than 5 years 

old. IPCC notes that integrated assessment models likely underestimate costs because they do not 

include significant impacts that have not yet been monetized. IPCC estimates as high as 

$350/ton. Stern (2002) estimates $25-30/ton or higher. NHTSA’s lower value of $0 suggests the 

US might benefit economically by letting other countries bear the costs of unabated American 

greenhouse gas emissions. This is unethical and unfounded. NHTSA’s paraphrasing of Tol that 

many studies fail to consider potentially beneficial impact of climate change and don’t 

adequately account for how future development patterns and adaptations could reduce potential 

impacts isn’t cited as a finding by Tol and didn’t contribute to the Tol range of estimates. 
I-23

Comment: National Automobile Dealers Association, 2008-0089-223.1, Pg. 8 states that 

NHTSA should consider incorporating into its analysis the $2.97 per metric ton recently paid by 

the U.S. House of Representatives for carbon offsets. See: http://cao.house.gov/press/cao20080205.shtml. 

Comment: Environmental Defense Fund, 2008-0089-0224.1, Pg 1-2 and following 

EDF recommends that social cost of carbon (SCC) estimates be based on a rigorous metaanalysis 

that screens for studies that meet key quality criteria. In particular, included studies should use 

the same low discount rates (3 percent at maximum) and should come from recent literature. To 

the extent possible, the studies should account for a broad range of potential climate impacts and 

risks of catastrophic impacts from climate change. A risk assessment framework may be more 

appropriate than a benefit cost analysis in light of the inherent uncertainties in SCC estimates. 

Comment: Natural Resources Defense Council, 2008-0089 225.1 Pg. 2, 27 states that the social 

cost of carbon used by NHTSA is based on an arbitrary range of values and incorrectly relies on 

a central estimate of $7 per metric ton of CO2. Unmitigated, costs of dangerous climate change 

are very likely much higher than estimates in standard literature, and NHTSA must use a 

reasonable risk premium in its calculations. They provide a report entitled The Cost of Climate 

Change: What We’ll Pay if Global Warming Continues Unchecked. The report was published by 

NRDC in May 2008. It estimates the potential costs of climate change for the United States and 

identifies the most vulnerable regions for specific types of climate change effects. The report 

includes NRDC’s policy recommendations to combat climate change, including further 

increasing fuel economy standards. 

Comment: Sierra Club, 2008-0089-0226.1, Pg. 2, 6-8 states that NHTSA’s value is too low and 

was obtained haphazardly. NHTSA needs to consider the costs of adverse impacts of global 

warming cited by the USDA and NOAA. NHTSA took a low-end carbon study average value 

and further reduced its validity by cutting it in half. NHTSA’s price barely takes a thumb off the 

scale. NHTSA value is far below current estimates. NHTSA’s decision to average $0 and $14 is 

flawed. The $14 value is itself an average so cannot be used as the max value. Also the Tol $14 

value is in 1995 dollars – the 2005 value would be $19. Tol (2005) ways the max value is in the 

$55-95 range. NHTSA should not rule out the $95 value. Using $0 as the min is wrong because 

NHTSA has been chastised by the court for doing this in the past and several government reports 

say the impact of CO2 emissions on the economy is significant. The estimate from (Stern, 2006) 

is $85. EPA’s recent analysis is that it could be as high as $22-40. The futures market value in 

2011 under the ETS is already up to $45. The current European Prices for carbon under ETS 

have been $15-25. The USDA predicts increasing crop failures, decreased livestock 

productivity, more forest fires, more drought, strains on water resources, etc. NOAA predicts 

more heat waves, more droughts, more intense hurricanes, more winter storms. Hurricane 

Katrina demonstrated that the social and economic costs of extreme weather events can be 

staggering. 

Comment: U.S. Senate, 2008-0089-0454, Pg. 1-4 stated that NHTSA’s value for SCC is too low. 

Also NHTSA should throw out the lower bound estimate of $0 in determining the value of SCC. 

NHTSA’s averaging of $0 & $14 is likely to be found arbitrary and capricious. NHTSA should 
I-24

use a number higher than $14 for the upper bound in the averaging because the Tol $14 is itself 

an average. 

Agency response: All of the emissions issues are answered together. See Chapter VIII and the 

preamble to the final rule for our response. 

Emissions worldwide versus only U.S. emissions 

Comment: Alliance, 2008-0089-0179.1, P9, P34, Att3, S8, states that NHTSA should only 

account for U.S. CO2 benefits, not globally. NERA uses a 20 percent factor for U.S. versus 

global. EPCA says when considering maximum feasible, the Secretary of Transportation should 

consider the need of the United States to conserve energy. They argue that phrase is an 

extraterritoriality canon and by law NHTSA must limit consideration of social costs of carbon to 

domestic impacts. 

Comment: Center for Biological Diversity, 2008-0089-0222.1, Pg. 7, 11 stated that NHTSA 

must take into account the costs of climate change outside the US. NHTSA fails to understand 

the tremendous threats and challenges posed by global climate change. The air basin for GHG is 

the global atmosphere. Benefits should be estimated wherever they are experienced. Not doing 

so vastly underestimates the true costs of climate change. Restricting to the US carries the 

terrible and arrogant implication that the people of the US believe that people in other countries 

should bear the environmental and economic burdens caused by American consumer 

preferences. Nothing in EPCA, NEPA, or other applicable law allows NHTSA to restrict to the 

US. The impact on the developing world is disproportionate. 

Comment: National Automobile Dealers Association, 2008-0089-223.1, Pg 8 stated that 

NHTSA should only count domestic impacts of reducing the social costs of motor vehicle CO2. 

Air “Pollutants” Criteria pollutant reduction benefits associated with the proposed CAFE 

standards are overstated as the negative impact of inhibited fleet turnover was not accounted for. 

With respect to greenhouse gases, NHTSA should account only for any domestic impacts of 

reducing the social costs of motor vehicle CO2, given that EPCA focuses on U.S. energy security 

and all other costs and benefits evaluated with respect to the proposed CAFE standards are 

domestic only. 

Comment: U.S. Senate, 2008-0089-0454, p. 3 stated that NHTSA shouldn’t ignore the 

international benefits from GHG reduction. NHTSA’s argument that it should exclude nondomestic benefits for consistency with prior CAFÉ rulemakings is irrelevant because NHTSA 

has not previously valued SCC. OMB specifically allows for the consideration of non-domestic 

benefits. The U.S. is obligated under the 1992 U.N. Framework Convention on Climate Change 

to consider global impacts. If every nation ignored non-domestic benefits, each would set 

emissions standards that are far short of socially optimal. NHTSA’s treatment of SCC would put 

the rule at substantial litigation risk. 

Emissions Growth rate in the value of carbon emissions over time 

Comment: Center for Biological Diversity, 2008-0089-0222.1, Pg. 8, states that the growth rate 

over time is 2-4% per year and cites the IPCC. 
I-25

Agency response: See Chapter VIII and the preamble to the final rule for our response. 

Emission reductions values for Criteria pollutants 

(CO, VOC, NOx, fine particulate matter (PM), and sulfur dioxide (SO2) 

Comment: Mark A. Delucchi, 2008-0089-0025, NHTSA needs to include more externalities. It 

is not clear what kinds of damages are included in your $/ton estimates (e.g., page 24403). You 

should include health damages, visibility, crop damages, materials damages, and naturalecosystem damages. I am fairly sure that the EPA damage estimates do not include all of these. 

You can find peer-reviewed estimates of damages in most of these categories on my faculty web 

page. 

Comment: Alliance, 2008-0089-0179.1, Pg. 9 P37, Att 2 P107-108, stated that NHTSA should 

use published EPA estimates on conventional pollutants, not ad/hoc EPA/NHTSA estimates. 

Upstream emissions will not be reduced. NHTSA did not take into account the new source 

review standards, and otherwise assumed away federal and state laws that would have the effect 

of requiring offsets from the upstream refineries that NHTSA attempts to claim credit for. The 

upstream emission factors aren’t realistic. NHTSA needs to consider the fleet-turnover effect. 

Most criteria pollutants will worsen for decades. NHTSA did not consider that consumers will 

delay purchasing new more fuel efficient vehicles in the current marketplace prior to an 

expensive new government mandate. 

Comment: Ford, 2008-0089-0202.1, Pg. 10 recommended that NHTSA consider using CO2 

mitigation cost in their analysis in lieu of emission damage cost. Although vehicles are often 

perceived to be the major source of CO2 emissions, in fact, 70 percent of man-made emissions in 

the United States come from sources other than transportation. Power generation, home energy 

use and other industries are just a few. It should also be noted that it would be more cost 

effective to remove CO2 from the utility sector than the vehicle sector presently. As shown in 

Chart 4, when it comes to the auto industry, light duty cars and trucks contribute only about 20 

percent of CO2 emissions in the U.S. And on a global scale, that figure is about 11 percent. No 

single sector can provide the total solution. All sectors must contribute. 

Comment: Center for Biological Diversity, 2008-0089- 0222.1, Pg. 11, stated that NHTSA must 

include in its benefits analysis emissions of methane, nitrous oxide, and hydroflourocarbons. 

They represent large amounts of GHGs. Nitrous oxide emissions are equivalent to 29 million 

metric tons of CO2. NHTSA must analyze the impacts of the standard in relation to the 

emissions scenarios and impacts identified in Bernstein (2007). 

 

Agency response: In response to Mr. Delucchi’s comment, NHTSA is confident that the damage 

cost estimates it used in the NPRM to value reductions in criteria air pollutants and their 

chemical precursors include the full ranges of human health impacts known to be associated with 

exposure to each of these pollutants. Differences between these damage costs and the estimates 

by OMB cited by commenters reflect the fact that the estimates provided to NHTSA by EPA 

apply specifically to emissions by motor vehicles, and include separate costs for emissions from 

stationary sources such as petroleum refineries where such differences are appropriate. The 
I-26

estimates provided by EPA also reflect more up-to-date knowledge about the human health 

impacts of exposure to criteria air pollutants and the economic costs associated with those 

impacts than do the estimates reported by OMB. Thus in the analysis it conducted for this Final 

Rule, NHTSA has continued to use the damage cost estimates supplied by EPA to determine the 

economic costs or benefits from changes in emissions of criteria air pollutants that result from 

higher CAFE standards. 

In response to comments provided by NERA on behalf of the Alliance, NHTSA acknowledges 

that it may have overestimated reductions in upstream emissions of some criteria air pollutants 

(particularly PM and NOx) resulting from fuel savings in the analysis it conducted for the 

NPRM. NHTSA has taken two steps to remedy this possible overestimation. First, the agency 

used updated emission factors for vehicles used to transport crude petroleum and refined fuel, 

including ocean tankers, railroad locomotives, barges, and heavy-duty trucks supplied by EPA to 

recalculate the emissions factors for each stage of fuel production and distribution in Argonne’s 

GREET model. These updated emission factors reflect the effects of recent and pending EPA 

regulations on vehicle emissions and fuel composition, and result in significant reductions in the 

upstream emission rates for fuel production and distribution estimated using GREET. These 

lower upstream emission rates reduce NHTSA’s estimates of emissions during fuel production 

and distribution under both Baseline and alternative CAFE standards, and by doing so also lower 

the reductions in upstream emissions projected to result from any increase in CAFE standards 

from their Baseline levels. 

In addition, NHTSA notes that the estimates of reductions in upstream emissions it reported in 

the NPRM incorrectly included reductions in ocean tanker emissions for transportation of crude 

petroleum from overseas to ports or offshore oil terminals in the U.S. Since most of these 

emissions probably occur outside of the U.S., they should not be included in NHTSA’s estimates 

of upstream emissions reductions, since those are intended to represent changes in domestic

emissions of criteria air pollutants.29 NHTSA has revised its analysis for this Final Rule to 

exclude reductions in ocean tanker emissions. 

In response to comments by Sierra Research and NERA submitted by the Alliance, NHTSA 

notes that there are currently two cap-and-trade programs governing emissions of criteria 

pollutants by large stationary sources. The Acid Rain Program seeks to limit NOx and SO2 

emissions, but applies only to electric generating facilities.30 The NOx Budget Trading Program 

is also primarily intended to reduce electric utility emissions, but does include some other large 

industrial sources such as refineries; however, as of 2003, refineries participating in the program 

accounted for less than 5% of total NOx emissions by U.S. refineries.31 In addition, some 

 

29 Emissions from ocean tankers while in port areas, as well as pipeline or truck emissions occurring during 

transportation of crude petroleum from import terminals to U.S. refineries, do occur within the U.S., and reductions 

in these emissions should be included when estimating changes in domestic emissions. However, it is not possible 

to separate these emissions from those that occur in foreign ports or on the open oceans, so NHTSA’s analysis does 

not include reductions in them. As a consequence, the analysis may underestimate reductions in upstream emissions 

occurring within the U.S. 

30 For a detailed description of the Acid Rain program . see 

http://www.epa.gov/airmarkt/progsregs/arp/basic.html#princips (last accessed October 6, 2008). 31 Estimated from EPA, NOx Budget Trading Program (SIP Call) 2003 Progress Report, Appendix A, 
I-27

refineries could be included among the sources of NOx emissions that will be controlled under 

EPA’s Clean Air Interstate Rule, which is scheduled to take effect beginning in 2009. However, 

refinery NOx emissions could only be affected in states that specifically elect to include sources 

other than electric generating facilities in their plans to comply with the rule, and EPA has 

indicated that it expects states to achieve the emissions reductions required by the Clean Air 

Interstate Rule primarily from the electric power industry.32 Thus the agency continues to 

assume that the reduction in domestic gasoline refining estimated to result from the adopted 

CAFE standard will be reflected in reduced refinery emissions of criteria pollutants. 

NHTSA also notes in response to comments by Sierra Research and NERA submitted by the 

Alliance that emissions occurring during refueling at retail stations are included in the emissions 

factors estimated using EPA’s MOBILE emission factor model, which also accounts for 

expected future reductions in these emissions. Thus NHTSA believes that reductions in 

refueling emissions were correctly estimated in its NPRM analysis, and has not revised its 

procedures for doing so. 

Finally, in response to comments by the Alliance and NERA, NHTSA acknowledges that the 

effect of higher prices for new vehicles on the retention and use of older vehicles is potentially 

significant, depending on the magnitude of expected price increases. Based on detailed 

econometric analysis of the effects of new vehicle prices and other variables on retirement rates 

for used vehicles very similar to the analysis conducted by NERA for the Alliance, NHTSA 

concludes that price increases for 2011 cars and light trucks likely to result from higher CAFE 

standards are unlikely to cause significant or lasting changes in retirement rates for older 

vehicles. NHTSA also notes that the vehicles whose retirement rates would be most affected by 

increases in prices for model year 2011 passenger cars and light trucks are those that will be 10-

15 years of age at the time when 2011 vehicles are offered for sale.33 These include cars and 

light trucks produced during model years 1996 through 2005, and NHTSA’s analysis of their 

emission rates at those ages predicted using EPA’s MOBILE6.2 motor vehicle emission factor 

model suggests that they will not be dramatically higher than emission rates for comparable new 

2011 models. Thus the effect on total motor vehicle emissions of criteria air pollutants resulting 

from any reduction in new vehicle sales and accompanying increase in use of older vehicles 

caused by increased prices for new 2011 cars and light trucks is likely to be modest. 

Externalities - Monopsony effect 

Comment: Mark A. Delucchi, 2008-0089-0025, recommends use global warming damages in 

the U.S. only. Your discussion on p. 24414 is correct: if you include Paul Leiby's estimate of the 

 http://www.epa.gov/airmarkets/cmprpt/nox03/NBP2003AppendixA.xls, and National Air Quality and 

Emissions Trends Report 2003, Table A-4, http://www.epa.gov/air/airtrends/aqtrnd03/pdfs/a4.pdf 32 The Clean Air Interstate Rule also requires reductions in SO2 emissions and establishes an emissions trading 

program to achieve them, but only electric generating facilities are included in the rule’s SO2 emissions trading 

program; see EPA, Clean Air Interstate Rule: Basic Information, http://www.epa.gov/cair/basic.html#timeline

(last accessed October 6, 2008) and http://www.epa.gov/cair/pdfs/cair_final_fact.pdf (last accessed October 6, 

2008). 33 This conclusion is based on detailed econometric analysis of the effects of new vehicle prices and other variables 

on retirement rates for used vehicles conducted by the Volpe Center. This analysis concluded that retirement rates 

for 10-15 year old vehicles are most sensitive to changes in new vehicle prices. 
I-28

monopsony cost (e.g., p. 24411) -- which in a global accounting is a transfer and not a resource 

cost -- on the grounds that your counting costs and benefits to the U. S. only, then consistency 

requires that you count global warming damages in the U. S. only. It is possible to estimate U. S. 

damages only: I have done it in the following report, available on my faculty web page: 

Summary of the Nonmonetary Externalities of Motor-Vehicle Use. Delucchi, Mark A. ITSDavis. Report #9 in the series: The Annualized Social Cost of Motor-Vehicle Use in the United 

States, Based on 1990-1991 Data. October 2004. Publication No. UCD-ITS-RR-96-3 (9) rev. 1. 

Revision of report originally published in September 1998. 

Agency response: We concur with this comment and include monopsony when counting global 

warming damages in the U.S. only. See Chapter VIII for more discussion on monopsony. 

Externalities - Supply disruption costs 

Comment: Union of Concerned Scientists, 2008-0089-0201.13, Pg. 24, 31 stated that NHTSA’s 

value is too low. ORNL assesses the benefits of reduced oil consumption for reducing supply 

disruption and market price spikes at $14.51 per barrel. This is a conservative assessment as it 

excludes all military costs and the foreign policy impact of oil import reliance. 

Agency response: We use the same data source, ORNL, but find a much smaller value. See 

Chapter VIII for more discussion on supply disruption costs. 

Externalities - Military costs 

Comment: Air Resources Board, 2008-0089-0173.14, appears to recommend that reductions in 

military outlays equivalent to $0.03-0.15 per gallon of fuel saved be included as benefit from 

fuel savings attributable to higher CAFE standards. Comment consists of recent article authored 

by Mark Delucchi and James Murphy, published in journal Energy Policy (citation: Energy 

Policy 36 (2008) 2253– 2264). Article attempts to estimate total U.S. military outlays that are 

directly attributable to securing flow of oil imports to the U.S. from the Persian Gulf region, and 

the fraction of these that are attributable to meeting U.S. demand for motor vehicle fuel. Authors 

conclude that these amount to $15 billion annually, or $0.03-0.15 per gallon of fuel consumed by 

U.S. motor vehicles. 

Comment: Mark A. Delucchi, 2008-0089-0025 stated that military costs should not be zero (p. 

24411). I have just published a peer-reviewed article in Energy Policy that can serve as one basis 

for making a non-zero estimate of the cost. 

Comment: Public Citizen, 2008-0089-0187, Pg. 4 objects to the zero valuation of military 

security costs associated with oil consumption. NHTSA states “that while costs for U.S. 

military security may vary over time in response to long-term changes in the actual level of oil 

imports into the U.S., these costs are unlikely to decline in response to any reduction in U.S. oil 

imports resulting from raising future CAFE standards for passenger cars and light trucks.”23

NHTSA justifies this claim by stating that there are other national security and foreign policy 

objectives served by military actions in the Middle East. NHTSA used similar logic to justify 

assigning zero value to reducing CO2 emissions in the light truck rule. The Ninth Circuit Court of 
I-29

Appeals rejected this justification in Centerfor Biological Diversity v. NHTSA, finding that 

uncertainty about how to assign a value was not a justification for setting the value at zero.24

Comment: Attorney General of the States, 2008-0089-0199.1, Pg. 11. It is true that an increase 

in CAFE standards will not, in and of itself, eliminate these energy security costs. The same could 

be said as to global warming costs. It is also the case, however, that the impact of higher CAFE 

standards on energy security is not zero. Energy security costs are a necessary piece of the puzzle 

in assessing all of the costs and benefits of a CAFE standard. In fact, a recent peer-reviewed 

economic analysis did assign values to the military savings attributable to decreased oil 

imports. See Mark A. DeLucchi & James J. Murphy, US Miliary Expenditures to Protect the 

Use of Persian Gulf Oil Imports, 36 Energy Policy 2253 (2008) (assigning a cost of between 

$0.03 and $0.15 per gallon, and referencing earlier work on this issue). 

Comment: Consumer Federation of America, 2008-0089-0183, Pg, 47-48, 61-62 stated that a 

zero value is simply wrong. NHTSA should use 30 cents/gallon. The fact that the statute had 

energy independence and security in its title should have alerted NHTSA to the likelihood that 

Congress considers the military and strategic value of oil important. 

Comment: Natural Resources Defense Council, 2008-0089 225.1, Pg. 2 and following, the 

economic value of military security to protect oil supplies should be non-zero and positive. 

When NHTSA used zero it ignored the U.S. military security-related benefits of reduced oil 

consumption, such as enhanced flexibility to respond to supply threats and move the country in 

the direction of oil being a nonstrategic resource. The report also suggests that NHTSA should 

include the benefits from lower oil use that would result from the subsequent marginal decline in 

the need for military resources protecting a strategic commodity (oil).

Comment: Sierra Club, 2008-0089-0226.1, Pg. 2, 7 stated that NHTSA must recognize the 

national security costs of oil. The military-related expenses are tremendous. See the 2005 report 

of the International Center for Technology Assessment. NHTSA’s decision to ignore military 

costs is arbitrary and capricious. 

Agency response: The Deluchi estimates are clearly identified as savings that would result if 

demand for petroleum-based fuels by U.S. motor vehicles were completely eliminated. The 

article includes little or no discussion of the extent to which military outlays would vary in 

response to marginal reductions in U.S. fuel consumption of the scale likely to result from higher 

AFE standards or other fuel conservation measures, indicating only that any reduction in U.S. 

military outlays would result from policy decisions to be made by Congress. The agency 

believes at this time that military outlays would not vary depending upon the fuel economy 

standards and uses $0.00 in the main analysis, with a sensitivity analysis examining the impact of 

$0.05 per gallon for military outlays. 

While NHTSA believes that military expenditures appropriated by the U.S. Congress are not 

directly related to changes in domestic petroleum consumption, the agency recognizes that 

reductions in petroleum consumption may provide other benefits that are more difficult to 

quantify, by reducing some constraints on U.S. diplomatic and military action. U.S. foreign 

policy decisions consider a wide range of U.S. interests, including the maintenance of secure 

petroleum supplies. Reduced consumption of petroleum might allow the U.S. to more 
I-30

vigorously pursue other foreign policy interests, by reducing concerns about the implications of 

pursuing these other interests for the availability and continuity of petroleum imports. 

The agency recognizes, however, that both the effect of reducing U.S. petroleum imports on the 

flexibility of its foreign policy initiatives and the economic value of such additional flexibility 

are highly uncertain. Reducing petroleum consumption is likely to have unpredictable effects on 

both military actions and diplomatic initiatives, and even if the U.S. government planned and 

signaled its foreign policy intentions under various levels of petroleum consumption in advance, 

NHTSA is unaware of any accepted methods for establishing the economic value of increased 

freedom in designing military or diplomatic actions. And because the nation’s foreign policy 

intentions are not communicated in advance, the agency would need to develop a procedure for 

anticipating how military and diplomatic actions would respond to future changes in petroleum 

consumption. Nevertheless, in its future rulemaking activities, NHTSA will investigate whether 

practical methods for predicting and valuing in economic terms any increased flexibility in U.S. 

foreign policy that is likely to result from reduced petroleum imports exist or can be developed. 

Financial Impacts of Raising CAFE Standards and ability of manufacturers to finance fuel 

economy improvements 

In the PRIA, the agency admitted that the agency does not have the capability to predict the 

capital investment needs of the automobile industry to install fuel economy technologies, nor the 

capability to determine the level of capital investments available to specific manufacturers in the 

future. We asked several questions regarding the manufacturers’ financial capabilities in 

meeting the proposal and the alternatives examined. Specifically we asked: 

For each of the model years 2011-2015, please provide the best possible estimate of the 

incremental capital investments required for your company to comply with the 

alternatives discussed in this analysis 

Please discuss whether you anticipate that your firm will to be able to raise the 

incremental capital investments necessary to meet the levels predicted in answer to the 

questions above. If the answer is no, what level appears likely to be achievable. What 

alternatives are available to raise the incremental capital investments necessary? 

Essentially, the agency received no comments about the companies’ abilities to raise capital or 

finance the capital investments necessary to meet alternative levels of the standard. Instead, it 

received comments that the proposal wasn’t feasible or that the standard are inconsistent with 

those in the European Union or Japan, or that they are currently losing money. 

Comment: General Motors, 2008-0089-0162, Pg. 9, stated that NHTSA assumes that 

manufacturers either have the capital or the ability to borrow funds to meet the proposed 

standards. That assumption ignores the reality facing GM. None of the supporting studies, nor 

NHTSA’s modeling process, quantitatively address the real world constraints that exist in terms 

of technical and financial resources. The roll-out rate may substantially exceed the capability of 

GM to actually implement. If the future standards cannot be achieved by technology, then 

compliance can only be achieved by product eliminations, plant closings and job losses. They 
I-31

provide in Attachment 6 a section from GM’s 10-K statement, that is a general statement 

indicating that sales levels in the industry are projected to decline in 2008. They have relatively 

high fixed costs and high unit contribution margins, such that small changes in the number of 

vehicles sold can materially adversely affect their operation and financial conditions. 

Agency response: GM does not specifically address their potential to finance technology 

improvements and NHTSA does not have the wherewithal to know how to determine what level 

of capital financing will be available to GM in the future. 

Comment: The Alliance, 2008-0089-0179.1, Pg. 8, 20, 21, state that NHTSA should account for 

the industry’s capital constraints. NHTSA recognized capital constraints in the 2008-2011 light 

truck rulemaking. Why has NHTSA changed course on that issue? 

Rod Lache of Deutsche Bank stated “we do not expect automakers to be able to pass all of these 

costs along to consumers”. Quote “an agency is arbitrary and capricious if the agency ... 

entirely failed to consider an important aspect of the problem, offered an explanation for its 

decision that runs counter to the evidence before the agency ... entirely failed to consider an 

important aspect of the problem, offered an explanation for its decision that runs counter to the 

evidence before the agency, or is so implausible that it could not be ascribed to a difference in 

view of the product of agency expertise.” 

Agency response: The agency did not take into account capital constraints in the 2008-2011 light 

truck rulemaking. The agency recognizes that vehicle manufacturers must have sufficient lead 

time to incorporate changes and new features into their vehicles. In making its lead time 

determinations, the agency considered the fact that vehicle manufacturers follow design cycles 

when introducing or significantly modifying a product. We have applied the same rationale here. 

If the market (or regulation) drives manufacturers to make changes, they must do so to sell their 

vehicles. The Alliance provides no estimate of their own on how to account for capital 

constraints. 

Comment: Mitsubishi, 2008-0089-0197.1, Pg. 1, 5-6 stated that the NPRM requires extremely 

expensive and complex adjustments to product plans to meet very strict standards for cars and 

trucks in MY 2011. MMC would likely suffer severe financial difficulties. The NPRM has not 

considered capital constraints. MMC requests NHTSA consider capital constraints in the final 

rule. The product development cycle is already underway for MY 2011. Retail prices for 

MMC’s compact vehicles, which comprise the majority of our overall sales in the US market, are 

expected to double as a result of the standard. In FY 2007, MMC had an operating income 

deficit of $178M. In 2008, MMC forecasts net sales in North America will drop by 25.5% and 

that ordinary income in the US will further decline by an additional $92M. We are still in the 

process of recovery after our alliance with DAG dissolved in 2004. MMC has limited access to 

additional capital for investments in new technologies. 

Agency response: Mitsubishi provides no estimate of their own on how to account for capital 

constraints. 

See Chapter VII for our general discussion of financial impacts. 
I-32

Inequality of impacts on smaller manufacturers 

Comment: BMW, 2008-0089-0146.2, Pg. 2 and 0146.3 Pg. 1 stated that the standard is costly to 

small manufacturers. Niche manufacturers (such as BMW whose vehicles offer extraordinary 

safety, comfort, and convenience features, and so have a high mass per footprint density) have to 

fulfill more ambitious requirements. BMW requests an option of not using the footprint, but a 

standard increase per year. 

Comment: Fuji (Subaru), 2008-0089-0157, Pg. 2-4, 6-8 stated that the standards aren’t fair to 

small manufacturers. The passenger car standard requires virtually nothing of the high volume 

manufacturers but requires large fuel economy increases among small manufacturers. Small 

manufacturers don’t have the same capability to offset targets for smaller footprint vehicles with 

larger vehicles. Subaru proposes small manufacturers be provided an option to pay civil penalties 

based on their target fuel economy, instead of meeting the target. 

Comment: Ferrari, 2008-0089-0168, Pg. 3-5 stated that NHTSA’s assertion that its proposal will 

not have a significant economic impact on small businesses is wrong. NHTSA does not always 

grant petitions from small manufacturers for alternative standards. Ferrari’s fines will increase 

significantly. Also the standards aren’t fair to niche manufacturers, specializing in higher 

performance sport vehicles. The same set of gas guzzler vehicles can be penalized or not under 

the standard, depending on whether they are made by a small manufacturer or a large one (who 

can offset these with other vehicles exceeding the standard). This is discrimination. 

Comment: Porsche, 2008-0089-0174.1, Pg. 12-13 stated that the standards result in inequities 

for smaller limited line manufacturers. The footprint-only attribute assigns to smaller limited 

line manufacturers targets that are beyond the reach of their vehicle fleets. The only choices for 

these manufacturers are to leave the market, restrict product or pay exorbitant civil penalties. The 

car standard requires virtually no improvement by the larger full line manufacturers during the 

early years. The standards were set using only the 7 largest manufacturers. From MY 2007 to 

MY 2011 Porsche is required to increase its passenger car fleet an average of nearly 10% per 

year, over twice the predicted annual industry average. 

Comment: Volkswagen, 2008-0089-0181, Pg. 3 commented that an alternative attribute in 

addition to footprint should be used to equalize cost burden on all manufacturers. Volkswagen 

argued that the footprint attribute alone when applied to the passenger car fleet creates challenges for 

some automakers with limited product range and/or limited market segments. For some automakers it 

appears that their products or fleet mix demonstrate unfavorable correlation to the footprint curves as 

generated by NHTSA and result in additional burden for those automakers. NHTSA should consider 

alternative compliance approaches to alleviate the stringency applied to limited product line producers. An 

example of this is the uniform increase concept. 

Comment: Mercedes, 2008-0089-0190, Pg. 3-4 stated that the requirements on manufacturers 

excluded when setting the standard are disproportionate to those imposed on larger full line 

manufacturers. The standard requires virtually no improvement by the 7 largest manufacturers. 
I-33

The targets require colossal investment by the excluded manufacturers to modify their fleets. 

Even then, these companies many still be subject to severe civil penalties. Mercedes would need 

to improve its fleet in MY 2011 by 28% over MY 2007. 

Comment: Mitsubishi, 2008-008900197.1, Pg. 2, 5 stated that the standard puts manufacturers 

with smaller average footprints at a competitive disadvantage. The targets were set using 

manufacturers that have larger average footprints. These manufacturers face disproportionately 

burdensome requirement in the early years. It is more difficult for these manufacturers to 

negotiate supplier contracts to purchase new components. Large suppliers can negotiate more 

cost effective supplier contracts and in some instances co-develop or internally develop new 

components before the market creates an economy of scale. Small and midsize companies are 

also at a disadvantage in terms of when new components are received from suppliers. The 

supply of new components is limited due to supplier capacity and output. The sizable demand 

for new components from larger manufactures is fulfilled first by suppliers. 

Comment: Ford, 2008-0089-0202.1, Pg. 3 stated the agency should revise the proposal to ensure 

that all manufacturers have a comparable burden, or at least ensure that whatever differences 

may exist will not hinder any manufacturer's ability to compete in the marketplace. Given the 

manner which NHTSA has chosen to draw the car and truck curves, some manufacturers have 

tasks to improve their fuel economy every model year, while others do not. In particular, the 

proposal gives domestic full-line manufacturers significant tasks relative to their competitors. 

This is not inevitable; it is a reflection of the particular shapes that NHTSA has chosen for the 

curves. 

Comment: Association of International Automobile Manufacturers (AIAM), 2008-0089-205.1, 

Pg. 3 stated that the abrupt increase in fuel economy required in the early years is particularly 

severe for smaller companies. Smaller companies face required increases in fuel economy of 17-

88% from 2007 to 2011. Smaller companies tend to have fewer resources to implement major 

changes on an expedited basis. These companies tend to produce vehicles that fall in the steep 

central portion of the car curve. They have a limited range of product offerings, so have fewer 

options for achieving required fuel economy increases. Redesign cycles may not coincide with 

the 2011 start date. 

Agency response: For the final rule the agency is including all manufacturers (not just the largest 

seven producers) in determining the CAFE requirements. We will have one standard that is 

applicable to all medium to large size passenger car manufacturers (very small companies – less 

than 10,000 sales worldwide - can petition for alternative standards). While the current form of 

the standard may cause difficulty for some manufacturers, the standard is designed more to deal 

with the overall industry than with particular, niche vehicle makers. 

For purposes of this rulemaking, the agency is not interested in providing an alternative flat 

standard that includes a set year-by-year increase in the CAFE levels. The current CAFE 

structure is designed to be attribute-based per legislative mandate. We also have the 

simultaneous objectives of improving industry-wide fuel savings, GHG emissions, and 

preserving safety. NHTSA has an attribute-based approach which provides no incentive to build 

smaller cars just to meet a fleet-wide average, because smaller vehicles will be subject to more 
I-34

stringent fuel economy standards. The approach is to determine what level of fuel economy can 

be achieved primarily by new technology. 

Leadtime issues 

Comments: With the exception of Borg Warner, 2008-0089-0142 Page 1, that stated that 

leadtime and levels are very aggressive but possible, the remainder of the commenters on 

leadtime stated that the proposed requirements in the early years were too aggressive or beyond 

the maximum feasible level for their company. Included in this group were: 

Fuji (Subaru), 2008-0089-0157, Pg. 2, 5, 7-8 

General Motors, 2008-0089-0162, Pg. 2, 

The Alliance, 2008-0089-0179.1, Pg. 23 

Mercedes Benz, 2008-0089-0190.1, Pg. 3 

Mitsubishi, 2008-0089-0197.1, Pg. 1-2 

AIAM, 2008-0089-0205.1,Pg. 3-5 

Toyota, 2008-0089-212, Pg. 2 wants a 3.3% improvement per year, not 4.5%. 

Mercatus Center, 2008-0089-216.1 

National Automobile Dealers Association (NADA), 2008-0089-223.1, Pg. 2 

Washington Legal Foundation, 2008-0089 228, Pg. 3,5

Agency response: The costs for technologies and effectiveness and the leadtime issues were all 

addressed in consultation with our contractor. The model year 2011 requirements are not as 

aggressive in the final rule as proposed in the NPRM. 

Learning curve

In the PRIA for some of the technologies, we included a learning factor. The “learning curve” 

describes the reduction in unit production costs as a function of accumulated production volume 

and small redesigns that reduce costs. 

Comment: Borg Warner, 2008-0089-0142, Pg. 1, stated that the learning curve assumptions 

aren’t correct. Learning curve do not apply to many of their products. The technologies are well 

developed and in high volumes in other parts of the world, so our price/cost estimates already 

represent higher volumes. In fact, increasing global volumes could lead to higher prices if 

demand for certain raw materials exceeds supply. 

Comment: The Alliance, 2008-0089-0179.1, Pg. 6-7 believes the learning curve assumptions are 

not supported. Martec’s updated 2008 analysis explains that its corrected and original study both 

fully accounted for learning effects. 

Comment: AIAM, 2008-0089-0205.1-Pg. 5 stated that some of NHTSA’s cost estimates may 

reflect double counting of the cost learning curve effect. The learning curve estimates in the 

2002 NAS study and the EEA and Martec reports already reflect to some degree learning curve 

considerations. 

Comment: Public Citizen, 2008-0089-0187,Pg. 7 The agency has included “learning curves” 

to attempt to model the reductions in cost of compliance due to economy of scale effects. 

Public Citizen observes that economy of scale effects should be accounted for; however, we 
I-35

wish to point out that again these effects are often estimated incorrectly. In a survey of emission 

reduction regulations, the author finds: “In all cases except one, the early estimates [of cost of 

compliance] were at least double the later ones, and often much greater.” Inaction based on 

inflated estimates of cost of compliance cannot be tolerated in the face of an energy crisis and 

environmental catastrophe. 

Comment: Honda, 2008-0089-0191, Pg 6 stated that learning curve costs should be raised in 

early years and decreased in later years. The cost estimates provided to NHTSA through NAS, 

Energy and Environmental Analysis Inc (EEA), and the Martec Group all assume high volume 

production and thorough product development. Thus, these costs already include substantial 

amounts of learning. Proper application of learning factors would increase costs for early, low 

volume production of these technologies, to reflect that they have not yet achieved the learning 

and cost reductions assumed by NAS, EEA, and Martec. Once sales exceed about 300,000 per 

year per manufacturer, the learning factors could begin to decrease the cost estimates from 

NAS, EEA, and NHTSA. But the learning factors must be applied consistently to both raise 

costs in the early years and decrease them in later years, not just reduce costs. 

Agency response: For the final rule, the learning curve assumptions were all reviewed in 

consultation with our contractor (Ricardo). The learning curve assumptions have been changed 

and are addressed in Chapter V. 

Marginal cost = Marginal benefit (MC=MB) versus total cost = total benefit (TC=TB) 

approach in setting final rule 

In the NPRM, the agency provided alternatives which included both MC=MB and TC=TB. 

However, the proposal was based on MC=MB. 

Comment: The Alliance 2008-0089-0179.1, Att3, P-7 commended NHTSA for using MC=MB, 

rather than TC=TB stating that TC=TB costs $12.5 billion more, but only yields $7 billion in 

benefits. 

Comment: Attorney General of the States, 2008-0089-0199.1, Pg. 9 stated that the standard 

should maximize energy conservation instead of net economic benefits. Congress has already 

made the judgment that energy conservation is the highest priority among the factors for NHTSA 

to balance. Center for Biological Diversity, 508 F.3d at 527-28 (discussing Center for Auto 

Safety v. NHTSA, 793 F.2d 1322 (D.C. Cir. 1986)). To achieve this goal, NHTSA should set the 

standards at a level where the total costs equal total benefits.2 From a societal point of view, 

there cannot be substantial adverse consequences if the costs do not outweigh the benefits. We 

urge NHTSA to set the standard at a level where total costs equal total benefits. 

Comment: Union of Concerned Scientists, 2008-0089-201.1 and 2008-0089-0201.13 Pg. 3-4, 

25-30 recommends against the use of a marginal cost-marginal benefit analysis, and believes 

NHTSA should instead use a total cost-total benefit analysis to determine maximum feasible fuel 

economy standards. The use of a TC=TB analysis would maximize the need to conserve energy 

while ensuring consumers are as “well off” as they are today. An analysis of the recommended 

form would reduce the impact of any inaccurate monetizing of the benefits of reduced fuel 

consumption, and would increase the economically practicable fleet average between 2.8 and 5.7 
I-36

miles per gallon. MC=MB is very sensitive to different valuations of benefits, making it more 

error prone. An MC=MB analysis that excludes or undervalues even some of the benefits is 

fundamentally flawed.

Agency response: For purposes of this rulemaking, NHTSA has concluded that the maximum 

feasible standards are represented by the level at which net benefits are maximized. NHTSA 

recognizes that the overarching purpose of EPCA is energy conservation, and considers the 

need to conserve energy as part of its balancing of the four statutory factors. However, NHTSA 

disagrees with the Attorneys General that there would be no substantial adverse consequences 

for purposes of this rulemaking from setting the standards at the level represented by TC = TB. 

Based on NHTSA’s analysis and given the unique circumstances surrounding this rulemaking, 

including the economic crisis and the concurrent burden on manufacturers, NHTSA has 

concluded that TC = TB would be beyond the maximum feasible level at which the MY 2011 

standards could be set. However, the agency will reconsider in future rulemakings whether to 

set standards at the level of TC = TB. 

Market Failure 

Executive Order 12866 requires that all new federal regulations specify the market failure that 

will be addressed by the rulemaking. The agency state that the Energy Policy and Conservation 

Act (EPCA) directs the Department to balance the technological and economic challenges related 

to fuel economy with the nation's need to conserve energy. Congress decided that the market 

would not balance these challenges in the best interest of the nation, and that the Department 

should regulate fuel economy. 

Comment: The Consumer Federation of America, 2008-0089-0183 -pp. 37-40 stated that 

NHTSA’s view of market failure is very narrow, generally admitting only a problem of 

externalities that are not internalized. We suspect there are other sources of market failure, like 

information problems, agency problems, perverse incentives, etc. Moreover the problem is not 

limited to the demand side of the market. There are imperfections in the supply side. NHTSA 

discovers that there are fuel savings technologies that pay for themselves, but have not been 

moved into the vehicle fleet. Since this cannot be explained by externalities market failure, there 

must be other market failures operating. 

NHTSA’s pro industry view of the world blames the market failure on the consumer, when in 

fact the problem is the automakers. 

Agency response: NHTSA didn’t present a view of the world, just a statement that Congress 

requires it to set fuel economy standards. 

Comment: The Mercatus Center, 2008-0089-216.1 questions whether there is failure in the 

“market” for fuel economy that needs to be regulated. To support this assertion they present 

evidence of recent market forces (e.g. rising fuel costs) driving fuel economy standards above 

current CAFE standards. They also suggest that drivers are becoming more willing to demand 

and pay for fuel economy due to heightened awareness of environmental externalities (CO2 

emissions). 
I-37

Agency response: We see no need to debate the needs for regulation, since Congress requires us 

to set fuel economy standards. 

On-road fuel economy adjustment – 20 percent 

In the NPRM, the agency reduced the EPA test data by 20 percent to account for on-road fuel 

economy in determining the benefits of the proposal. 

Comment: There were two comments on this issue (Sierra Research 2008-0089-0046, Page 76, 

and Air Resource Board 2008-0089-0173.11, p10). Sierra Research employed a different 

adjustment factor, adjusting the EPA dynamometer test results downward by 10% for the city 

cycle and 22% for the highway cycle to better reflect real world driving (18% reduction used for 

a hybrid). The Air Resource Board presented a study “Analysis of In-Use Fuel Economy 

Shortfall Based on Voluntarily Reported MPG Estimates”, by Greene et al., Nov. 2005. 

Agency response: The agency will rely on the published EPA final rule guidelines and continue 

using 20 percent. The report by Greene et al. was completed prior to EPA’s changes to its 

labeling regulations. Neither commenter suggested that NHTSA use these numbers instead of 

EPA’s for analyzing fuel savings. 

Payback Period 

In the PRIA, we assume in the sales impact analysis section that consumers will only value fuel 

savings over a 5 year time horizon. 

Comment: Mark A. Delucchi, 2008-0089-0025, states that you should not do a "payback" 

analysis with a zero discount rate and a 5-year payback period, because there is no economic 

theory or consumer behavioral evidence to support this.

Agency response: Commenter provides no alternative, other than using a full lifetime payback 

period. NHTSA disagrees that consumers think in that long term.

Comment: Sierra Research, 2008-0089-0046, Pg. 77, considers 5 years and 20 years, but say that 

average consumers are more likely to consider the time they own the car to be 5 years. 

Comment: Consumer Federation of America, 2008-0089-0183, Pg. 53-59 state that a simple 

payback is one of the weaker economic concepts for evaluating investment. It is not clear that 

one must assume a payback for any component of a vehicle purchase, but if one does, the logical 

connection is between the period of ownership and the payback, not the loan period. 

Most alternative investment opportunities available to consumers do not yield a 5 year payback 

period. Hybrids, many of which have payback periods of ten year or more, are flying off auto 

dealer lots. There is a logical inconsistency in saying that consumer decisions to buy vehicles 

reflects undiscounted treatment of fuel savings, but auto industry sales reflect discounted fuel 

savings. 
I-38

Agency response: We don’t have an inconsistency in our analysis, the consumer decision is in 

the same section where we estimate the impact on auto industry sales. When we do our MC=MB 

analysis it is from a societal perspective and full lifetime benefits are calculated. 

Comment: Union of Concerned Scientists (UCS), 2008-0089-201.1 states that NHTSA should 

modify its resale value estimate. UCS asserts that the agency’s cost-benefit analysis ignores the 

fact that fuel efficient vehicles have higher resale values than inefficient vehicles. UCS asserts 

that NHTSA’s assumed 5-year resale evaluation timeline is unfounded. Also, citing a CBO 

study, commenter asserts that the assumption of a fixed resale value rate ignores the fact that fuel 

efficient vehicles are valued more highly on the used vehicle market 

Agency response: Assuming that more fuel efficient vehicles have a higher resale value would 

be inconsistent with our assumption that consumers only think 5 years into the future for a 

payback period. Essentially we would be assuming that if a vehicle is sold in 5 years, consumers 

think about the fuel that would be saved in years 6 to 10, and how the next purchasers would 

value that and how that would affect the resale value. But if consumers keep their vehicle, and 

don’t sell it, they don’t think about the fuel savings in years 6 to 10. 

Comment: National Automobile Dealers Association (NADA), 2008-0089-223.1, Pg. 7 

The proposal reasonably assumes that buyers value any fuel savings associated with the purchase 

of a new motor vehicle over a five-year period, rather than over a vehicle’s full useful life. Even 

at high fuel prices, consumers who view fuel economy as an important purchase criteria are hard 

pressed to make the case for buying a more fuel efficient new vehicle if the up-front capital costs 

associated with doing so cannot be recouped in short order. Thus, NHTSA should assume that 

most prospective purchasers will not invest in fuel economy improvements that do not exhibit a 

payback of five years or sooner. Of course, for purposes of calculating payback, real-world 

purchaser finance costs, opportunity costs, and additional maintenance costs all should be 

accounted for. 

Agency response: NADA essentially agrees with out methodology.

Price of Gasoline

Projected future fuel prices are a critical input into the regulatory impact analysis of alternative 

CAFE standards, because they determine the value of fuel savings both to new vehicle buyers 

and to society. In the PRIA we relied on the most recent fuel price projections from the U.S. 

Energy Information Administration’s (EIA) Annual Energy Outlook (AEO) in analyzing the 

proposed standards. Specifically, the agency used the AEO 2008 Early Release forecasts of the 

Reference Case inflation-adjusted (constant-dollar) retail gasoline and diesel fuel prices, which 

NHTSA stated represent the most up-to-date estimate of the most likely course of future prices 

for petroleum products.34 In Jun 2008, EIA released the full AEO 2008 with an updated 

 

34 U.S. Department of Energy, Energy Information Administration, Annual Energy Outlook 2008, Early Release, 

Reference Case Table 12. Available at http://www.eia.doe.gov/oiaf/aeo/pdf/aeotab_12.pdf (last accessed August 29, 

2008). EIA released the full AEO 2008 in June 2008, which NHTSA stated in the NPRM it would use in the final 

rule. EIA explained upon releasing the full AEO 2008 that it had been updated from the Early Release to reflect 
I-39

Reference Case, a Low Case, and a High Case. Federal government agencies generally use 

EIA’s projections in their assessments of future energy-related policies. We received a large 

number of comments indicating that we should rely on the High Case for the final rule. There 

were a few comments favoring the reference case or other prices of gasoline. A summary of 

their comments are: 

Comment: Sierra Research, 2008-0089-0046, Pg. 77, 

Do sensitivity analysis on fuel price using $2.50, $3.00, and $3.50 

Comment: Consumer Federation of America, 2008-0089-0183 -pp. 45-46, 49-51 

NHTSA’s price is not consistent with the real world. EIA’s high price seems much more 

appropriate. EIA’s projections have been consistently low. They have been off by 35% but their 

projection for 2015 does not reflect this adjustment. 

Comment: Environment America, National Wildlife Federation, National Resources Defense 

Council, Pew Environment Group, Sierra Club, Union of Concerned Scientists, 2008-089-0119 

NHTSA should use a higher price of gas 

Comment: Members of Congress (21), 2008-0089-0145.1 

NHTSA used EIA’s forecast of fuel prices that range from $2.42 per gallon in 2016 to $2.51 in 

2030. When compared to the prices at the pumps, these numbers are nothing short of absurd. 

For modeling purposes, NHTSA uses EIA’s higher gasoline price scenario, which ranges from 

$3.14 in 2016 to $3.74 in 2030 demonstrates that technology is available to cost-effectively 

achieve 35 mpg by 2015. On June 11, 2008, Guy Caruso testified before the House Select 

Committee on Energy Independence and Global Warming that NHTSA should use EIA’s higher 

gasoline price scenario in setting fuel economy standards. They urge us to promulgate final fuel 

economy standards based on the EIA’s high gasoline price scenario (which they understand will 

soon be revised) to comply with the EISA directive that maximum feasible standards be 

required. 

Comment: Air Resources Board, 2008-0089-0173, Pg 2. 

Want NHTSA to use a higher price of fuel, at least the EIA high price case scenario. 

NHTSA dramatically underestimated the future price of fuel. They provide several sources 

indicating higher fuel prices. EIA’s recent propensity to hurriedly revise its estimates upward, 

and EIA’s own recent forecast puts fuel at $3.92/gallon in 2009, resulting in a significant 

divergence from their short term and long term forecast. 

Comment: Air Resource Board, 2008-0089-0173.6, Pg. 8 

 EIA’s expectations of the effect of EISA, which was enacted after the Early Release was made public. The full 

AEO 2008 is available at http://www.eia.doe.gov/oiaf/aeo/pdf/0383(2008).pdf (last accessed August 29, 2008). 
I-40

Absent supply disruptions, it will be difficult to sustain oil prices above $100/barrel (2008 

dollars) over the next 10 years. This is based on an analysis by the Federal Reserve Bank of 

Dallas that examined the impacts of expected future demand, geopolitical factors, exchange rate 

movements, the ability of suppliers to meet demand, and non-conventional oil sources. 

Comment: The City of Key West, 2008-0089-0182 

Urges NHTSA to use $3.40 per gallon in setting standards. 

Comment: Public Citizen, 2008-0089-0187 

NHTSA’s sensitivity analysis shows that the level of fuel economy standards is highly 

sensitive to the price of gasoline. The agency’s estimate for the high price scenario would set 

the car standard at 37.4 mpg in 2011, almost 20 percent higher than the agency’s “optimized” 

scenario. 

Comment: Attorney General of the States, 2008-0089-0199.1, Pg. 11 

NHTSA acknowledges that a significant factor in the agency’s analysis of maximum fuel economy 

is the price of gasoline. 73 Fed. Reg. at 24,476-1; see also PRIA at IX-1 2 (table IX- 5a). As 

such, it is important that future gasoline price estimates be the best available estimates. NHTSA 

used gasoline prices of between $2.25 and $2.51 per gallon, depending on the future year. 

PRIA at VIII-20 (table VIII-3). This is startling, given that in June 2008 the national average 

price for gasoline reached $4.13 per gallon. See Energy Information Administration, Weekly 

Retail Gasoline and Diesel Prices (downloaded June 25, 2008 and enclosed). Unless NHTSA 

can provide publicly-available, mainstream documentation supporting an almost fifty percent 

drop from current prices, it must substantially re-calibrate those estimates.

Comment: Union of Concerned Scientists, 2008-0089-0201.13, Pg. 24-25 

NHTSA’s value for price of gasoline is too low. A more plausible, yet still conservative, 

estimate would be to average the past few year’s prices. The EIA estimates are too low given 

current oil prices, the increased global demand for energy from countries such as China and 

India, and the increased use of market mechanisms (such as emissions trading) to limit carbon 

emissions. 

Comment: Northeast States for Coordinated Air Use Management (NESCAUM), 2008-0089-

204.1, Pg. 2, Currently, the average price of a gallon of gasoline exceeds $4.00 and the principal 

reason given is high global demand in a supply constricted market. There is little expectation that 

the gap between supply and demand will be narrowed in the foreseeable future. Therefore, 

assuming this reasoning is correct, the price of gasoline should remain high; certainly well above 

the mid-$2.00 range. We urge NHTSA to reevaluate the effect of a wider range of gasoline 

prices to the $4.00 per gallon level and above. We would expect the results to show that there are 

more fuel savings technologies capable of cost-effectively achieving greater overall average fuel 

economy, even according to NHTSA’s conservative “net societal benefit” cost-analysis 

approach. 

Comment: American Council for an Energy-Efficient Economy (ACEEE), 2008-0089-211.1 
I-41

Work with EIA to produce an up-to-date fuel price projection for purposes of the final rule or, 

failing that, use the High Price projection from AEO 2008. EIA Administrator’s comments 

before the House Select Committee on Energy Independence and Global Warming 

“EIA's High Price forecast [does not] necessarily capture fully current understanding of how 

high fuel prices are likely to be in the coming decades.”

Comment: State of Wisconsin Department of Natural Resources, 2008-0089-219.1 

NHTSA should use the high price fuel scenario from DOE. 

Comment: Center for Biological Diversity, 2008-0089-0222.1, Pg. 9-10 

NHTSA’s price is too low and impossible to justify. NHTSA needs to run the model with 

today’s average gas price of $4.09/gallon. There is no indication that oil prices will subside in 

the long term. NHTSA needs to use reality-based inputs. Today’s gas price must be the starting 

point for the analysis. 

Comment: National Automobile Dealers Association, 2008-0089-223.1, Pg. 7 

Fuel Prices Projected future fuel prices are critical to determining the value of fuel savings and 

the cost beneficial fuel economy standards for passenger cars and light trucks. To this end, 

NHTSA should continue to rely on the most recent reference case fuel price projections of the 

U.S. Energy Information Administration’s (EIA). As demonstrated by the many years where 

EIA’s projections fell above or below reality, forecasting future fuel prices is by no means an 

exact science. Despite the inherent volatility or uncertainty of fuel prices, EIA and NHTSA 

would be remiss if they were to arbitrarily abandon the best models and data available or to use 

“high” or “low” price case projections that are inherently not probabilistic. For example, the use 

of a high price case to justify unduly costly CAFE standards could lead to decreased new motor 

vehicle sales and a commensurate lower than projected rate of fuel energy savings and 

greenhouse gas reduction benefits. 

Comment: Natural Resources Defense Council, 2008-0089 225.1, Pg. 2 – pp 2 following 

NHTSA should use the higher fuel price estimate. NHTSA relies on the Energy Information 

Administration’s Reference Case forecast for fuel prices. However, both the Reference and High 

Case forecasts have consistently underestimated fuel prices and NHTSA must choose a 

reasonable forecast consistent with likely price trajectories.

Comment: Sierra Club, 2008-0089-0226.1, Pg. 2, 4-5 

NHTSA’s price is too low. At a minimum NHTSA should use the high EIA forecast. NHTSA 

should examine other fuel price estimates, such as the oil futures market price predictions. 

NHTSA’s prices are not consistent with today’s gas prices, futures market projections or the 

assessment of the EIA Administrator that higher prices are more appropriate to setting the 

standards. EIA has vastly underestimated the price in recent years. Secretary Peters commented 
I-42

on the oil price problem. The oil futures market price predictions run consistently above $130 per 

barrel. 

Comment: U.S. Senate, 2008-0089-0454, Pg. 1, 4 

NHTSA’s gas prices are far below what consumers are paying today, and we do not believe it’s 

reasonable to assume that the price of gas will drop precipitously, as NHTSA has done. Guy 

Caruso told Congress that NHTSA should use the EIA high price. NHTSA’s treatment of gas 

prices would put the rule at substantial litigation risk. 

Agency response: 

NHTSA has carefully considered available evidence, recent trends in petroleum and fuel prices, 

and the comments it received on the NPRM analysis. After doing so, NHTSA has decided to use 

EIA’s High Price Case forecast in its final rule analysis and to determine the MY 2011 CAFE 

standards. As NHTSA recognized in the NPRM, commenters are correct that projected future 

fuel prices have the largest effect of all the economic assumptions that NHTSA employs in 

determining benefits both to new vehicle buyers and to society, and thus on CAFE stringency. 

This is why it is vital that NHTSA base its fuel price assumptions on what it believes to be the 

most accurate forecast available that covers the expected lifetimes of MY 2011 passenger cars 

and light trucks, which can extend up to 25-35 years from the date they are produced. The long 

time horizon of NHTSA’s analysis also makes it critical that the agency not rely excessively on 

current price levels as an indicator of the prices that are likely to prevail over an extended future 

period. Instead, NHTSA relies largely on EIA’s professional expertise and extensive experience 

in developing forecasts of future trends in energy prices, as do most other federal agencies. 

In addition, NHTSA notes that several manufacturers employed fuel prices consistent with or 

exceeding the AEO 2008 High Price Case for the time period covered by the rulemaking in their 

revised product plan estimates of fuel economy and sales for individual models. If the agency 

employs fuel price forecasts that differ from those used by manufacturers, it may incorrectly 

attribute the fuel savings resulting from increased market demand for fuel economy to higher 

CAFE standards, or conversely, underestimate the fuel savings resulting from increased 

standards by attributing too much of the increase in fuel economy to higher market demand. 

Given manufacturers’ assumptions about fuel prices, the agency’s estimates of fuel savings and 

economic benefits resulting from the standards adopted in this final rule are conservative, 

because they are likely to underestimate fuel savings attributable to the increase in fuel economy 

above its market-determined level that CAFE standards will require. 

Although some commenters suggested that NHTSA develop its own fuel price forecasts based 

on then-current pump prices, NHTSA does not believe that it has the independent capability to 

provide a more reliable prediction of future fuel prices, or that it would have the credibility of 

EIA’s forecasts. If NHTSA had assumed that that fuel prices would remain at their mid-2008 

peak levels throughout the lifetimes of MY 2011 cars and light trucks, the agency would have 

overvalued the benefits attributed to fuel savings, and thus likely have established excessively 

stringent standards. While petroleum prices were rising at the time the NPRM was published, 

eventually reaching nearly $140 per barrel, since then global average prices for crude oil have 
I-43

declined to levels as low as $35 per barrel.35 The recent extreme volatility in petroleum and fuel 

prices illustrates the danger in relying on current prices as an indicator of their likely future 

levels, and gives NHTSA greater confidence in relying on EIA’s forecasts of future movements 

in fuel prices in response to changes in demand and supply conditions in the marketplace. 

While NHTSA also agrees with the commenters that the sensitivity analysis demonstrates that 

higher CAFE standards could be established if higher fuel price assumptions were employed, the 

agency cannot simply choose to employ higher fuel price assumptions because it wishes to raise 

CAFE levels. Doing so would be inconsistent with the agency’s approach of using what it 

concludes is the most reliable estimate of the benefits from conserving fuel when establishing 

fuel economy standards. NHTSA recognizes that predicting future oil prices is difficult, 

particularly during periods when world economic conditions are as volatile as they are today. 

Nevertheless, NHTSA continues to believe that EIA’s fuel price forecasts as reported in its AEO 

represent the most reliable estimates of future fuel prices, and thus of the benefits from reducing 

fuel consumption through higher CAFE standards. While NHTSA recognizes that other 

forecasts exist, the agency believes the EIA forecasts are preferable for its purposes, since they 

are the product of an impartial government agency with considerable and long-standing expertise 

in this field. Any simple extrapolation of current or recent retail fuel prices, which commenters 

recognize have shown extreme volatility in recent months, is likely to provide a considerably less 

reliable forecast of future prices than the current AEO. Each time EIA issues a new AEO, it 

considers recent and likely future developments in the world oil market, the effect of the current 

geopolitical situation on oil supply and prices, and conditions in the domestic fuel supply 

industry that affect pump prices.36 

For example, the Overview section to AEO 2008 states that because EISA was passed between 

the Early Release and the time of publication for AEO 2008, EIA updated the Reference Case to 

reflect the impact it expected EISA to have on fuel prices. EIA also updated its projections for 

the AEO 2008 Reference Case “to better reflect trends that are expected to persist in the 

economy and in energy markets,” including a lower projection for U.S. economic growth (a key 

determinant of U.S. energy demand), higher price projections for crude oil and refined petroleum 

products, slower projected growth in energy demand, higher forecasts of domestic oil production 

(particularly in the near term), and slower projected growth in U.S. oil imports.37 Thus NHTSA 

is confident that EIA is aware of and has accounted reasonably for current political and 

economic conditions that are likely to affect future trends in fuel supply, demand, and retail 

prices. 

Although a majority of commenters asserted that EIA’s Reference Case forecast is likely to 

underestimate future fuel prices significantly, and that NHTSA’s reliance on the Reference Case 

resulted in insufficiently stringent proposed CAFE standards, they did so in an environment 

 

35 Energy Information Administration, World Crude Oil Prices, data for week ended 1/2/2009, available at 

http://tonto.eia.doe.gov/dnav/pet/pet_pri_wco_k_w.htm (last accessed February 12, 2009). 36 AEO 2008 states as follows with regard to factors which EIA accounts for in developing the Reference Case: 

As noted in AEO2007, energy markets are changing in response to readily observable factors, which 

include, among others: higher energy prices; the growing influence of developing countries on worldwide 

energy requirements; recently enacted legislation and regulations in the United States; changing public 

perceptions on issues related to emissions of air pollutants and greenhouse gases and the use of alternative 

fuels and; and the economic viability of various energy technologies. 37 AEO 2008 Overview, at http://www.eia.doe.gov/oiaf/aeo/overview.html (last accessed October 10, 2008). 
I-44

when retail fuel prices were at or above $4.00 per gallon. Many commenters stated that at a 

minimum, NHTSA should use EIA’s High Price Case as the source for its fuel price forecasts, 

primarily because those appeared to be more consistent with then-current fuel prices. As one 

illustration, NRDC cited EIA’s own International Energy Outlook 2008, published the same 

month as the AEO 2008, which stated that given “...current market conditions, it appears that 

world oil prices are on a path that more closely resembles the projection in the high price case 

than in the reference case.”38 Commenters also cited EIA Administrator Caruso’s June 2008 

statement that “We’re on the higher price path right now. If you were to ask me today what I 

would use, I would use the higher price.” NHTSA also notes that several manufacturers in their 

confidential product plan submissions indicated that they had based their product plans on gas 

price estimates that were either between EIA’s Reference and High Price Cases, or above even 

the High Price Case. 

The AEO High Price Case is best understood in the context of its relationship to the Reference 

Case. EIA described the Reference Case as follows in AEO 2008: 

The reference case represents EIA’s current judgment regarding exploration and 

development costs and accessibility of oil resources in non-OPEC countries. It also 

assumes that OPEC producers will choose to maintain their share of the market and will 

schedule investments in incremental production capacity so that OPEC’s conventional oil 

production will represent about 40 percent of the world’s total liquids production.39

 In contrast, EIA describes its Low Price case in the following terms: 

The low price case assumes that OPEC countries will increase their conventional oil 

production to obtain approximately a 44-percent share of total world liquids production, 

and that conventional oil resources in non-OPEC countries will be more accessible and/or 

less costly to produce (as a result of technology advances, more attractive fiscal regimes, 

or both) than in the reference case. With these assumptions, non-OPEC conventional oil 

production is higher in the low price case than in the reference case.40

Finally, EIA describes its High Price case as follows: 

The high price case assumes that OPEC countries will continue to hold their production 

at approximately the current rate, sacrificing market share as global liquids production 

increases. It also assumes that oil resources in non-OPEC countries will be less accessible 

and/or more costly to produce than assumed in the reference case.41

As these descriptions emphasize, EIA’s Low and High Price Cases are based on specific 

assumptions about the possible behavior of oil-producing countries and future developments 

affecting global demand for petroleum energy, and how these might differ from the behavior 

 

38 Energy Information Administration (2008) International Energy Outlook 2008: Complete Highlights. June 25.

39 AEO 2008, at 199. Available at http://www.eia.doe.gov/oiaf/aeo/pdf/0383(2008).pdf (last accessed October 10, 

2008). 

40 Id. 41 Id. 
I-45

assumed in constructing its Reference Case. However, this distinction does not necessarily 

imply that EIA expects either its Low Price or High Price Case forecast to be more accurate than 

its Reference Case forecast, since EIA offers no assessment of which set of assumptions 

underlying its Low Price, Reference, and High Price cases it believes is most reliable. 

EIA did recognize that world oil prices at the time the final version of AEO 2008 were above 

even those forecast in its High Price Case. However, it attributed this situation to short-term 

developments, most or all of which were likely to prove transitory, as evidenced by its statement 

in the Overview to AEO 2008: 

As a result of recent strong economic growth worldwide, transitory shortages of 

experienced personnel, equipment, and construction materials in the oil industry, and 

political instability in some major producing regions, oil prices currently are above EIA’s 

estimate of the long-run equilibrium price.42 

This observation is consistent with EIA’s statement in IEO 2008 that current market conditions 

appeared to place world oil prices on a path closer to the High Price Case than the Reference 

Case. While EIA clearly expects prices to remain high in the near term, this does not necessarily 

imply that it expects its High Price Case forecast to be more reliable over the extended time 

horizon spanned by AEO 2008. 

NHTSA has seriously considered the comments it received on the fuel price forecasts used in the 

NPRM analysis, and paid close attention to recent developments in the world oil market and in 

U.S. retail fuel prices. The agency has also reviewed forecasts of world oil prices and U.S. fuel 

prices available from sources other than EIA, as well as the views expressed by petroleum 

market experts, professional publications, and press reports.43 The agency notes that although 

both the views of experts and projections of petroleum prices differ widely, the emerging 

consensus appears to be that world petroleum and U.S. retail fuel prices are likely to remain at 

levels that are more consistent with those forecast in the AEO 2008 High Price Case than with 

the Reference Case forecasts over the foreseeable future.44 

Over the period from 2011, when the standards adopted in this final rule would take 

effect, and 2030, the outer time horizon of the AEO 2008 forecasts, retail gasoline prices in the 

 

42 Id., at 5. 43 These include EIA, Short-Term Energy Outlook, various issues, available at 

http://www.eia.doe.gov/emeu/steo/pub/contents.html (last accessed November 13, 2008); International Energy 

Agency, World Energy Outlook 2008, summary available at 

http://www.iea.org/Textbase/npsum/WEO2008SUM.pdf (last accessed November 13, 2008); AJM Petroleum 

Consultants, The AJM Price Forecast, available at http://www.ajmpetroleumconsultants.com/index.php?page=priceforecast (last accessed Novemebr 13, 2008); PetroStrategies, Inc, Survey of Oil Price Forecasts, available at 

http://www.petrostrategies.org/Graphs/Oil_Price_Forecasts.htm (last accessed November 13, 2008); International 

Monetary Fund, World Economic Outlook, October 2008, Chapter 3: Is Inflation Back? Commodity Prices and 

Inflation, available at http://www.imf.org/external/pubs/ft/weo/2008/02/pdf/c3.pdf (last accessed November 13, 

2008); and Federal Reserve Bank of Dallas Economic Letter, Volume 3, No. 5, May 2008, available at

http://www.dallasfed.org/research/eclett/2008/el0805.html (last accessed November 13, 2008). 44 In the AEO High Price Case, prices for imported petroleum are projected to average about $75 per barrel over the 

next 10 years, while U.S. retail gasoline prices are forecast to average $2.90 per gallon over that same period; see 

AEO 2008, High Price Case Table 12, available at http://www.eia.doe.gov/oiaf/aeo/excel/aeohptab_12.xls (last 

accessed October 19, 2008). 
I-46

AEO 2008 High Price case are projected to rise steadily from $2.95 to $3.62 per gallon, 

averaging $3.28 per gallon (all prices expressed in 2007 dollars). For the years 2031 and 

beyond, the agency’s analysis assumes that retail fuel prices will remain at their forecast values 

for the year 2030, or $3.62 per gallon. These prices are significantly higher than the AEO 2008 

Revised Early Release Reference Case forecast used in the agency’s NPRM analysis, which 

averaged $2.34 per gallon (in 2006 dollars) over that same period.45 After deducting state and 

federal fuel taxes, this revised forecast results in an average value of $3.08 per gallon of fuel 

saved over the lifetimes of 2011 passenger cars and light trucks. Because of the uncertainty 

surrounding future gasoline prices, the agency also conducted sensitivity analyses using EIA’s 

Reference and Low Price case forecasts of retail fuel prices. 

NHTSA is aware that EIA recently released a preliminary version of its Annual Energy 

Outlook 2009, which appears to confirm then-EIA Administrator Caruso’s testimony before the 

House Select Committee in June 2008 that the future path of gasoline prices likely more closely 

resembles the AEO 2008 High Price Case than the 2008 Reference Case. However, the agency 

has elected not to use this newly-available forecast of fuel prices, in part because it did not have 

adequate time to replicate the entire analysis reported in this rule using revised forecasts of fuel 

prices.46 Moreover, the forecast of gasoline prices from AEO 2009 Early Release averages 

$3.45 over the period from 2009-30, only slightly higher than the comparable figure for the AEO 

2008 High Price forecast the agency relied upon in preparing this analysis. Thus incorporating 

EIA’s newest forecast would be unlikely to have an effect on the fuel economy standards 

adopted in this rule. 

In its future CAFE rulemaking activities, the agency will continue to rely on EIA’s 

Annual Energy Outlook as its primary source for fuel price forecasts. As indicated previously, 

NHTSA continues to believe that the forecasts reported in EIA’s Annual Energy Outlook 

represent the most suitable estimates of future fuel prices for the purpose of assessing the 

economic benefits from reducing fuel consumption through higher CAFE standards. Under 

normal conditions, the agency is likely to view EIA’s Reference Case forecast as the most 

reliable basis for estimating benefits from reducing future fuel consumption, although the agency 

will retain the option of drawing its forecasts from other scenarios presented in AEO if, as here, 

it deems that circumstances warrant. The agency will also continue to monitor fuel price 

forecasts available form other forecasts, and to consider their implications for its choice among 

alternative price scenarios developed by EIA. 

 

45 The fuel price forecasts reported in EIA’s AEO 2008 Revised Early Release and Final Release reflect the 

estimates effects of various provisions of EISA – including the requirement to achieve a combined CAFE level of 35 

mpg by model year 2020 – on the demand for and supply of gasoline and other transportation fuels. Thus the fuel 

price forecasts reported in these versions of AEO 2008 may already account for the reduction in fuel demand 

expected to result form the CAFE standards adopted in this Final Rule, whereas the agency’s analysis of their effects 

would ideally use fuel price forecasts that do not assume the adoption of higher CAFE standards for model years 

2011-20. However, the agency notes that the difference between the Reference Case forecasts of retail gasoline 

prices for 2011-30 between EIA’s Early Release of AEO 2008, which did not incorporate the effects of EISA, and 

its subsequent Revised Early Release, which did reflect EISA, averaged only $0.0004 (i.e., less than one-half cent) 

per gallon over the period 2011-30, This suggests that accounting for the effect of EISA would have had only a 

minimal effect on the fuel price forecasts used in this analysis. 46 U.S. Energy Information Administration, Annual Energy Outlook 2009 Early Release, available at 

http://www.eia.doe.gov/oiaf/aeo/index.html (last accessed February 12, 2009). 
I-47

Product restrictions 

Comment: Recreation Vehicle Industry Association (RVIA), 2008-0090 229, Pg. 3-5 wants a 

3.2% adjustment in the curve for “heavy tow capable” vehicles if its Trailer Weight Rating is 

equal to or greater than 7,700 lbs. per the SAE J2897 recommended practice. 75% of RVIA 

product in any year are towable products, travel trailers, pop-up campers, truck campers, or fifthwheel trailers. In order to safety tow and stop these vehicles they need a truck that is properly 

equipped. An aggressive CAFE standard will force manufacturers to scale back vehicle power 

or make weight based changes to SUVs and light trucks. If there is a serious sales impact, there 

is a serious possibility that towable RV industry sales will be impacted. Given that towable RV 

shipments were 261,000 units and thousands of American workers produce those units, NHTSA 

cannot overlook the impact of its proposal no RV industry jobs and sales. 

Trailers owners will have four choices, retail older tow vehicles, use light weight under powered 

vehicles, purchase larger trucks (over 8,500 lbs. GVWR), or abandon their vehicles. 

Agency response: The agency’s methodology for setting the standards gives appropriate weight 

to and already accounts for towing needs. 

Rebound Effect 

Comment: Mark A. Delucchi, 2008-0089-0025 Pg. 1. Without giving a specific figure this 

commenter stated that the rebound effect coefficient should be lower than the value used by 

NHTSA because more weight should be given to the Small and Van Dender study. He also 

noted that Hughes et al. recently found a very low short-run price elasticity of demand for 

gasoline [The Energy Journal, 29(1), January 2008].47

Comment: Sierra Research, 2008-0089-0046-1, Pg. 74. Based on a 1999 paper by Greene of 

Oak Ridge National Laboratory48, the rebound effect is 20%, they use a “conservative” 17%. As 

Greene explains, it is well documented that increased fuel economy produces a long term 

rebound effect of 20%. In other words, a 100% improvement in fuel economy induces a 20% 

increase in vehicle travel. 

Comment: Air Resources Board, 2008-0089-0173-1, Pg. 10. The California Air Resources 

Board states that NHTSA “declines to adopt two critical findings from previous analysis: 1) the 

future decline in value of rebound effect as household real income increases, and 2) as fuel prices 

 

47 2008 Volume 29 Number 1 Evidence of a Shift in the Short-Run Price Elasticity of Gasoline Demand Jonathan E. 

Hughes*, Christopher R. Knittel** and Daniel Sperling*** 

Understanding the sensitivity of gasoline demand to changes in prices and income has important implications for 

policies related to climate change, optimal taxation and national security. The short-run price and income elasticities 

of gasoline demand in the United States during the 1970s and 1980s have been studied extensively. However, 

transportation analysts have hypothesized that behavioral and structural factors over the past several decades have 

changed the responsiveness of U.S. consumers to changes in gasoline prices. We compare the price and income 

elasticities of gasoline demand in two periods of similarly high prices from 1975 to 1980 and 2001 to 2006. The 

short-run price elasticities differ considerably: and range from -0.034 to -0.077 during 2001 to 2006, versus -0.21 to 

-0.34 for 1975 to 1980. The estimated short-run income elasticities range from 0.21 to 0.75 and when estimated with 

the same models are not significantly different between the two periods. 48 David L. Greene, et al, “Fuel Economy Rebound Effect for U.S. Household Vehicles”, The Energy Journal, Vol. 

20, No. 3, 1999. 
I-48

increase, people are forced to spend a larger share of their income on fuel, thus becoming more 

sensitive to fuel prices. The Air Resources Board recommends a rebound effect in the range of a 

maximum of 10 per cent. 

Comment: Air Resources Board, 2008-0089-0173.15. In an additional comment by the Air 

Resources Board, testimony by Small is cited to show a marked decline in rebound effect for 

California to 1% for a single year vs. 4.9% in the years 1975-2001. A number of variables and 

additional effects to rebound were modeled and given in Small’s testimony. While no clear 

recommendation is given for a change in NHTSA’s value for rebound effect, the clear 

implication is that the value should probably be lower. 

Comment: Alliance, 2008-0089-0179.1, P9, Att3 S-8. In this attachment to other comments by 

the Alliance a supporting study by NERA is summarized. NERA cites four economic effects 

which increase external costs and one effect which reduces external costs as being directly 

impacted by a higher rebound effect. The primary discussion is on net benefits with respect to 

the Volpe model; and NERA provides data which increases overall costs due to an assumption of 

a higher rebound effect of 20%. 

Comment: Public Citizen, 2008-0089-0187, Pg. 4. This commenter states that NHTSA has 

“assumed a very high rebound effect – 15 percent.” Furthermore, it is stated that NHTSA looked 

at 29 estimates and attempts to reflect the current conditions; however according to the Small and 

Van Dender study, “most empirical measurements of the rebound effect rely heavily on variations 

in the fuel price,” which raises again the question of whether NHTSA’s assumptions about the 

rebound effect are colored by the estimates of future fuel price. 

Comment: Union of Concerned Scientists 2008-0089-0201.7, Pg. 1 etc. and Union of Concerned 

Scientists, 2008-0089-0201.11. These comments focus on a paper authored by Kenneth Small 

and Kurt Van Dender, prepared for the State of California Air Resources Board, the California 

Environment Protection Agency, and the California Energy Commission. The article attempts to 

estimate the magnitude of rebound effect in the short-run and long-run rebound effect using 

cross-sectional time series U.S. data from 1966-2001. For the U.S. as a whole authors estimate a 

rebound effect of 5.3 % in the short run, and 26% for the long run, with the latter estimate very 

similar to the consensus from the authors’ literature review. The authors also conclude that the 

rebound effect declines with increases in income. The estimates of the rebound effect during 

future years presented in this study are specific to California, in that they reflect California 

household incomes, fuel prices, and fuel economy, and in any case have been superseded by 

several updates to the original study published by Small and Van Dender, CARB, and EPA. 

Comment: Environmental Defense Fund, 2008-0089-0224.1, Pg. 3. NHTSA selected the 

rebound effect of 15 per cent based on the review of studies conducted from 1983 through 2005. 

However, a recent literature review suggests that many previous studies overestimated the 

rebound effect because of problems with model specification. Also, latest research work suggests 

that the rebound effect decreases over time with rising income. 

Agency response: The rebound effect is generally considered to be that effect where an 

improvement in fuel economy induces a percentage increase in demand for vehicle travel. 

Considering the empirical evidence on the rebound effect as a whole, but according greater 
I-49

importance to the updated estimates from studies allowing the rebound effect to vary – 

particularly the Small and Van Dender study – NHTSA originally proposed a final rebound value 

of 15 percent to evaluate the fuel savings and other effects of alternative standards for the time 

period covered by this rulemaking. 

Of the 7 organizations commenting on the subject of rebound effect, 2 recommended a higher 

value and 5 recommended a lower value than the 15 per cent used by NHTSA. NHTSA had 

previously evaluated 22 studies containing 66 estimates covering the period 1983 to 2005 to 

determine the basis for selecting a single value for rebound effect. NHTSA tentatively attached 

greater significance to studies that allow the rebound effect to vary in response to changes in the 

various factors that have been found to affect its magnitude. Recently, a review of this by 

NHTSA with other agencies and consultants has determined that in light of previous studies and 

the fact that net benefits will be determined on the basis of rebound effect, the value of 15 per 

cent will be used for the final rule. (See Chapter VIII for more discussion about the rebound 

effect.) 

Regulatory Flexibility Analysis 

Comment: National Automobile Dealers Association, 2008-0089-223.1, Pg. 9 stated that a full 

regulatory flexibility analysis must be undertaken. Many of the nation’s dealerships are directly 

impacted by the proposal and are small businesses as defined by the SBA. Moreover, the 

overwhelming majority of these dealerships have 200 employees or less, that standard 

established by DOT in a recently published rule that examined that issue (72 Federal Register 

15614-7 (April 2, 2007). Therefore, a full regulatory flexibility analysis must be undertaken to 

examine what modifications may be necessary to lessen the regulation’s potential impact on 

motor vehicle dealerships.

Agency response: Dealers are not directly impacted by the CAFE rules, they are indirectly 

impacted. Dealers are not a regulated entity under CAFE. 

Retail Price Equivalent Multiplier 

Typically cost estimates for technologies, for example when the agency has a cost tear down 

study for a safety countermeasure, are provided on a variable cost basis. NHTSA applied an 

indirect cost multiplier in the NPRM of 1.5 to the estimate of the vehicle manufacturers’ direct 

costs for producing or acquiring each fuel economy-improving/CO2 emission-reducing 

technology. Historically for safety and fuel economy purposes, NHTSA used an almost identical 

multiplier, 1.51, for the markup from variable costs or direct manufacturing costs to consumer 

costs. The markup takes into account fixed costs, burden, manufacturer’s profit, and dealers’ 

profit. NHTSA’s methodology for determining this markup was peer-reviewed. This value is 

based on an examination of auto industry financial reports49. 

Comment: The Alliance 2008-0089-0169.1 cited the Martec Cost study and stated that the 

agency should use a 2.0 Retail Price Equivalent (RPE) markup factor. In order for a company to 

 

49 Spinney, Bruce C., CPA, NHTSA “Advanced Air Bag System Cost Weight and Leadtime Analysis Summary 

Report” Docket No. 2007-27453-10. 
I-50

remain financially viable, that Retail Price Equivalent (RPE) markup factor must be at least 2.0. 

This estimate of RPE was documented by Dr. Winn V. Bussmann in a submission that provided a 

correction to the earlier Jack Faucett study. In addition as part of that submission, Dr. Bussmann 

also showed with more recent financial data that an estimate of 2.0 for RPE is still valid. 

Commodity prices for many of the materials necessary for these technologies have increased 

dramatically in the last two years and are at record highs. These prices are significant factors in 

determining manufacturing variable costs. 

The Alliance 2008-0089-0179.1, P6, P17, Attachment 2 P1, 

The Alliance believes the retail price equivalent markup should be 2.0, not 1.5, based on 

Wynn V. Bussman, “Study of Industry-Average Mark-up Factors to Estimate Retail Price 

Equivalents”, Jan. 24, 2008, and Attachment 4. Also, Argonne National Laboratory report 

recommended 2.0. NHTSA misused the Argonne report by citing 1.5 RPE for outsourced 

components. See Sierra Report Attachment at 61. 

Agency Response: The agency disagrees with a 2.0 RPE. Commodity prices do not affect the 

RPE. NHTSA has its own report on mark-up factors justifying 1.51 that we rely upon. This 

report implicitly includes historical levels of outsourced components. 

Comment: Alliance, 2008-0089-0195.1, Attachment 4, P1-3 

The Jack Faucett Associates (JFA), used by a draft EPA staff report in 2005 (EPA420-R-05-012) 

analysis that estimates a markup factor of 1.26 does not accurately account for full costs. The 

work done by Sierra Research indicates a mark-up factor of at least 2.0 would be necessary. JFA 

failed to recognize that research and development and other indirect costs were combined with 

direct manufacturing costs. JFA also assumed that emission control equipment does not change 

dealer overhead expenses. The author of the study has agreed that the study underestimates the 

markup factor. Correcting the problems would result in a markup factor of at least 1.7. 

The CARB justification for its markup of 1.4 is that it fell between the 1.26 factor and 1.5 

suggested in a paper published by Argonne National Laboratory. CARB apparently 

misinterpreted Argonne’s reference to a 1.5 markup factor, which would be appropriate for 

certain categories of components, such as batteries that are developed entirely by vendors. The 

same paper makes it clear that the markup for engines and transmissions primarily developed by 

OEMs would be 2.0 to 2.05. 

The NRC and NESCCAF markup factors of 1.4, are contributed to a consultant Mr. Duleep, who 

has since testified that “1.4 might represent the low end of the scale of markups” and that markup 

factors as high as 2.0 would be appropriate for certain items. 

Pg. 11, Dr. Bussmann estimates inbound and outbound transportation costs at 6% of direct 

manufacturing costs. 

Agency response: NHTSA has used a RPE of 1.51 for years and agreed with EPA to use 1.5 for 

this rulemaking. The commenter does not analyze NHTSA’s methodology. 
I-51

Comment: The Air Resources Board, 2008-0089-0173, p 8, stated that 

NHTSA’s RPE methodology is unsound. The cost to incorporate a technology is the same 

regardless of vehicle production. NHTSA’s approach implies an engineering cost of $35.2 

million for a vehicle model with 50,000 unit production, but $352 million for a vehicle model 

with 500,000 production. 

Agency response: The markup is for many other factors than just engineering costs. It includes 

all fixed costs, manufacturer profit and dealer profit. 

Comment: Air Resources Board, 2008-0089-0173.4, P4 

ARB objects to Sierra’s RPE of 2.0, and suggests adjustment to 1.4. They argue that many 

components are sourced to suppliers. Since the manufacturer doesn’t bear the burden of R&D 

and investment and some level of warranty, a 2.0 markup is not appropriate and should be 

adjusted to 1.4. 

Agency response: NHTSA’s 1.5 RPE includes the historical levels of outsourcing. 

Comment: Northeast States for Coordinated Air Use Management (NESCAUM), 2008-0089-

204.1, Page 4, All reported costs and benefits, attributed to NESCCAF by NHTSA, should be 

reviewed carefully for errors and amended accordingly, using a 1.4 RPE not 1.5. Information 

from a 2004 NESCCAF5 study entitled “Reducing Greenhouse Gas Emissions from Light-Duty 

Motor Vehicles” is cited in the NHTSA proposal. Some of this information is reported in a way 

that is either confusing or incorrect. For example, NHTSA applies a 1.5 retail price equivalent 

(RPE) factor to the manufacturer costs presented in Appendix C of the NESCCAF report, and at 

other times uses a 1.4 RPE – and presents both costs as NESCCAF costs. In the report, 

NESCCAF only used a 1.4 RPE. The reporting of costs using the 1.5 multiplier as NESCCAF 

costs is incorrect and leads to uncertainty as to how the costs were developed. A specific case is 

the cost of a turbocharger. NHTSA states the NESCCAF turbocharger cost is $600. In this case, 

NHTSA applied a 1.5 RPE factor to manufacturer costs presented in Appendix C of the 

NESCCAF report to arrive at the $600 cost. This is different from the cost that NESCCAF 

developed. Conversely, on page 24369 of the Federal Register notice, NHTSA accurately states 

the NESCCAF cylinder deactivation costs ranged from $161 to $210. This cost accurately 

reflects manufacturer costs presented in Appendix C of the NESCCAF report, multiplied by the 

1.4 retail price equivalent used by NESCCAF.

Agency response: NHTSA notes that the analysis for this final rule relies on entirely new cost 

estimates for fuel economy technologies developed by the agency in response to comments and 

in coordination with an international engineering consulting firm, Ricardo, Inc., based on a bill 

of materials approach and not based on the 2004 NESCCAF study, so the issue of apparent 

inconsistency in the RPE factor applied to those estimates noted by NESCAUM and CARB is no 

longer relevant. The agency also notes that both the production and application of fuel economyimproving technologies include separate engineering cost components. Developing these 

technologies and readying them for high-volume production entails significant initial 

investments in product design and engineering, while as the NPRM pointed out, applying 

individual technologies to specific vehicle models can entail significant additional costs for 
I-52

accompanying engineering changes to its existing drive train, development and testing of 

prototype versions, recalibrating engine operating parameters, and integrating the technology 

with other attributes of the vehicle. While design and engineering costs for developing fuel 

economy-improving technologies are included in the production cost estimates for individual 

technologies, additional engineering costs incurred by manufacturers in applying them to specific 

vehicle models are included in NHTSA’s estimate of the RPE factor. Finally, the agency notes 

that its estimate of the RPE factor includes is consistent with high-volume production and 

application of fuel economy technologies, because it assumes that initial design and engineering 

costs to develop and begin production of these technologies will be recovered over large 

production volumes. Thus, NHTSA believes that CARB’s concerns about potential doublecounting of engineering costs for developing and applying fuel economy technologies reflect a 

failure to recognize that engineering costs arise in both their development and application. The 

agency also believes that CARB’s concern about whether NHTSA’s RPE factor assumes the 

spreading of initial design and engineering costs for developing these technologies over 

insufficiently high production volumes is unfounded. 

In response to the concerns expressed by the Alliance and others that NHTSA’s RPE factor is too 

low, the agency notes that the RPE factor of 2.0 reported in the Argonne and Sierra Research 

studies includes various categories of production overhead costs (for product development and 

engineering, depreciation and amortization of production facilities, and warranty) that are 

included in NHTSA’s estimates of production costs for fuel economy technologies. When 

applied to technology production costs defined to include these components, the agency’s RPE 

factor of 1.5 is thus consistent with full recovery of these cost components. This conclusion is 

independent of whether overhead costs for developing and producing fuel economy technologies 

are initially borne by equipment suppliers or by vehicle manufacturers themselves. 

Consequently, NHTSA has continued to employ an RPE factor of 1.5 in its analysis for this final 

rule. 

Comment: National Automobile Dealers Association, 2008-0089-223.1, P 7 

When calculating fuel economy technology costs, NHTSA uses a 1.5 multiplier to account for 

related additional costs, including “dealer profit.” NHTSA should review whether its estimates 

include all dealer costs-of–sales when calculating “dealer profit” and the extent to which it has 

properly accounted for the finance costs consumers typically pay when purchasing new 

automobiles. NADA would be happy to meet with NHTSA staff to discuss these issues further. 

Agency response: The dealer markup does not include finance costs. Those are not a societal 

cost but a transfer payment from the purchaser to the lender. 

Sales Impacts and Related Employment Impacts 

In the NPRM the agency presented an analysis of how sales and employment might be affected 

by higher fuel economy standards. The standards are expected to increase the price of passenger 

cars and light trucks, while reducing fuel expenditures in the future. Because the proposed 

alternative is based on a marginal cost/marginal benefit analysis, sales were estimated to slightly 

increase under this scenario. In other words, consumers would believe they would save more in 

fuel economy expenditures in the future than the initial price increase of the vehicle. 
I-53

Comment: The Alliance 2008-0089-0179.1, P5, P44 (gives table), Att3, S6-7, Att3 S5, 17, A-1-9 

presents the results of an analysis by NERA which finds that NHTSA’s proposed standards 

would reduce the sales of new vehicles by 856,000 and create associated job losses of 82,000. 

NERA finds that NHTSA’s sales increase makes no economic sense. Where is the market 

failure? NERA has a new vehicle market model. If improving fuel economy would increase 

sales, why haven’t manufacturers included these measures in their plans? NHTSA has either 

overestimated benefits or underestimated costs, or both. 

Agency response: NHTSA consulted with a contractor to examine benefit and cost estimates. 

The commenter offers no advice on how to change the NHTSA analysis. 

Comment: Ford, 2008-0089-0202.1, pp 5-6 believes that the combination of benefit 

overestimation, misunderstanding of our current technology deployment, and specific technology 

incompatibilities has led to an over-estimation of the potential fuel economy improvements on 

Ford's products. Ford believes there will be a loss of sales due to overestimation of technology 

application for benefits. 

It is a common practice to use hedonic pricing technique ..[which] determines the price of a 

vehicle by the characteristics of the car such as towing, cargo volume, performance etc. We 

recommend that NHTSA modify its analysis to incorporate this technique into its analysis. 

NHTSA treated the difference between the technology costs (of increasing the fuel economy of 

each vehicle model) and value of fuel savings as the "effective price" to vehicle buyers. The 

"effective price" calculated was then assumed to represent consumer valuation of fuel economy. 

This is conceptually inaccurate. First, it was implicitly assumed that the technology costs 

incurred by the manufacturers can be fully passed on to buyers. In the competitive environment 

of the U.S. automotive market, this is not true. Second, using alternative gasoline price 

assumptions will change the estimates of "effective price". A higher gasoline price assumption 

will lower the effective price estimates, holding everything else constant. The Sierra Research 

Inc. (Sierra) analysis, dated June 26, 2008, estimates that a consumer would not breakeven over a 

20 year period unless gas prices are sustained at $4.47 a gallon. Sierra also concluded that by 

using a more conservative payback period of 5 years the estimated breakeven gas price would 

have to be $6.59. 

Agency response: The agency does not believe it needs a hedonic pricing technique. We are 

estimating the incremental costs and benefits to the same make/model by adding fuel economy 

technologies only. All other parts of the vehicle are not impacted and we hold the performance 

of the vehicle at an equivalent level. Inputs to the model (e.g. the price of technology, the price 

of gasoline, etc.) do change the results. So, when Sierra Research assumes higher prices and 

lower effectiveness for various technologies, it is easy to see how their results would be very 

different. Assuming that manufacturers cannot pass on price increases to consumers has 

important implications for the automobile manufacturers, but in this analysis it makes it a better 

deal for consumers and sales should increase. 

Comment: The Consumer Federation of America, 2008-0089-0183-pp. 22, 43 states that 

NHTSA ignores that pushing the industry to produce more fuel efficient cars might improve 

employment opportunities by better aligning supply and demand. NHTSA has it backwards. It 
I-54

is more likely that the absence of significantly increasing fuel economy standards in the past half 

decade has led to significant sales losses, than vice versa. 

Agency response: From an industry perspective, sales have been at an all-time high in recent 

years. Only in the last two years when the price of gasoline went up greatly would a better 

alignment of supply and demand for more fuel efficient vehicles have improved sales. 

Comment: The United Auto Workers (UAW) 2008-0089-0226.3, pp 2, is concerned the NPRM 

could lead to more job loss and threaten health care coverage for retirees of the Detroit-based 

mfrs. The CAFÉ increase would impose enormous, separate retooling costs on these companies. 

In light of the serious economic difficulties already facing these firms, this could lead to even 

more job loss and potentially threaten health care coverage for over half a million retirees and 

their families. 

Agency response: As discussed by the larger companies, the footprint attribute-based system is 

an advantage over the flat rate standards. If the American companies do not improve fuel 

economy and lose market share, the job losses may be even more. 

Safety standards impact on vehicle weight, or fuel economy 

All of the vehicle weight comments were confidential. See Chapter IV. 

Size/safety Impacts 

See Chapter IV 

Uncertainty Analysis 

Comment: Alliance, 2008-0089-0179.1, Pg. 40-41 stated that NHTSA should reevaluate its 

statistical model on uncertainty. Technology changes are more uncertain the farther the attempts 

to peer into the future, yet the uncertainty analysis shows 100 percent certainty that the changes 

will be cost beneficial for MY 2014 and 2015. 

Agency response: Let us consider the effectiveness of a technology as an example. It is true that 

if you consider each individual technology, that the farther you peer into the future, the more 

uncertain the results. However, we are looking at a group of technologies, some of which could 

be more effective than we currently predict and some of which could be less effective than we 

currently predict. While this final rule is limited to one model year, theoretically, one could 

assume effectiveness is plus or minus ten percent in the first year, 15 percent in the second year, 

20 percent in third year, etc. That would unnecessarily complicate the model since we believe 

that the combined range in the later years will be close to the combined range in the earlier years 

of the standard. 

We could simply increase the range symmetrically by some arbitrary factor, but, assuming the 

same normal distribution that is employed for most of the variables in our uncertainty analysis, 

increasing the range of both costs and benefits proportionally would be unlikely to significantly 

impact the conclusions of the uncertainty analysis. Thus, the agency would not increase this 

range of uncertainty by progressively more for successive model years, were this a multi-year 
I-55

rulemaking. As it is not, the issue of changing levels of uncertainty over time is largely 

academic for purposes of this rulemaking. 
II-1

II. NEED OF THE NATION TO CONSERVE ENERGY

The Energy Policy and Conservation Act (EPCA) states that: 

“When deciding maximum feasible average fuel economy ... the Secretary of 

Transportation shall consider technological feasibility, economic practicability, the 

effect of other motor vehicle standards of the Government on fuel economy, and the 

need of the United States to conserve energy.”50

Thus, (EPCA) specifically directs the Department to balance the technological and economic 

challenges related to fuel economy with the nation's need to conserve energy. The concerns 

about energy security and the effects of energy prices and supply on national economic wellbeing that led to the enactment of EPCA persist today. The demand for petroleum grew in the 

U.S. up through the year 2005 and is now declining slowly averaging approximately 18.5 million 

barrels per day in 200751. World demand, however, is expected to continue to rise until 203052.

Since 1970, there have been a 

series of events that suggest that the 

behavior of petroleum markets is a 

matter for public concern. 

• Crude oil prices are over 

$100 per barrel in August 

2008 and in June 2008 

reached at over $140 per 

barrel. As recently as 1998, 

crude prices averaged about 

$13 per barrel ($15.85 in 

2006 dollars).53 Gasoline 

prices have more than doubled during this ten year period.54

• U.S. domestic oil production peaked in 1970 at 9.7 million barrels per day. Between 

1970 and 2006, U.S. domestic production declined by 47 percent, while U.S. petroleum 

consumption increased by 20 percent. Net petroleum imports now account for 73 percent 

of U.S. domestic petroleum consumption55. 

• Worldwide oil demand is fairly inelastic: declining prices do not induce large increases 

in consumption, while higher prices do not significantly restrain consumption. For 

 

50 49 USC 32902(f) 

51 Energy Information Administration, Petroleum Basic Statistics, August, 2008. See 

http://www.eia.doe.gov/basics/quickoil.html

52 Energy Information Administration, International Petroleum (Oil) Consumption, August, 2008. See 

http://www.eia.doe.gov/emeu/international/oilconsumption.html

53 Energy Information Administration, Annual Energy Review 2006, Table 5.21, p. 171. See: 

http://www.eia.doe.gov/emeu/aer/pdf/pages/sec5_51.pdf 54 Energy Information Administration, Annual Energy Review 2006, Table 5.24, p. 177. See: 

http://www.eia.doe.gov/emeu/aer/pdf/pages/sec5_57.pdf 55 Energy Information Administration, Annual Energy Review 2006, Table 5.1, p. 125. See: 

http://www.eia.doe.gov/emeu/aer/pdf/pages/sec5_5.pdf

0

2

4

6

8

10

12

14

16

18

20

2000 2001 2002 2003 2004 2005 2006 2007

Year

Million barrels/day

Domestic

Production

Imports

Total
II-2

example, the price of unleaded regular gasoline rose from an average of $2.59 in 2006 to 

$2.80 in 2007 (an 8.1 percent increase) and vehicle miles traveled decreased by 0.6 

percent. Within the United States, demand for gasoline, diesel, and jet fuel within the 

transportation sector is particularly inelastic. 

• Demand for oil may increase significantly in Asia and worldwide in the future resulting 

in upward oil cost pressure. 

• Foreign oil production facilities, refineries, and supply chains have been disrupted from 

time to time, either by wars, political action by oil producers, civil unrest, or natural 

disasters. 

• High oil prices, sometimes induced by disruptions in oil markets, have often coincided 

with rising inflation and subsequent economic recessions. 

• Greenhouse gas emissions from the consumption of petroleum have become a subject of 

increasing public policy concern, both in the United States and internationally. 

Greenhouse gases in general and carbon dioxide in particular have not thus far been 

subject to national regulation. Studies by multiple sources suggest that rising 

atmospheric concentrations of greenhouse gases will damage human health and 

welfare.56 There is a direct linkage between the consumption of fossil energy and 

emissions of the greenhouse gas carbon dioxide, as essentially all of the carbon in 

hydrocarbon fuels is oxidized into carbon dioxide when the fuel is combusted. Reducing 

U.S. fossil petroleum consumption will generally induce a proportional reduction in 

carbon dioxide emissions. 

Energy is an essential input to the U.S. economy, and having a strong economy is essential to 

maintaining and strengthening our national security. Secure, reliable, and affordable energy 

sources are fundamental to economic stability and development. Rising energy demand poses a 

challenge to energy security, given increased reliance on global energy markets. As noted 

above, U.S. energy consumption has increasingly been outstripping U.S. energy production. 

Table II-1 presents trend data on the production and consumption of petroleum for 

transportation. Domestic petroleum production has been decreasing over time, while imports of 

petroleum have been increasing to meet the rising U.S. demand for petroleum. 

Conserving energy, especially reducing the nation’s dependence on petroleum, benefits 

the U.S. in several ways. Improving energy efficiency has benefits for economic growth 

and the environment, as well as other benefits, such as reducing pollution and improving 

security of energy supply. More specifically, reducing total petroleum use decreases our 

economy’s vulnerability to oil price shocks. Reducing dependence on oil imports from 

regions with uncertain conditions enhances our energy security and can reduce the flow 

of oil profits to certain states now hostile to the U.S. 

 

56 IPCC 2007: Climate Change 2007: Synthesis Report: Contributions of Working Groups I, II, and III to the 

Fourth Assessment Report of the Intergovernmental Panel on Climate Change, [Core writing team, Pachauri, R.K. 

and Reisinger, A. 9eds.)] (Published by the Intergovernmental Panel on Climate Change, 2008). Available at 

http://www.ipcc.ch/, .
II-3

This reformed CAFE final rule encourages conservation of petroleum for transportation by the 

application of broader use of fuel saving technologies, resulting in more fuel-efficient vehicles, 

i.e. vehicles requiring less fuel consumption per unit mile.

Table II-1 

Petroleum Production and Supply 

(millions of barrels per day)57

 Domestic 

Petroleum 

Production 

Net 

Petroleum 

Imports 

U.S. 

Petroleum 

Supply 

World 

Petroleum 

Consumption 

Import 

Share of 

U.S. 

Supply 

1975 8.4 6.1 14.4 52.8 42% 

1985 9.0 5.1 14.0 54.0 36% 

1995 6.6 8.8 15.4 62.4 57% 

2005 5.2 13.7 18.9 84.3 73% 

DOE 

Predictions 

 

2015 6.2 9.9 16.0 95.7 62% 

2025 6.0 10.1 16.1 106.5 63% 

2030 5.6 11.0 16.6 112.5 66% 

Table II-2 

Transportation Consumption by Mode 

(thousands of barrels per day)58

 

Passenger 

Cars 

Light 

Trucks 

Total Light 

Vehicles 

Total 

Transportation 

Light 

Vehicles as 

% of Trans. 

1975 4,842 1,087 6,081 8,474 72% 

1985 4,665 1,785 6,450 9,552 68% 

1995 4,440 2,975 7,415 11,347 65% 

2005 5,050 3,840 8,890 13,537 66% 

 

57 “Petroleum Production and Consumption and Some Important Percent Shares, 1950-2006”, Transportation 

Energy Data Book: Edition 26 (2007), Table 1.12. http://cta.ornl.gov/data/Index.shtml 

“Comparison of petroleum projections, 2015, 2025, and 2030”, Department of Energy, Energy Information 

Administration, Annual Energy Outlook 2007, Table 23. http://www.eia.doe.gov/emeu/aer/contents.html 58 Transportation Energy Data Book, Table 1.14. http://cta.ornl.gov/data/chapter1.shtml . 
III-1

III. ALTERNATIVES 

In developing the proposed alternatives for the NPRM, the agency considered the four statutory 

factors underlying maximum feasibility as defined in EPCA (technological feasibility, economic 

practicability, the effect of other standards of the Government on fuel economy, and the need of 

the nation to conserve energy) as well as other relevant considerations such as safety. NHTSA 

assessed what fuel saving technologies would be available, how effective they are, and how 

quickly they could be introduced. This assessment considered technological feasibility, 

economic practicability and associated energy conservation. We also considered other standards 

to the extent captured by EPCA59 and environmental and safety concerns. This information was 

factored into the computer model used by NHTSA for applying technologies to particular vehicle 

models. 

In developing its proposed standards, the agency used a net benefit-maximizing analysis that 

placed monetary values on relevant externalities (both energy security and environmental 

externalities, including the benefits of reductions in CO2 emissions) and produced what is called 

the “optimized scenario.” The optimized standards reflect levels such that total benefits minus 

total costs are higher than at every other examined level of stringency. The agency also 

reviewed the results of the model’s estimates of stringencies maximizing net benefits to assure 

that the results made sense in terms of balancing EPCA’s statutory factors and in meeting 

EISA’s requirements for improved fuel economy. 

The agency proposed the “Optimized (7%)” alternative. In this alternative the agency used a 7 

percent discount rate to value benefits and set the proposed mpg levels where marginal costs 

equal marginal benefits. It is one of six alternatives examined in the analysis using a 7 percent 

discount rate. We also examined a second optimized scenario when discounting benefits at 3 

percent “Optimized (3%). In general order of increasing severity (see Table 1), the seven 

scenarios examined are: 

1: “25% Below Optimized”: This alternative mirrors the absolute difference in mpg derived 

from the 25% Above Optimized scenario in going the same mpg amount below the Optimized 

7% alternative 

2: “Optimized (7%) An increase in the standard based upon availability of technologies and a 

marginal cost/benefit analysis, as was used in setting the MY 2008-2011 light truck standard. 

The mpg levels are set using a 7 percent discount rate for benefits. 

3: “25% Above Optimized”: This alternative looks at the mpg levels of the Optimized (7%) 

and the Total Cost Equals Total Benefit alternative and picks mpg levels that are 25 percent of 

that difference. 

4: “50% Above Optimized”: This alternative looks at the mpg levels of the Optimized (7%) 

and the Total Cost Equals Total Benefit alternative and picks mpg levels that are 50 percent of 

that difference. 

5: “Optimized (3%) An increase in the standard based upon availability of technologies and a 

marginal cost/benefit analysis, as was used in setting the MY 2008-2011 light truck standard, 

except that the mpg levels are set using a 3 percent discount rate for benefits. 

 

59 71 Fed. Reg. 17566, 17669-70; April 6, 2006. 
III-2

6: “Total Costs Equal Total Benefits”: An increase in the standard to a point where essentially 

total costs of the technologies added equals total benefits. In this analysis, for brevity, at times it 

is labeled “TC = TB”. 60 

7: “Technology Exhaustion”: An increase in the standard based upon the maximum usage 

(based on NHTSA’s perspective) of available technologies, disregarding the cost impacts. 61

 

 

Table III-1 

NPRM Alternative CAFE Levels 

Projected Harmonic Average for the Fleet62

(in mpg) 

Passenger Cars MY 2011 MY 2012 MY 2013 MY 2014 MY 2015 

25% Below Optimized 30.5 31.2 31.9 32.8 33.5 

Optimized (7%) 31.0 32.3 33.1 33.9 34.7 

25% Above Optimized 31.5 33.3 34.2 35.3 36.1 

50% Above Optimized 31.7 34.0 35.1 36.4 37.6 

Optimized (3%) 32.2 34.5 35.5 37.0 38.2 

TC = TB 32.3 35.0 36.1 37.6 38.8 

Technology Exhaustion 32.3 35.2 36.6 38.5 39.9 

 

Light Trucks 

25% Below Optimized 24.3 25.5 27.3 27.3 27.4 

Optimized (7%) 24.4 25.8 27.5 28.0 28.4 

25% Above Optimized 24.4 26.1 27.8 28.5 29.5 

50% Above Optimized 24.6 26.3 28.0 28.9 30.0 

Optimized (3%) 24.4 25.8 27.7 28.2 28.8 

TC = TB 24.7 26.5 28.5 29.5 30.5 

Technology Exhaustion 24.7 26.6 29.4 30.3 31.3 

For the final rule, the agency considered the same seven alternatives: 

When discussing an alternative we provide the discount rate in parenthesis afterwards to keep 

track of which alternative we are discussing. There is one notable difference between the NPRM 

 

60 The agency considered the “TC=TB” alternative because one or more commenters in the rulemaking on 

standards for MY 2008-2011 light trucks urged NHTSA to consider setting the standards on this basis rather than on 

the basis of maximizing net benefits. In addition, while the Ninth Circuit Court of Appeals concluded that EPCA 

neither requires nor prohibits the setting of standards at the level at which net benefits are maximized, the Court 

raised concerns about tilting the balance more toward reducing energy consumption and CO2. 61 This was accomplished by determining the stringency at which a reformed standard would require every 

manufacturer to apply every technology estimated to be potentially available. At such stringencies, all but one 

manufacturer would be expected to fail to comply with the standard, and many manufacturers would owe large civil 

penalties as a result. The agency considered this alternative because the agency wished to explore the stringency 

and consequences of standards based solely on the potential availability of technologies at the individual 

manufacturer level. 

62 The values represent the higher of the manufacturer’s plans and the alternative level of the standard. 
III-3

and final rule in terms of discount rate. For all of the alternatives below, a 3 percent discount 

rate is used for the social cost of carbon and the intergenerational benefits. In general order of 

increasing severity, the seven scenarios examined are: 

1: “25% Below Optimized (7%)”: This alternative mirrors the absolute difference in mpg 

derived from the 25% Above Optimized scenario in going the same mpg amount below the 

Optimized 7% alternative 

2: “Optimized (7%)”: An increase in the standard based upon availability of technologies and a 

marginal cost/benefit analysis. The mpg levels are set using a 7 percent discount rate for 

benefits. 

3: “25% Above Optimized (7%)”: This alternative looks at the mpg levels of the Optimized 

(7%) and the Total Cost Equals Total Benefit (7%) alternative and picks mpg levels that are 25 

percent of that difference. 

4: “50% Above Optimized (7%)”: This alternative looks at the mpg levels of the Optimized 

(7%) and the Total Cost Equals Total Benefit (7%) alternative and picks mpg levels that are 50 

percent of that difference. 

5: “Optimized (3%)”: An increase in the standard based upon availability of technologies and a 

marginal cost/benefit analysis, except that the mpg levels are set using a 3 percent discount rate 

for benefits. 

6: “Total Costs Equal Total Benefits (7%)”: An increase in the standard to a point where 

essentially total costs of the technologies added equals total benefits. In this analysis, for brevity, 

at times it is labeled “TC = TB (7%)”. 

7: “Technology Exhaustion (7%)”: An increase in the standard based upon the maximum usage 

(based on NHTSA’s perspective) of available technologies, disregarding the cost impacts. 
IV-1

IV. IMPACT OF OTHER FEDERAL MOTOR VEHICLE STANDARDS

ON FUEL ECONOMY 

Introduction

The Energy Policy and Conservation (EPCA or the Act) requires that fuel economy standards be 

set at the maximum feasible level after taking into account the following criteria: (1) 

technological feasibility, (2) economic practicability, (3) the impact of other Government 

Standards on fuel economy, and (4) the need of the Nation to conserve energy. Using MY 2010 

as a baseline, or the manufacturers’ plans already provided to NHTSA on specific rulemakings, 

this section discusses the effects of other government regulations on model year (MY) 2011 

passenger car and light truck fuel economy. 

The Impact on Weight of Safety Standards and Voluntary Safety Improvements 

The fuel economy impact of safety improvements will typically take the form of increased 

vehicle weight, which reduces the fuel economy of the vehicle. The manufacturer’s estimates of 

weight and fuel economy impact have already been included in their baseline fuel economy 

projections. In some instances the manufacturers’ weight estimates are similar to NHTSA’s, in 

some instances they are less than NHTSA’s, but often they are more than NHTSA’s. The 

agency’s estimates are based on cost and weight tear-down studies of a few vehicles and cannot 

possibly cover all the variations in the manufacturers’ fleets. NHTSA requested and various 

manufacturers provided estimates of increases in weight resulting from safety improvements. 

We have broken down our analysis of the impact of safety standards that might affect the MY 

2011 fleets into three parts: 1) those NHTSA final rules with known effective dates, 2) proposed 

rules or soon to be proposed rules by NHTSA, without final effective dates, and 3) currently 

voluntary safety improvements planned by the manufacturers. 

Weight Impacts of Required Safety Standards (Final Rules)

The National Highway Traffic Safety Administration (NHTSA) has issued two final rules on 

safety standards that become effective for passenger cars and light trucks for MY 2011. These 

have been analyzed for their potential impact on passenger car and light truck weights, using 

manufacturers’ voluntary plans as a baseline. 

1. FMVSS 126, Electronic Stability Control 

2. FMVSS 214, Side Impact Oblique Pole Test 
IV-2

FMVSS 126, Electronic Stability Control

The phase-in schedule for vehicle manufacturers is: 

Table IV-1 

Model Year Production Beginning Date Requirement 

2009 September 1, 2008 55% with carryover credit 

2010 September 1, 2009 75% with carryover credit 

2011 September 1, 2010 95% with carryover credit 

2012 September 1, 2011 All light vehicles 

The final rule requires 75 percent of all light vehicles to meet the ESC requirement for MY 2010, 

95 percent of all light vehicles to meet the ESC requirements by MY 2011, and all light vehicles 

must meet the requirements by MY 2012. 

The agency’s analysis of weight impacts found that ABS adds 10.7 lbs. and ESC adds 1.8 lbs. 

per vehicle for a total of 12.5 lbs. Based on manufacturers’ plans for voluntary installation of 

ESC, 85 percent of passenger cars in MY 2010 would have ABS and 52 percent would have 

ESC. Thus, the total incremental added weight over manufacturers’ plans in MY 2011 for 

passenger cars would be about 1.8 lbs. (0.10*10.7 + 0.43*1.8). Light trucks manufacturers’ 

plans show that 99 percent of all light trucks would have ABS and that 74 percent would have 

ESC by MY 2010. Thus, for light trucks the incremental weight impacts of adding ESC would 

be 0.4 lbs. (0.21*1.8) in MY 2011. 

FMVSS 214, Oblique Pole Side Impact Test

The phase-in requirements for the side impact test are as shown below in Table IV-2: 

Table IV-2 

FMVSS 214 Final Rule Phase-In Schedule 

Phase-in Date Percent of each manufacturer’s light vehicles that must comply 

during the production period 

September 1, 2010 to 

August 31, 2011 

20 percent (excluding vehicles GVWR > 8,500 lbs.) 

September 1, 2011 to 

August 31, 2012 

40 percent vehicles (excluding vehicles GVWR > 8,500 lbs.) 

September 1, 2012 to 

August 31, 2013 

60 percent vehicles (excluding vehicles GVWR > 8,500 lbs.) 

September 1, 2013 to 

August 31, 2014 

80 percent vehicles (excluding vehicles GVWR > 8,500 lbs.) 

On or after 

September 1, 2014 

All vehicles including limited line vehicles, except vehicles with 

GVWR > 8,500 lbs., alterers, and multi-stage manufacturers 

On or after 

September 1, 2015 

All vehicles, including vehicles with GVWR > 8,500 lbs., 

excluding alterers and multi-stage manufacturers 

On or after 

September 1, 2016 

All vehicles, including vehicles with GVWR > 8,500 lbs., alterers 

and multi-stage manufacturers 
IV-3

A teardown study of 5 thorax air bags resulted in an average weight increase per vehicle of 4.77 

pounds (2.17 kg).63 A second study64 performed teardowns of 5 window curtain systems. One 

of the window curtain systems was very heavy (23.45 pounds). The other four window curtain 

systems had an average weight increase per vehicle of 6.78 pounds (3.08 kg), a figure which is 

assumed to be average for all vehicles in the future. 

Based on manufacturers’ plans to voluntarily provide window curtains and torso bags, we 

estimate that 90 percent of passenger cars and light trucks would have window curtains for MY 

2010 and 72 percent would have torso bags. A very similar percentage is estimated for MY 

2011. Thus, the final rule requiring 20 percent compliance is not likely to impact manufacturers’ 

weights in MY 2011. 

Weight Impacts of Proposed/Planned Safety Standards

Proposed FMVSS 216, Roof Crush

On August 23, 2005, NHTSA proposed amending the roof crush standard to increase the roof 

crush standard from 1.5 times the vehicle weight to 2.5 times the vehicle weight65. The NPRM 

proposed to extend the standard to vehicles with a GVWR of 10,000 pounds or less, thus 

including many light trucks that had not been required to meet the standard in the past. The 

proposed effective date was the first September 1 occurring three years after publication of the 

final rule. A Supplemental NPRM was published by the agency in January 2008, asking for 

public comment on a number of issues that may affect the content of the final rule, including 

possible variations in the proposed requirements. In the PRIA, the average passenger car weight 

was estimated to increase by 4.0 pounds and the average light truck weight was estimated to 

increase by 6.1 pounds for a 2.5 strength to weight ratio. Based on comments to the NPRM, the 

agency believes that this weight estimate is likely to increase. However, the agency does not yet 

have an estimate for the final rule. Regardless, the final rule will not be effective for MY 2011 

vehicles. 

 Planned NHTSA initiative on Ejection Mitigation

The agency is planning on issuing a proposal on ejection mitigation. The likely result of the 

planned proposal is for window curtain side air bags (likely to be used to meet the FMVSS 214 

oblique pole test in all vehicles) to be larger and for a rollover sensor to be installed. Preliminary 

agency estimates are that current curtain bags need be widened by 28% to fully cover the 

window opening area. According to a cost & weight analysis (DOT HS 809 842), head air bags 

(loomed cloth) installed in a vehicle weigh 2.59 lbs and the inflators weigh 4.73 lbs. Thus, the 

incremental weight would be about 2 lbs. (2.59 lbs + 4.73 lbs) x 0.28 = 2 lbs. However, this 

analysis is not complete at this time and will not be effective for MY 2011 vehicles. 

Summary – Overview of Anticipated Weight Increases

 

63 Khadilkar, et al. “Teardown Cost Estimates of Automotive Equipment Manufactured to Comply with Motor 

Vehicle Standard – FMVSS 214(D) – Side Impact Protection, Side Air Bag Features”, April 2003, DOT HS 809 

809. 

64 Ludtke & Associates, “Perform Cost and Weight Analysis, Head Protection Air Bag Systems, FMVSS 201”, page 

4-3 to 4-5, DOT HS 809 842. 

65 See 70 FR 53753, the PRIA is in Docket No. 22143, entry #2 “Preliminary Regulatory Impact Analysis, FMVSS 

216, Roof Crush Resistance,” August 2005. 
IV-4

Table IV-3 summarizes estimates made by NHTSA regarding the weight added by the above 

discussed standards or likely rulemakings. NHTSA estimates that weight additions required by 

final rules and likely NHTSA regulations effective in MY 2011, compared to the MY 2010 fleet 

and manufacturers’ plans, will increase passenger car weight by at least 10.4 lbs. and light truck 

weight by at least 10.6 lbs. 

Table IV-3 

NHTSA Estimates of Weight Additions Due to Final Rules or Likely NHTSA Regulations for 

MY 2011 Compared to Manufacturers’ Plans 

Standard 

Added Weight 

in pounds 

Passenger Car

Added Weight 

in kilograms 

Passenger Car

Added Weight 

in pounds 

Light Trucks

Added Weight 

in kilograms 

Light Trucks

126 – ESC 1.8 0.8 0.4 0.2 

Based on NHTSA’s weight-versus-fuel-economy algorithms, a 3-4 pound increase in weight 

equates to a loss of 0.01 mpg in fuel economy. Thus, the agency’s estimate of the safety/weight 

effects for cars is 0.006 mpg or less and for light trucks is 0.001 mpg or less for already issued or 

likely future safety standards. 

CONFIDENTIAL SUBMISSIONS 

Weight Impacts of Potential Future Voluntary Safety Improvements 

At the time the agency requested information about fuel economy plans and capabilities for the 

future, the agency also requested information on weight increases that could occur due to safety 

improvements. Several manufacturers provided confidential information about plans they had to 

meet final rules, proposed safety standards, or to voluntarily increase safety for the years 2011-

2015. Several of these plans were to meet IIHS offset frontal and side impact testing. Most of 

these improvements will be installed on vehicles by MY 2011. [ ] The 

areas covered above and the regulatory areas described as final, proposed, and voluntary safety 

initiatives from manufacturers that have confidential increases for the period after MY 2010 are 

shown in the following tables. 
IV-5

[Table IV-4 

Confidential Submissions of Weight Impacts After MY 2010 

 Ford 

 Car MY Light Truck MY 

Final Rules 

2011 2012 2013 2014 2015 

Total

2011 2012 2013 2014 2015 

Total

126 ESC 

214 Side Impact 

Total Final Rule 

Increments 

Proposed Rules 

216 Roof Crush 

226 

Ejection 

Mitigation 

Total Proposed Rule 

Increments 

Voluntary and Other 

Rules 

202a Head Restraints 

TBD Ped. Protection 

TBD 

Public Domain 

ratings (TBD for 

finer details) 

 EDR part 563 

N/A Voluntary 

N/A Other 

Total Voluntary and 

Other Rule Increments 

 Total by Year 
IV-6

 Chrysler 

 Car MY Light Truck MY 

Final Rules 

2011 2012 2013 2014 2015 

Total

2011 2012 2013 2014 2015 

Total

126 ESC 

214 Side Impact 

Total Final Rule 

Increments 

Proposed Rules 

216 Roof Crush 

226 

Ejection 

Mitigation 

Total Proposed Rule 

Increments 

Voluntary and Other 

Rules 

202a Head Restraints 

TBD Ped. Protection 

TBD 

Public Domain 

ratings (TBD for 

finer details) 

 EDR part 563 

N/A Voluntary 

N/A Other 

Total Voluntary and 

Other Rule Increments 

 Total by Year 
IV-7

 GM 

 Car MY Light Truck MY 

Final Rules 

2011 2012 2013 2014 2015 

Total

2011 2012 2013 2014 2015 

Total

126 ESC 

214 Side Impact 

Total Final Rule 

Increments 

Proposed Rules 

216 Roof Crush 

226 

Ejection 

Mitigation 

Total Proposed Rule 

Increments 

Voluntary and Other 

Rules 

202a Head Restraints 

TBD Ped. Protection 

TBD 

Public Domain 

ratings (TBD for 

finer details) 

 EDR part 563 

N/A Voluntary 

N/A Other 

Total Voluntary and 

Other Rule Increments 

 Total by Year 

] 
IV-8

Vehicle Weight, Size and Safety 

For many years there has been a controversy over the effect of vehicle size and weight on vehicle 

safety. With each fuel economy rulemaking, the debate continues. The following discussion 

provides NHTSA’s point of view, the most serious comments on the issue, and NHTSA’s 

response to those comments. 

 

NHTSA believes that an attribute based Reformed CAFE system removes the incentive to 

downsize that is inherent in the traditional fleet-wide CAFE flat standard requirement. The 

agency believes that the attribute based standard is likely to have beneficial impacts on safety 

compared to the flat standard. Other things being equal, smaller vehicles provide less protection 

to their occupants in the event of a crash because there is less vehicle mass to absorb the crash 

energy and less interior space to buffer occupants from sheet metal intrusion. In addition, 

smaller vehicles are generally more likely to roll over. In single vehicle crashes, smaller vehicles 

are less safe than larger vehicles. When you hit a tree, more weight helps you knock that tree 

down and reduce your delta V, and more interior space allows you to ride down the crash safer. 

In multi-vehicle crashes, both individual vehicle size and the relative size of the involved 

vehicles play a role in determining the injury outcome of occupants of both vehicles. Generally, 

larger vehicles will provide better protection, but often at the expense of occupants of smaller 

vehicles. If larger vehicles were to be reduced in size, it would likely decrease the chance of 

injury in crashes with smaller vehicles, but it would also likely increase the chance of injury for 

the occupants of the larger vehicles. The makeup of any future mix-shifts in vehicle sales is 

purely speculative and the overall impact on injuries in multi-vehicle crashes of any future mixshifts in vehicle size is unknown. However, downsizing is likely to increase the crash risk for 

vehicle occupants in single vehicle crashes, which make up 30% of all crashes and 57% of all 

fatalities. An attribute based system will require improvements in fuel economy for all vehicle 

sizes, and will thus minimize incentives to downsize vehicles. There may be other incentives for 

consumers to demand smaller vehicles (for example, an increase in the price of gasoline), but 

those external factors would not be influenced by the final rule structure. 

We would like to clarify that our analysis does not mandate weight reduction, or any specific 

technology application for that matter. Our analysis relied exclusively on other fuel-saving 

technologies for passenger cars and only applied weight reduction to light trucks that have a curb 

weight greater than 5,000 lbs. to demonstrate that manufacturers can comply with the fuel 

economy levels without the need for what NHTSA believes are potentially unsafe compliance 

measures. 

 

We first present a recent historical perspective of the debate:

The NAS study (2002) 

The 2002 National Academy of Sciences (NAS)66 report made explicit links between weight and 

vehicle safety. The NAS study conclusions were divided, with 11 of 13 committee members 

 

66 “Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards”, National Research 

Council, 2002. The link for the NAS report is http://www.nap.edu/books/0309076013/html/
IV-9

representing the majority view and 2 of 13 the minority view. The findings of the majority 

presented on page 77 were: 

“In summary, the majority of the committee finds that the downsizing and weight reduction that 

occurred in the late 1970s and early 1980s most likely produced between 1,300 and 2,600 crash 

fatalities and between 13,000 and 26,000 serious injuries in 1993. The proportion of these 

casualties attributable to CAFE standards is uncertain. It is not clear that significant weight 

reduction can be achieved in the future without some downsizing, and similar downsizing would 

be expected to produce similar results. Even if weight reduction occurred without any 

downsizing, casualties would be expected to increase. Thus, any increase in CAFE as currently 

structured could produce additional road casualties, unless it is specifically targeted at the 

largest, heaviest light trucks.” ... 

“Some might argue that this improving safety picture means that there is room to improve fuel 

economy without adverse safety consequences. However, such a measure would not achieve the 

goal of avoiding the adverse safety consequences of fuel economy increases. Rather, the safety 

penalty imposed by increased fuel economy (if weight reduction is one of the measures) will be 

more difficult to identify in the light of the continuing improvement in traffic safety. Just 

because these anticipated safety innovations will improve the safety of vehicles of all sizes does 

not mean that downsizing to achieve fuel economy improvements will have no safety costs. 

If an increase in fuel economy is effected by a system that encourages either downweighting or 

the production and sale of more small cars, some additional traffic fatalities would be expected. 

Without a thoughtful restructuring of the program, that would be the trade-off that must be made 

if CAFE standards are increased by any significant amount.” 

The minority view summarized on page 123 was: 

 “The relationship between vehicle weight and safety are complex and not measurable 

with any reasonable degree of certainty at present. The relationship of fuel economy to safety is 

even more tenuous. But this does not mean that there is no reason for concern. Significant fuel 

economy improvements will require major changes in vehicle design. Safety is always an issue 

whenever vehicles must be redesigned. 

 In addition, the distribution of vehicle weights is an important safety issue. Safety 

benefits should be possible if the weight distribution of light-duty vehicles could be made more 

uniform, and economic gains might result from even partly correcting the negative externality 

that encourages individuals to transfer safety risks to others by buying ever larger and heavier 

vehicles. 

 Finally, it appears that in certain kinds of accidents, reducing weight will increase safety 

risk, while in others it may reduce it. Reducing the weights of light-duty vehicles will neither 

benefit nor harm all highway users, there will be winners and losers....” 

The Kahane Study (NHTSA - 2003) 

The Kahane study67 estimates the effect of 100-pound reductions in heavy light trucks and vans 

(LTVs), light LTVs, heavy passenger cars, and light passenger cars. It compares the fatality 

rates of LTVs and cars to quantify differences between vehicle types, given drivers of the same 

 

67 “Vehicle Weight, Fatality Risk and Crash Compatibility of Model Year 1991-99 Passenger Cars and Light 

Trucks”, Charles J. Kahane, Ph. D., NHTSA, October 2003, DOT HS 809-662. 
IV-10

age/gender, etc. In this analysis, the effect of “weight reduction” is not limited to the effect of 

mass per se but includes all the factors that were naturally or historically confounded with mass 

in 1991-1999 cars, such as length, width, structural strength and size of the occupant 

compartment. The rationale here is that when you add length, width or strength to a car, you will 

also make it heavier. The one exception could be a sweeping replacement of existing materials 

with light, high-strength components. But when you are looking at historical data – at cars of a 

certain era (namely, 1991-1999), they tend to be built in similar ways, and there is essentially a 

continuum from lighter and smaller cars to heavier, bigger and stronger cars. 

Some of its findings are: 

 “Heavy vehicles had lower fatality rates per billion miles of travel than lighter vehicles of 

the same general type. When two vehicles collide, the laws of physics favor the occupants on 

the heavier vehicle (momentum conservation). Furthermore, heavy vehicles were in most cases, 

longer, wider and less fragile than light vehicles. In part because of this, they usually had greater 

crashworthiness, structural integrity and directional stability. They were less rollover-prone and 

easier for the average driver to control in a panic situation. In other words, heavier vehicles 

tended to be more crashworthy and less crash-prone. Some of the advantages for heavier 

vehicles are not preordained by the laws of physics, but were nevertheless characteristic of the 

MY 1991-99 fleet. Offsetting those advantages, heavier vehicles tended to be more aggressive in 

crashes, increasing risk to occupants of the vehicles they collide with.” 

Six different crash modes were analyzed (principal rollover, fixed object, 

pedestrian/bicycle/motorcyclist, and multi-vehicle crashes with heavy truck, light trucks, and 

passenger cars). Summing all these crash modes together, the net annual effects per 100-pound 

weight reduction were: 

For passenger cars weighing less than 2,950 pounds – fatalities increased by 597 

For passenger cars weighing 2,950 pounds or more – fatalities increased by 216 

For light trucks weighing less than 3,870 pounds – fatalities increased by 234 

For light trucks weighing 3,870 pounds or more – fatalities increased by 71 

In all cases, annual fatalities increased with a reduction in weight. However, further analysis of 

the Kahane study found that the net safety effect of removing 100 pounds from a light truck is 

zero for the group of all light trucks with a curb weight greater than 3,900 lbs. 68 Given the 

significant statistical uncertainty around that figure, we determined that there is a crossover 

weight, which occurs somewhere between 4,264 and 6,121 pounds, with a point estimate at 

5,085 pounds, above which there is no safety penalty for reducing vehicle weight. This is 

because the added harm for other road users from the additional weight exceeds any benefits for 

the occupants of the vehicles. NHTSA embodied this finding in its CAFE rulemaking by 

restricting materials substitution in its development of stringency levels to vehicles over 5,000 

pounds and used 5,000 lbs. as the threshold for considering weight reduction of specific models. 

In the MY 2008-2011 light truck final rule, NHTSA included weight reduction as a fuel 

improving technology for light trucks over 5,000 lbs. curb weight where we determined that 

 

68Kahane, Charles J., PhD, Vehicle Weight, Fatality Risk and Crash Compatibility of Model Year 1991-99 

Passenger Cars and Light Trucks, October 2003. DOT HS 809 662. Page 161. Docket No. NHTSA-2003-16318 

(http://www.nhtsa.dot.gov/cars/rules/regrev/evaluate/pdf/809662.pdf)
IV-11

weight reduction would not reduce overall safety and would be a cost-effective choice. We are 

applying the same methodology in this final rule, weight reduction is considered a technology 

that can be applied to light trucks over 5,000 lbs. curb weight. 

The agency believes a number of conclusions can be drawn from these studies: 

• Heavier vehicles are more crashworthy and less crash prone.69 

• The net impacts on safety, considering the six different crash modes, of reducing weight 

are negative for all but the larger light trucks. However, this type of analysis can not 

examine extreme cases. For example, if there were a large mix shift from 50 percent 

passenger car and 50 percent light truck sales, to 80 percent compact or smaller passenger 

cars and 20 percent pickup truck sales, this analysis cannot determine the net impacts on 

safety. Nothing in the manufacturer’s plans suggests a drastic change in the mix of 

vehicles, nor is there any incentive, in our opinion, for such a change based on NHTSA’s 

attribute based final rule on fuel economy. 

• Lighter vehicles fare worse in single vehicle collisions. In 2006, 57 percent of all 

passenger car and light truck fatalities were in single vehicle crashes and 43 percent were 

in multi-vehicle crashes. Fatalities are almost split between rollovers (29 percent) and 

fixed or non-fixed objects (28 percent). 

• Reducing weight increases the likelihood of rolling over. When you are sliding sideways 

and digging into mud or grass or hit a curb, all things being equal, the lighter vehicle is 

more prone to rolling over. Increasing track width (part of the footprint calculation) 

reduces the likelihood of rolling over. Track width is more important than weight for 

rollovers. Rollover is the only area in which track width is the most important factor. 

Weight is more important than track width or wheelbase in the other five crash modes 

investigated.70 

• Reducing weight increases the likelihood of being killed in a fixed or non-fixed object 

crash. If you run into a tree, you are safer if you knock that tree down than if the tree 

stops your vehicle. A heavier vehicle has a better chance of knocking the tree down. 

The Kahane report also examined the total fatality crash rates in all crash modes; including 

fatalities to occupants of the case vehicle (i.e. in rollovers, single vehicle and multi-vehicle 

crashes), occupants of the other vehicle it collided with (to account for aggressive vehicles) and 

pedestrians. Kahane used VMT data based on CDS odometer readings and controlled for age 

and gender based on State data on nonculpable crash involvements (induced exposure). With 

these controls, the societal fatality rates per billion miles were: 

 

69 See Kahane study, page xiv Table 3 for prorated fatal crash involvements per billion miles. 

70 See Kahane (Docket No. 2003-16318-16) 
IV-12

TABLE IV-5 

ADJUSTED FATAL-CRASH INVOLVEMENT RATES 

PER BILLION CASE VEHICLE MILES, BY VEHICLE TYPE 

(Case vehicles are MY 1996-99 light trucks and 4-door cars with air bags in CY 1996-2000, 

adjusted for age/gender, rural/urban, day/night, speed limit, and other factors) 

 

 Average Fatal 

 Curb Crash Involvements 

Vehicle Type and Size Weight Per Billion Miles 

Very small 4-door cars 2,105 15.73 

Small 4-door cars 2,469 11.37 

Mid-size 4-door cars 3,061 9.46 

Large 4-door cars 3,596 7.12 

Compact pickup trucks 3,339 11.74 

Large (100-series) pickup trucks 4,458 9.56 

Small 4-door SUVs 3,147 10.47 

Mid-size 4-door SUVs 4,022 13.68 

Large 4-door SUVs 5,141 10.03 

Minivans 3,942 7.97 

In other words, mid-size cars had somewhat lower societal fatal crash rates than SUVs that 

weighed considerably more. Large cars and minivans had the lowest rates. 

The DRI Studies (2003, 2004, 2005) 

Honda sponsored DRI to complete several reports, which it asserted demonstrated that limited 

weight reductions would not reduce safety and could possibly decrease overall fatalities. Honda 

stated that the 2003 study by DRI found that reducing weight without reducing size slightly 

decreased fatalities, and that this was confirmed in a 2004 study by DRI71 that assessed new data 

and methodology changes in the 2003 Kahane Study. Honda asserted that the DRI results tend to 

confirm “that curb weight reduction would be expected to decrease the overall number of 

fatalities.” 

DRI submitted an additional study, Supplemental Results on the Independent Effects of Curb 

Weight, Wheelbase, and Track Width on Fatality Risk in 1985-1998 Model Year Passenger Cars 

and 1985-1997 Model Year LTVs, Van Auken, R.M. and J. W. Zellner, May 20, 2005 (Docket 

No. 2003-16128-1456). This DRI study concluded that reductions in footprint are harmful to 

safety, whereas reductions in mass while holding footprint constant would benefit safety. The 

DRI study disagreed with NHTSA’s finding that mass had greater influence than track width or 

wheelbase on the fatality risk of passenger cars in non-rollover crashes. 

 

71 See Docket Nos. 2003-16318-2, 2003-16318-3, 2003-16318-7, and 2003-16318-17. 
IV-13

NHTSA disagrees with the numerical findings of the DRI reports on the safety effects of mass, 

track width and wheelbase. As a consequence, we also cannot endorse the inferences by Honda 

and others, based on those reports, that mass reductions in small cars are harmless as long as we 

maintain wheelbase and track width or even as long as we limit the reductions to material 

substitution (although we agree those seem to be the least harmful ways to lose mass). 

DRI has over the years issued various analyses of historic fatal crash rates with three measures of 

cars size – curb weight, track width and wheelbase – treated as if they were three independent 

variables.72 In general, the results are that reductions in track width and wheelbase are 

associated with substantial increases in fatal crash risk, whereas reduction in mass per se, if track 

width and wheelbase are held constant, is associated with reductions in risk. Based in part on 

these analyses, Honda and various others have inferred that future mass reductions, while track 

width and wheelbase remained unchanged – by substituting lighter materials of equal strength or 

by other means – would apparently benefit safety.73

NHTSA is generally skeptical of analyses that include mass, track width and wheelbase as 

separate independent variables. Although it is true that, for any given curb weight, there may be 

some variations in the track widths and wheelbases of make-models at that curb weight, these 

variations are not, as it were, random but are usually confounded with other factors such as the 

vehicle’s design or market class. Specifically, sporty 2-door coupes such as Ford Mustang and 

Chevrolet Camaro have exceptionally short wheelbase for their mass. They also have 

exceptionally high fatal crash rates. Inclusion of sporty 2-door coupes in the analysis produces a 

finding that higher wheelbase increases safety but higher mass decreases safety. These findings 

are spurious unless you sincerely believe either: (a) the high fatality rates of Mustang and 

Camaro are due to their short wheelbases and have nothing to do with their drivers’ speeding, 

drinking and risk-taking – or (b) it is the short wheelbases of Mustangs and Camaros that impels 

their drivers to drink, speed and take risks, and if you transplanted these drivers to Grand 

Marquis and LeSabres they would become safe, prudent, and sober. 

Therefore, NHTSA restated in its response to public comments74 on its 2003 weight-safety report 

that it is imperative that analyses be limited to a set of make-models that do not vary greatly in 

style and market class, but rather represent a gradually varying continuum of lighter to heavier 

cars used for similar purposes – namely, 4-door sedans or station wagons excluding police cars. 

In their most recent, 2005 analysis, DRI agreed, at least for comparison purposes, to limit some 

of their analyses to 4-door cars excluding police cars.75 DRI further claimed that they could now 

mimic NHTSA’s logistic regression approach for an analysis of MY 1991-1998 4-door cars in 

CY 1995-1999 crashes. DRI claimed this new analysis still showed results directionally similar 

to their earlier work – increased risk for lower track width and wheelbase, reduced risk for lower 

mass – although the wheelbase and mass effects were no longer statistically significant after 

removing the 2-door cars from the analysis. 

 

72 Docket No. NHTSA-2003-16318-7, Docket No. NHTSA-2003-16318-17. 

73 http://www.arb.ca.gov/cc/ccms/meetings/042108/4_21_current_techn_4_german.pdf 74 Docket No. NHTSA-2003-16318-16. 

75 Docket No. NHTSA-2003-16318-17. 
IV-14

The actual numbers – DRI vs. NHTSA 

In MY 1991-1998, the average car weighing N+100 pounds had .34 inches larger track width 

and 1.01 inches longer wheelbase than the average car weighing N pounds. Thus, you might say 

the “typical” or “historical” 100-pound weight reduction would have been accompanied by a .34 

inch track-width reduction and a 1.01 inch wheelbase reduction. But if you disassociate these 

three measures and treat them as independent parameters, DRI’s logistic regression of MY 1991-

1998 4-door cars excluding police cars attributes the following effects: 

DRI 

Reduce mass by 100 pounds 379 fewer fatalities

Reduce track width by .34 inches 1000 more fatalities 

Reduce wheelbase by 1.01 inches 207 more fatalities 

Reduce mass by 100 lb., track by .34” and WB by 1.01” 828 more fatalities 

Now, DRI may claim to have mimicked our database and analysis method, but clearly their data 

are not the same as NHTSA’s or their analysis is not the same. Because if you apply NHTSA’s 

logisitic regression analyses to NHTSA’s database, exactly as described in the agency’s response 

to comments on its 2003 report,76 except for limiting the data to MY 1991-1998 (instead of 

1991-1999), just as DRI did, the effects are not at all like DRI’s: 

NHTSA 

Reduce mass by 100 pounds 485 more fatalities 

Reduce track width by .34 inches 334 more fatalities 

Reduce wheelbase by 1.01 inches 9 more fatalities 

Reduce mass by 100 lb., track by .34” and WB by 1.01” 828 more fatalities 

That is the principal reason we cannot accept DRI’s results or the inferences that Honda or 

anybody else makes from DRI’s results: we get quite different results when we apply our 

analysis to our database, even when we make the analysis as similar to DRI’s as possible. DRI 

may have tried to mimic our results, but they’re obviously doing something differently. 

Intuitively, weight reductions that (1) hold track width and wheelbase constant and (2) are the 

result of materials substitution are likely to be less harmful to safety than other types of weight 

reductions. But because we disagree with DRI’s numerical results, we cannot conclude at this 

point that such weight reductions would be intrinsically harmless, let alone beneficial, if applied 

to small cars. 

Even though our analyses continue to attribute a much larger effect for mass than for track 

width or wheelbase in small cars, we still do not claim that mass per se is the “magic bullet” 

that increases or decreases fatality risk in non-rollover crashes. There might not be any 

single magic bullet, but rather mass and a variety of other factors historically correlated with 

mass. The importance of our analyses is that they do not corroborate the “easy way out” 

offered by DRI: that track width and wheelbase explain the entire size-safety effect and then 

some, and that mass can be reduced without any harm and maybe even with a benefit. Our 

 

76 Docket No. NHTSA-2003-16318-16. 
IV-15

results show, until we have a better understanding of all the size-related factors that affect 

safety, we cannot assume that mass reductions in small cars are harmless as long as we 

maintain wheelbase and track width or even as long as we limit the reductions to material 

substitution (although we agree those seem to be the least harmful ways to lose mass). 

While NHTSA agrees that limited weight reduction to heavier vehicles will not reduce safety, we 

disagree with DRI’s overall conclusion, cited by Honda, that weight reductions while holding 

footprint constant would significantly benefit safety in lighter vehicles. NHTSA’s analyses of 

the relationships between fatality risk, mass, track width and wheelbase in 4-door 1991-1999 

passenger cars (Docket No. 2003-16318-16) found a strong relationship between track width and 

the rollover fatality rate, but only a modest (although significant) relationship between track 

width and fatality rate in non-rollover crashes. Even controlling for track width and wheelbase – 

e.g., by holding footprint constant – weight reduction in the lighter cars is strongly, significantly 

associated with higher non-rollover fatality rates in the NHTSA analysis. By contrast, the DRI 

study of May 20, 2005 analyzed 4-door cars and found a strong relationship between track width 

and fatality risk, and non-significant associations of mass and wheelbase with fatality risk 

(Docket No. 2005-22223-78, p. 31). In other words, when DRI analyzed the same group of 

vehicles as NHTSA, they did not get the same results. 

The agency continues to believe that weight reduction in lighter vehicles would reduce safety. 

However, we also believe that weight reductions in the heavier light trucks, while holding 

footprint constant, will not likely result in a net reduction in safety. In our opinion, it is 

impossible to reduce weight and maintain footprint unless you (a) substitute light for heavy 

materials in a big way or (b) remove features that customers want and are willing to pay for. In 

that sense, DRI’s contention that weight is unimportant could only be true for material 

substitution, because under present circumstance weight reduction usually also means size 

reduction, and DRI agrees with NHTSA that a reduction in footprint is harmful to safety. 

Important Comments to Previous Dockets 

General Motors (Docket No. 2005-22223-1493) and the Alliance (Docket No. 2005-22223-1642) 

were more explicit in their concerns over the safety impact associated with weight reduction. 

The Alliance stated that the fundamental laws of physics dictate that smaller and/or lighter 

vehicles are less safe than larger/heavier counterparts with equivalent safety designs and 

equipment. General Motors agreed that improvements in material strength, flexibility, and 

vehicle design have helped improve overall vehicle and highway safety. But, General Motors 

added, for a given vehicle, reducing mass generally reduces net safety. Further, General Motors 

stated that it does not intentionally reduce mass by replacing it with advanced materials, 

presuming that such action alone will result in improved protection for the occupants in a lighter 

vehicle; instead GM continues to believe that vehicles with larger mass will provide better 

protection to occupants involved in a crash than a vehicle of the same design with less mass, 

given equivalent crashes. 

General Motors also questioned the agency’s reliance on a 5,000 lbs. minimum vehicle weight 

for considering weight reduction, which was based on the finding of the 2003 Kahane report. 

General Motors stated that the agency’s conclusion is inconsistent with the sensitivity analysis 
IV-16

performed by William E. Wecker Associates, Inc.77 and submitted to the ANPRM docket. 

General Motors stated that the inflection point on the Wecker report’s graph for General Motors 

light trucks in both the periods of MYs 1991-1995 and MYs 1996-1999 is higher than 5,000 

pounds. 

Additionally, General Motors stated that the NPRM did not acknowledge or respond to the main 

point of the Wecker report, which was that Dr. Kahane’s “analysis alone does not support the 

proposition that a crossover weight at or near 5,085 pounds is a robust, accurate description of 

the field performance of the fleet.” 

We believe that General Motors was confusing the 5,085 lbs. crossover weight (where the safety 

effect of mass reduction in a vehicle weighing exactly 5,085 lbs., is zero) with the breakeven 

point, which is the point where the total effect of reducing all vehicles heavier than the 

breakeven weight by an equal amount is zero. NHTSA estimated that the breakeven point as 

described in the NPRM is 3,900 lbs., if footprint is held constant. 

If the 3,900 lbs. estimate were perfectly accurate, we would be confident that weight reductions 

in vehicles down to 3,900 pounds would not result in net harm to safety. However, there is 

considerable uncertainty about the crossover weight and also the breakeven point. Therefore, in 

our analysis, we limited weight reduction to vehicles with a curb weight greater than 5,000 

pounds. We believe that the 5,000 lbs. limit is sufficient so that we can be confident that such 

weight reductions will not have net harm on safety. 

Advocates for Highway and Auto Safety commented that Kahane’s (NHTSA’s) 2003 analysis 

may not apply if the effects of size and weight reductions are disaggregated, “weight reductions 

without corresponding reductions in vehicle wheelbase length and track width could be expected 

to produce net benefits in reducing occupant crash risks.” This is essentially the DRI argument. 

NHTSA’s response is that Footprint (especially track width) is an important variable in terms of 

a vehicle’s propensity for rollovers, a type of crash that accounts for 29 percent of all light 

vehicle occupant traffic fatalities. Track width is one of the two vehicle properties that define 

Static Stability Factor (SSF). SSF was used as a single predominant factor to predict rollover 

rate in the agency’s original rollover NCAP, and it is still the most powerful element in the 

agency’s current rollover NCAP risk model that also factors in a road maneuver test. Wheelbase 

does not have a direct effect on rollover resistance. However, there are hypotheses that an 

increase in wheelbase could reduce loss-of-control crashes by making the vehicle react slower in 

yaw and thereby reduce the number of single-vehicle pavement departure crashes that produce 

most rollovers. Currently, the agency does not have any data to substantiate this theory.78 

Environmental Defense (Docket No. 2005-22223-1805) commented that by limiting the use of 

weight reduction to heavier vehicles, the agency disregarded the likelihood that manufacturers 

would rely on weight reduction in smaller, lighter vehicles. Environmental Defense suggested 

that the improved baselines should reflect this weight reduction strategy. 

 

77 Docket No. 2003-16128-1112 

78 See Kahane (Docket No. 2003-16318-16) 
IV-17

Environmental Defense asserted that weight reduction is among the most common and costeffective options available to manufacturers for improving vehicle fuel economy across the light 

truck fleet. Environmental Defense referenced estimates presented in DeCicco (2005) that 

suggest that the cost per pound of weight reduced through use of high-strength steel and 

advanced engineering techniques has been as low as, or lower than, 31 cents per pound reduced. 

Moreover, Environmental Defense stated, the exclusion of mass reduction in NHTSA’s analysis 

bears no relation to what will actually happen in the marketplace when standards are 

implemented. Environmental Defense argued that absent safety regulations prohibiting the use 

of mass reductions, manufacturers are likely to choose this compliance alternative in vehicles of 

all weights as a cost-effective way to comply with CAFE. Environmental Defense stated that 

NHTSA should consider the potential for mass reduction among its compliance alternatives for 

all light trucks. 

 

As stated above, the agency does not dictate which fuel-savings technologies must be applied to 

vehicles. Mass reduction is a compliance alternative for all light vehicles. However, one of 

NHTSA’s considerations in setting fuel economy standards is to set standards that will not force 

the manufacturers to reduce safety. The standards set by the agency are those capable of being 

achieved by the manufacturers without the need to reduce safety. If the agency were to consider 

weight reduction as a compliance option, we are concerned that the resulting increased 

stringency would force unsafe downweighting. 

A group of experts at a workshop sponsored by the International Council on Clean 

Transportation (ICCT) examined many of the size/safety reports and wrote a June 2007 report 

“Sipping Fuel and Saving Lives: Increasing Fuel Economy Without Sacrificing Safety.”79 

NHTSA agrees with two of the three ICCT report findings. We agree that fuel economy 

technologies exist that don’t affect safety. We agree that reducing weight (on vehicles over 5, 

000 lbs) can make certain vehicles less aggressive and reduce their weight and probably improve 

safety. Many, but not all of the experts at the workshop, agreed with the last conclusion: 

“Advanced technologies can decouple size from mass, creating important new possibilities for 

increasing fuel economy and safety without compromising functionality”. We continue to 

believe, until someone demonstrates to the contrary with some kind of rigorous, scientific 

analysis, that reducing weight on smaller lighter vehicles will only make them more dangerous in 

single-vehicle crashes, because of fundamental physics. 

A study examined similar safety issues - “The “Arms Race” on American Roads: The Effect of 

Sport Utility Vehicles and Pickup Trucks of Traffic Safety”, Michelle J. White, University of 

California San Diego, Journal of Law and Economics, Volume XLVII, October 2004. The 

White paper finds that “When drivers shift from cars to light trucks or SUVS, each crash that 

involves fatalities from light truck or SUV occupants that is prevented comes at a cost of at least 

4.3 additional crashes that involve deaths of car occupants, pedestrians, bicyclists, or 

motorcyclists.” 

 

79 See www.theicct.org/documents/ICCT_SippingFuelFull_2007.pdf 
IV-18

The White study is an analysis of NHTSA’s National Automotive Sampling System, General 

Estimates System and, as such, looks at the fatality risk given that a crash occurred. However, it 

does not control for VMT (likelihood of a crash given a mile of driving). Furthermore, the study 

does not address the safety of big cars vs. small cars or big LTVs versus small LTVs. Whether 

overall safety would be improved by shifting sales from SUV and pickups to passenger cars 

depends on what size of passenger cars you shifted to (see the table above), if you shifted to 

small or very small passenger cars, overall safety would decrease. 

Another study examined the size/safety issues – “The Fatality Risks of Sports Utility Vehicles, 

Vans, and Pickups Relative to Cars”, Ted Gayer, Georgetown University, The Journal of Risk 

and Uncertainty, 28-2, 103-133, 2004. This study finds that “Using a cross-sectional variation in 

snow depth as an instrument to determine VMT, the results suggest that light trucks are 2.63 to 

4.00 times more likely to crash than cars.” “...once one adjusts for the greater frequency of 

crashes by light trucks, the aggregate risk they pose substantially dominates the risk from cars. 

Indeed a world of light trucks would lead to three to ten times more fatalities than a world of 

cars.” 

This study does not address the safety of big cars vs. small cars or big LTVs versus small LTVs. 

This analysis using snow depth exaggerates the difference in crash frequency and fatality rates 

between passenger cars and light trucks. Kahane’s study also adjusted the raw data for VMT, 

but we have used odometer readings by age of vehicle to control for VMT and found no such 

discrepancy in crash rates. The table above from the Kahane study does not show light trucks 

having substantially higher fatality rates than passenger cars. 

A 2001 study by Dr. Leonard Evans,80 modeled the risk of driver fatality in car 1 in a head-on 

collision with car 2. The equations in the report indicate that reducing the curb weight of car 1 

would increase the risk to the driver of car 1, while reducing the curb weight of car 2 would 

decrease the risk to the driver of car 1. However, the equations also indicate that reducing the 

wheelbase of either car increases the total risk to both drivers. 

In a 2004 SAE paper, Dr. Evans claimed that increasing the amount of lightweight materials in 

vehicle design can provide reduced occupant risk both in two-vehicle and single-vehicle crashes, 

and also reduce risk for occupants in other vehicles81. However, he produced no analysis using 

real world data of vehicles with lightweight material to substantiate that claim82. 

In an amicus brief, the Insurance Institute for Highway Safety83stated “Crash safety should be a 

consideration in how the balance is struck between programs to improve air quality and our 

efforts to protect people in crashes. Physics dictates that vehicle weight and size will always 

matter in a crash. Research in the private, public, and nonprofit sectors have demonstrated the 

 

80 Evans, L., “Causal Influence of Car Mass and Size on Driver Fatality Risk”, American Journal of Public Health, 

Vol. 91, No. 7, July 2001, pp 1076-1081. 81 Evans, L., “How to make a car lighter and safer,” SAE 2004-01-1 172, Society of Automotive Engineers, 11 

March 2004. 

82 In NHTSA’s opinion, there are not enough vehicles made from lightweight material on the road to support an 

analysis using real world crash data. 

83 Filed in the United States Court of Appeals for the Second Circuit, March 21, 2008, No. 07-4342-cv(L), March 

21, 2008, Green Mountain Chrysler Plymouth Jeep..., by Michele Fields and Stephen L. Oesch of IIHS. 
IV-19

relationship between vehicle size and weight and crash injuries. Simply put, Vermont’s 

regulation encourages production of smaller, lighter vehicles which will lead to increased traffic 

fatalities.” IIHS discusses research by NHTSA and IIHS that have led to the conclusion that 

“Vehicle downsizing has compromised safety because in most cases, smaller and lighter vehicles 

are less protective of their occupants than larger, heavier vehicles.” IIHS calculated the vehicle 

death rates by make model using driver deaths per million registered vehicle years, presented this 

data, and ranked them. “None of the 15 vehicles with the lowest driver death rates were mini or 

small models. ... Eleven of the 16 vehicles with the highest driver death rates were small cars 

and none were large or very large. ... The pattern is unmistakable. There is an inverse 

relationship between driver death rates and vehicle size...” 

Comments to the NPRM Docket 

In this section we present and discuss the comments to the NPRM Docket (2008-0089). 

Comment: Insurance Institute for Highway Safety (IIHS) 2008-0089-220.1, P1-2 

IIHS was concerned that a manufacturer may increase footprint rather than add technology, or 

they could reduce mass, while keeping same footprint. The use of vehicle footprint will mitigate 

much of the potential for automakers to downweight or downsize vehicles to improve fuel 

economy and, hence, will help maintain the safety benefits associated with those attributes. IIHS 

believe that weight is a better discriminator (more direct approach) than footprint and that 

reducing vehicle mass typically reduces crashworthiness. Automakers could use lighter 

materials, maintaining the same size and structural performance, thus limiting the safety 

consequences. 

Agency Response: We agree with most of IIHS’s statements except that we believe footprint is a 

better attribute than weight for setting the MY 2011 CAFE standards. 

Comment: Air Resources Board, (2008-0089-0173), pp 6-7 

The Air Resource Board state that NHTSA should expand the use of weight reductions to 

vehicles under 5,000 pounds. They were struck by apparent dichotomy between adopting size 

attribute to promote vehicle safety, but yet restrict weight reduction to vehicles under 5,000 

pounds. NHTSA relies on the Kahane study (which assumes that weight and size are completely 

correlated), but ignores more recent studies by Dynamic Research Inc. that have shown 

otherwise. Pg. 2 - Expert report by David Greene (Ahmad and Greene 2005) concludes that 

there has been no relationship between fuel economy and traffic fatalities and there should be 

none in the future. 

Agency Response: The relationship is entirely too complex to examine by a macro analysis as 

was completed by Ahmad and Greene. This report is a long-term (1966-2002) time-series 

analysis of the annual number of crash fatalities in the United States, the average fuel economy 

of the vehicles on the road that year, and some other factors such as the price of fuel, the national 

speed limit, population, and annual vehicle miles traveled. The conclusion is that national 

fatalities did not increase, in fact tended to decrease, from the early 1970s forward, while fuel 

economy improved. Therefore, fuel economy has not had an adverse effect on safety. Suffice it 

to say that this is an exceedingly “macro” level to examine the relationships between fuel 
IV-20

economy and fatality risk. Long-term time-series analyses are unlikely to separate the effects of 

downsizing for the other demographic, economic, and technological trends that have had an 

impact on fatality rates over the period. For instance, seat belt use has risen from 14 percent to 

82 percent, many life-saving safety features (e.g., front and side airbags) have been added to 

vehicles, impaired driving is not as accepted, and so forth. It is general knowledge that traffic 

fatalities are now lower than 1970, primarily as a result of the major safety advances just 

mentioned. But the relevant question in the safety/fuel economy context is, “Would fatalities 

have been even lower if cars had not been downsized?” To analyze that relationship accurately, 

it would be necessary to compare the fatality risk of small and large vehicles, not just the trend in 

total fatalities, over this long period. 

. 

Comment: P3, States that Kahane’s finding that the increase in single vehicle crashes and 

rollover crashes was surprising and there was no clear and compelling scientific law that would 

predict that result. 

Agency Response: There is a compelling logical example to explain the results. In a single 

vehicle crash, you’d rather knock a tree down than be stopped by the tree. More weight helps 

you knock the tree down. Lighter cars roll over at a much higher rate than heavier cars. It is 

easier for a lighter car to be tripped and roll over. 

Comment: P3, Examined NHTSA frontal crash test data and found no correlation between 

vehicle weight and occupant protection. 

Agency Response: Frontal crash test data is the wrong data to analyze for this comparison, 

because the vehicle strikes a rigid barrier, which is like a vehicle striking its own twin. 

Comment: P3, Examined NHTSA data on rollover propensity and found that rollover risk 

increased with weight. This is entirely due to a greater propensity for light trucks to roll over. 

For passenger cars, there was no correlation between rollover propensity and weight, the same 

held within class of light trucks. This led them to suspect that it was not the vehicles themselves, 

but the drivers and the environment in which they were operated. 

Agency Response: The Kahane study shows a direct correlation between size/weight of 

passenger cars and rollover propensity. Smaller cars rollover much more frequently. Kahane’s 

study specifically controlled by the driver and environment characteristics. 

Comment: Greene reiterates a principal argument from his dissent to the 2002 NAS report, 

namely that mass per se, intuitively, should not have any safety effect other than on the relative 

risk of two vehicles that collide with each other. Therefore, all the empirical data showing 

higher fatality rates for lighter vehicles in single-vehicle crashes and elsewhere are due to 

something other than mass. Therefore, we may reduce mass without harming safety. 

Agency response: Although mass per se, strictly speaking, may have little direct causal effect on 

fatality risk in most types of crashes, there are many other parameters that are naturally and 

historically highly correlated with mass, such as size, rigidity, structural integrity, and the 

driver’s perception of maneuverability, that affect the frequency and severity of crashes. Unless 

we can determine exactly what these parameters are and demonstrate ways to reduce mass 
IV-21

without affecting any of these other parameters, we cannot simply ignore the empirical data 

showing higher fatality rates for lighter vehicles. . 

Comment: The Wenzel/Ross studies show that fatality risk has less to do with a vehicle’s weight 

than with the type of drivers who choose that vehicle. Luxury imports have low fatality risk 

because they have good drivers, etc. 

Agency response: See our critique of the Wenzel/Ross study in our response to public comments 

on the 2003 report. Specifically, the analysis did not control for driver age/gender and other 

factors such as urbanization and region of the country. After controlling for these, most of the 

difference between luxury cars and other cars disappears. 

Comment: Noland and Ahmad/Greene’s long-term (1966-2002) time-series analyses show little 

correlation between downsizing and trends in fatalities. The roads are safer now than in 1966, 

despite downsizing during the 1970s. 

Agency response: Long-term time-series analyses are unlikely to tease out the effect of 

downsizing from the numerous other demographic, economic and technological trends that have 

an impact on fatality rates. 

Comment: Alliance, 2008-0089-0179.1 P10

Weight and safety are correlated, as NHTSA has recognized. 

Comment: Lawrence Berkley National Laboratory (2008-0089-0194.1) pp. 4-7, 9 

They disagree with NHTSA that larger or heavier vehicles are inherently safer than smaller or 

lighter vehicles. Kahane’s analysis has flaws. Through careful design and material substitution, 

vehicle mass can be reduced without compromising safety. 

The risk to persons other than the driver imposed by crossover SUVs decreases as size increases. 

There is no consistent relationship between driver fatality risk and car size for frontal crashes 

with another car or object. The additional protection that size provides to drivers of light trucks 

comes at a cost to the drivers of the cars they crash into. Driving behavior tends to be worse in 

subcompact and compact cars, which tends to overstate the fatality risk in smaller cars. There is 

no strong relationship between vehicle mass and fatality risk to drivers in a front crash with an 

object. They also argue that Kahane’s regression analysis would likely change if updated to 

today’s vehicles, due to advances in safety devices such as ESC and the increased prevalence of 

crossover SUVs. 

Agency response: The commenter provides and opinion with no analysis to back it up. We 

don’t believe they are considering the big picture – fatality increase comes from single vehicle 

and rollover crashes, or the incremental picture – ESC affects everyone and doesn’t discriminate 

by weight, and lighter crossovers will be less safe than heavier crossovers. 

Comment: Mercatus Center (2008-0089-0216.1) 

Mercatus argues that NHTSA has not fully accounted for the decline in vehicle safety as a result 

of implementing fuel saving technologies, such as lighter vehicles that could result in higher 

death and injury rates. 
IV-22

Agency response: We believe that manufacturers can meet the CAFE requirements without 

making lighter vehicles, however nothing prevents them from doing so. It would be impossible 

for us to predict how the manufacturers might react to our requirements and market forces, thus 

we would have no confidence in a prediction that tried to account for a decline in safety. 

Comment: Center for Biological Diversity (2008-0089-0222.1), pp. 12

NHTSA misrepresented the 2002 NAS findings. NHTSA fails to consider the potential benefits 

of lower vehicle weight. NAS found that weight reduction for vehicles over 4,000 lbs would 

result in a safety benefit. 

Agency response: We have updated the Kahane report and the 4,000 lbs., which is what the 

NAS findings were based upon. See the previous discussion about 5,000 lbs. 

Comment: Sierra Club (2008-0089-0226.1), pp. 3, 13-15

NHTSA’s analysis of the relationship between vehicle weight and safety is flawed. NHTSA 

should revise its policy position on the weight/safety issue to take into account new materials and 

vehicle design options that can improve safety while reducing weight. 

The industry is already demonstrating that weight reduction is a safe and effective strategy for 

improving fuel economy. The disparity in weights of vehicles is much more important to 

occupant safety than the average weight of vehicles. Specific design features play a more 

important role than weight. The disparity in vehicle weight has decreased dramatically, 

eliminating the most severe weight disparity crashes. NHTSA has not taken into account 

improvements in structural integrity and safety technology, such as light-weight high-strength 

materials. William Haddon said size is more important than weight for safety. The safety of 

small cars continues to improve. NHTSA recognizes the retrospective nature of the Kahane study 

yet continues to use it to constraint future fuel economy. 

Agency response: They provide no proof that their theory is correct. We have discussed all of 

these issues above. 

Comment: Aluminum Association of America (2008-0089-184) 

NHTSA’s weight-safety study was retrospective, looking at 1990s vehicles, and not predictive. 

In the future, there could be extensive use of new materials, new designs enabled by the use of 

these materials, and new crash-avoidance technologies that will change the distribution of crash 

types. 

Agency response: We agree this study is based on a group of vehicles manufactured from similar 

materials (steel), where weight was highly correlated with size and structural strength. 

Relationships might conceivably be different in a future fleet where a wide variety of materials is 

used to build cars. We should caution, though, that the use of new materials is still at an early 

stage and will be for some years. NHTSA also agrees that, intuitively, substitution of strong, 

lightweight materials would be a less harmful to down-weight than reducing the size of the 

vehicles. But there is not yet sufficient evidence to conclude that material substitution is 

harmless, let alone beneficial to safety. 
IV-23

Comment: Public Citizen (2008-0089-0187) 

NHTSA’s 2003 study obfuscates findings which show that reducing weight from only the 

heaviest vehicles actually improves safety and overlooks the relationship between the difference 

in vehicle weight. 

Agency response: The 2003 estimates do include the benefits of improved fleet compatibility 

when the heaviest vehicles are reduced in weight. Compatibility is a safety concern that NHTSA 

has been investigating for some time now. The commenters’ point that any compatibility 

benefits should be weighed against any disbenefits associated with downweighting is logically 

correct. However, NHTSA research on compatibility has shown that compatibility is 

substantially influenced by factors other than mass, including vehicle geometry, stiffness, and 

crush space. While we do not know the precise effect of these factors, it is fair to say that simply 

downweighting heavier vehicles would not effectively address the compatibility issue. Thus, 

there are no currently available analyses that would allow NHTSA or anyone to quantify the 

compatibility benefits simply from weight reduction. 

Comment: Natural Resources Defense Council (2008-0089-225.1)

They discuss information from the Wenzel and Ross study. NHTSA’s own 2003 study 

demonstrates that safety would have improved if drivers had shifted from LTVs to passenger 

cars. Crossover SUVs have lower fatality risk than truck-based SUVs. 

Agency response: This appears to be correct, based on fatal crashes per million registration years. 

However, the statistics presented by Wenzel and Ross should be viewed with caution because 

they have not been adjusted for differences in driver age and gender, urbanization and 

geographical region, and average miles driven per year. The unadjusted data certainly tends to 

favor the lighter cars while making pickup trucks look worse. It may also favor crossover SUVs 

if they are more popular with female drivers in urban areas of low-fatality States (relative to 

truck-based SUVs). 

Comment: The “crossover weight” for LTVs, estimated at 5,084 pounds in NHTSA’s 2003 

study, will decrease over time as crash-avoidance measures such as ESC reduce single-vehicle 

crashes (where weight and size helps) relative to multivehicle crashes (where weight and size in 

the big LTV increases harm in the vehicles hit by that LTV). By restricting weight reduction to 

vehicles weighing 5,000 pounds or more, NHTSA is limiting the cost-effective measures that 

manufacturers can use to improve fuel economy. 

Agency response: Wenzel and Ross’ argument appears to be directionally correct. We should 

note, however, that weight reduction is not restricted to any particular group of vehicles. 

Manufacturers may reduce weight in any vehicles they want, and will be more inclined to do so 

if ESC reduces hazards associated with instability of lighter vehicles. The PRIA only uses the 

5,000 pound criterion to determine where NHTSA believes standards can and should be more 

stringent than what can be achieved by cost-effective weight-neutral technologies alone. 
IV-24

Comment: Wenzel and Ross question the relationship between weight and safety in NHTSA’s 

2003 report. NHTSA’s computation of the 5,000 pound crossover weight for LTVs is based on 

existing vehicles, and does not take into account future down-weighting, without downsizing, 

using lightweight high-strength materials. 

Agency response: This argument appears to be directionally correct. Material substitution 

would presumably have less effect in single-vehicle crashes than traditional downsizing, and that 

could shift the crossover weight downward. But that has yet to be proven. 

Comment: Sierra Club (2008-0089-0226.1) 

Weight reduction across all vehicles is a safe and effective strategy for improving fuel economy. 

Agency response: This is a persistent misconception. Fatality risk will increase in single-vehicle 

crashes if a given vehicle is reduced in weight, regardless what happens to other vehicles on the 

road. In multivehicle crashes, there is some improvement in compatibility if vehicle weights are 

more uniform, but there is also an overall increase in crash risk when weights are reduced across 

the board. 

Comment: The relationship between weight and fatality risk in the 2003 report, based on the 

actual fatality rates of 1991-1999 vehicles across the spectrum from light to heavy, overstates the 

harm if weight is reduced by substitution of strong, lightweight materials. 

Agency response: This argument appears to be directionally correct. Material substitution 

would presumably have less effect in single-vehicle crashes than weight reduction achieved by 

downsizing. However, we cannot quantify this future effect, because we have no crash data yet 

on these future vehicles. We should also note that one of the reasons for higher fatality rates in 

lighter cars is that they are more crash-prone, even in non-rollover crashes. We do not yet 

understand why this is, and therefore we cannot conclude that weight reduction through material 

substitution will be less harmful than other forms of weight reduction in this regard. 

Views of Other Government Agencies 

After our proposal was published and after the comment period had closed for the proposal, EPA 

published an Advance Notice of Proposed Rulemaking (ANPRM) on regulating greenhouse gas 

emissions under the Clean Air Act.84 The ANPRM was accompanied by a Vehicle Technical 

Support Document – Mobile Source.85 The Technical Support Document contains a discussion 

on pp. 15 -17 of the safety issues. EPA provided a brief summary of the issues involved and 

cited no new work in that area. 

Agency response: The work cited by EPA has already been addressed by NHTSA within the 

Regulatory Impact Analysis discussion of the 2002 NAS study and within NHTSA’s responses 

to other comments to the NPRM docket regarding the Wenzel and Ross study. 

 

84 73 FR 44354 (July 30, 2008). 

85 Docket No. EPA-HQ-OAR-2008-0318-0084. 
IV-25

Footprint and safety 

The impact of CAFE standards on motor vehicle and passenger safety has long been recognized 

as an integral part of the agency's process of determining maximum feasible average fuel 

economy. The agency notes that there are no compelling studies that quantify the precise and 

separate effects of vehicle size and weight on safety, in part because there is a high degree of 

correlation between size and weight among vehicles now in widespread use. The agency has 

determined that an attribute system based on footprint with the continuous function would 

minimize incentives for design changes that would reduce motor vehicle safety. In a weightbased system, a manufacturer can add weight to a vehicle in order to take advantage of a 

category with a lower fuel economy target. As discussed above, this up-weighting can have 

positive and negative safety implications, with possibly negative impacts for the fleet as a whole 

if weight is added to heavier light trucks. A manufacturer could not as readily increase footprint 

as it could vehicle weight. 

In order to increase footprint, a manufacturer would have to either extend a vehicle’s track width, 

wheelbase, or both. Maintaining and increasing track width should play a positive role in 

limiting rollover vulnerability, whereas maintaining and increasing wheelbase should play a 

positive role in improving handling – especially directional stability, which is crucial in 

preventing unintended off-road excursions that often lead to rollovers – and maximizing crush 

space (though total length is probably more closely correlated with crush space than is 

wheelbase). 

This is mentioned in Dr. Kahane’s response to safety studies submitted by Dynamic Research, 

Inc., by Marc Ross (University of Michigan) and Tom Wenzel (Lawrence Berkeley National 

Laboratory), and submitted by William E. Wecker Associates. 

Dr. Kahane wrote: 

”The objective of the NHTSA study was to calibrate the historical (MY 1991-99) 

relationships of vehicle mass and fatality risk, after controlling for driver age/gender, 

geographical location, and vehicle equipment. In this type of analysis, “vehicle mass” 

incorporates not only the effects of mass per se but also the effects of many other size 

attributes that are historically and/or causally related to mass, such as wheelbase, track 

width and structural integrity. (As vehicles get longer and wider, they almost always get 

heavier.) 

The study does not claim that mass per se is the specific factor that increases or decreases 

fatality risk (except in its role in determining the relative Delta V of two vehicles that 

collide). On the contrary, Chapter 5 of the NHTSA report shows that certain 4,000-

pound SUVs have significantly higher fatal-crash rates than 3,500-pound cars. The study 

only shows the historical relationship between mass – taking into account all the other 

size attributes that have typically varied with mass – and fatality risk, for vehicles of the 

same type. If historical relationships between mass and other size attributes continue, in 

the absence of compelling reasons that would change those relationships, future changes 

in mass are likely to be associated with similar changes in fatality risk. (However, the 

increased use of advanced restraint systems and sophisticated crash avoidance safety 

devices in recent and future production vehicles could have a noticeable impact on the 

historical relationship between vehicle mass and fatality risk in future vehicle fleets.) 
IV-26

In that sense, it is irrelevant whether mass, wheelbase, track width or some other attribute 

is the principal causal factor on fatality risk. If you decrease mass, you will also tend to 

reduce wheelbase, track width and other dimensions of size. If manufacturers respond to 

this proposal by building lighter vehicles of constant size, the historical relationship 

between mass and safety would gradually weaken.” 

Changes in technology could influence the relationship between weight and size. There is 

emerging evidence that vehicle weight can be reduced without reductions in size or safety 

through the use of high strength, lightweight materials. Currently, we do not observe many 

vehicles built with lightweight materials in the historical data and therefore cannot separate the 

impact of size versus weight when lightweight materials are utilized. However, the impact of 

weight, whether it comes from reducing size or material substitution, will be the same for single 

vehicle impacts (rollovers and fixed and non-fixed object impacts). 

Attribute-based standards eliminate the incentive for manufacturers to respond to CAFE 

standards in ways harmful to safety.86 Because each vehicle model has its own target (based on 

the attribute chosen), attribute-based standards provide no incentive to build smaller vehicles 

simply to meet a fleet-wide average, because the smaller vehicles will be subject to more 

stringent fuel economy and emissions targets. 

 

86 The 2002 NAS Report, on which NHTSA relied in reforming the CAFE program for light trucks, described at 

length and quantified the potential safety problem with average fuel economy standards that specify a single 

numerical requirement for the entire industry. See National Academy of Sciences, “Effectiveness and Impact of 

Corporate Average Fuel Economy (CAFE) Standards,” (“NAS Report”) National Academy Press, Washington, DC 

(2002), 5, finding 12. Available at http://www.nap.edu/openbook.php?record_id=10172&page=R1 (last accessed 

Dec. 2, 2007). 
IV-27

Fuel Economy Impacts of Other Government Emission Standards 

Federal Motor Vehicle Emissions Standards

As discussed above, because the addition of weight to a vehicle is only relevant to its ability to 

achieve the MY 2011 CAFE standards if it occurs in that timeframe, NHTSA only considers 

Federal motor vehicle emissions standards that become effective during the timeframe. 

In the NPRM, NHTSA explained that on December 27, 2007, EPA published a final rule for fuel 

economy labeling that employs a new vehicle-specific, 5-cycle approach to calculating fuel 

economy labels which incorporates estimates of the fuel efficiency of each vehicle during high 

speed, aggressive driving, air conditioning operation and cold temperatures into each vehicle’s 

fuel economy label.87 The rule took effect starting with MY 2008, and will not impact CAFE 

standards or test procedures, or add weight to a vehicle or directly impact a manufacturer’s 

ability to meet the CAFE standards. It will, however, allow for the collection of appropriate fuel 

economy data to ensure that existing test procedures better represent real-world conditions, and 

provide consumers with a more accurate estimate of fuel economy based on more comprehensive 

factors reflecting real-world driving use. 

CARB commented that the NPRM had not addressed certain federal and California emissions 

regulations that NHTSA had analyzed in previous rulemakings, and stated that “NHTSA must 

analyze the potential effect of these emissions regulations on its proposed standards.” CARB 

further stated that “the NPRM must analyze the impact of California’s ZEV regulations through 

at least MY 2011,” which the commenter stated would “require NHTSA to consider the impact 

of rapidly shifting technologies that manufacturers will apply to meet a combination of 

government mandates and market conditions, most notably the electrification of vehicle 

drivetrains.”88

In response, NHTSA reiterates that emissions standards that are completely phased in before MY 

2011 are already accounted for in the agency’s baseline for this rulemaking. EPA’s “Tier 2” 

standards, which apply to all vehicles currently subject to CAFE and are designed to focus on 

reducing the emissions most responsible for the ozone and particulate matter (PM) impact from 

these vehicles, are scheduled to be completely phased in by 2009.89 EPA’s onboard vapor 

recovery (ORVR) system standards, which apply to all passenger cars and light trucks below 

8,500 pounds GVWR, were completely phased in by MY 2008.90 Thus, there is no additional 

effect of these emissions regulations on MY 2011 vehicles for NHTSA to analyze, beyond what 

manufacturers have already included in their product plans in order to comply with these 

regulations, which NHTSA already accounts for.91

NHTSA agrees with CARB, however, that portions of the ZEV standards come into effect during 

MY 2011, although compliance with these standards is also already accounted for in 

 

87 See 71 FR 77872 (Dec. 27, 2006). 88 CARB comments at 10-11, Docket No. NHTSA-2008-0089-0173. 

89 See 65 FR 6698 (Feb. 10, 2000). 90 See 59 FR 16262 (Apr. 6, 1994). 91 Additionally, in calculating criteria pollutant emissions factors for analyzing air quality impacts, MOBILE6.2 

accounted for EPA’s emission control requirements for passenger cars and light trucks, including exhaust (tailpipe) 

emissions, evaporative emissions, and the Tier 2 program. See FEIS § 3.3.2. 
IV-28

manufacturers’ product plans and thus forms part of NHTSA’s baseline analysis. The State of 

California has established several emission requirements under section 209(b) of the Clean Air 

Act as part of its Low Emission Vehicle (LEV) program. California initially promulgated these 

section 209(b) standards in its LEV I standards, and has subsequently adopted more stringent 

LEV II standards, also under section 209(b). The relevant LEV II regulations have been 

completely phased in for passenger cars and light trucks as of MY 2007. 

The LEV II Program has requirements for “zero emission vehicles” (ZEVs) that apply to 

passenger cars and light trucks up to 3,750 pounds loaded vehicle weight (LVW) beginning in 

MY 2005, while trucks between 3,750 and 8,500 pounds are phased in to the ZEV regulation 

from 2007-2012. The ZEV requirements begin at 10 percent of vehicles sold by a manufacturer 

in California in 2005, and ramp up to 16 percent for 2018 under different paths. California will 

allow the 16 percent requirement to be met by greater numbers of “partial ZEVs” until 2018, 

which include ultra-clean gasoline-engine vehicles and hybrids. 

Compliance with the ZEV requirements is most often achieved through more sophisticated 

combustion management, frequently involving some of the technologies considered by NHTSA 

in its analysis. The associated improvements and refinement in engine controls generally 

improve fuel efficiency and have a positive impact on fuel economy.92 However, such gains 

may be diminished because the advanced technologies required by the program can affect the 

impact of other fuel economy improvements, primarily due to increased weight. The agency has 

considered this potential impact in our evaluation of manufacturer product plans, many of which 

voluntarily identified particular models as ZEV or PZEV-compliant. This indicates to NHTSA 

that the manufacturers have already included compliance with these standards in their product 

plans, which in turn indicates that compliance with these standards is already accounted for in 

the agency’s baseline. 

 

92 NESCAUM, “White Paper: Comparing the Emissions Reductions of the LEV II Program to the Tier 2 Program,” 

October, 2003. 
V-1

V. FUEL ECONOMY ENHANCING TECHNOLOGIES AND THE 

VOLPE MODEL

A. The Volpe Model 

In developing today’s final CAFE standards, NHTSA has made significant use of results 

produced by the CAFE Compliance and Effects Model (commonly referred to as the 

Volpe model), which DOT’s Volpe National Transportation Systems Center developed 

specifically to support NHTSA’s CAFE rulemakings. 

As discussed above, the agency has used the Volpe model to estimate the extent to which 

manufacturers could attempt to comply with a given CAFE standard by adding 

technology to fleets that the agency anticipates they will produce in future model years. 

This exercise constitutes a simulation of manufacturers’ decisions regarding compliance 

with CAFE standards. 

The model also calculates the costs, effects, and benefits of technologies it estimates 

could be added in response to a given CAFE standard. It calculates costs by applying the 

cost estimation techniques discussed above and by accounting for the number of affected 

vehicles. It accounts for effects such as changes in vehicle travel, changes in fuel 

consumption, and changes in greenhouse gas and criteria pollutant emissions. It does so 

by applying the fuel consumption estimation techniques, the vehicle survival and mileage 

accumulation forecasts, the rebound effect estimate and the fuel properties and emission 

factors. Considering changes in travel demand and fuel consumption, the model 

estimates the monetized value of accompanying benefits to society, as discussed in 

Chapter VIII. The model calculates both the current (i.e., undiscounted) and present (i.e., 

discounted) value of these benefits. 

The Volpe model has other capabilities that facilitate the development of a CAFE 

standard. It can be used to fit a mathematical function forming the basis for an attributebased CAFE standard, following the steps described below. It can also be used to 

evaluate many (e.g., 200 per model year) potential levels of stringency sequentially, and 

identify the stringency at which specific criteria are met. For example, it can identify the 

stringency at which net benefits to society are maximized, the stringency at which a 

specified total cost is reached, or the stringency at which a given average required fuel 

economy level is attained. The model can also be used to perform uncertainty analysis 

(i.e., Monte Carlo simulation), in which input estimates are varied randomly according to 

specified probability distributions, such that the uncertainty of key measures (e.g., fuel 

consumption, costs, benefits) can be evaluated. 

Nothing in EPCA requires NHTSA to use the Volpe model. In principle, NHTSA could 

perform all of these tasks through other means. For example, in developing the MY 2011 

standards promulgated today, the agency did not use the Volpe model’s curve fitting 

routines, because they could not be modified in time to implement the changes discussed 

below to this aspect of the agency’s analysis. In general, though, these model capabilities 

greatly increase the agency’s ability to rapidly, systematically, and reproducibly conduct 

key analyses relevant to the formulation and evaluation of new CAFE standards. 
V-2

NHTSA received comments from the Alliance and CARB encouraging NHTSA to 

examine the usefulness of other models. Examples of other models and analyses that 

NHTSA and Volpe Center staff have considered for the final rule include DOE’s NEMS, 

Oak Ridge National Laboratory’s (ORNL) Transitional Alternative Fuels and Vehicles 

(TAFV) model, Sierra Research’s VEHSIM model and the California Air Resources 

Board’s (CARB) analysis supporting California’s adopted greenhouse gas emissions 

standards for light vehicles. 

DOE’s NEMS represents the light-duty fleet in terms of five car “manufacturers” and 

four truck “manufacturers,” twelve vehicle market classes (e.g., “standard pickup”), and 

sixteen powertrain/fuel combinations (e.g., methanol fuel-cell vehicle). Therefore, as 

currently structured, NEMS is unable to estimate manufacturer-specific implications of 

attribute-based CAFE standards. The analysis of manufacturer-specific implications is 

useful in setting the standard, because any given standard will have differential impacts 

on individual manufacturers, depending on the composition of their vehicle fleets. In 

order to balance national-level costs and benefits, assessment of individual 

manufacturer’s costs and compliance strategies is appropriate.93

TAFV accounts for many powertrain/fuel combinations, having been originally designed 

to aid understanding of possible transitions to alternative fueled vehicles, but it also 

represents the light duty fleet as four aggregated (i.e., industry-wide) categories of 

vehicles: small cars, large cars, small light trucks, and large light trucks. Thus, again, as 

currently structured, TAFV is unable to estimate manufacturer-specific implications of 

attribute-based CAFE standards. 

Sierra Research’s vehicle simulation model, VEHSIM, which was originally developed 

by General Motors, calculates the fuel economy for a specified vehicle design over a 

specified driving cycle. Despite theoretical advantages in terms of explicit representation 

of physical phenomena underlying fuel consumption, VEHSIM has significant 

shortcomings as a tool for model-by-model evaluation of the entire future light vehicle 

fleet. Although submitted after the close of the comment period specified in the NPRM, 

comments by several state Attorneys General and other state and local official questioned 

the need and merits of full vehicle simulation within the context of CAFE analysis, 

stating that 

Computer simulation models such as VEHSIM are not practical except 

perhaps during vehicle development to determine the performance of 

specific vehicle models where all vehicle engineering parameters are 

known and can be accounted for in the inputs to the model. Such an 

exercise is extremely data intensive, and extending it to the entire fleet 

 

93 In principle, if all manufacturers freely traded fuel economy credits among themselves, fleetwide 

estimates of compliance costs and benefits would approximate the sum of individual manufacturer costs 

and benefits. However, major manufacturers have repeatedly indicated that they do not intend to trade 

credits, and statutory language prohibits NHTSA from considering the benefits of trading in setting 

standards. 
V-3

makes it subject to multiple errors unless the specific parameters for each 

vehicle model are known and accounted for in the model inputs.94

Nevertheless, the Volpe model could, in principle, be modified to use VEHSIM or any 

other vehicle simulation tool to estimate fuel consumption. However, in practice, 

NHTSA and Volpe Center staff are skeptical that doing so will be either feasible or 

meaningful as long as CAFE analysis continues to be informed by forecasts of the future 

vehicle market—forecasts that, though detailed, will not foreseeably contain the 

extensive information needed to perform full vehicle simulation. The information 

required for full vehicle simulation is not only exponentially greater than NHTSA 

currently requests of manufacturers, but for future vehicles, the information may not yet 

exist, as manufacturers may not have completed the design of future vehicles. 

CARB’s analysis of light vehicle GHG emissions standards uses two levels of 

accounting. First, based on a report prepared for NESCCAF, CARB represents the lightduty fleet in terms of five “representative” vehicles, each with engineering properties 

estimated by CARB to meaningfully typify the engineering characteristics of a given type 

of vehicle (e.g., small cars). NHTSA is concerned that such a limited a number of such 

vehicles does not reasonably represent the engineering properties of individual vehicle 

models that vary widely both among manufacturers and within manufacturers’ individual 

fleets. This concern was reflected in comments by the Alliance. For each of these five 

vehicles, NESCCAF’s report contains the results of full vehicle simulation given several 

pre-specified technology “packages.” Second, to evaluate manufacturer-specific 

regulatory costs, CARB represents each manufacturer’s fleet as two average test weights, 

one for each of California’s two proposed regulatory classes. Even for a flat standard 

such as that considered by California, NHTSA is concerned that this level of aggregation 

would hinder reasonable estimation of compliance costs faced by individual 

manufacturers. Further, use of CARB’s methods would not enable NHTSA to estimate 

manufacturer-specific implications of the attribute-based CAFE standards. Under an 

attribute-based standard, the CAFE level required of a given manufacturer depends on the 

specific mix of vehicles sold by that manufacturer, not the average properties of that 

manufacturers’ fleet. As noted above, it is useful to estimate national level costs and 

benefits of a standard applied at the level of individual manufacturer’s fleets by assessing 

individual manufacturer’s costs and compliance strategies. 

On the other hand, NHTSA recognizes that a more aggregated representation of the 

fleet—such as CARB’s five-vehicle approach—may be the only way that full vehicle 

simulation could be integrated into CAFE analysis. Although NHTSA has not yet been 

able to conduct an analysis with the advantages of both detailed representation of 

 

94 Attorneys General of the States of California, Arizona, Connecticut, Illinois, Maryland, Massachusetts, 

New Jersey, New Mexico, Oregon, and Vermont, the Executive Officer of the California Air Resources 

Board, the Commissioner of the New Jersey Department of Environmental Protection, the Secretary of the 

New Mexico Environment Department, the Secretary of the Commonwealth of Pennsylvania Department 

of Environmental Protection, and the Corporation Counsel of the City of New York, Supplemental 

Comments Regarding Alliance of Automobile Manufacturers Comments, Docket No. NHTSA-2008-0089-

0495, October 8, 2008, p. 3. 
V-4

manufacturers’ fleets and full integration of full vehicle simulation, the agency cannot 

rule out the possibility of such an analysis in the future. 

Although the Volpe model has limitations, having considered other tools and analytical 

approaches, NHTSA concludes that for this final rule, the Volpe model is a sound and 

reliable tool available for the development and evaluation of potential CAFE standards. 

However, the agency will continue to consider other methods for evaluating potential 

CAFE standards in the future as well as to examine ways to improve the Volpe model. 

NHTSA notes that some commenters questioned the transparency of the Volpe model, 

which Public Citizen and the Center for Biological Diversity (CBD) referred to as a 

“black box.” In response to these comments, the agency notes that model documentation, 

which is publicly available in the rulemaking docket, explains how the model is installed, 

how the model inputs (all of which, except for manufacturers’ confidential product plans, 

are available to the public) and outputs are structured, and how the model is used. The 

model can be used on any Windows-based personal computer with Microsoft Office 2003 

and the Microsoft .NET framework installed (the latter available without charge from 

Microsoft). The executable version of the model is available upon request, and has been 

provided to manufacturers, consulting firms, academic institutions, governmental and 

nongovernmental organizations, research institutes, foreign government officials, and a 

variety of other organizations. The current version of the model was developed using 

Microsoft Development Environment 2003, and every line of computer code (primarily 

in C#.NET) has been made available to individuals who have requested the code. With 

the code, anyone is capable of running the model using market forecast data that they 

obtain or estimate on their own. Given the comprehensive disclosure of information 

about the Volpe model and the fact that many entities and individuals have made use of 

it, the characterization of the Volpe model as a “black box” is not accurate. 

Although NHTSA currently uses the Volpe model as a tool to inform its consideration of 

potential CAFE standards, contrary to the assertions of some commenters, the Volpe 

model does not determine the CAFE standards NHTSA proposes or promulgates as final 

regulations. The results it produces are completely dependent on inputs selected by 

NHTSA, based on the best available information and data available in the agency’s 

estimation at the time standards are set. In addition to identifying the input assumptions 

underlying its decisions, NHTSA provides the rationale and justification for selecting 

those inputs. NHTSA also determines whether to use the model to estimate at what 

stringency net benefits are maximized, or to estimate other stringency levels, such as the 

point where total costs equal total benefits. NHTSA also determines whether to use the 

model to evaluate the costs and effects of stringencies that fall outside of the scope of 

maximum feasible. For example, the standards for the “Technology Exhaustion” 

Alternative examined by NHTSA and discussed later in this section, were estimated 

outside the model, which was subsequently used to estimate corresponding costs and 

effects.95 Finally, NHTSA is guided by the statutory requirements of EPCA as amended 

by EISA in the ultimate selection of a CAFE standard. 

 

95 By definition, the “maximum technology” scenario far exceeds the maximum feasible CAFE standard. 
V-5

NHTSA does not agree with Public Citizen that the agency “does not establish what is 

technologically feasible and economically practicable based on an independent 

assessment of the current vehicle fleet and the available technology to improve the fleet, 

but rather accepts industry inputs, which are run through the black box of the Volpe 

model and a variety of ‘optimization’ factors, which are tied to maximizing industry-wide 

benefits.” The manufacturers’ plans are only the starting point for the agency’s 

determination of how much technology can and should be required consistent with the 

statutory factors, and the Volpe model is often tested using inputs developed without 

reliance on manufacturers’ product plans. NHTSA considers the results of analyses 

conducted by the Volpe model and analyses conducted outside of the Volpe model, 

including analysis of the impacts of carbon dioxide and criteria pollutant emissions, 

analysis of technologies that may be available in the long term and whether NHTSA 

could expedite their entry into the market through these standards, and analysis of the 

extent to which changes in vehicle prices and fuel economy might affect vehicle 

production and sales. Using all of this information—not solely that from the Volpe 

model—the agency considers the governing statutory factors, along with environmental 

issues and other relevant societal issues such as safety, and promulgates the maximum 

feasible standards based on its best judgment on how to balance these factors. 

This is why the agency considered seven regulatory alternatives, only one of which 

maximizes net benefits based on the agency’s determination and assumptions. The others 

assess alternative standards that in many cases exceed the point at which net benefits are 

maximized. These comprehensive analyses, which also included scenarios with different 

economic input assumptions as presented in the FEIS and FRIA, are intended to inform 

and contribute to the agency’s consideration of the “need of the United States to conserve 

energy,” as well as the other statutory factors. 49 U.S.C. § 32902(f). Additionally, the 

agency’s analysis considers the need of the nation to conserve energy by accounting for 

economic externalities of petroleum consumption and monetizing the economic costs of 

incremental CO2 emissions in the social cost of carbon. As mentioned above, NHTSA 

will continue to consider other methods for determining future CAFE standards in future 

rulemakings. 

NHTSA retained the constrained logistic function for the final rule. The considerations 

included: 

• A relatively flat standard for larger vehicles acts as a de facto ‘backstop’ 

for the standard in the event that future market conditions encourage 

manufacturers to build very large vehicles. Nothing prevents manufacturers 

from building larger vehicles. With a logistic curve, however, vehicles 

upsizing beyond some limit face a flat standard that is increasingly difficult 

to meet. 

• A constrained logistic curve doesn’t impose unachievable fuel economy 

standards on vehicles that have unusually small footprints, thus continuing to 

keep manufacturing fuel-efficient small vehicles available as a compliance 

option. Infeasible sections of the curve may be unimportant for the industry 

at large while having a particular adverse impact on manufacturers that 
V-6

specialize in very large or small vehicles, for example, two-seater sports car. 

• The transition from the ‘flat’ portions of the curve to the ‘slope’ portions of 

the curve is smooth and gradual, reducing the incentive for manufacturers to 

achieve compliance through marginal changes in vehicle size. 

• The inflection points are set by the data and can potentially vary from year 

to year, rather than being chosen by NHTSA. 

NHTSA retained footprint as the attribute for purposes of this rulemaking’s attributebased standards in part because we believed changing a vehicle’s footprint would involve 

significant costs for manufacturers, probably requiring a redesign of the vehicle. 

Congress recently mandated that NHTSA set attribute-based fuel economy standards 

“and express each standard in the form of a mathematical function.”96 NHTSA uses a 

continuous, constrained logistic function for expressing the passenger car and light 

truck standards, which takes the form of an S-curve, and is defined according to the 

following formula: 

( )

( )

1

1 11

1

FOOTPRINT c d

FOOTPRINT c d

TARGET

e

a ba e

−

−

= ⎛ ⎞ + − ⎜ ⎟ ⎝ ⎠ +

Here, TARGET is the fuel economy target (in mpg) applicable to vehicles of a given 

footprint (FOOTPRINT, in square feet), b and a are the function’s lower and upper 

asymptotes (also in mpg), e is approximately equal to 2.718,97c is the footprint (in square 

feet) at which the inverse of the fuel economy target falls halfway between the inverses 

of the lower and upper asymptotes, and d is a parameter (in square feet) that determines 

how gradually the fuel economy target transitions from the upper toward the lower 

asymptote as the footprint increases. Figure V-1 below shows an example of a logistic 

target function, where b = 20 mpg, a= 30 mpg, c = 40 square feet, and d = 5 square feet: 

 

96 49 U.S.C. § 32902(a)(3)(A). 

97 e is the irrational number for which the slope of the function y = numberx

 is equal to 1 when x is equal to 

zero. The first 8 digits of e are 2.7182818. 
V-7

Figure V-1. Sample Logistic Curve 

Continuous function:

NHTSA explained in the NPRM that it examined the relative merits of both step 

functions and continuous functions in its rulemaking for MY 2008-2011 light trucks, and 

described the agency’s rationale for choosing a continuous function for the CAFE 

program. A step function, in the CAFE context, would separate the vehicle models along 

the spectrum of attribute magnitudes into discrete groups, and each group would be 

assigned a single fuel economy target, so that the average of the groups would be the 

average fleet fuel economy. A continuous function, in contrast, would assign each 

vehicle model (and indeed, any vehicle model at any point along the spectrum) its own 

unique fuel economy target, based on its particular attribute magnitude. Thus, two 

vehicles models built by different manufacturers could have the same fuel economy 

target, but only if they had identical magnitudes of the attribute. In other words, a 

continuous function is a mathematical function that defines attribute-based targets across 

the entire range of possible attribute values. These targets are then applied through a 

harmonically-weighted formula to derive regulatory obligations for fleet averages. 

The agency fit the fuel economy curves for this final rule for MY 2011 according to the 

following four step procedure: 

In Step 1, NHTSA determined the fuel economies obtained by exhausting available 

technologies on each vehicle in the MY 2011 updated product plans of the seventeen 

manufacturers to which the standards apply (BMW, Chrysler, Daimler, Ferrari, Ford, 

General Motors, Honda, Hyundai, Maserati, Mitsubishi, Nissan, Porsche, Subaru, Suzuki, 

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80 90 100

Footprint (Square Feet)

Target (Miles per Gallon)

LIMITUPPER

LIMIT

LOWER
V-8

Tata, Toyota, Volkswagen). In exhausting technologies, the agency has focused this Step 

on the engineering aspects of available technologies, essentially setting aside economic 

considerations. 

In Step 2, NHTSA determined initial values for parameters A and B for each vehicle type 

(passenger car and light truck) as follows. (The values of these parameters will be 

revised in Step 4.) For passenger cars (respectively, light trucks), NHTSA set the initial 

value of the parameter A to be the harmonic average fuel economy among the vehicles of 

the given vehicle type (produced by the seventeen manufacturers used Step 1) comprising 

the lower tenth (respectively, tenth) percentile of footprint values. NHTSA set the initial 

value of B to be the harmonic average fuel economy among the vehicles of the given 

vehicle type (produced by the seventeen manufacturers) comprising the upper ninth 

(respectively, sixth) percentile of footprint values. NHTSA set A and B in this manner, 

rather than fitting them, for example, through regression, in order to ensure that the upper 

and lower fuel economy values reflect the smallest and largest models in the fleet. 

NHTSA chose the percentile values it used by examining the fuel economies of the 

largest and smallest car and truck models, and determining its best assessment of 

appropriate cohorts, acknowledging that there are no canonical choices. 

Figure V-2 

Distribution of Passenger Car Footprint Values 

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

<35

35.5-3636.5-3737.5-3838.5-3939.5-4040.5-4141.5-4242.5-4343.5-4444.5-4545.5-4646.5-4747.5-4848.5-4949.5-5050.5-5151.5-5252.5-5353.5-5454.5-5555.5-5656.5-5757.5-5858.5-5959.5-60

Footprint (sf)

Percent of Vehicle Models

smallest 10%

Volkswagen Jetta

and smaller

largest 9%

Jeep Wrangler 4-Door

and larger
V-9

Figure V-3 

Distribution of Light Truck Footprint Values 

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

42.5-4344-44.545.5-4647-47.548.5-4950-50.551.5-5253-53.554.5-5556-56.557.5-5859-59.560.5-6162-62.563.5-6465-65.566.5-6768-68.569.5-7071-71.572.5-7374-74.575.5-76

Footprint (sf)

Percent of Vehicle Models

smallest 10%

Hyundai Santa Fe

and smaller

largest 6%

Toyota Tundra and larger

In Step 3, NHTSA determined initial values for parameters C and D for each vehicle type 

as follows. For a given vehicle type, NHTSA set the initial values of C and D to be the 

values for which the average (equivalently, sum) of the absolute values of the differences 

between the optimized fuel consumption from Step 1 for the given vehicle type and the 

values obtained by applying the following function 

( )

( ) x C D

x C D

e

e

A B A f x /

/

1

1 1 1 ( ) −

−

+

⎟

⎠

⎞ ⎜

⎝

⎛ = + −

to the corresponding vehicle footprints is minimal, where the values of A and B are taken 

from those determined in Step 2 and where e denotes the base of the natural logarithm 

(which is approximately equal to 2.71828). That is, NHTSA determined C and D by 

minimizing the average absolute residual, commonly known as the MAD (Mean 

Absolute Deviation) approach, of the corresponding constrained logistic curve. NHTSA 

fit the curve in fuel consumption space rather than fuel economy space because the 

manufacturer targets are in terms of the harmonic average fuel economy, and so it is more 

important that the curve fit the fuel consumption data well than that it fit the fuel 

economy data well. NHTSA uses MAD in this Step instead of minimizing the sum of the 

square errors (another common approach in curve fitting) in order to lessen the influence 

of outliers. NHTSA believes that it is more appropriate to use unweighted data in fitting 

the curve rather than weighting the data by sales because of large variations in model 

sales and because each vehicle model contributes an equal amount of information to 

understanding the underlying relationship between fuel economy and footprint. 
V-10

For passenger cars, this procedure yielded a curve with the following coefficients: A = 

37.82 mpg, B = 27.70 mpg, C = 51.41 square feet, D = 1.91 square feet. This curve, 

shown below on a fuel consumption (i.e., gpm) basis, produced an average absolute 

difference of 18 percent. 

Figure V-4 

Fitted Curve for Passenger Cars 

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

30 35 40 45 50 55 60 65 70

Footprint (sf)

Fuel Consumption (gpm)

For light trucks, the same procedure yielded a curve with the following coefficients: A = 

36.43 mpg, B = 26.43 mpg, C = 56.41 square feet, and D = 4.28 square feet. This curve, 

shown below on a fuel consumption (i.e., gpm) basis, produced an average absolute 

difference of 14 percent. 
V-11

Figure V-5 

Fitted Curve for Light Trucks 

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

30 35 40 45 50 55 60 65 70 75 80

Footprint (sf)

Fuel Consumption (gpm)

 In Step 4, NHTSA determined for each model year and vehicle class the integer value of 

t that maximized the societal net benefits (considering the seventeen manufacturers to 

which the standards apply) achieved by a fuel economy standard under which fuel 

consumption targets were defined by the function 

( )

( )

/

/

1 11 ( ) 0.0001 1

xC D

xC D

e

gx t A BA e

−

−

⎛ ⎞ =+ − + ⎜ ⎟ ⎝ ⎠ +

using the values of A and B determined in Step 2, and the values of C and D determined 

in Step 3.98 NHTSA reset the values of 1/A and 1/B to be 1/A + 0.0001t and 1/B + 

0.0001t, respectively. That is, NHTSA set the stringency of the curves to maximize 

societal net benefits. 

Parameter Values of the Fuel Economy Curves in This Final Rule 

Parameter Values for Passenger Cars Parameter Values for Light Trucks 

Model A B C D A B C D 

2011 31.20 24.00 51.41 1.91 27.10 21.10 56.41 4.28

The corresponding target functions are presented below graphically, and on a mile per 

gallon basis, for both passenger cars and light trucks: 

 

98 This procedure uniformly shifts the upward and downward (depending on whether t is positive or 

negative), but on the same gallon per mile basis corresponding to the harmonic averaging of fuel economy 

values. 
V-12
V-13

Figure V-6. Final Passenger Car Target Functions 

2011

20

25

30

35

40

45

35 40 45 50 55 60 65 70

Footprint (sf)

Target (mpg)

2011
V-14

Figure V-7. Final Light Truck Target Functions 

2011

20

25

30

35

40

45

35 40 45 50 55 60 65 70

Footprint (sf)

Target (mpg)

2011

B. Technologies – Costs and Effectiveness 

Fuel economy-improving technologies 

As explained above, pursuant to the President’s January 26, 2009 memorandum, this final 

rule establishes passenger car and light truck CAFE standards for one year, MY 2011. 

 Although this final rule establishes standards for that year alone, the agency undertook a 

comprehensive analysis of fuel economy-improving technologies with a time horizon 

similar to the one considered in the 2002 National Academy of Sciences (NAS) CAFE 

report. Like NAS, the agency considered technologies that are readily available, well 

known and could be incorporated into vehicles once production decisions are made (these 

are referred to as “production intent” technologies). Other technologies considered, 

called “emerging”, are beyond the research phase and under development, but are not 

widely used at this time. The agency did not consider technologies in the research stage 

because their costs and/or performance are not presently well known. 
V-15

The agency has elected to include the full analysis in this final rule for several reasons. 

First, it supplements the analysis of fuel saving technology released by the 2002 NAS 

study. Second, it places in meaningful context the portion of the analysis that relates 

directly to MY 2011, showing which technologies are not available for that year and why. 

The agency typically evaluates technologies within a time context spanning more than a 

single model year, even if the rulemaking itself addresses only a single year as in the 

current rulemaking, because when manufacturers add technologies to vehicle models in 

order to meet CAFE standards, they tend to phase them in over several model years, 

consistent with vehicle redesign and refresh schedules, supplier contract procedures, the 

need for testing and validation of new technologies, and so forth. Consequently, although 

the final rule establishes standards for MY 2011 only, NHTSA believes that including the 

entire technology analysis will increase public understanding of the agency’s estimates 

for MY 2011 of technology costs, effectiveness, and availability, as well as manufacturer 

vehicle freshening and redesign cycles. 

With that in mind, the following section details the cost and effectiveness estimates 

completed for technologies in the production intent or emerging technology phase 

timeline The estimates are drawn from an analysis conducted in the summer of 2008. It 

relied as much as possible on published studies and confidential product plan data 

submitted by manufacturers on July 1, 2008 in response to the agency’s NPRM request 

for comments published May 2, 2008. The analysis was conducted by engineers from 

DOT and Ricardo, an international consulting firm that specializes in automotive 

engineering consulting (discussed below). The engineering team used all data available 

at that time, along with their expert opinion to derive cost and effectiveness estimates for 

technologies either in production or in the emerging stage of production for purposes of 

this rulemaking. 

The agency believes that the resulting estimates are the best available for MY 2011, 

given the information that existed at the time. NHTSA recognizes, however, that the 

analysis of and public debate over the cost and effectiveness of the various fuel saving 

technologies is an ongoing one. It recognizes too that aspects of its technology analysis 

will likely require updating or otherwise merit revision for the next CAFE rulemaking. 

As time progresses, new research occurs, new studies become available and product plan 

information changes. As with all CAFE rulemakings and pursuant to the President’s 

memorandum, the agency will take a fresh look at all of its technology-related 

assumptions for the purpose of future rulemakings. 

A. NHTSA analyzes what technologies can be applied beyond those in the 

manufacturers’ product plans

One of the key statutory factors that NHTSA must consider in setting maximum feasible 

CAFE standards for each model year is the availability and feasibility of fuel saving 

technologies. When manufacturers submit their product plans to NHTSA, they identify 

the technologies they are planning for each vehicle model in each model year. They also 

provide their assessments of the costs and effectiveness of those fuel saving technologies. 

The agency uses the manufacturers’ product plan data to ascertain the “baseline” 

capabilities and average fuel economy of each manufacturer. Given the agency’s need to 
V-16

consider economic practicability in determining how quickly additional fuel saving 

technologies can be added to the manufacturers’ vehicle planned fleets, the agency 

researches and develops, based on the best available information and data, its own list of 

technologies that it believes will be ready for implementation during the model years 

covered by the rulemaking. This includes developing estimates of the costs and 

effectiveness of each technology and lead time needs. The resultant technology 

assumptions form an input into the Volpe model. The model simulates how 

manufacturers can comply with a given CAFE level by adding technologies beyond those 

they planned in a systematic, efficient and reproducible manner. The following sections 

describe NHTSA’s fuel-saving technology assumptions and methodology for estimating 

them, and their applicability to MY 2011 vehicles. 

B How NHTSA decides which technologies to include 

1. How NHTSA did this historically, and how for the NPRM

In the agency’s last two CAFE rulemakings, which established light truck CAFE 

standards for MYs 2005-2007 and MYs 2008-2011, NHTSA relied on the 2002 National 

Academy of Sciences’ report, “Effectiveness and Impact of Corporate Average Fuel 

Economy Standards”99 (“the 2002 NAS Report”) for estimating potential fuel economy 

effectiveness values and associated retail costs of applying combinations of technologies 

in 10 classes of production vehicles. The NAS study was commissioned by the agency, 

at the direction of Congress, in order to provide independent and peer reviewed estimates 

of cost and effectiveness numbers. The NAS list was determined by a panel of experts 

formed by the National Academy of Sciences, and was then peer-reviewed by individuals 

chosen for their diverse perspectives and technical expertise in accordance with 

procedures approved by the Report Review Committee of the National Research. 

In the NPRM for the MY 2011-2015 CAFE standards, NHTSA explained that there has 

been substantial advancement in fuel-saving automotive technologies since the 

publication of the 2002 NAS Report. New technologies, i.e., ones that were not assessed 

in the NAS report, have appeared in the market place or are expected to appear in the 

timeframe of the proposed rulemaking. Also, new studies have been conducted and 

reports issued by several other organizations providing new or different information 

regarding the fuel economy technologies that will be available and their costs and 

effectiveness values. To aid the agency in assessing these developments, NHTSA 

contracted with the NAS to update the fuel economy section, Chapter 3, of the 2002 NAS 

Report. However, as NHTSA explained, the NAS update was not available in time for 

this rulemaking. 

Accordingly, NHTSA worked with EPA staff to update the technology assumptions, and 

used the results as a basis for its NPRM. EPA staff published a related report and 

submitted it to the NAS committee.100 

 

99 National Research Council, “Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) 

Standards,” National Academy Press, Washington, DC (2002). Available at

http://www.nap.edu/openbook.php?isbn=0309076013 (last accessed October 11, 2008). 100 EPA Staff Technical Report: Cost and Effectiveness Estimates of Technologies Used to Reduce LightDuty Vehicle Carbon Dioxide Emissions, EPA 420-R-08-008, March 2008. 
V-17

2. NHTSA’s contract with Ricardo for the final rule

NHTSA specifically sought comment on the estimates, which it had developed jointly 

with EPA, of the availability, applicability, cost, and effectiveness of fuel-saving 

technologies, and the order in which the technologies were applied. See 73 FR 24352, 

24367. To aid the agency in analyzing those comments and increasing the accuracy, 

clarity and transparency of its technology assumptions and methodologies employed in 

developing them, it hired an international consulting firm, Ricardo, which specializes in 

automotive engineering consulting. Ricardo, which describes itself as an eco-innovation 

technology company, is a leading independent provider of technology, product 

innovation, engineering solutions, software and strategic consulting. Its skill base 

includes the state-of-the-art in low emissions and fuel-efficient powertrain and vehicle 

technology. Its customers include government agencies here and abroad and the world’s 

automotive, transport and new-energy industries.101 For example, it has provided 

technical consulting on low CO2 strategies to the UK Department for Transport (DfT).102 

Additionally, in December 2007, Ricardo completed an important study for EPA titled 

“A Study of Potential Effectiveness of Carbon Dioxide Reducing Vehicle 

Technologies.”103 

Ricardo’s role was as a technical advisor to NHTSA staff. In this capacity, Ricardo 

helped NHTSA undertake a comprehensive review of the NPRM technology assumptions 

and all comments received on those assumptions, based on both old and new public and 

confidential manufacturer information. NHTSA and Ricardo staff reviewed and 

compared comments on the availability and applicability of technologies, and the logical 

progression between them. NHTSA also reviewed and compared the methodologies used 

for determining the costs and effectiveness of the technologies as well as the specific 

estimates provided. Relying on the technical expertise of Ricardo and taking into 

consideration all the information available, NHTSA revised its estimates of the 

availability and applicability of many technologies, and revised its estimate of the order 

in which the technologies were applied and how they are differentiated by vehicle class, 

as well as the costs and effectiveness estimates and used the revised numbers in analyzing 

alternative levels of stringency. 

While NHTSA sought Ricardo’s expertise and relied significantly on their assistance as a 

neutral expert in developing its technical assumptions, it retained responsibility for the 

final estimates. The agency believes that the representation of technologies for MY 

2011—that is, estimates of the availability, applicability, cost, and effectiveness of fuelsaving technologies, and the order in which the technologies were applied—used in this 

 

101 More information about Ricardo’s work is available at their website, http://www.ricardo.com (last 

accessed September 20, 2008). Its 2007 Annual Report provides a comprehensive view of some of its 

current work. See http://www.ricardo.com/investors/download/annualreport2007.pdf (last accessed 

September 22, 2008). 

102 Ricardo UK Ltd., “Understanding manufacturers’ responses to policy measures to incentivise fuel 

efficiency,” Oct. 5, 2007. Available at

http://www.dft.gov.uk/consultations/closed/co2emissions/ricardoreport.pdf (last accessed Oct. 4, 2008). 103 A slightly updated (June 2008) version of Ricardo’s study for EPA is available on EPA’s website, at 

http://www.epa.gov/otaq/technology/420r08004a.pdf (last accessed September 20, 2008). 
V-18

rulemaking is more accurate than that used in the NPRM, and is the best available for 

purposes of this rulemaking. 

C. What technology assumptions has NHTSA used for the final rule? 

1. How do NHTSA’s technology assumptions in the final rule differ from those 

used in the NPRM?

This final rule uses the same basic framework as the NPRM. However, NHTSA made 

several changes to its technology assumptions based on comments and information 

received during the rulemaking. As in the NPRM and the MY 2008-2011 light truck 

rule, the agency relied on the Volpe model CAFE Compliance and Effects Modeling 

System which was developed by the Department or Transportation’s Volpe National 

Transportation Systems Center (Volpe Center) to apply technologies. The model, known 

as the Volpe model, is the primary tool the agency has used in conducting a “compliance 

analysis” of various CAFE stringencies. The Volpe model relied on the same types of 

technology related inputs as in previous rules, including market data files, technology 

cost and effectiveness estimates by vehicle classification, technology synergies, phase-in 

rates, learning curve adjustments, and technology decision trees. 

Regarding the decision trees, both the structure of the trees and ordering of the 

technologies were revised. The decision trees have been expanded so that NHTSA is 

better able to track the incremental and net/cumulative cost and effectiveness of each 

technology, which substantially improves the “accounting” of costs and effectiveness for 

the final rule.104 The revised decision trees also have improved integration, accuracy, and 

technology representations. 

In revising the decision trees, NHTSA updated, combined, split and/or renamed 

technologies. Several technologies were added, while others were deleted. The three 

technologies that were deleted because they do not appear in either public or confidential 

data and are primarily in the research phase of development are: Camless Valve 

Actuation, Lean-Burn Gasoline Direct-Injection and Homogenous Charge Compression 

 

104 In addition to the (simplified) decision trees, as published in this document, NHTSA also utilized 

“expanded” decision trees in the final rule analysis. Expanded decision trees graphically represent each 

unique path, considering the branch points available to the Volpe model, which can be utilized for applying 

fuel saving technologies. For instance, the engine decision tree shown in this document has 20 boxes 

representing engine technologies, whereas the expanded engine decision tree requires a total of 45 boxes to 

accurately represent all available application variants. Expanded decision trees presented a significant 

improvement, compared to the NPRM analysis, in the overall assessment and tracking of applied 

technologies since they allowed NHTSA staff to accurately view and assess both the incremental and the 

accumulated, or net cost and effectiveness at any stage of technology application in a decision tree. 

Because of the large format of the expanded decision trees, they could not be included in the Federal 

Register, so NHTSA refers the reader to Docket No. NHTSA-2008-0177. Expanded decision trees for the 

engine, electrification/transmission/hybridization, and the vehicle technologies (three separate decision 

trees) were developed for each of the 12 vehicle technology application classes and the three expanded 

decision trees for the Large Car subclass have been placed in the docket as an example for the reader’s 

information. 
V-19

Ignition.105 NHTSA also added three advanced technologies based on confidential 

manufacturer submissions which showed these technologies as being emerging and 

currently under development. These technologies are: Combustion Restart, Exhaust Gas 

Recirculation Boost, and Plug-in Hybrids. 

The Volpe model was modified to allow a non-linear phase-in rate across the five model 

years, rather than a constant phase-in rate as was used in the NPRM and in previous rules. 

Most technology applications have tighter phase-in caps in the early years to provide for 

additional lead time. 

In the NPRM, NHTSA applied volume-based learning factors to technology costs for the 

first time. These learning factors were developed using the parameters of learning 

threshold, learning rate (decremented over two cycles), and the initial (unlearned) cost. 

In the NPRM, NHTSA applied a learning rate discount of 20 percent each time a 

technology was projected for use on 25,000 vehicles per manufacturer, which was the 

threshold volume for learning rate discounts. The discounts were only taken twice, at 

25,000 and 50,000 vehicles. A technology was viewed as being fully learned out at 

100,000 units. 

The agency also reconsidered volume-based learning factors and made significant 

revisions. First, the volume learning is now applied on an industry basis as opposed to a 

manufacturer basis. This takes into account the fact that the automobile industry shares 

best practices and that manufacturers learn from that sharing to produce their vehicles at 

lower costs. For the final rule, the revised learning threshold is set to 300,000 vehicles 

per year by the automobile industry. This number was developed based on comments 

indicating that many of the publicly available technology cost estimates are based on 

production quantities of 900,000 to 1.5 million vehicles by at least 3 manufacturers. The 

agency notes, however, that none of the technologies applied in MY 2011 receive 

volume-based learning, due to the time frame applicable. 

For the technologies applied in the final rule, a time-based learning factor was used in 

response to public comments from Ford and others. This learning factor was not applied 

in the NPRM. Time-based learning is applied to widely available, high volume, stable 

and mature technologies typically purchased under negotiated multi-year contractual 

agreement with suppliers. This type of an agreement is typical of most supplier-provided 

fuel saving technologies. With time-based learning, the initial cost of a technology is 

reduced by a fixed amount in its second and subsequent year of availability. A fixed rate 

3 percent year-over-year cost reduction is applied up to a maximum of 12 percent cost 

reduction. 

In the NPRM NHTSA divided vehicles into ten subclasses based on technology 

applicability: four for cars and six for trucks. NHTSA assigned passenger cars into one 

of the following subclasses: Subcompact, Compact, Midsize, or Large Car. NHTSA 

 

105 We note that GM included lean burn HCCI in its restructuring plans submitted to Congress, but the 

restructuring plans were submitted too late for the agency to consider them in its technology analysis, 

among other reasons. GM Restructuring Plan, p. 22. 
V-20

assigned light trucks into one of the following subclasses: Minivan, Small SUV, Medium 

SUV, Large SUV, Small Pickup Truck, or Large Pickup Truck. In its 2008 NPRM for 

MY 2011-2015, NHTSA included some differentiation in cost and effectiveness numbers 

between the various classes to account for differences in technology costs and 

effectiveness that are observed when technologies are applied on to different classes and 

subclasses of vehicles. 

For the final rule, NHTSA, working with Ricardo, increased the accuracy of its 

technology assumptions by reexamining the subclasses developed for the purpose of 

modeling technology application. For passenger cars, NHTSA divided vehicles into 

eight subclasses based on technology applicability by creating a performance class under 

each of the four subclasses. For trucks, NHTSA established four subclasses, including a 

minivan subclass, and small, midsize and large SUV/Pickup/Van subclasses. NHTSA 

also provided more differentiation in the costs and effectiveness values by vehicle 

subclass. The agency found it important to make that differentiation because the agency 

estimated that some technologies would have different implications for large vehicles 

than for smaller vehicles. 

In summary, the revisions to NHTSA’s methodology for technology application and cost 

and effectiveness estimates are designed to respond to comments, many of which focused 

on various inaccuracies and lack of clarity in the NPRM. NHTSA believes that the 

methodology for the final rule, as compared to the NPRM methodology, is much clearer, 

more accurate, and more representative of likely manufacturer behavior, although, of 

course, manufacturers are free to respond to the CAFE standards with whatever 

application of technology they choose. The revised technology related assumptions help 

substantially ensure the technological feasibility and economic practicability of the MY 

2011 CAFE standards promulgated in this final rule. 

2. How are the technologies applied in the model?

For the final rule, as in the NPRM, NHTSA made significant use of the CAFE Volpe 

model as discussed above. The NPRM contained a detailed discussion of the Volpe 

model and specifically stated its two primary objectives as 1) identifying technologies 

that manufacturers could apply in order to comply with a specified CAFE standard, and 

2) calculating the cost and effects of manufacturers’ technology applications. The NPRM 

also discussed other modeling systems and approaches that NHTSA considered to 

accomplish these same objectives, and also discusses why ultimately the agency chose to 

use the Volpe model (see 79 FR 24352, 24391). However, having done so for this final 

rule does not limit the agency’s ability to use another approach for future CAFE 

rulemakings, and NHTSA will continue to consider other methods for estimating the 

costs and effects of adding technologies to manufacturers’ future fleets. 

The Volpe model relies on several inputs and data files to conduct the compliance 

analysis, and each of these are discussed in detail in the NPRM. Many of these inputs 

contain economic and environmental data required for the full CAFE analysis. However, 

for the purposes of applying technologies, the subject of this section, the Volpe model 

primarily uses three data files, one that contains data on the vehicles being manufactured, 
V-21

one that identifies the appropriate stage within the vehicle’s life-cycle for the technology 

to be applied, and one that contains data/parameters regarding the available technologies 

the model can apply. These inputs are discussed below. 

The Volpe model begins with an “initial state” of the domestic vehicle market, which in 

this case is the market for passenger cars and light trucks to be sold during the period 

covered by the final rule. The vehicle market is defined on a model, engine, and 

transmission basis, such that each defined vehicle model refers to a separately-defined 

engine and a separately-defined transmission. For the final rule, this represented roughly 

5,500 cars and trucks, 700 engines, and 600 transmissions. The information, which is 

stored in a file called the “vehicle market forecast,” is informed significantly by product 

plans provided to NHTSA by vehicle manufacturers.106 However, the Volpe model does 

not require that the market forecast be based on confidential product plans, and the model 

is often tested using input files developed using only publicly- and commerciallyavailable information. EPCA does not require NHTSA to use manufacturers’ 

confidential product plans as a basis for setting future CAFE standards, and the agency 

will continue to base its market forecasts on whatever it determines is the best available 

information, whether from public, commercially-available, or confidential sources. 

In addition to containing data about each vehicle, engine, and transmission, this file 

contains information for each technology under consideration as it pertains to the specific 

vehicle (whether the vehicle is equipped with it or not), the model year the vehicle is 

undergoing redesign, and information about the vehicle’s subclass for purposes of 

technology application. 

The market forecast file provides NHTSA the ability to identify, on a technology by 

technology basis, which technologies may already be present (manufactured) on a 

particular vehicle, engine, or transmission, or which technologies are not applicable (due 

to technical considerations) to a particular vehicle, engine, or transmission. These 

identifications are made on a model-by-model, engine-by-engine, and transmission-bytransmission basis. For example, if Manufacturer X advises NHTSA that Vehicle Y will 

be manufactured with Technology Z, then for this vehicle Technology Z will be shown as 

used. Or alternatively, NHTSA might conclude based on its own assessment that for a 

given four cylinder engine, Manufacturer A cannot utilize a particular Technology C due 

to an engineering issue that prohibits it. In this case, NHTSA would, in the market 

forecast file, indicate that Technology C should not be applied to this particular engine 

(i.e., is unavailable). Since multiple vehicle models may be equipped with this engine, 

this may affect multiple models. In using this aspect of the market forecast file, NHTSA 

ensures the Volpe model only applies technologies in an appropriate manner, since before 

any application of a technology can occur, the model checks the market forecast to see if 

it is either already present or unavailable. 

 

106 The market forecast is developed by NHTSA using the product plan information provided to the agency 

by individual vehicle manufacturers in response to NHTSA’s requests. The submitted product plans contain 

confidential business information (CBI), which the agency is prohibited by federal law from disclosing. 
V-22

Manufacturers typically plan vehicle changes to coincide with certain stages of a 

vehicle’s life cycle that are appropriate for the change, or in this case the technology 

being applied. For instance, some technologies (e.g., those that require significant 

revision) are nearly always applied only when the vehicle is expected to be redesigned. 

Other technologies can be applied only when the vehicle is expected to be refreshed or 

redesigned and some others can be applied at any time, regardless of whether a refresh or 

redesign event is conducted. Accordingly, the model will only apply a technology at the 

particular point deemed suitable. These constraints are intended to produce results 

consistent with manufacturers’ product planning practices. For each technology under 

consideration, NHTSA stipulates whether it can be applied any time, at refresh/redesign, 

or only at redesign. The data forms another input to the Volpe model, as discussed in 

detail below, called the Technology Refresh and Redesign Application table. Each 

manufacturer identifies its planned redesign model year for each of its vehicles, and this 

data is also stored in the market forecast file. 

NHTSA assigns one of 12 subclasses to each vehicle manufactured in the rulemaking 

period. The vehicle subclass data is used for the purposes of technology application. 

Each vehicle’s class is stored in the market forecast file. When conducting a compliance 

analysis, if the Volpe model seeks to apply technology to a particular vehicle, it checks 

the market forecast to see if the technology is available and if the refresh/redesign criteria 

are met. If these conditions are satisfied, the model determines the vehicle’s subclass, 

which it then uses to reference another input called the technology input file. 

In the technology input file, NHTSA has developed a separate set of technology data 

variables for each of the twelve vehicle subclasses. Each set of variables is referred to as 

an “input sheet,” so for example, the subcompact input sheet holds the technology data 

that is appropriate for the subcompact subclass. Each input sheet contains a list of 

technologies available for members of the particular vehicle subclass. The following 

items are provided for each technology: a brief description, its abbreviation, the decision 

tree with which it is associated, the (first) year in which it is available, the upper and 

lower cost and effectiveness (fuel consumption reduction) estimates, the learning type 

and rate, the cost basis, its applicability, and the phase-in values. 

The input sheets are another method NHTSA uses to determine how to properly apply, or 

in some cases constrain, a technology’s application, as well as to establish the costs and 

fuel consumption changes that occur as it is applied. Examples of how technologies are 

applied (or constrained) include the “Applicability” variable: if it is set to “TRUE,” then 

the technology can be applied to all members of the vehicle subclass (a value of 

“FALSE” would prevent the Volpe model from applying the technology to any member). 

Another example would be the “Year Available” variable, which if set to “2012” means 

the model can apply it to MY 2012 and later members, but cannot apply the technology 

to MY 2011 models. The “Learning Type” and “Learning Rate” define reductions in 

technology costs, if any are appropriate, that the Volpe model may apply under certain 

conditions, as discussed in the Learning Curve section below. “Phase-in Values” are 

intended to address the various constraints that limit a manufacturer’s ability to apply 

technologies within a short period of time. For phase-ins, once the model applies a given 
V-23

technology to a percentage of a given manufacturers’ fleet up to a specified phase-in cap, 

the model then ceases to apply it further instead applying other technologies. 

Perhaps the most important data contained in the input sheets are the cost and 

effectiveness information associated with each technology. One important concept to 

understand about the cost and effectiveness values is that they are “incremental” in 

nature, meaning that the estimates are “referenced” to some prior technology state in the 

decision tree in which the applied technology is represented, typically the preceding 

technology. Therefore, when considering values shown in the input sheet, the reader 

must understand that in all but a few cases they cannot fully deduce the accumulated or 

“NET” cost and effectiveness, referenced back to the base condition (i.e., start of the 

decision tree), without performing a more detailed analysis. The method for conducting 

this analysis, and a brief example of how it is done, is discussed in the Decision Tree 

section below. For the final rule, to help readers better understand Volpe model net or 

accumulated costs and fuel consumption reductions, NHTSA has published net values to 

key technology locations on the decision trees (e.g., to diesel engine conversion, or a 

strong hybrid). See the Tables showing Approximate Net Technology Costs and 

Approximate Net Technology Effectiveness. The tables have been produced for each of 

the four vehicle subclasses in the passenger car, performance passenger car, and light 

truck vehicle groups. 

The incremental costs of some technologies are dependent on certain factors specific to 

the vehicle to which they are applied. For instance, when the Material Substitution 

technology is applied, the cost of application is based on a cost per unit weight reduction, 

in dollars per pound, since the weight removed is a percentage of the curb weight of the 

vehicle (which differs from one vehicle to the next). Similarly, some engine technologies 

need to be calculated on a cost per cylinder basis, or a cost per configuration basis (i.e., a 

cost per bank basis, so that a V-configured engine would cost twice as much as an in-line, 

single bank engine). For each technology, the input sheet also contains a Cost Basis 

variable which indicates whether the costs need to be adjusted in this manner. This 

functionality, some of which is new for the final rule, allows NHTSA to estimate more 

accurately the costs of technology application, since in the NPRM the vehicles in a 

subclass were assumed to have common cylinder counts and configurations (thus the 

costs were underestimated for some vehicles and overestimated for others). 

Lastly for the technology input file, the term “synergy” as it applies to the Volpe 

modeling process refers to the condition that occurs when two or more technologies are 

applied to a vehicle and their effects interact with each other, resulting in a different net 

effect than the combination of the individual technologies. The term synergy usually 

connotes a positive interaction (e.g., 1 + 1 is more than 2), but as used here it also 

includes negative interactions (e.g., 1 + 1 is less than 2). Synergies are discussed in 

greater detail below, and the values for the synergy factors NHTSA used in the final rule 

are stored in the technology input file. 

In some cases more than one decision tree path can lead to a subsequently applied 

technology. For example, the power split hybrid technology can be reached from one of 
V-24

two prior transmission technologies (CVT or DCTAM). Accordingly the incremental 

cost and effectiveness for applying the technology may vary depending on the path and 

the modifications made in the prior technology. To ensure accurate tracking of net costs 

and effectiveness, the Volpe model utilizes path correction factors, as discussed further in 

the decision tree discussion below. This functionality is an improvement to the final rule, 

and the specific factors used are stored in the technology input sheets. A copy of the final 

rule input sheets, titled “2011-2015_LV_CAFE_FinalRuleInputSheets20081019.pdf,” 

can be obtained from the final rule docket. 

One additional concept to understand about how the Volpe model functions is called an 

“engineering constraint,” a programmatic method of controlling technology application 

that is independent of those discussed above. NHTSA has determined that some 

technologies are only suitable or unsuitable when certain vehicle, engine, or transmission 

conditions exist. For example, secondary axle disconnect is only suitable for 4WD 

vehicles, and cylinder deactivation is unsuitable for any engine with fewer than 6 

cylinders, while material substitution is only available for vehicles with curb weights 

greater than 5,000 pounds. Additionally, in response to comments received, an 

engineering constraint was added for purposes of the final rule to prevent the cylinder 

deactivation technology from being applied to vehicles equipped with manual 

transmissions, due primarily to driveability and NVH concerns documented by the 

commenter. Where appropriate and required, NHTSA has utilized engineering 

constraints to ensure accurate application of the fuel saving technologies. 

3. Technology application decision trees

Several changes were made to the Volpe model between the analysis reported in the 

NPRM and the final rule. This section will discuss two of those changes: first, the 

updates to the set of technologies; and second, the updates to the logical sequence 

for progressing through these technologies, which NHTSA describes as “decision 

trees.” 

As discussed above, the set of technologies considered by the agency has evolved since 

the NPRM. The set of technologies now included in the Volpe model is shown below in 

Table V-1, with abbreviations used by the model to refer to each technology in the 

interest of brevity. 
V-25

Table V-1. Revised Final Rule Technology Set for Volpe Model 

Technology Abbreviation 

Low Friction Lubricants LUB 

Engine Friction Reduction EFR 

VVT - Coupled Cam Phasing (CCP) on SOHC CCPS 

Discrete Variable Valve Lift (DVVL) on SOHC DVVLS 

Cylinder Deactivation on SOHC DEACS 

VVT - Intake Cam Phasing (ICP) ICP 

VVT - Dual Cam Phasing (DCP) DCP 

Discrete Variable Valve Lift (DVVL) on DOHC DVVLD 

Continuously Variable Valve Lift (CVVL) CVVL 

Cylinder Deactivation on DOHC DEACD 

Cylinder Deactivation on OHV DEACO 

VVT - Coupled Cam Phasing (CCP) on OHV CCPO 

Discrete Variable Valve Lift (DVVL) on OHV DVVLO 

Conversion to DOHC with DCP CDOHC 

Stoichiometric Gasoline Direct Injection (GDI) SGDI 

Combustion Restart CBRST 

Turbocharging and Downsizing TRBDS 

Exhaust Gas Recirculation (EGR) Boost EGRB 

Conversion to Diesel (from CBRST) DSLC 

Conversion to Diesel (from TRBDS) DSLT 

Electric Power Steering EPS 

Improved Accessories IACC 

12V Micro-Hybrid MHEV 

Higher Voltage/Improved Alternator HVIA 

Integrated Starter Generator ISG 

6-Speed Manual/Improved Internals 6MAN 

Improved Auto. Trans. Controls/Externals IATC 

Continuously Variable Transmission CVT 

6/7/8-Speed Auto. Trans with Improved Internals NAUTO 

Dual Clutch or Automated Manual Transmission DCTAM 

Power Split Hybrid PSHEV 

2-Mode Hybrid 2MHEV 

Plug-in Hybrid PHEV 

Material Substitution (1%) MS1 

Material Substitution (2%) MS2 

Material Substitution (5%) MS5 

Low Rolling Resistance Tires ROLL 

Low Drag Brakes LDB 

Secondary Axle Disconnect SAX 

Aero Drag Reduction (10%) AERO 
V-26

As in the NPRM, each technology is assigned to one of the five following categories 

based on the system it affects or impacts: engine, transmission, electrification/accessory, 

hybrid or vehicle. Each of these categories has its own decision tree that the Volpe 

model uses to apply technologies sequentially during the compliance analysis. The 

decision trees were designed and configured to allow the Volpe model to apply 

technologies in a cost-effective, logical order that also considers ease of implementation. 

For example, effective software or control logic changes are implemented before 

replacing a component or system with a completely redesigned one, which is typically a 

much more expensive option. 

Each technology within the decision trees has an incremental cost and an incremental 

effectiveness estimate associated with it, and the estimates are specific to a particular 

vehicle subclass. Each technology’s incremental estimate takes into account its position 

in the decision tree path. If a technology is located further down the decision tree, the 

estimates for the costs and effectiveness values attributed to that technology are 

influenced by the incremental estimates of costs and effectiveness values for prior 

technology applications. In essence, this approach accounts for “in-path” effectiveness 

synergies and cost effects that occur between the technologies in the same path. When 

comparing cost and effectiveness estimates from various sources and those provided by 

commenters, it is vital that the estimates are evaluated in the proper context, especially as 

concerns their likely position in the decision trees and other technologies that may be 

present or missing. Not all estimates provided by commenters can be considered an 

“apples-to-apples” comparison with those used by the Volpe model, since in some cases 

the order of application, or included technology content, is inconsistent with that assumed 

in the decision tree. 

For the final rule, significant revisions have been made to the sequence of technology 

applications within the decision trees, and in some cases the paths themselves have been 

modified and additional paths have been added. The additional paths allow for a more 

accurate application of technology, insofar as the model now considers the existing 

configuration of the vehicle when applying technology. In this analysis, single overhead 

camshaft (SOHC), dual overhead camshaft (DOHC) and overhead valve (OHV) 

configured engines now have separate paths that allow for unique path-dependent 

versions of certain engine technologies. Thus, the cylinder deactivation technology 

(DEAC) now consists of three unique versions that depend on whether the engine being 

evaluated is an SOHC, DOHC or OHV design; these technologies are designated by the 

abbreviations DEACS, DEACD and DEACO, respectively, to designate which engine 

path they are located on. Similarly the last letter for the Coupled Cam Phasing (CCP) 

and Discrete Variable Valve Lift (DVVL) abbreviations are used to identify which path 

the technology is applicable to. 

Use of separate valvetrain paths and unique path-dependent technology variations also 

ensures that the incremental cost and effectiveness estimates properly account for 

technology effects so as not to “double-count.” For example, in the SOHC path, the 

incremental effectiveness estimate for DVVLS assumes that some pumping loss 

reductions have already been accomplished by the preceding technology, CCPS, which 
V-27

reduces or diminishes the effectiveness estimate for DVVLS because part of the 

efficiency gain associated with the reduction of the pumping loss mechanism has already 

occurred. Commenters pointed out several instances in the NPRM where doublecounting appeared to have occurred, and the accounting approach used in the final rule 

resolves these concerns. 

In reviewing NPRM comments, NHTSA noted several questions regarding the retention 

of previously applied technologies when more advanced technologies (i.e., those further 

down the decision tree) were applied. In response, NHTSA has clarified the final rule 

discussions on this issue. In both the NPRM and final rule, as appropriate and feasible, 

previously-applied technologies are retained in combination with the new technology 

being applied, but this is not always the case. For instance, one exception to this would 

be the application of diesel technology, where the entire engine is assumed to be 

replaced, so gasoline engine technologies cannot carry over. This exception for diesels, 

along with a few other technologies, is documented below in the detailed discussion of 

changes to each decision tree and corresponding technologies. 

As the Volpe model steps through the decision trees and applies technologies, it 

accumulates total or “NET” cost and effectiveness values. Net costs are accumulated 

using an additive approach while net effectiveness estimates are accumulated 

multiplicatively. To help readers better understand the accumulation process, and in 

response to comments expressing confusion on this subject, the following examples 

demonstrate how the Volpe model calculates net values. 

Accumulation of net cost is explained first as this is the simpler process. This example 

uses the Electrification/Accessory decision tree sequentially applying the EPS, IACC, 

MHEV, HVIA and ISG technologies to a subcompact vehicle using the cost and 

effectiveness estimates from its input sheet. As seen in Table V-2 below, the input sheet 

cost estimates have a lower and upper value which may be the same or a different value 

(i.e., a single value or a range) as shown in columns two and three. The Volpe model 

first averages the values (column 4), and then sums the average values to calculate the net 

cost of applying each technology (column 5). Accordingly, the net cost to apply the 

MHEV technology for example would be ($112.50 + $192.00 + $372.00 = $676.50). Net 

costs are calculated in a similar manner for all the decision trees. 
V-28

Table V-2. Sample Volpe Model Net Cost Calculation 

Tech. Abrev.

Lower INCR 

Cost

Upper INCR 

Cost

Avg. INCR 

Cost NET Cost

EPS 105.00 $ 120.00 $ 112.50 $ $ 112.50

IACC 173.00 $ 211.00 $ 192.00 $ $ 304.50

MHEV 372.00 $ 372.00 $ 372.00 $ $ 676.50

HVIA 84.00 $ 84.00 $ 84.00 $ $ 760.50

ISG 1,713.00 $ 1,713.00 $ 1,713.00 $ $ 2,473.50

Example Net Cost Calculation: 

Elect./Acc. Path, Subcompact Vehicle Subclass

The same decision tree, technologies, and vehicle are used for the example demonstrating 

the model’s net effectiveness calculation. Table V-3 below shows average incremental 

effectiveness estimates in column two; this value is calculated in the same manner as the 

cost estimates above (average of lower and upper value taken from the input sheet). To 

calculate the change in fuel consumption due to application of the EPS technology with 

incremental effectiveness of 1.5 percent (or 0.015 in decimal form, column 3), when 

applied multiplicatively, means that the vehicle’s current fuel consumption ‘X’ would be 

reduced by a factor of (1 – 0.015) = 0.985,107 or mathematically 0.985*X. To represent 

the changed fuel consumption in the normal fashion (as a percentage change), this value 

is subtracted from 1 (or 100%) to show the net effectiveness in column 5. 

As the IACC technology is applied, the vehicle’s fuel consumption is already reduced to 

0.985 of its original value. Therefore the reduction for an additional incremental 1.5 

percent results in a new fuel consumption value of 0.9702, or a net 2.98 percent 

effectiveness, as shown in the table. Net effectiveness is calculated in a similar manner 

for the all decision trees. It should be noted that all incremental effectiveness estimates 

were derived with this multiplicative approach in mind; calculating the net effectiveness 

using an additive approach will yield a different and incorrect net effectiveness. 

 

107 A decrease in fuel consumption (FC) means the fuel economy (FE) will be increased since fuel 

consumption and economy are related by the equation FC = 1/FE. 
V-29

Table V-3. Sample Volpe Model Net Effectiveness Calculation 

Tech. 

Abrev.

Avg. 

INCR 

Eff. %

Avg. INCR 

Eff. 

(decimal)

Multiplicative FC Reduction

Current FC * (1-Avg INCR)

Net 

Effect.

(1 - Red)

EPS 1.50% 0.0150 1 * (1 - 0.015) = 0.985 1.50%

IACC 1.50% 0.0150 0.985 * (1 - 0.015) = 0.9702 2.98%

MHEV 1.95% 0.0195 0.9702 * (1 - 0.0195) = 0.9513 4.87%

HVIA 0.55% 0.0055 0.9513 * (1 - 0.0055) = 0.9461 5.39%

ISG 6.10% 0.0610 0.9461 * (1 - 0.061) = 0.8884 11.16%

Example Net Effectiveness Calculation: 

Elect./Acc. Path, Subcompact Vehicle Subclass

To improve the accuracy of accumulating net cost and effectiveness estimates for the 

final rule, “path-dependent corrections” were employed. The NPRM analysis had the 

potential to either overestimate or underestimate net cost and effectiveness depending on 

which decision tree path the Volpe model followed when applying the technologies. For 

example, if in the NPRM analysis a diesel technology was applied to a vehicle that 

followed the OHV path, the net cost and effectiveness could be different from the net 

estimates for a vehicle that followed the OHC path even though the intention was to have 

the same net cost and effectiveness. In order to correct this issue, the final rule analysis 

has added path-dependent correction tables to the input sheets. The model uses these 

tables to correct net cost and effectiveness estimate differences that occur when multiple 

paths lead into a single technology that is intended to have the same net cost and 

effectiveness no matter which path was followed.108 Path-dependent corrections were 

used when applying cylinder deactivation (on the DOHC path), turbocharging and 

downsizing, diesel and strong hybrids. This is essentially an accounting issue and the 

path-dependent corrections are meant to remedy the accuracy issues reported in the 

NPRM comment responses. 

The following paragraphs explain, in greater detail, the revisions to the decision trees and 

technologies from the NPRM to the final rule. Revisions were made in response to 

comments received and pursuant to NHTSA’s analysis, and were made to improve the 

accuracy of the Volpe compliance analysis, or to correct other concerns from the NPRM 

analysis. 

Engine Technology Decision Tree 

Figure V-8 below shows the final rule decision tree for the engine technology 

 

108 The correction tables are used for path deviations within the same decision tree. However, there is one 

exception to this rule, specifically that the tables are used to keep the model from double-counting cost and 

effectiveness estimates when both the CBRST and MHEV are applied to the same vehicle. Both 

technologies try to accomplish the same goal of reducing fuel consumption, by limiting idle time, but 

through different means. If either of these technologies exists on a vehicle and the Volpe model applies the 

other, the correction tables are used to remove the cost and effectiveness estimates for CBRST, thus 

ensuring that double-counting does not occur. 
V-30

category. For the final rule, NHTSA removed camless valve actuation (CVA), leanburn GDI (LBDI), and homogenous charge compression ignition (HCCI) from the 

decision trees because these technologies were determined to be still in the research 

phase of development. NHTSA did not receive any new information or comments 

that suggested these technologies are under development, so NHTSA removed them 

from the decision trees. At the top of the engine decision tree Low Friction Lubricants 

(LUB) and Engine Friction Reduction (EFR) technologies are retained as utilized in 

the NPRM. 

As stated above, SOHC, DOHC and OHV engines have separate paths, whereas as the 

NPRM only made the distinction between OHC and OHV engines. The separation of 

SOHC and DOHC engines allowed the model to more accurately apply unique pathdependent valvetrain technologies including variations of Variable Valve Timing 

(VVT), Variable Valve Lift (VVL) and cylinder deactivation that are tailored to either 

SOHC or DOHC engines. This separation also allowed for a more accurate method of 

accounting for net cost and effectiveness compared to the NPRM. For both the SOHC 

and DOHC paths, VVL technologies were moved upstream of cylinder deactivation in 

response to comments from the Alliance, additional confidential manufacturer 

comments and submitted product plan trends, and NHTSA’s analysis. Confidential 

comments stated that applying cylinder deactivation to an OHC engine is more 

complex and expensive than applying it to an OHV engine. The Alliance additionally 

stated that cylinder deactivation is very application-dependent, and is more effective 

when applied to vehicles with high power-to-weight ratios. Taking in account the 

application-specific nature of cylinder deactivation and the fact the VVL technologies 

are more suitable to a broader range of applications, NHTSA moved VVL 

technologies “upstream” of cylinder deactivation on the SOHC and DOHC to more 

accurately represent how a manufacturer might apply these technologies. 
V-31

Figure V-8. Engine Technology (EngMod) Decision Tree 
V-32

On the OHV path, the ordering of cylinder deactivation (DEACO) then Coupled Cam 

Phasing (CCPO), which is opposite the order of the SOHC and DOHC paths, was 

retained as defined in the NPRM. This ordering depicts most accurately how 

manufacturers would actually implement these technologies and was reflected in the 

submitted product plans for OHV engines, which are largely used on trucks with high 

power-to-weight ratios. After the application of CCPO on the OHV decision tree, the 

model chooses between Discrete Variable Valve Lift (DVVLO) and the conversion to 

a dual overhead camshaft engine (CDOHC). This conversion now includes Dual Cam 

Phasing (DCP) instead of Continuously Variable Valve Lift (CVVL) because it is 

assumed that DCP, with its higher application rates, would more likely be applied than 

CVVL, with its lower application rates. 

At this stage, and similar to the NPRM, the decision tree paths all converge into 

Stoichiometric Gasoline Direct Injection (SGDI). All previously applied technologies 

are retained with the assumption that SGDI is applied in addition to the pre-existing 

engine technologies. After SGDI, a newly defined technology, Combustion Restart 

(CBRST), has been added. 

The “branch point” after CBRST has been limited to two paths instead of the three 

paths in NPRM. This is due to the removal of HCCI from the final rule decision trees. 

The final rule engine decision tree allowed the model to apply either Turbocharging 

and Downsizing (TRBDS) or the conversion to diesel (DSLC). TRBDS is considered 

to be a completely new engine that has been converted to DOHC, if not already 

converted, with only LUB, EFR, DCP, SGDI and CBRST applied. 

The conversion to diesel is also considered to be a completely new engine that 

replaces the gasoline engine (although it carries over the LUB and EFR technologies). 

If the model chooses to follow the TRBDS path, the next technology that can be 

applied is another newly-added technology, EGR Boost (EGRB). After EGRB, the 

model is allowed to then convert the engine to diesel (DSLT). It should be noted that 

the path-dependent variations of diesel, (DSLC) and (DSLT), result in the exact same 

technology. The net cost and effectiveness estimates are the same for both but 

DSLT’s incremental cost and effectiveness estimates are slightly lower to account for 

the TRBDS and EGRB technologies that have already been applied. 

Electrification/Accessory Technology Decision Tree

This path, shown in Figure V-9, was named simply “Accessory Technology” in the 

NPRM. Electric Power Steering (EPS) is now the first technology in this decision tree, 

since it is a primary enabler for both mild and strong hybrids. Improved Accessories 

(IACC) has been redefined to include only an intelligent cooling system and follows EPS 

(in the NPRM, IACC was the first technology in the tree). The 42-volt Electrical System 

(42V) technology has been removed because it is no longer viewed as the voltage of 

choice by manufactures and is being replaced by higher voltage systems. Micro-Hybrid 

(MHEV), which follows IACC, has been added as a 12-volt stop/start system to replace 

Integrated Starter/Generator with Idle-Off (ISGO), which was on the 

“Transmission/Hybrid Technology” decision tree in the NPRM. Higher Voltage / 
V-33

Improved Alternator (HVIA), a higher efficiency alternator that can incorporate higher 

voltages (greater than 42V) follows MHEV. Integrated Starter Generator Hybrid (ISG) 

replaced IMA/ISAD/BSG Hybrid (which was also on the Transmission/Hybrid 

Technology decision tree in the NPRM) as a higher voltage hybrid system with limited 

regenerative capability. ISG takes into account all the previously applied 

Electrification/Accessory technologies and is the final step necessary in order to convert 

the vehicle to a (full) strong hybrid. All Electrification/Accessory technologies can be 

applied to both automatic and manual transmission vehicles. 

Transmission Technology Decision Tree 

This decision tree, shown in Figure V-9, contains two paths: one for automatic 

transmissions and one for manual transmissions. On the automatic path, the Aggressive 

Shift Logic (ASL) and Early Torque Converter Lockup (TORQ) technologies from the 

NPRM have been combined into an Improved Auto Trans Controls/Externals (IATC) 

technology, as both these technologies typically include only software or calibrationrelated transmission modifications. This technology was moved to the top of the decision 

tree since it was deemed to be easier and less expensive to implement than a major 

redesign of the existing transmission. The 5-Speed Automatic Transmission (5SP) 

technology from the NPRM has been deleted due to several factors. First, the updated 

decision tree logic seeks to optimize the current hardware as an initial step, instead of 

applying an expensive redesign technology. Second, NHTSA determined an industry 

trend of 4-speed automatics going directly to 6-speed automatics, as reflected in the 

submitted product plans. And finally, confidential manufacturer comments indicated that 

in some cases 5-speed transmissions offered little or no fuel economy improvement over 

4-speed transmissions (primarily due to higher internal mechanical and hydraulic losses, 

and increased rotating mass), making the technology less attractive from a cost and 

effectiveness perspective. In the final rule, both 4-speed and 5-speed automatic 

transmissions get the IATC technology applied first, before progressing through the rest 

of the transmission decision tree. 

After IATC the decision tree splits into a “Unibody only” and “Unibody or Ladder 

Frame” paths, which is identical to the NRPM version of the decision tree. Both of these 

paths represent a conversion to new and fully optimized designs. The Unibody only path 

contains the Continuously Variable Transmission (CVT) technology, while the Unibody 

or Ladder Frame path has the 6-Speed Automatic Transmission (6SP) technology being 

replaced by 6/7/8-Speed Automatic Transmission with Improved Internals (NAUTO). 

The NAUTO technology represents a new generation of automatics with lower internal 

losses from gears and hydraulic systems. 

The NPRM technology “Automated Manual Transmission (AMT)” has been renamed 

Dual Clutch Transmission/Automated Manual Transmission (DCTAM) to more 

accurately reflect the true intent of this technology to be a Dual Clutch Transmission 

(DCT). The NPRM’s use of the abbreviation “AMT” was confusing to many 

commenters, including the Alliance, BorgWarner, Chrysler, Ford and General Motors, 

and appeared to indicate that the NPRM analysis applied true automated manual 

transmissions, which exhibit a torque interrupt characteristic that many in the industry 
V-34

feel will not be customer acceptable. DCT does not have the torque interrupt concern. 

The technology DCTAM for the final rule assumes the use of a DCT type transmission 

only. 

The manual transmission path only has one technology application, like the NPRM. 

However, the technology being applied has been defined as conversion to a 6-Speed 

Manual with Improved Internals (6MAN) instead of a conversion to a 6/7/8-Speed 

Manual Transmission as defined in the NRPM. Extremely limited use of manual 

transmissions with more than 6 speeds is indicated in the updated product plans, so 

NHTSA believes this is a more accurate option for replacing a 4 or 5-speed manual 

transmission. 

Hybrid Technology Decision Tree 

The strong hybrid options, 2-Mode (2MHEV) and Power Split (PSHEV), are no longer 

sequential as defined in the NPRM’s Transmission/Hybrid decision tree. For the final 

rule, the model only applies strong hybrid technologies when both the 

Electrification/Accessory and Transmission (automatic transmissions only) technologies 

have been fully added to the vehicle, as seen in Figure V-9. The final rule analysis and 

logic ensures that the model does not double-count the cost and effectiveness estimates 

for previously applied technologies that are included (e.g., EPS) or replaced (e.g., 

transmission) by strong hybrid systems, which is responsive to General Motors’ comment 

stating that the NPRM analysis had the potential to double-count effectiveness estimates 

when applying strong hybrids. For the final rule analysis, when the Volpe model applies 

strong hybrids it now takes into account that some of the fuel consumption reductions 

have already been accounted for when technologies like EPS or IACC have been 

previously applied. Once all the Electrification/Accessory and Transmission 

technologies have been applied, the model is allowed to choose between the application 

of 2MHEV, PSHEV and the newly added Plug-in Hybrid Vehicle (PHEV). The NPRM 

decision tree required the Volpe model to step through 2MHEV in order to apply 

PSHEV. This updated final rule decision tree is a more realistic representation of how 

manufacturers might apply strong hybrids, and allows the Volpe model to choose the 

strong hybrid that is most appropriate for each vehicle based on its vehicle subclass or the 

most cost-effective technology application. The PHEV technology was added to the 

decision tree in the final rule based upon information in the public domain and submitted 

product plans showing that limited quantities of these vehicles will be available from 

some manufacturers in this timeframe. 
V-35

Figure V-9. Electrification/Accessory, Transmission and Hybrid Technology 

Decision Tree 

 

Vehicle Technology Decision Tree 

Material Substitution (MS1), (MS2) and (MS5) are now located on dedicated material 

substitution path in the Vehicle Technology Decision Tree, shown in Figure V-10. Low 

Rolling Resistance Tires (ROLL), Low Drag Brakes (LDB) and Secondary Axle 

Disconnect (SAX) now reside as a separate path, due to the relocation of material 

substitution technologies. Secondary Axle Disconnect has been redefined for the final 

rule to apply to 4WD vehicles only to more accurately reflect feasible applications of this 

technology. Aerodynamic Drag Reduction (AERO) remains a separate tree, and is now a 

10 percent reduction for both car and truck classes (excluding performance cars, which 

are exempt). 
V-36

Figure V-10. Vehicle Technology Decision Tree 
V-37

4. Division of vehicles into subclasses based on technology 

applicability, cost and effectiveness 

In assessing the feasibility of technologies under consideration, the agency evaluated 

whether each of these technologies could be implemented on all types and sizes of 

vehicles and whether some differentiation is necessary with respect to the potential to 

apply certain technologies to certain types and sizes of vehicles, and with respect to the 

cost incurred and fuel consumption achieved when doing so. The 2002 NAS Report 

differentiated technology application using ten vehicle classes (4 cars classes and 6 truck 

classes, including subcompact cars, compact cars, midsize cars, large cars, small SUVs, 

midsize SUVs, large SUVs, small pickups, large pickups, and minivans), but did not 

determine how cost and effectiveness values differ from “class” to “class.” NAS’s 

purpose in separating vehicles into these “classes” was to create groups of “like” 

vehicles, i.e., vehicles similar in size, powertrain configuration, weight, and consumer 

use, and for which similar technologies are applicable. This vehicle differentiation is 

done solely for the purpose of applying technologies to vehicles and assessing their 

incremental costs and effectiveness, and should not be confused with, the regulatory 

classifications pursuant to 49 CFR Part 523 discussed in Chapter XI. 

The Volpe model, which NHTSA has used to perform analysis supporting today’s notice, 

divides the vehicle fleet into subclasses based on model inputs, and applies subclassspecific estimates, also from model inputs, of the applicability, cost, and effectiveness of 

each fuel-saving technology. Therefore, the model’s estimates of the cost to improve the 

fuel economy of each vehicle model depend upon the subclass to which the vehicle 

model is assigned. 

In its MY 2005-2007 and MY 2008-2011 light truck CAFE standards as well as NPRM, 

NHTSA performed analysis using the same vehicle classes defined by NAS in its 2002 

Report. In its 2008 NPRM for MY 2011-2015, NHTSA included some differentiation in 

cost and effectiveness numbers between the various classes to account for differences in 

technology costs and effectiveness that are observed when technologies are applied on to 

different classes and subclasses of vehicles. The agency found it important to make that 

differentiation because the agency estimated that, for example, engine turbocharging and 

downsizing would have different implications for large vehicles than for smaller vehicles. 

For the final rule, NHTSA, working with Ricardo, increased the accuracy of its 

technology assumptions by reexaming the subclasses developed for the purpose of 

modeling technology application and by providing more differentiation in the costs and 

effectiveness values by vehicle subclass. 

In the request for comments accompanying the NPRM, NHTSA asked manufacturers to 

identify the style of each vehicles model they submit in their product plans from eight 

possible groupings (convertible, coupe, hatchback, pickup, sedan, sport utility, van, or 

wagon) or sixteen possible market segments (cargo van, compact car, large car, large 

pickup, large station wagon, midsize car, midsize station wagon, mini-compact, minivan, 

passenger van, small pickup, small station wagon, special purpose, sport utility truck, 

subcompact car, and two-seat car). NHTSA also requested that manufacturers identify 

many specific characteristics relevant to each vehicle model, such as the number of 
V-38

cylinders of the vehicle’s engine and other engine, transmission and vehicle 

characteristics. This information was evaluated by NHTSA staff, entered in NHTSA’s 

market data file, and used by NHTSA to assess how to divide the vehicles into subclasses 

for purposes of differentiating the applicability, effectiveness, and cost of available 

technologies. 

In response to the NPRM, the Alliance commented that NHTSA’s classification approach 

is not robust enough. With regard to subclasses of cars, the Alliance stated that NHTSA 

did not distinguish high-performance and sports cars which cannot accommodate certain 

technologies without changing the purpose and configuration of the vehicle. With regard 

to subclasses of trucks, the Alliance argued that SUVs were not adequately distinguished 

by size. The Alliance further stated the classification used by Sierra Research in its 

report to distinguish groups of like vehicles for technology application purposes was 

more realistic and representative of differences in market segments than NHTSA’s 

classification. The Alliance suggested that NHTSA consider the classes identified by 

Sierra Research in the final rule. 

NHTSA is not adopting Sierra’s approach to classification for the following reasons. 

First, Sierra’s classification scheme is too dependent on vehicle characteristics for which 

NHTSA often did not receive complete information from manufacturers. For example, 

although NHTSA requested that manufacturers provide estimates of the aerodynamic 

drag coefficient of each vehicle model planned for MY2011-2015, the agency received 

no estimates for many vehicles. NHTSA believes manufacturers are too far from 

production on many vehicles to confidently provide such estimates. Second, Sierra’s 

classification scheme is, for NHTSA’s purposes, excessively fine-grained. Sierra’s 

analysis relied on 25 subclasses in total, 13 for cars and 12 for trucks. While their report 

provided tables comparing their classes to those of NHTSA’s and cited product examples 

for each class, it did not provide a reason for why this detailed differentiation would 

significantly improve the outcome. NHTSA’s review of the Sierra report did not reveal 

many differences in technology-application between these subclasses. In addition, the 

agency does not believe that the effort required by the agency to create a more detailed 

yet more complex modeling structure based on 25 subclasses would result in significant 

improvement in the accuracy of the results. Sierra may have found this additional 

differentiation important for the full vehicle simulation approach that the Alliance 

claimed should be used throughout NHTSA’s analysis. However, as discussed below, 

NHTSA has concluded that this approach is neither necessary nor practical for CAFE 

analysis. 

The agency agrees with the Alliance, however, that some refinement in the classification 

approach used by NHTSA in the NPRM is merited in order to ensure the practicability of 

technologies being added. The agency also believes that the limited differentiation in 

costs and effectiveness values by vehicle class needs to be expanded in order to better 

account for fuel savings and costs. 

For the final rule, NHTSA first reexamined the Volpe model technology output files from 

the NPRM to identify where and why technologies may have been inappropriately 
V-39

applied by the model. Where this reexamination revealed logical errors, the Volpe model 

was revised accordingly. However, the review revealed that most of the observed 

inaccuracies resulted from the manner in which vehicles were assigned to subclasses for 

the purpose of technology applications. NHTSA also reviewed the confidential vehicle 

level information received from manufacturers, how manufacturers classified their 

vehicles by style or market segment groupings requested by NHTSA and the specific 

engine, transmission and other vehicle characteristics identified by the manufacturers for 

each vehicle model. This conclusion was among those that led NHTSA to assign more 

staff to perform quality control when reviewing and integrating manufacturers’ product 

plans. 

In order to improve the accuracy of technology application modeling, NHTSA examined 

at the car and truck segments separately. First, for the car segment, NHTSA plotted the 

footprint distribution of vehicles in the product plans and divided that distribution into 

four equivalent footprint range segments. The footprint ranges were named Subcompact, 

Compact, Midsize, and Large classes in ascending order. Cars were then assigned to one 

of these classes based on their specific footprint size. Vehicles in each range were then 

manually reviewed by NHTSA staff to evaluate and confirm that they represented a fairly 

reasonable homogeneity of size, weight, powertrains, consumer use, etc. However, as the 

Alliance pointed out, some vehicles in each group were sports or high-performance 

models. Since different technologies and cost and effectiveness estimates are appropriate 

for these vehicles, NHTSA created a performance subclass within each car class to 

maximize the accuracy of technology application. To determine which cars would be 

assigned to the performance subclasses, NHTSA graphed (in ascending rank order) the 

power-to-weight ratio for each vehicle in a class. An example of the Compact subclass 

plot is shown below. The subpopulation was then manually reviewed by NHTSA staff to 

determine an appropriate transition point between “performance” and “non-performance” 

models within each class. 

Compact Subclass - P/W Ratio in Ascending Order

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Power (HP) / Curb Wght. (Lbs)

Compact

Transition Area

Normal Perf. High Perf.
V-40

A total of eight classes (including performance subclasses) were identified for the car 

segment: Subcompact, Subcompact Performance, Compact, Compact Performance, 

Midsize, Midsize Performance, Large, Large Performance. In total, the number of cars 

that were ultimately assigned to a performance subclass was less than 10 percent. The 

table below shows the difference in the classification between the NPRM and Final Rule 

and provides examples of the types of vehicles assigned to each. 

NPRM Car Subclasses 

Class Example vehicles 

Subcompact Chevy Aveo, Chevy Corvette, Ford Mustang (V8), 

Honda Civic, Mazda Miata, Saturn Sky 

Compact Audi S4 Quattro, Chevy Camaro (V6), Chevy 

Cobalt, Daimler CL600, Mazda RX8, Nissan 

Sentra 

Midsize Bentley Arnage, Cadillac CTS, Honda Accord, 

Nissan Altima & G37 Coupe, Toyota Camry 

Large Audi A8, Cadillac DTS, Hyundai Azera 

Final Rule Car Subclasses 

Class Example vehicles 

Subcompact Chevy Aveo, Honda Civic 

Subcompact Performance Mazda Miata, Saturn Sky 

Compact Chevy Cobalt, Nissan Sentra and Altima 

Compact Performance Audi S4 Quattro, Mazda RX8 

Midsize Chevy Camaro (V6), Toyota Camry, Honda 

Accord, Hyundai Azera 

Midsize Performance Chevy Corvette, Ford Mustang (V8), Nissan G37 

Coupe 

Large Audi A8, Cadillac CTS and DTS 

Large Performance Bentley Arnage, Daimler CL600 

For light trucks, in reviewing the updated manufacturer product plans and in 

reconsidering how to divide trucks into classes and subclasses based on technology 

applicability, NHTSA found less of a distinction between SUVs and pickup trucks than 

appeared to exist in earlier rulemakings. Manufacturers appear to be planning fewer 

ladder-frame and more unibody pickups, and many pickups will share common 

powertrains with SUVs. Consequently, NHTSA condensed the classes available to 

trucks, such that SUVs and pickups are no longer divided. Recognizing structural 

differences between various types of “Vans,” NHTSA revisited how it assigned the 

different types of “Vans.” Instead of merging minivans, cargo vans, utility and multipassenger type vans under the same class, as it did for the NPRM and in previous rules, 

NHTSA formed a separate minivan class, because minivans (e.g., the Honda Odyssey) 

are expected to remain closer in terms of structural and other engineering characteristics 
V-41

than vans (e.g., Ford’s E-Series—also known as Econoline—vans) intended for more 

passengers and/or heavier cargo. 

The remaining vehicles (other vans, pickups, and SUVs) were then segregated into three 

footprint ranges and assigned a class of Small Truck/SUV, Midsize Truck/SUV, and 

Large Truck/SUV based on their footprints. NHTSA staff then manually reviewed each 

population for inconsistent vehicles based on engine cylinder count, weight (curb and/or 

gross), or intended usage, since these are important considerations for technology 

application, and reassigned vehicles to classes as appropriate. This system produced four 

truck segment classes—minivans and small, medium, and large SUVs/Pickups/Vans. The 

table below shows the difference in the classification between the NPRM and Final Rule 

NPRM Truck Subclasses 

Class Example vehicles 

Minivans Dodge Caravan, Ford Econoline, Toyota Sienna 

Small Truck Chevy Colorado, Toyota Tacoma, Ford Ranger 

Large Truck Chevy Silverado 

Small SUV Ford Escape, Nissan Rouge 

Midsize SUV Jeep Wrangler 4-door, Volvo XC70 

Large SUV Toyota Sequoia 

Final Rule Truck Subclasses 

Class Example vehicles 

Minivans Dodge Caravan, Toyota Sienna 

Small 

SUV/Pickup/Van 

Ford Escape & Ranger, Nissan Rogue, 

Midsize 

SUV/Pickup/Van 

Chevy Colorado, Jeep Wrangler 4-door, Volvo 

XC70, Toyota Tacoma 

Large 

SUV/Pickup/Van 

Chevy Silverado, Ford Econoline, Toyota Sequoia 

Based on a close review of detailed output from the Volpe model, NHTSA has concluded 

that its revised classification for purposes of technology applicability substantially 

improves the overall accuracy of the results as compared to the system employed in the 

NPRM. The new method uses footprint as a first indicator for both the car and truck 

segments, and all are then manually reviewed for the types of technologies applicable to 

them and revised by NHTSA to ensure that they have been properly assigned. The 

addition of the performance subclasses in the car segment and the condensing of classes 

in the truck segment further refine the system. The new method increases the accuracy of 

technology application without overly complicating the Volpe modeling process, and the 

revisions address comments received in response to the NPRM. 

5. How did NHTSA develop technology cost and effectiveness estimates for the 

final rule?
V-42

In the NPRM, NHTSA employed technology cost and effectiveness estimates developed 

in consultation with EPA. They represented NHTSA and EPA staff’s best assessment of 

the costs for each technology considered based on the available public and confidential 

information and data sources that the agencies had back in 2007 when the rulemaking 

was initiated. EPA also published a report and submitted it to the NRC committee on 

fuel economy of light-duty vehicles.109

Public comments on the NPRM’s technology cost estimates generally fell into four 

categories: (1) that costs are underestimated because NHTSA did not account for all 

changes/costs required to apply a technology or because although NHTSA correctly 

identified all the changes required, it did not cost those changes appropriately; (2) that 

costs are underestimated because the Retail Price Equivalent (RPE) factors have been 

applied incorrectly to technologies; (3) that costs are either over- or underestimated 

because learning curves have been applied incorrectly to technologies; and (4) that cost 

assumptions are overly simplified as applied to the full range of fleet vehicles and do not 

properly account for the differences in cost impacts across vehicle and engine types (e.g., 

technologies applied to a sub-compact car will be unique to those same technologies 

applied to a large SUV). Many commenters also stated that they found it difficult to 

understand how NHTSA and EPA had derived the cost estimates. In addition to 

commenting on NHTSA’s methodology, many commenters, particularly manufacturers, 

also submitted their own cost estimates for each technology and requested that NHTSA 

consider them for the final rule. 

As explained above, NHTSA contracted with Ricardo to aid the agency in analyzing the 

comments on the technology assumptions used in the NPRM, and relied considerably on 

Ricardo’s expertise in developing the final technology cost and effectiveness estimates 

based on that analysis. For every technology included in NHTSA’s analysis of 

technology costs and effectiveness, Ricardo and NHTSA engineers reviewed the 

comments thoroughly and exercised their expertise in assessing the merits of the 

comments, and in resolving the differences and determining which estimates should be 

used for the final rule. 

For each technology, NHTSA relied on Ricardo’s experience with “bill of materials” 

(BOM) costing. Some commenters criticized NHTSA for not using a BOM as the basis 

for its cost analysis. The 2008 Martec report,110 which updated the Martec report on 

which the 2004 NESCCAF study was based, was submitted by auto industry commenters 

to NHTSA’s NPRM docket for the agency’s consideration. This report provides cost 

estimates developed on a “bill of materials” basis and methodology. NHTSA, with 

Ricardo’s assistance, reviewed the “bill of materials” methodology in the Martec report 

and found it to be, compared to the methodology used in the NPRM, a more defensible 

and transparent basis for evaluating the costs of applicable technologies. 

 

109 EPA Staff Technical Report: Cost and Effectiveness Estimates of Technologies Used to Reduce LightDuty Vehicle Carbon Dioxide Emissions. EPA420-R-08-008, March 2008. 

110 Martec, “Variable Costs of Fuel Economy Technologies,” June 1, 2008.
V-43

A bill of materials in a general sense is a list of components that make up a system—in 

this case, an item of fuel economy-improving technology. In order to determine what a 

system costs, one of the first steps is to determine its components and what they cost. In 

cases in which it was not practicable for the agency and Ricardo to estimate the cost of 

each component on a BOM basis because there was a shift to a more advanced 

technology and or because of difficulty in accounting for the sum of costs of all added 

components less the sum of costs of all deleted components (e.g., in the transition from a 

gas engine to a diesel engine), incremental costs were estimated to be those of the entire 

new technology platform (in this example, the diesel engine) less those of the entire old 

technology platform (in this example, the gas engine). This “net difference” process was 

only used where developing a ground-up description of all component changes 

necessitated by the incremental technology was deemed to be impracticable. 

With that framework in mind, Ricardo and NHTSA engineers proceeded with reviewing 

cost information for each major component of each technology. They compared the 

multiple sources available in the docket and assessed their validity. While NHTSA and 

Ricardo engineers relied considerably on the 2008 Martec Report for costing contents of 

some technologies, they did not do so for all. When relevant publicly available 

information and data sets, including the 2008 Martec report, were determined to be 

incomplete or non-existent, NHTSA looked to prior published data, including the NPRM, 

or to values provided to NHTSA by commenters familiar with the material costs of the 

described technologies. 

Generally, whenever cost information for a technology component existed in a nonconfidential and publicly available report submitted to the NPRM docket and that 

information agreed with Ricardo’s independent review of cost estimates based on 

Ricardo’s historical institutional knowledge, Ricardo and NHTSA cited that information. 

Ricardo and NHTSA were able to take that approach frequently, as is evident in the 

explanation of the cost figures of each technology. When that approach was not possible, 

but there was confidential manufacturer data that had been submitted to NHTSA in 

response to the NPRM, and those costs were consistent with Ricardo’s independentlyreviewed cost estimates, NHTSA and Ricardo cited those data. When multiple 

confidential data sources differed greatly and conflicted with the Martec valuation or 

when the technical assumptions described by NHTSA for purposes of this rulemaking did 

not match exactly with the content costed by either Martec or other commenters, NHTSA 

and Ricardo engineers used component-level data to build up a partial cost, substituting 

Ricardo’s institutional knowledge for the remaining gaps in component level data. 

Occasionally, NHTSA and Ricardo found that some cost information submitted by the 

public was either not very clearly described or revealed a lack of knowledge on the part 

of the commenter about NHTSA’s methodology. In those cases, and in cases for which 

no cost data (either public or confidential) was available, NHTSA worked with Ricardo 

either to confirm the estimates it used in the NPRM, or to revise and update them. 
V-44

In several cases, values described in the NPRM were simply adjusted from 2006 dollars 

to 2007 dollars, using a ratio of GDP values for the associated calendar years.111 In many 

instances, an RPE factor of 1.5 was determined to have been omitted from the cost 

estimates provided in the NPRM, so NHTSA applied the multiplier where necessary to 

calculate the price to the consumer. 

Finally, in response to comments stating that cost estimates for individual technologies 

should be varied, based on the type and size of vehicle to which they are applied, NHTSA 

worked with Ricardo to account for that. Additionally, application of some technologies 

might be more or less expensive, depending on content (e.g., with or without a noise 

attenuation package), for particular vehicles. In these cases, NHTSA and Ricardo 

described a range of costs for this technology, and referred to sources that indicate the 

appropriate boundaries of that range. 

The agency notes that several technologies considered in the final rule have been updated 

with substantially different cost estimates relative to those costs described in the NPRM. 

For example, RPE estimates for turbocharging and downsizing (TRBDS), diesel 

technologies (DSLT) and hybrid technologies (like ISG) are much higher than the costs 

cited in the NPRM for those technologies. This is due in large part to the updated cost 

estimates of the 2008 Martec Report and others, referenced in the final rule, which reflect 

the dramatic rise of global costs for raw materials associated with the above 

technologies since the 2004 Martec report and other prior referenced cost estimates were 

conducted. The NPRM costs were not updated to reflect that rise in commodities prices. 

As described in the 2008 Martec Report, advanced battery technologies with substantial 

copper, nickel or lithium content, and engine technologies employing high 

temperature steels or catalysts with considerable platinum group metals usage, have 

experienced tremendous inflation of raw material prices since the cost studies referenced 

in the NPRM were conducted. As of the time the sources were developed, prices of 

nickel, platinum, lithium, copper, dysprosium and rhodium had demonstrated cost 

inflation amounting to between 300 and 750 percent of global prices at the time of the 

original NESCCAF study112 and this is reflected in the higher costs described in the 2008 

Martec report, and thus in the final rule. NHTSA is aware that commodity prices, like 

those for steel and platinum group metals described above, have dropped over the last 

several months. However, there is little information in the record to determine how 

prices of components used in MY 2011 could be impacted by the prices of metals and 

other commodities over the last few years. It is not clear whether the prices of 

components built and used in MY 2011 are more likely to reflect the high price of 

commodities in the years prior to 2008, the current low prices of commodities, the prices 

of commodities closer to MY 2011, or some mixture of these. The agency notes, though, 

as mentioned above, that manufacturers’ product plans were submitted along with 

manufacturers’ indications that these plans were generally informed by expectations that 

relatively high commodity prices would prevail in the future. Therefore, in the 

expectation that economic conditions will improve by MY 2011, the agency relies on the 

 

111 NHTSA examined the use of the CPI multiplier instead of GDP for adjusting these dollar values, but 

found the difference to be exceedingly small – only $0.14 over $100. 

112 2008 Martec report, at 13-20. 
V-45

commodity prices reflected in, for example, the 2008 Martec report. However, the 

agency further notes that these decisions are limited to the MY 2011 rulemaking. We 

intend to monitor commodity prices carefully and will adjust affected technology costs as 

appropriate in future rulemakings. 

Some commenters referenced the price differential between vehicles with advanced 

technologies and more standard versions as evidence of those advanced technologies’ 

costs, and argued that NHTSA should consider these price differentials in its cost 

estimation process. In response, NHTSA believes that the “bottom-up, material cost 

based” cost estimation methodology employed for the final rule is preferable to 

estimating costs based on manufacturer price differentials between versions of vehicle 

models. Wherever possible, technologies were costed based on the estimation of variable 

material cost impacts to vehicle manufacturers at a fixed point in time (in 2007 dollar 

terms) for a prescribed set of component changes anticipated to be required in 

implementing the technology on a particular platform (e.g., wastegate turbo, increased 

high nickel alloyed exhaust manifolds, air charge cooler, etc. for TRBDS). The content 

assumptions are modified or scaled to account for differences across the range of vehicle 

sizes and functional requirements and associated material cost impacts are adjusted to 

account for the revised content. The material cost impacts to the vehicle manufacturers 

are then summed and converted to retail price equivalent impacts by multiplying by 1.5 

to account for fixed costs and other overheads incurred in the implementation of new 

vehicle technologies but not contained in the variable material price impacts to the 

manufacturers. 

In employing this methodology, NHTSA relied on information provided to NHTSA by 

the suppliers and vehicle manufacturers themselves. Though this estimation process 

relies on often confidential data and employs a simplifying assumption in relating all 

variable material costs to retail impacts through the use of a consistent 1.5 RPE, the 

methodology is preferable to a “top-down, retail price based” methodology as might be 

used by comparing retail price differences of vehicles with different technologies. The 

“bottom-up” approach offers the benefits of providing a consistent and reasonable 

assessment of true, total costs for all technologies independent of geographic, or strategic 

pricing policies by vehicle manufacturers that could result in selling products at substandard or even negative margins. For many vehicle manufacturers, contribution to 

corporate profit varies dramatically across vehicle segment. Given that vehicle pricing is 

often decoupled from true costs and will vary with sales cycle, product maturity, 

geography, vehicle class, and marque, a “top-down” approach, while offering improved 

data transparency, is inherently limited in providing a consistent means of cost 

estimation. As such, NHTSA has adopted the described “bottom-up” cost estimation 

approach and has attempted to mitigate transparency issues with a reliance on Martec 

2008 (where in agreement with other provided cost data), because it provides a detailed 

description of the costed content. Fundamentally, NHTSA believes that a “bottom-up” 

cost estimation methodology with a common RPE adjustment factor offers an intuitive, 

consistent process across all technologies, whether mature or otherwise, that avoids the 

pitfalls of reliance on significantly more variable and volatile pricing policies. 
V-46

Regarding estimates for technology effectiveness, NHTSA, working with Ricardo, also 

reexamined its NPRM estimates and those in the EPA Staff Technical Report,113 which 

largely mirrored NHTSA’s NPRM estimates. We compared these estimates to estimates 

provided in comments, reports and confidential data received in response to our NPRM. 

Comments on the NPRM’s effectiveness estimates generally fell into three categories: 

(1) that NHTSA did not account sufficiently for fuel economy or performance impacts 

because it used the Volpe model approach rather than full vehicle simulation; (2) that the 

synergy values used did not properly account for technology interactions; and (3) that 

NHTSA made errors when using estimates provided by manufacturers. In addition to 

commenting on NHTSA’s methodology, many commenters, particularly manufacturers, 

also submitted their own fuel consumption reduction estimates for each technology and 

requested that NHTSA consider them for the final rule. 

For each technology, NHTSA also relied on Ricardo’s experience with “bill of materials” 

(BOM) technology descriptions. Some commenters argued that the same BOM used as 

the basis for the cost analysis could and should be used to define the technologies being 

studied for effectiveness. In fact, Ricardo’s methodology for cost and effectiveness 

estimates for this rule was to define a vehicle class-specific BOM or BOMs, depending 

upon the number of variants possible within a class and within a decision tree. These 

BOMs were defined for the baseline configuration for each class and then for each 

incremental step in the decision tree. Use of a consistently-defined BOM is very 

important to estimating the impacts of technologies accurately, as it helps to ensure that 

technologies are not applied to baseline vehicles that already contain the technology (with 

the exception of items that are not well-defined such as aerodynamic drag reduction, 

reduced rolling resistance tires, weight reduction, and engine friction reduction.) 

In defining these BOMs, Ricardo relied on its experience working with industry over 

many years and its recent experience preparing the December 2007 study for EPA. 

Ricardo built on its vehicle simulation work for EPA to help NHTSA evaluate 

appropriate effectiveness values for individual fuel-saving technologies. In considering 

the comments, NHTSA and Ricardo evaluated the 10 “vehicle subclasses” used in the 

NPRM for applicability of technologies and determined that the cost and effectiveness 

estimates could be more accurate by revising the “vehicle subclasses” as described above 

so that they better represented the parameters of the vehicles they included. This, in turn, 

enabled NHTSA and Ricardo to distinguish more clearly the differences in fuel 

consumption reduction occurring when a technology is added to different vehicles. 

Then, with the BOM framework applied to more precisely-defined vehicle subclasses, 

NHTSA and Ricardo engineers reviewed effectiveness information from multiple sources 

for each technology. Together, they compared the multiple sources available in the 

docket and assessed their validity, taking care to ensure that common BOM definitions 

and other vehicle attributes such as performance, refinement, and drivability were not 

compromised. 

 

113 EPA Staff Technical Report: Cost and Effectiveness Estimates of Technologies Used to Reduce LightDuty Vehicle Carbon Dioxide Emissions. EPA420-R-08-008, March 2008. 
V-47

Generally, whenever relevant effectiveness information for a technology component 

existed in a non-confidential and publicly-available report submitted to the NPRM 

docket, and that information agreed with Ricardo’s independent review of estimates 

based on Ricardo’s historical institutional knowledge, NHTSA and Ricardo cited that 

information. NHTSA and Ricardo were able to take that approach frequently, as is 

evident in the explanation of the effectiveness for each technology. When that approach 

was not possible, but there was confidential manufacturer data that had been submitted to 

NHTSA in response to the NPRM, and those values were consistent with Ricardo’s 

independently-reviewed estimates, NHTSA and Ricardo cited those data. When multiple 

confidential data sources differed greatly or when the technical assumptions described by 

NHTSA for purposes of this rulemaking did not match the content included in Ricardo’s 

study for EPA or in other comments, NHTSA and Ricardo engineers relied on Ricardo’s 

experience and an understanding of the maximum theoretical losses that could be 

eliminated by particular technologies to build up an effectiveness estimate, substituting 

Ricardo’s institutional knowledge for the remaining gaps in data. 

Occasionally, NHTSA and Ricardo found that some fuel consumption reduction 

information submitted by the public was either not very clearly described or revealed a 

lack of knowledge on the part of the commenter about NHTSA’ methodology. In those 

cases, and in cases for which no effectiveness data (either public or confidential) was 

available, NHTSA worked with Ricardo either to confirm the estimates it used in the 

NPRM, or to revise and enhance them. In other cases, the commenters appeared unsure 

how to evaluate the data from the NPRM, and so NHTSA and Ricardo provided more 

detailed explanations on the process used or the components involved. 

In response to comments stating that estimates for individual technologies should be 

varied based on the type and size of vehicle to which they are applied, NHTSA worked 

with Ricardo to account for those differences mostly through the refined vehicle subclass 

definitions. However, even after making these adjustments, there are still some classes 

that require spanning different engine architectures and performance thresholds. Just as 

the application of some technologies might be more or less expensive, depending on 

content (e.g., with or without a noise attenuation package), particular vehicle 

technologies may have more or less impact between classes where maintaining 

equivalent performance led to a reduced effectiveness. In these cases, NHTSA and 

Ricardo described a range of effectiveness values for this technology, and referred to 

sources that indicate the appropriate boundaries of that range. 

With Ricardo’s assistance, the technology cost and effectiveness estimates for the final 

rule were developed consistently, using this systematic approach. While NHTSA still 

believes that the ideal estimates for the final rule would be those that have been through a 

peer-reviewed process such as that used for the 2002 NAS Report, and will continue to 

work with NAS, as required by EISA, to update the technology cost and effectiveness 

estimates for subsequent CAFE rulemakings, this approach, combined with the BOM 

methodology for cost and effectiveness, expanded number and types of vehicle 

subclasses and the changes to the synergistic effects described below, not only help to 

address the concerns raised by commenters, but also represent a considerable 
V-48

improvement in terms of accuracy and transparency over the approach used to develop 

the cost and effectiveness estimates in the NPRM. 

6. Learning curves

As explained in the NPRM, historically NHTSA did not explicitly account for the cost 

reductions a manufacturer might realize through learning achieved from experience in 

actually applying a technology. However, based on its work with EPA, in the NPRM 

NHTSA employed a learning factor for certain newer, emerging technologies. The 

“learning curve” describes the reduction in unit incremental production costs as a 

function of accumulated production volume and small redesigns that reduce costs.

The NPRM implemented technology learning curves by using three parameters: (1) the 

initial production volume that must be reached before cost reductions begin to be realized 

(referred to as “threshold volume”); (2) the percent reduction in average unit cost that 

results from each successive doubling of cumulative production volume (usually referred 

to as the “learning rate”); and (3) the initial cost of the technology. The majority of 

technologies considered in the NPRM did not have learning cost reductions applied to 

them. 

NHTSA assumed that learning-based reductions in technology costs occur at the point 

that a manufacturer applies the given technology to the first 25,000 cars or trucks, and are 

repeated a second time as it produces another 25,000 cars or trucks for the second 

learning step.114 NHTSA explained that the volumes chosen represented the agency’s 

best estimate for where learning would occur, and that they were better suited to 

NHTSA’s analysis than using a single number for the learning curve factor, because each 

manufacturer would implement technologies at its own pace in the rule, rather than 

assuming that all manufacturers implement identical technology at the same time. 

NHTSA further assumed that after having produced 25,000 cars or trucks with a specific 

part or system, sufficient learning will have taken place such that costs will be lower by 

20 percent for some technologies and 10 percent for others. For those technologies, 

NHTSA additionally assumed that another cost reduction would be realized after another 

25,000 units. If a technology was already in widespread use (e.g., on the order of several 

million units per year) or expected to be so by the MY 2011-2012 time frame, NHTSA 

assumed that the technology was “learned out,” and that no more cost reductions were 

available for additional volume increases. If a technology was not estimated to be 

available until later in the rulemaking period at that time, like MY 2014-2015, NHTSA 

did not apply learning for those technologies until those model years. Most of the 

technologies for which learning was applied after MY 2014 were adopted from the 2004 

NESCCAF study, which was completed by Martec. Whenever source data, like the 2004 

NESCCAF study, indicated that manufacturer cost reduction from future learning would 

occur, NHTSA took that information into account. 

Comments received regarding NHTSA’s approach to technology cost reductions due to 

manufacturer learning generally disagreed with the agency’s method. The Alliance, 

AIAM, Honda, GM, and Chrysler all commented that NHTSA had substantially 

 

114 NHTSA treated car and truck volumes separately for determining those sales volumes. 
V-49

overestimated, and essentially “double-counted,” learning effects by applying learning 

reductions to component costs, specifically Martec estimates, which were already at high 

volume. The Alliance submitted the 2008 Martec Report, which stated that NHTSA had 

“misstated” Martec’s approach to cost reductions due to learning in the NPRM. As 

Martec explained, 

Martec did not ask suppliers to quote prices that would be valid for three years, 

and Martec did not receive cost reductions from suppliers for some components in 

years two and three. Rather, industry respondents were asked to establish mature 

component pricing on a forward basis given the following conditions: at least 

three (3) manufacturers demanding 500,000 units per year and at least three (3) 

globally-capable suppliers available to supply the needs of each manufacturer. 

In no case did Martec ask industry respondents to provide low volume, launch or 

transition costs for fuel consumption/CO2 reducing technologies. Martec 

specifically designed the economic parameters in order to capture the effects of 

learning which is a reality in the low margin, high capital cost, high volume, 

highly competitive global automotive industry. Applying additional reductions 

attributable to “learning” based on 25,000 unit improvements in cumulative 

volume after production launch (as described on pages 118-125 of the NHTSA 

NPRM) on top of Martec’s mature costs is an error. Martec’s costs are based on 

1.5-2.0 equivalent modules of powertrain capacity (500,000 units/year) so 25,000 

unit incremental changes in cumulative production, as defined by NHTSA, will 

have no effect on costs. 

The 2008 Martec Report also stated that current industry practice consists of using 

competitive bidding based on long-term, high-volume contracts that are negotiated before 

technology implementation decisions are made. Martec stated that this practice considers 

the effects of volume, learning, and capital depreciation. Martec also indicated that most 

of the technologies evaluated in the study are in high volume production in the global 

automotive industry today, and thus this forms a solid basis from which to estimate future 

costs. 

Honda also commented on NHTSA’s 25,000 unit (per manufacturer per year) volume 

threshold stating that, in their experience, costs were only likely to decrease due to 

learning at volumes exceeding about 300,000 units per year per manufacturer. GM 

agreed, stating that suppliers do not respond to, change processes, or change contract 

terms for relatively small volume changes like NHTSA’s 25,000 unit increment, thus 

volume changes of this magnitude have no effect on component pricing. GM also 

commented that its learning cycles are based on time, not volume, and agreed with 

Martec’s assessment that contracts with suppliers typically specify volumes and costs 

over a period, which are usually equal to a product life cycle, a 4- to 5-year period. 

Ford commented that base costs in the automotive industry are determined by a target 

setting process, where manufacturers develop pricing with suppliers for a set period, and 

manufacturers receive cost reductions from the suppliers due to learning as time passes, 

apparently at a set amount year over year for several years. Ford also commented that 

NHTSA’s approach to learning curves had not accounted for current economic factors, 
V-50

like increases in commodity and energy prices, and cited the example of costs of batteries 

for hybrids and PHEVs which Ford stated “are not likely to depend solely on experience 

learned, but, to a large extent, on the additional energy and material costs they incur 

relative to the vehicles without the new technology.” Ford commented that NHTSA 

should account for these costs, and the factor of declining vehicle sales, in its learning 

curve approach. 

BorgWarner, a components supplier, commented that learning-related costs savings are 

valid for technologies that “start at low volume” (commenter’s emphasis). BorgWarner 

argued, however, that NHTSA’s assumed learning curve would not apply to the 

technologies it supplies to manufacturers,115 since these components are well-developed 

and in high volume use already, and are thus already “learned out.” BorgWarner further 

commented that an increase in demand could in fact lead to higher prices if demand for 

raw materials exceeded supply. 

UCS, in contrast, commented that NHTSA had not accounted for enough cost reductions 

due to learning. UCS stated that NHTSA should have provided “source data” for 

manufacturer-specific learning curves, and argued that NHTSA’s approach was 

“fundamentally flawed” for two primary reasons: first, because NHTSA had not 

considered the fact that manufacturers engage in joint ventures to develop new 

technologies, and second, because manufacturers may also learn from one another 

“through the standard practice of tearing down competitors’ products.” UCS argued that 

NHTSA’s learning-based cost reductions should account for these methods of learning. 

UCS further stated that NHTSA should not “treat[] car and truck sales volumes 

separately when estimating learning curves” because there may be much overlap in terms 

of technology application, especially for vehicles like crossovers which may be either 

cars or trucks. UCS concluded that NHTSA should use EPA’s suggested learning factor 

of 20 percent, citing EPA’s Staff Technical Report. 

Public Citizen agreed that NHTSA should account for economies of scale, but argued that 

NHTSA should not have relied on initial cost estimates from industry, which the 

commenter stated were “often overestimated.” Public Citizen cited a 1997 briefing paper 

by the Economic Policy Institute in support of this point, and argued that compliance cost 

estimates were often much lower than actual costs. Public Citizen concluded that 

NHTSA’s use of learning curve factors “impedes transparency” in NHTSA’s analysis. 

Agency response: Based on the comments received and on its work with Ricardo, 

NHTSA has revised its approach to accounting for technology cost reductions due to 

manufacturer learning. The method of learning used in the NPRM has been retained, but 

the threshold volume has been revised and is now calculated on an industry-wide 

production basis. However, learning of this type, which NHTSA now refers to as 

“volume-based” learning, is not applicable to any technologies for MY 2011. 

Additionally, NHTSA has adopted a fixed rate, year-over-year (YOY) cost reduction for 

 

115 BorgWarner manufacturers and supplies turbochargers, dual clutch transmissions, variable valve timing 

systems, diesel engine components (EGR and starting), aggressive shift logic and early torque convertor 

lockup systems. 
V-51

widely-available, high-volume, mature technologies, in response to comments from Ford 

and others. NHTSA refers to this type cost reduction as “time-based” learning. For each 

technology, if learning is applicable, only one type of learning would be applied, either 

volume-based or time-based (i.e., the types are independent of each other). These 

revisions are discussed below. 

For volume-based learning, NHTSA considered comments from UCS and decided to 

revise the method used to calculate the threshold volume from a per-manufacturer to an 

industry-wide production volume basis. NHTSA agreed with UCS’ comment that cars 

and trucks may share common components—this is true across many makes and models 

which share common engines, transmissions, accessory systems, and mild or strong 

hybrid systems, all of which can potentially utilize the technologies under consideration. 

These systems are often manufactured by suppliers who contract with multiple OEMs, all 

of whom benefit (in the form of cost reductions for the technology) from the supplier’s 

learning. The 2008 Martec Report and the BorgWarner comments additionally both 

indicated that when manufacturers demand components in high volumes, suppliers are 

able to pass on learning-based savings to all manufacturers with whom they contract. 

Thus, it made sense to NHTSA to revise its method of determining whether the threshold 

volume has been achieved from an annual per-manufacturer to an annual industry-wide 

production volume basis. 

NHTSA also changed the threshold volume for volume-based learning from 25,000 to 

300,000 units. The 2008 Martec Report and comments from multiple manufacturers 

indicated that 25,000 units was far too small a production volume to affect component 

costs. In response, NHTSA began with the Martec estimate that technologies were fully 

learned-out at 1.5 million units of production (which met the production needs of three 

manufacturers, according to that report). NHTSA then applied two cycles of learning in a 

reverse direction to determine what the proper threshold volume would be for these 

conditions. One cycle would be applied at 750,000 units (1.5 million divided by 2, which 

would represent the second volume doubling) and one at 375,000 units (750,000 divided 

by 2, which would represent the first volume doubling). NHTSA thus estimated that the 

Martec analysis would suggest a threshold volume of 375,000 units. However, the 

agency notes that Martec stated that it chose the 1.5 million units number specifically 

because Martec knew it was well beyond the point where learning is a factor, which 

means that 1.5 million was beyond the cusp of the learning threshold. NHTSA therefore 

concluded that 375,000 units should represent the upper bound for the threshold volume 

for Martec’s analysis. 

Having determined this, NHTSA sought to establish a lower bound for the threshold 

volume. The 2008 Martec report indicated that production efficiencies are maximized at 

250,000-350,000 units (which averages to 300,000 units), and that manufacturers 

consequently target this range when planning and developing manufacturing operations. 

Honda also cited this production volume. Thus, for three manufacturers, the annual 

volume requirement would be 900,000 units.116 NHTSA concluded this could also 

 

116 An industry volume of 900,000 would imply a threshold volume of 225,000 units according to 

NHTSA’s analysis. This is still nine times the value used at the NPRM. 
V-52

represent high volume where learned costs could be available, and considered it as a 

lower bound estimate. With the upper and lower values established, and given that 

Martec specifically indicated that 1.5 million did not represent the cusp of the learning 

threshold, NHTSA chose the mid-point of 1.2 million units as the best estimate of annual 

industry volumes where learned costs would be experienced. For proper forward 

learning, this would mean the first learning cycle would occur at 300,000 and the second 

at 600,000. Accordingly NHTSA has established the threshold volume for the final rule 

at 300,000 industry units per year. 

Having established the threshold volume, NHTSA next considered which technologies to 

apply volume learning to. Comments confirmed that NHTSA had been correct in the 

NPRM to assume that learning would be applicable to low-volume, emerging 

technologies that could benefit from economies of scale, so NHTSA consulted 

confidential product plans to determine the volumes of technologies to be applied by 

manufacturers during the rulemaking period. If the product plans indicated that the 

technologies would be in high-volume use (i.e., above 600,000 units produced annually 

for cars and trucks by all manufacturers) at the beginning of its first year of availability, 

then volume-based learning was not considered applicable, since at this volume the 

technology would be available at learned cost. If the volume was below 600,000 units 

annually, then NHTSA also looked at the Volpe model’s application of the technology. 

If the model applied more than 600,000 units within the first year of availability, NHTSA 

did not apply volume-based learning. If neither manufacturers nor the model applied 

more than 600,000 units within the first year, then volume learning was applied to the 

technology. 

Based on this analysis, NHTSA determined that volume-based learning would be 

applicable to three technologies for purposes of the final rule: integrated starter 

generator, 2-mode hybrid, and plug-in hybrid. For these three technologies, and where 

the agency’s initial cost estimates reflected full learning, NHTSA reverse-learned the cost 

by dividing the estimate by the learning rate twice to properly offset the learned cost 

estimate. NHTSA used a 20 percent learning rate in the NPRM for these technologies, 

and concluded that that rate was still applicable for the final rule. This learning rate was 

validated using manufacturer-submitted current and forecast cost data for advancedbattery hybrid vehicle technology, and accepted industry forecasts for U.S. sales volumes 

of these same vehicles. This limited study indicated that cost efficiencies were 

approximately 20 percent for a doubling of U.S. market annual sales of a particular 

advanced battery technology, and the learning rate was thus used as a proxy for other 

advanced vehicle technologies. 

Commenters also indicated that learning-related cost reductions could occur not only as a 

result of production volume changes, but also as a function of time. For example, Ford 

stated that technology cost reductions were negotiated as part of the contractual 

agreement to purchase components from suppliers, a target-setting process which Ford 

described as common in the automotive industry. In this arrangement suppliers agree to 

reduce costs on a fixed percentage year over year according to negotiated terms. GM 

described a cost reduction process that occurs over the course of a product life cycle, 
V-53

typically no less than 4-5 years, where costs are reduced as production experience 

increases. GM stated that its cost reductions included engineering, manufacturing, 

investment, and material costs, and were also defined through supplier contracts that 

anticipate volume and costs over the whole period. The components involved are 

assumed to be high volume, mature technologies being used in current vehicle 

production. These are the types of components that would typically be subject to “costdown”117 efforts that target savings through small, incremental design, manufacturing, 

assembly, and material changes on a recurring or periodic basis. 

In response to these comments, NHTSA has adopted this approach as an additional type 

of learning related cost reduction, referring to it as “time-based” learning. For purposes 

of the final rule, time-based learning is applied to high-volume, mature technologies 

likely to be purchased by OEMs on a long-term contractual basis. This would include 

most of the fuel-saving technologies under consideration, except those where volumebased learning is applied, or those where components might consist of commodity 

materials, such as oil or rubber, where pricing fluctuations prevent long-term or fixed 

value contracts. NHTSA has used a 3 percent reduction rate for time-based learning, 

based on confidential manufacturer information and NHTSA’s understanding of current 

industry practice. Thus, if time-based learning is deemed applicable, then in year two of 

a technology’s application, and in each subsequent year (if any), the initial cost is reduced 

by 3 percent. This approach is responsive to comments about compliance costs 

estimation, and improves the accuracy of projecting future costs compared to the NPRM. 

With regard to the comments from UCS, NHTSA recognizes that joint-venture 

collaboration and competitor tear-downs are methods used by manufacturers for 

designing and developing new products and components, but notes that these methods are 

used prior to the manufacturing stage, and thus are not considered manufacturing costs. 

NHTSA has received no specific manufacturer learning curve-related data, and thus has 

no “source data” to disclose. NHTSA continues to use a 20 percent learning factor for 

volume-based learning, which is consistent with EPA’s learning factor recommended by 

UCS for NHTSA’s use. 

With regard to the comments from Public Citizen, although NHTSA reviewed the paper 

cited by the commenter, the agency found its analysis largely irrelevant to NHTSA’s 

estimation of cost reduction factors due to automobile manufacturer learning, and thus 

declines to adopt its findings. 

Table V-4 below shows the applicability and type of learning applied in the final rule. 

 

117 Cost-down efforts are a common practice in competitive manufacturing environments like the 

automotive industry. 
V-54

Table V-4—Application of learning-related cost reductions for technologies 

Technology Abbr. Learning 

Type

 Learning 

Rate

Low Friction Lubricants LUB

Engine Friction Reduction EFR

VVT - Coupled Cam Phasing (CCP) on SOHC CCPS TIME 3%

Discrete Variable Valve Lift (DVVL) on SOHC DVVLS TIME 3%

Cylinder Deactivation on SOHC DEACS TIME 3%

VVT - Intake Cam Phasing (ICP) ICP TIME 3%

VVT - Dual Cam Phasing (DCP) DCP TIME 3%

Discrete Variable Valve Lift (DVVL) on DOHC DVVLD TIME 3%

Continuously Variable Valve Lift (CVVL) CVVL TIME 3%

Cylinder Deactivation on DOHC DEACD TIME 3%

Cylinder Deactivation on OHV DEACO TIME 3%

VVT - Coupled Cam Phasing (CCP) on OHV CCPO TIME 3%

Discrete Variable Valve Lift (DVVL) on OHV DVVLO TIME 3%

Conversion to DOHC with DCP CDOHC TIME 3%

Stoichiometric Gasoline Direct Injection (GDI) SGDI TIME 3%

Combustion Restart CBRST TIME 3%

Turbocharging and Downsizing TRBDS TIME 3%

Exhaust Gas Recirculation (EGR) Boost EGRB TIME 3%

Conversion to Diesel following CBRST DSLC TIME 3%

Conversion to Diesel following TRBDS DSLT TIME 3%

Electric Power Steering EPS TIME 3%

Improved Accessories IACC TIME 3%

12V Micro-Hybrid MHEV TIME 3%

Higher Voltage/Improved Alternator HVIA TIME 3%

Integrated Starter Generator ISG VOLUME 20%

6-Speed Manual/Improved Internals 6MAN TIME 3%

Improved Auto. Trans. Controls/Externals IATC TIME 3%

Continuously Variable Transmission CVT TIME 3%

6/7/8-Speed Auto. Trans with Improved Internals NAUTO TIME 3%

Dual Clutch or Automated Manual Transmission DCTAM TIME 3%

Power Split Hybrid PSHEV TIME 3%

2-Mode Hybrid 2MHEV VOLUME 20%

Plug-in Hybrid PHEV VOLUME 20%

Material Substitution (1%) MS1

Material Substitution (2%) MS2

Material Substitution (5%) MS5

Low Rolling Resistance Tires ROLL

Low Drag Brakes LDB TIME 3%

Secondary Axle Disconnect – 4WD SAX TIME 3%

Aero Drag Reduction AERO TIME 3%
V-55

7. Technology synergies

When two or more technologies are added to a particular vehicle model to improve its 

fuel efficiency, the resultant fuel consumption reduction may sometimes be higher or 

lower than the product of the individual effectiveness values for those items.118 This may 

occur because one or more technologies applied to the same vehicle partially address the 

same source or sources of engine, drivetrain or vehicle losses. Alternately, this effect 

may be seen when one technology shifts the engine operating points, and therefore 

increases or reduces the fuel consumption reduction achieved by another technology or 

set of technologies. The difference between the observed fuel consumption reduction 

associated with a set of technologies and the product of the individual effectiveness 

values in that set is referred to for purposes of this rulemaking as a “synergy.” Synergies 

may be positive (increased fuel consumption reduction compared to the product of the 

individual effects) or negative (decreased fuel consumption reduction). 

For the NPRM, the Volpe model was modified to estimate the interactions of 

technologies using estimates of incremental synergies associated with a number of 

technology pairs identified by NHTSA. The use of discrete technology pair incremental 

synergies is similar to that in DOE’s National Energy Modeling System (NEMS).119 

Inputs to the Volpe model incorporate NEMS-identified pairs, as well as additional pairs 

for the final rule from the set of technologies considered in the Volpe model. However, 

to maintain an approach that was consistent with the technology sequencing developed by 

NHTSA, new incremental synergy estimates for all pairs were obtained from a first-order 

“lumped parameter” analysis tool created by EPA.120

The lumped parameter tool is a spreadsheet model that represents energy consumption in 

terms of average performance over the fuel economy test procedure, rather than explicitly 

analyzing specific drive cycles. The tool begins with an apportionment of fuel 

consumption across several loss mechanisms and accounts for the average extent to 

which different technologies affect these loss mechanisms using estimates of engine, 

drivetrain and vehicle characteristics that are averaged over the EPA fuel economy drive 

cycle. Results of this analysis were generally consistent with those of full-scale vehicle 

simulation modeling performed by Ricardo, Inc. However, regardless of a generally 

consistent set of results for the vehicle class and set of technologies studied, the lumped 

parameter tool is not a full vehicle simulation and cannot replicate the physics of such a 

 

118 More specifically, the products of the differences between one and the technology-specific levels of 

effectiveness in reducing fuel consumption. For example, not accounting for interactions, if technologies A 

and B are estimated to reduce fuel consumption by 10% (i.e., 0.1) and 20% (i.e., 0.2) respectively, the 

“product of the individual effectiveness values” would be 1 – 0.1 times 1 – 0.2, or 0.9 times 0.8, which 

equals 0.72, corresponding to a combined effectiveness of 28% rather than the 30% obtained by adding 

10% to 20%. The “synergy factors” discussed in this section further adjust these multiplicatively combined 

effectiveness values. 

119 U.S. Department of Energy, Energy Information Administration, Transportation Sector Module of the 

National Energy Modeling System: Model Documentation 2007, May 2007, Washington, DC, DOE/EIAM070(2007), at 29-30. Available at http://tonto.eia.doe.gov/ftproot/modeldoc/m070(2007).pdf (last 

accessed Oct. 24, 2008). 

120 EPA Staff Technical Report: Cost and Effectiveness Estimates of Technologies Used to Reduce Lightduty Vehicle Carbon Dioxide Emissions; EPA420-R-08-008, March 2008.
V-56

simulation. 

Many comments were received that stated this and pointed to errors in the synergies 

listed in the NPRM being in some cases inaccurate or even directionally incorrect. 

NHTSA recognizes that the estimated synergies applied for the NPRM were not all 

correct, and has reevaluated all estimated synergies applied in the analysis supporting 

today’s final rule. In response to commenters calling for NHTSA to use full vehicle 

simulation, either in the first instance or as a check on the synergy factors that NHTSA 

developed, the agency has concluded that the vehicle simulation analyses conducted 

previously by Ricardo provide a sufficient point of reference, especially considering the 

time constraints for establishing the final rule. NHTSA did, however, improve the 

predictive capability of the lumped parameter tool. 

The lumped parameter tool was first updated with the new list of technologies and their 

associated effectiveness values. Second, NHTSA conducted a more rigorous qualitative 

analysis of the technologies for which a competition for losses would be expected, which 

led to a much larger list of synergy pairings than was present in the NRPM. The types of 

losses that were analyzed were tractive effort, transmission/drivetrain, engine mechanical 

friction, engine pumping, engine indicated (combustion) efficiency and accessory (see 

Table V-5). As can be seen from Table V-5, engine mechanical friction, pumping and 

accessory losses are improved by various technologies from engine, transmission, 

electrification and hybrid decision trees and must be accounted for within the model with 

a synergy value. The updated lumped parameter model was then re-run to develop new 

synergy estimates for the expanded list of pairings. That list is shown in Tables IV-6a-d. 

The agency notes that synergies that occur within a decision tree are already addressed 

within the incremental values assigned and therefore do not require a synergy pair to 

address. For example, all engine technologies take into account incremental synergy 

factors of preceding engine technologies, and all transmission technologies take into 

account incremental synergy factors of preceding transmission technologies. These 

factors are expressed in the fuel consumption improvement factors in the input files used 

by the Volpe model. 

For applying incremental synergy factors in separate path technologies, the Volpe model 

uses an input table (see Tables IV-6a-d) which lists technology pairings and incremental 

synergy factors associated with those pairings, most of which are between engine 

technologies and transmission/electrification/hybrid technologies. When a technology is 

applied to a vehicle by the Volpe model, all instances of that technology in the 

incremental synergy table which match technologies already applied to the vehicle (either 

pre-existing or previously applied by the Volpe model) are summed and applied to the 

fuel consumption improvement factor of the technology being applied. Synergies for the 

strong hybrid technology fuel consumption reductions are included in the incremental 

value for the specific hybrid technology block since the model applies technologies in the 

order of the most effectiveness for least cost and also applies all available electrification 

and transmission technologies before applying strong hybrid technologies. 
V-57

As another possible alternative to using synergy factors, NHTSA has also considered 

modifying the Volpe model to apply inputs—for each vehicle model—specifying the 

share of total fuel consumption attributable to each of several energy loss mechanisms. 

The agency has determined that this approach, discussed in greater detail below, cannot 

be implemented at this time because the requisite information is not available. 
V-58

Table V-5. Loss Factors Considered in Synergy Analysis 

 

VEHICLE TRANS ENGINE ENGINE ENGINE ENGINE

Tractive Drivetrain Mechanical Pumping Accessory Indicated

Effort Losses Friction Losses Losses Efficiency

ENGINE

Low Friction Lubricants +

Engine Friction Reduction +

VVT - Coupled Cam Phasing (CCP) on SOHC - + +

Discrete Variable Valve Lift (DVVL) on SOHC - +

Cylinder Deactivation on SOHC + +

VVT - Intake Cam Phasing (ICP) - + +

VVT - Dual Cam Phasing (DCP) - + +

Discrete Variable Valve Lift (DVVL) on DOHC - +

Continuously Variable Valve Lift (CVVL) - +

Cylinder Deactivation on DOHC + +

Cylinder Deactivation on OHV + +

VVT - Coupled Cam Phasing (CCP) on OHV -+ +

Discrete Variable Valve Lift (DVVL) on OHV - +

Conversion to DOHC with DCP - + +

Stoichiometric Gasoline Direct Injection (GDI) +

Combustion Restart + ++

Turbocharging and Downsizing - +

Exhaust Gas Recirculation (EGR) Boost +

Conversion to Diesel + +

ELECTRIFICATION/ACCESSORY

Electric Power Steering +

Improved Accessories +

12V Micro-Hybrid + ++

Higher Voltage/Improved Alternator +

Integrated Starter Generator + + +

TRANSMISSION (MANUAL)

6-Speed Manual/Improved Internals + +

TRANSMISSION (AUTOMATIC)

Improved Auto. Trans. Controls/Externals + +

Continuously Variable Transmission - +

6/7/8-Speed Auto. Trans with Impr. Internals + +

Dual Clutch/Automated Manual Transmission +

(STRONG) HYBRID

Power Split Hybrid + + ++

2-Mode Hybrid + + ++

Plug-in Hybrid + + ++

VEHICLE 

Material Substitution (1%) +

Material Substitution (2%) +

Material Substitution (5%) +

Low Rolling Resistance Tires +

Low Drag Brakes +

Secondary Axle Disconnect - 4WD +

Aero Drag Reduction +

Lumped Parameter Synergy Analysis

+ Technology has a positive effect on fuel consumption

- Technology has a negative effect on fuel consumption
V-59

Table V-6a. Synergy pairings and values 

Technology A Technology B Subcompact 

PC

Subcompact 

Perf. PC Compact PC Compact Perf. PC Midsize PC Midsize Perf. PC

CCPS 6MAN -0.1% -0.1% -0.1% -0.1% -0.1% -0.1%

CCPS IATC -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CCPS CVT -0.8% -0.8% -0.8% -0.8% -0.8% -0.8%

CCPS NAUTO -0.4% -0.4% -0.4% -0.4% -0.4% -0.4%

CCPS MHEV -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

CCPS ISG -0.9% -0.9% -0.9% -0.9% -0.9% -0.9%

DVVLS 6MAN -0.1% -0.1% -0.1% -0.1% -0.1% -0.1%

DVVLS IATC -0.5% -0.5% -0.5% -0.5% -0.5% -0.5%

DVVLS CVT -1.4% -1.4% -1.4% -1.4% -1.4% -1.4%

DVVLS NAUTO -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

DVVLS MHEV -0.8% -0.8% -0.8% -0.8% -0.8% -0.8%

DVVLS ISG -1.0% -1.0% -1.0% -1.0% -1.0% -1.0%

DEACS 6MAN n.a. n.a. n.a. -0.2% n.a. -0.2%

DEACS IATC n.a. n.a. n.a. -0.6% n.a. -0.6%

DEACS CVT n.a. n.a. n.a. -1.7% n.a. -1.7%

DEACS NAUTO n.a. n.a. n.a. -0.9% n.a. -0.9%

DEACS MHEV n.a. n.a. n.a. -0.9% n.a. -0.9%

DEACS ISG n.a. n.a. n.a. -1.1% n.a. -1.1%

ICP 6MAN -0.1% -0.1% -0.1% -0.1% -0.1% -0.1%

ICP IATC -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

ICP CVT -0.8% -0.8% -0.8% -0.8% -0.8% -0.8%

ICP NAUTO -0.4% -0.4% -0.4% -0.4% -0.4% -0.4%

ICP MHEV -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

ICP ISG -0.9% -0.9% -0.9% -0.9% -0.9% -0.9%

DCP 6MAN -0.1% -0.1% -0.1% -0.1% -0.1% -0.1%

DCP IATC -0.4% -0.4% -0.4% -0.4% -0.4% -0.4%

DCP CVT -1.3% -1.3% -1.3% -1.3% -1.3% -1.3%

DCP NAUTO -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

DCP MHEV -0.8% -0.8% -0.8% -0.8% -0.8% -0.8%

DCP ISG -1.0% -1.0% -1.0% -1.0% -1.0% -1.0%

DVVLD 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

DVVLD IATC -0.6% -0.6% -0.6% -0.6% -0.6% -0.6%

DVVLD CVT -1.8% -1.8% -1.8% -1.8% -1.8% -1.8%

DVVLD NAUTO -1.0% -1.0% -1.0% -1.0% -1.0% -1.0%

DVVLD MHEV -0.9% -0.9% -0.9% -0.9% -0.9% -0.9%

DVVLD ISG -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

DEACD 6MAN n.a. n.a. n.a. -0.2% n.a. -0.2%

DEACD IATC n.a. n.a. n.a. -0.6% n.a. -0.6%

DEACD CVT n.a. n.a. n.a. -1.8% n.a. -1.8%

DEACD NAUTO n.a. n.a. n.a. -1.0% n.a. -1.0%

DEACD MHEV n.a. n.a. n.a. -0.9% n.a. -0.9%

DEACD ISG n.a. n.a. n.a. -1.1% n.a. -1.1%

CVVL 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CVVL IATC -0.6% -0.6% -0.6% -0.6% -0.6% -0.6%

CVVL CVT -1.8% -1.8% -1.8% -1.8% -1.8% -1.8%

CVVL NAUTO -1.0% -1.0% -1.0% -1.0% -1.0% -1.0%

CVVL MHEV -0.9% -0.9% -0.9% -0.9% -0.9% -0.9%

CVVL ISG -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

Synergies Fuel Consumption Improvement Synergy values by Vehicle Subclass

Positive values are positive synergies, negative values are dissynergies.
V-60

Table V-6b. Synergy pairings and values 

Technology A Technology B Subcompact 

PC

Subcompact 

Perf. PC Compact PC Compact Perf. PC Midsize PC Midsize Perf. PC

DEACO 6MAN n.a. n.a. n.a. -0.1% n.a. -0.1%

DEACO IATC n.a. n.a. n.a. -0.5% n.a. -0.5%

DEACO CVT n.a. n.a. n.a. -1.4% n.a. -1.4%

DEACO NAUTO n.a. n.a. n.a. -0.8% n.a. -0.8%

DEACO MHEV n.a. n.a. n.a. -0.9% n.a. -0.9%

DEACO ISG n.a. n.a. n.a. -1.2% n.a. -1.2%

CCPO 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CCPO IATC -0.6% -0.6% -0.6% -0.6% -0.6% -0.6%

CCPO CVT -1.7% -1.7% -1.7% -1.7% -1.7% -1.7%

CCPO NAUTO -0.9% -0.9% -0.9% -0.9% -0.9% -0.9%

CCPO MHEV -1.0% -1.0% -1.0% -1.0% -1.0% -1.0%

CCPO ISG -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

DVVLO 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

DVVLO IATC -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

DVVLO CVT -2.0% -2.0% -2.0% -2.0% -2.0% -2.0%

DVVLO NAUTO -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

DVVLO MHEV -1.0% -1.0% -1.0% -1.0% -1.0% -1.0%

DVVLO ISG -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

CDOHC 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CDOHC IATC -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

CDOHC CVT -2.0% -2.0% -2.0% -2.0% -2.0% -2.0%

CDOHC NAUTO -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

CDOHC MHEV -1.0% -1.0% -1.0% -1.0% -1.0% -1.0%

CDOHC ISG -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

CBRST 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CBRST IATC -0.6% -0.6% -0.6% -0.6% -0.6% -0.6%

CBRST CVT -1.8% -1.8% -1.8% -1.8% -1.8% -1.8%

CBRST NAUTO -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

CBRST MHEV -2.1% -2.1% -2.1% -2.1% -2.1% -2.1%

CBRST ISG -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

CBRST EPS -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CBRST IACC -0.4% -0.4% -0.4% -0.4% -0.4% -0.4%

CBRST HVIA -0.3% -0.3% -0.3% -0.3% -0.3% -0.3%

TRBDS 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

TRBDS IATC -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

TRBDS CVT -2.4% -2.4% -2.4% -2.4% -2.4% -2.4%

TRBDS NAUTO -1.3% -1.3% -1.3% -1.3% -1.3% -1.3%

TRBDS MHEV -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

TRBDS ISG -1.3% -1.3% -1.3% -1.3% -1.3% -1.3%

DSLC 6MAN -0.3% -0.3% -0.3% -0.3% -0.3% -0.3%

DSLC IATC 2.5% 2.5% 2.5% 2.5% 2.5% 2.5%

DSLC CVT -2.9% -2.9% -2.9% -2.9% -2.9% -2.9%

DSLC NAUTO -1.7% -1.7% -1.7% -1.7% -1.7% -1.7%

DSLC MHEV -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

DSLC ISG -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

DSLT 6MAN -0.3% -0.3% -0.3% -0.3% -0.3% -0.3%

DSLT IATC 2.5% 2.5% 2.5% 2.5% 2.5% 2.5%

DSLT CVT -2.9% -2.9% -2.9% -2.9% -2.9% -2.9%

DSLT NAUTO -1.7% -1.7% -1.7% -1.7% -1.7% -1.7%

DSLT MHEV -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

DSLT ISG -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

Synergies Fuel Consumption Improvement Synergy values by Vehicle Subclass

Positive values are positive synergies, negative values are dissynergies.
V-61

Table V-6c. Synergy pairings and values 

Technology A Technology B Large PC Large Perf. 

PC Minivan LT Small LT Midsize LT Large LT

CCPS 6MAN -0.1% -0.1% -0.1% -0.1% -0.1% -0.1%

CCPS IATC -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CCPS CVT -0.8% n.a. -0.8% -0.8% -0.8% n.a.

CCPS NAUTO -0.4% -0.4% -0.4% -0.4% -0.4% -0.4%

CCPS MHEV -0.7% -0.7% -0.7% -0.7% -0.7% n.a.

CCPS ISG -0.9% -0.9% -0.9% -0.9% -0.9% n.a.

DVVLS 6MAN -0.1% -0.1% -0.1% -0.1% -0.1% -0.1%

DVVLS IATC -0.5% -0.5% -0.5% -0.5% -0.5% -0.5%

DVVLS CVT -1.4% n.a. -1.4% -1.4% -1.4% n.a.

DVVLS NAUTO -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

DVVLS MHEV -0.8% -0.8% -0.8% -0.8% -0.8% n.a.

DVVLS ISG -1.0% -1.0% -1.0% -1.0% -1.0% n.a.

DEACS 6MAN -0.2% -0.2% -0.2% n.a. -0.2% -0.2%

DEACS IATC -0.6% -0.6% -0.6% n.a. -0.6% -0.6%

DEACS CVT -1.7% n.a. -1.7% n.a. -1.7% n.a.

DEACS NAUTO -0.9% -0.9% -0.9% n.a. -0.9% -0.9%

DEACS MHEV -0.9% -0.9% -0.9% n.a. -0.9% n.a.

DEACS ISG -1.1% -1.1% -1.1% n.a. -1.1% n.a.

ICP 6MAN -0.1% -0.1% -0.1% -0.1% -0.1% -0.1%

ICP IATC -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

ICP CVT -0.8% n.a. -0.8% -0.8% -0.8% n.a.

ICP NAUTO -0.4% -0.4% -0.4% -0.4% -0.4% -0.4%

ICP MHEV -0.7% -0.7% -0.7% -0.7% -0.7% n.a.

ICP ISG -0.9% -0.9% -0.9% -0.9% -0.9% n.a.

DCP 6MAN -0.1% -0.1% -0.1% -0.1% -0.1% -0.1%

DCP IATC -0.4% -0.4% -0.4% -0.4% -0.4% -0.4%

DCP CVT -1.3% n.a. -1.3% -1.3% -1.3% n.a.

DCP NAUTO -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

DCP MHEV -0.8% -0.8% -0.8% -0.8% -0.8% n.a.

DCP ISG -1.0% -1.0% -1.0% -1.0% -1.0% n.a.

DVVLD 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

DVVLD IATC -0.6% -0.6% -0.6% -0.6% -0.6% -0.6%

DVVLD CVT -1.8% n.a. -1.8% -1.8% -1.8% n.a.

DVVLD NAUTO -1.0% -1.0% -1.0% -1.0% -1.0% -1.0%

DVVLD MHEV -0.9% -0.9% -0.9% -0.9% -0.9% n.a.

DVVLD ISG -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

DEACD 6MAN -0.2% -0.2% -0.2% n.a. -0.2% -0.2%

DEACD IATC -0.6% -0.6% -0.6% n.a. -0.6% -0.6%

DEACD CVT -1.8% n.a. -1.8% n.a. -1.8% n.a.

DEACD NAUTO -1.0% -1.0% -1.0% n.a. -1.0% -1.0%

DEACD MHEV -0.9% -0.9% -0.9% n.a. -0.9% n.a.

DEACD ISG -1.1% -1.1% -1.1% n.a. -1.1% n.a.

CVVL 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CVVL IATC -0.6% -0.6% -0.6% -0.6% -0.6% -0.6%

CVVL CVT -1.8% n.a. -1.8% -1.8% -1.8% n.a.

CVVL NAUTO -1.0% -1.0% -1.0% -1.0% -1.0% -1.0%

CVVL MHEV -0.9% -0.9% -0.9% -0.9% -0.9% n.a.

CVVL ISG -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

Synergies Fuel Consumption Improvement Synergy values by Vehicle Subclass

Positive values are positive synergies, negative values are dissynergies.
V-62

Table V-6d. Synergy pairings and values 

Technology A Technology B Large PC Large Perf. 

PC Minivan LT Small LT Midsize LT Large LT

DEACO 6MAN -0.1% -0.1% -0.1% n.a. -0.1% -0.1%

DEACO IATC -0.5% -0.5% -0.5% n.a. -0.5% -0.5%

DEACO CVT -1.4% n.a. -1.4% n.a. -1.4% n.a.

DEACO NAUTO -0.8% -0.8% -0.8% n.a. -0.8% -0.8%

DEACO MHEV -0.9% -0.9% -0.9% n.a. -0.9% n.a.

DEACO ISG -1.2% -1.2% -1.2% n.a. -1.2% n.a.

CCPO 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CCPO IATC -0.6% -0.6% -0.6% -0.6% -0.6% -0.6%

CCPO CVT -1.7% n.a. -1.7% -1.7% -1.7% n.a.

CCPO NAUTO -0.9% -0.9% -0.9% -0.9% -0.9% -0.9%

CCPO MHEV -1.0% -1.0% -1.0% -1.0% -1.0% n.a.

CCPO ISG -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

DVVLO 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

DVVLO IATC -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

DVVLO CVT -2.0% n.a. -2.0% -2.0% -2.0% n.a.

DVVLO NAUTO -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

DVVLO MHEV -1.0% -1.0% -1.0% -1.0% -1.0% n.a.

DVVLO ISG -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

CDOHC 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CDOHC IATC -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

CDOHC CVT -2.0% n.a. -2.0% -2.0% -2.0% n.a.

CDOHC NAUTO -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

CDOHC MHEV -1.0% -1.0% -1.0% -1.0% -1.0% n.a.

CDOHC ISG -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

CBRST 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

CBRST IATC -0.6% -0.6% -0.6% -0.6% -0.6% -0.6%

CBRST CVT -1.8% n.a. -1.8% -1.8% -1.8% n.a.

CBRST NAUTO -1.1% -1.1% -1.1% -1.1% -1.1% -1.1%

CBRST MHEV -2.1% -2.1% -2.1% -2.1% -2.1% n.a.

CBRST ISG -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

CBRST EPS -0.2% -0.2% -0.2% -0.2% -0.2% n.a.

CBRST IACC -0.4% -0.4% -0.4% -0.4% n.a. n.a.

CBRST HVIA -0.3% -0.3% -0.3% -0.3% -0.3% n.a.

TRBDS 6MAN -0.2% -0.2% -0.2% -0.2% -0.2% -0.2%

TRBDS IATC -0.7% -0.7% -0.7% -0.7% -0.7% -0.7%

TRBDS CVT -2.4% n.a. -2.4% -2.4% -2.4% n.a.

TRBDS NAUTO -1.3% -1.3% -1.3% -1.3% -1.3% -1.3%

TRBDS MHEV -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

TRBDS ISG -1.3% -1.3% -1.3% -1.3% -1.3% n.a.

DSLC 6MAN -0.3% -0.3% -0.3% -0.3% -0.3% -0.3%

DSLC IATC 2.5% 2.5% 2.5% 2.5% 2.5% 2.5%

DSLC CVT -2.9% n.a. -2.9% -2.9% -2.9% n.a.

DSLC NAUTO -1.7% -1.7% -1.7% -1.7% -1.7% -1.7%

DSLC MHEV -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

DSLC ISG -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

DSLT 6MAN -0.3% -0.3% -0.3% -0.3% -0.3% -0.3%

DSLT IATC 2.5% 2.5% 2.5% 2.5% 2.5% 2.5%

DSLT CVT -2.9% n.a. -2.9% -2.9% -2.9% n.a.

DSLT NAUTO -1.7% -1.7% -1.7% -1.7% -1.7% -1.7%

DSLT MHEV -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

DSLT ISG -1.1% -1.1% -1.1% -1.1% -1.1% n.a.

Synergies Fuel Consumption Improvement Synergy values by Vehicle Subclass

Positive values are positive synergies, negative values are dissynergies.
V-63

8. How does NHTSA use full vehicle simulation? 

For regulatory purposes, the fuel economy of any given vehicle is determined by placing 

the vehicle on a chassis dynamometer (akin to a large treadmill that puts the vehicle’s 

wheels in contact with one or more rollers, rather than with a belt stretched between 

rollers) in a controlled environment, driving the vehicle over a specific driving cycle (in 

which driving speed is specified for each second of operation), measuring the amount of 

carbon dioxide emitted from the vehicle’s tailpipe, and calculating fuel consumption 

based on the density and carbon content of the fuel. 

One means of determining the effectiveness of a given technology as applied to a given 

vehicle model would be to measure the vehicle’s fuel economy on a chassis 

dynamometer, install the new technology, and then re-measure the vehicle’s fuel 

economy. However, most technologies cannot simply be “swapped out,” and even for 

those that can, simply doing so without additional engineering work may change other 

vehicle characteristics (e.g., ride, handling, performance, etc.), producing an “apples to 

oranges” comparison. 

Some technologies can also be more narrowly characterized through bench or engine 

dynamometer (i.e., in which the engine drives a generator that is, in turn, used to apply a 

controlled load to the engine) testing. For example, engine dynamometer testing could be 

used to evaluate the brake-specific fuel consumption (e.g., grams per kilowatt-hour) of a 

given engine before and after replacing the engine oil with a less viscous oil. However, 

such testing does not provide a direct measure of overall vehicle fuel economy or changes 

in overall vehicle fuel economy. 

For a vehicle that does not yet exist, as in NHTSA’s analysis of CAFE standards 

applicable to future model years, even physical testing can provide only an estimate of 

the vehicle’s eventual fuel economy. Among the alternatives to physical testing, 

automotive engineers involved in vehicle design make use of computer-based analysis 

tools, including a powerful class of tools commonly referred to as “full vehicle 

simulation.” Given highly detailed inputs regarding vehicle engineering characteristics, 

full vehicle simulation provides a means of estimating vehicle fuel consumption over a 

given drive cycle, based on the explicit representation of the physical laws governing 

vehicle propulsion and dynamics. Some vehicle simulation tools also incorporate 

combustion simulation tools that represent the combustion cycle in terms of governing 

physical and chemical processes. Although these tools are computationally intensive and 

required a great deal of input data, they provide engineers involved in vehicle 

development and design with an alternative that can be considerably faster and less 

expensive than physical experimentation and testing. 

Properly executed, methods such as physical testing and full vehicle simulation can 

provide reasonably (though not absolutely) certain estimates of the vehicle fuel economy 

of specific vehicles to be produced in the future. However, when analyzing potential 

CAFE standards, NHTSA is not actually designing specific vehicles. The agency is 

considering implications of new standards that will apply to the average performance of 
V-64

manufacturers’ entire production lines. For this type of analysis, precision in the 

estimation of the fuel economy of individual vehicle models is not essential; although it is 

important that the agency avoid systematic upward or downward bias, uncertainty at the 

level of individual models is mitigated by the fact that compliance with CAFE standards 

is based on average fleet performance. 

As discussed above, the Volpe Model, which the agency has used to perform the analysis 

supporting today’s final rule, applies an incrementally multiplicative approach to 

estimating the fuel savings achieved through the progressive addition of fuel-saving 

technologies. NAS’ use of the same approach in its 2002 report was, at the time and 

henceforth, criticized by a small number of observers as being prone to systematic 

overestimation of available fuel savings. This assertion was based on the fact that, 

among the technologies present on any given vehicle, more than one may address the 

same energy loss mechanism (notably, pumping losses on throttled engines). Once all 

energy losses of a given type are eliminated, even theoretical improvements attributable 

to that loss mechanism are no longer available. 

The most direct critique of NAS’ methods appeared in a 2002 SAE paper by four General 

Motors researchers (Patton, et al.), who compared some of NAS’ calculations to fuel 

consumption estimates obtained through vehicle testing and simulation, and concluded 

that, as increasing numbers of technologies were applied, NAS’ estimates became 

increasingly subject to overestimation of available fuel consumption reductions.121

In response to such concerns, which had also been raised as the NAS committee 

performed its analysis, the NAS report concluded that vehicle simulation performed for 

the committee indicated that the report’s incremental fuel savings estimates were “quite 

reasonable” for the less aggressive two of the three product development paths it 

evaluated. The report did, however, conclude that uncertainty increased with 

consideration of more technologies, especially under the more aggressive “path 3” 

evaluated by the committee. The report did not, however, mention any directional bias to 

this uncertainty.122

Notwithstanding this prior response to concerns about the possible overestimation of 

available fuel savings, and considering that analyses supporting the development of the 

NPRM, the Volpe model applies “synergy factors” that adjust fuel savings calculations 

when some pairs of technologies are applied to the same vehicle. These factors reduce 

uncertainty and the potential for positive or negative biases in the Volpe model’s 

estimates of the effects of technologies. 

As an alternative to estimating fuel consumption through incremental multiplication and 

the application of “synergy” factors to address technology interactions, NHTSA 

considered basing its analysis of fuel economy standards on full vehicle simulation at 

 

121 Patton, K.J., et al., General Motors Corporation, “Aggregating Technologies for Reduced Fuel 

Consumption: A Review of the Technical Content in the 2002 National Research Council Report on 

CAFE”, 2002-01-0628, Society of Automotive Engineers, Inc., 2002. 122 NRC (2002), op. cit., p. 151. 
V-65

every step. However, considering the nature of CAFE analysis (in particular, the analysis 

of fleets projected to be sold in the future by each manufacturer), as well as the quantity 

and availability of information required to perform vehicle simulation, the agency 

explained that it believed detailed simulation when analyzing the entire fleet of future 

vehicles is neither necessary nor feasible. Still, when estimating synergies between 

technologies, the agency did make use of vehicle simulation studies, as discussed above. 

The agency has also done so when re-estimating synergies before performing the analysis 

supporting today’s final rule. 

NHTSA also considered estimating changes in fuel consumption by explicitly accounting 

for each of several energy loss mechanisms—that is, physical mechanisms to which the 

consumption of (chemical) energy in fuel may be attributed. This approach would be 

similar to that proposed in 2002 by Patton et al. The agency invited comment on this 

approach, requested that manufacturers submit product plans disaggregating fuel 

consumption into each of nine loss mechanisms, and sought estimates of the extent to 

which fuel-saving technologies affect each of these loss mechanisms. 

In response to the NPRM, the Alliance presented a detailed analysis by Sierra Research, 

which used a modified version of VEHSIM (a vehicle simulation tool) to estimate the 

fuel consumption resulting from the application of various vehicle technologies to 25 

vehicle categories intended to represent the fleet. The Alliance commented that this 

simulation-based approach is more accurate than that applied by NHTSA, and indicated 

that Sierra’s ability to perform this analysis demonstrates that NHTSA should be able to 

do the same. 

General Motors also raised questions regarding the multiplicative approach to fuel 

consumption estimation NHTSA has implemented using the Volpe model. GM indicated 

that the Volpe model should be enhanced with modifications to “take into account the 

basic physics of vehicles.”123 Although GM’s comments did not explicitly mention 

vehicle simulation, GM did express full support for the Alliance’s comments. 

The California Air Resources Board (CARB) presented comparisons of different 

simulation studies, commenting that these demonstrate that the VEHSIM model used by 

Sierra Research “cannot accurately simulate vehicles that use advanced technologies such 

as variable valve timing and lift and advanced transmissions.”124 CARB also questioned 

Sierra Research’s simulation capabilities and suggested that, in support of actual product 

development, manufacturers neither contract with Sierra Research for such services nor 

make use of VEHSIM. CARB further commented that both AVL (which performed 

simulation studies for CARB’s evaluation of potential greenhouse gas standards) and 

 

123 GM comments at 2, Docket No. NHTSA-2008-0089-0162. 124 CARB comments at 5, Docket No. NHTSA-2008-0089-0173. In developing potential greenhouse gas 

(GHG) emissions standards for light vehicles, CARB made significant use of vehicle simulation results 

presented in “Reducing Greenhouse Gas Emissions from Light-Duty Motor Vehicles”, which was 

published in 2004 by the Northeast States Center for a Clean Air Future (NESCCAF). As NHTSA 

discussed in the NPRM, CARB’s and NESCCAF’s approach, which effectively reduces each 

manufacturer’s fleet to five “representative” vehicles and two average vehicle weights, is too limited for 

purposes of CAFE analysis. 
V-66

Ricardo (which has recently performed simulation studies and related analysis for both 

EPA and NHTSA) provide such services to manufacturers.125

However, the Alliance and GM have criticized technical aspects of the AVL and Ricardo 

vehicle simulation studies mentioned by CARB. Regarding the AVL vehicle simulations 

CARB utilized, GM raised concerns that, among other things, some of AVL’s 

simulations assumed the use of premium-grade gasoline, and some effectively assume 

vehicle performance and utility would be compromised.126 Similarly, the Alliance raised 

concerns that some of the simulations performed by Ricardo for EPA assumed the use of 

premium fuel, and that many of the simulations assumed vehicle performance would be 

reduced.127 The Alliance also indicated that the five vehicles analyzed by Ricardo for 

EPA were not representative of all vehicles in the fleet, leading to overstatement of the 

degree of improvement potentially available to vehicles that already use technologies not 

present in the vehicles examined by EPA. The Alliance further argued that the report did 

not reveal sufficient detail regarding important simulation details (related, e.g., to 

cylinder deactivation), that it failed to account for some parasitic and accessory loads, 

and that EPA directed Ricardo to unrealistically assume universal improvements in 

aerodynamics, tire efficiency, and powertrain friction.128

Although submitted after the close of the comment period specified in the NPRM, 

comments by several state Attorneys General and other state and local official questioned 

the need and merits of full vehicle simulation within the context of CAFE analysis, 

stating that 

Computer simulation models such as VEHSIM are not practical except 

perhaps during vehicle development to determine the performance of 

specific vehicle models where all vehicle engineering parameters are 

known and can be accounted for in the inputs to the model. Such an 

exercise is extremely data intensive, and extending it to the entire fleet 

makes it subject to multiple errors unless the specific parameters for each 

vehicle model are known and accounted for in the model inputs.129

 

125 California Air Resources Board, “Air Resources Board Staff Comments on Sierra and Martec NRC 

Presentations”, p. 2. 126 Testimony of Kenneth Patton (GM); Testimony of Kevin McMahon (Martec); Plaintiffs' Proposed 

Findings of Fact, June 15, 2007, pp. 103 -113. 

127 Alliance of Automobile Manufacturers, “Detailed Technical Comments on Ricardo ‘Study of Potential 

Effectiveness of Carbon Dioxide Reducing Vehicle Technologies’ Report”, March 6, 2008. 128 For the reader’s reference, Ricardo’s study for EPA was based on specific EPA-defined requirements, 

such as performing full vehicle simulations of 26 different technology packages on the EPA-specified 5 

baseline vehicles. Thus, to the extent that Ricardo’s numbers do not reflect specific differences in 

technology effectiveness by vehicle model, in conducting the analysis for NHTSA’s final rule, NHTSA and 

Ricardo drew on Ricardo’s knowledge to develop incremental benefits based in part on Ricardo’s 

simulation work. Ricardo also noted differences between its report for EPA and the EPA Staff Technical 

Report in terms of the incremental benefits for individual technologies developed by EPA based on 

Ricardo’s simulation. 

129 Attorneys General of the States of California, Arizona, Connecticut, Illinois, Maryland, Massachusetts, 

New Jersey, New Mexico, Oregon, and Vermont, the Executive Officer of the California Air Resources 

Board, the Commissioner of the New Jersey Department of Environmental Protection, the Secretary of the 

New Mexico Environment Department, the Secretary of the Commonwealth of Pennsylvania Department 

of Environmental Protection, and the Corporation Counsel of the City of New York, Supplemental 
V-67

Considering the comments summarized above, the analyses to which they refer, and the 

nature of the analysis the agency performs when evaluating potential CAFE standards, 

NHTSA has concluded that full vehicle simulation, though useful to manufacturers’ own 

product development efforts, remains neither necessary nor feasible for the MY 2011 

CAFE analysis. NHTSA’s basis for this conclusion is as follows: 

Full vehicle simulation involves estimating the fuel consumption (and, typically, 

emissions) of a specific vehicle over a specific driving cycle. Many engineering 

characteristics of the vehicle must be specified, including, but not limited to weight, 

rolling resistance, tire radius, aerodynamic drag coefficient, frontal area, engine maps130

and detailed transmission characteristics (gear ratios, shift logic, etc.), other drivetrain 

characteristics, and accessory loads. Additional engine test data would also be required 

in order to update engine maps when evaluating the application of advanced engine 

technologies. Driving cycles—vehicle speeds over time—are specified on a second-bysecond (or more finely-grained) basis. Using full vehicle simulation to estimate average 

fuel consumption under the test procedures relevant to CAFE involves many simulations 

to capture all the potential combinations of technologies that could be used. 

Given all of the requisite data representing a specific vehicle, full vehicle simulation can 

provide a powerful means of estimating vehicle performance while accounting for 

interactions between various vehicle components and systems. Full simulation can also 

provide a means of estimating vehicle performance under driving conditions not 

represented by the fuel economy test procedures. For an engineer involved in the design 

of a specific vehicle or vehicle component or system, or a manufacturer making specific 

decisions regarding the fleet of vehicles it will produce, vehicle simulation can be a 

powerful tool. However, even the most detailed simulation involving full combustion 

cycle simulation is not the “gold standard” for product design. Chrysler, for example, has 

portrayed simulation as one of several tools in its CAFE planning process, which also 

involves physical testing (i.e., bench testing, chassis dynamometer testing) of actual 

components and assembled vehicles.131

In purpose and corresponding requirements, NHTSA’s evaluation of regulatory options is 

fundamentally different from the type of product planning and development that a 

manufacturer conducts. A manufacturer must make specific decisions regarding every 

component that will be installed in every vehicle it plans to produce, and it must 

ultimately decide how many of each vehicle it will produce. Although manufacturers 

have some ability to make “mid-course adjustments,” that ability is limited by a range of 

factors, such as contracts and tooling investments. By comparison, NHTSA attempts 

 Comments Regarding Alliance of Automobile Manufacturers Comments, Docket No. NHTSA-2008-0089-

0495, October 8, 2008, p. 3. 

130 An engine map specifies the engine’s efficiency under many different operating conditions, each of 

which is defined in terms of rotational speed (i.e., revolutions per minute, or RPM) and load (i.e., torque). 131 Fodale, F., Chrysler LLC, “Fuel Economy/Fuels—Presented to NRC Committee on Fuel Economy of 

Light-Duty Vehicles”, November 27, 2007. 
V-68

only to estimate how a given manufacturer might attempt to comply with a potential 

CAFE standard; given the range of options available to each manufacturer, NHTSA has 

little hope of predicting specifically what a given manufacturer will do. CAFE standards 

require average levels of performance, not specific technology outcomes. Therefore, 

while it is important that NHTSA avoid systematic bias when estimating the potential to 

increase the fuel economy of specific vehicle models, it is not important that the agency’s 

estimates precisely forecast results for every future vehicle. 

Furthermore, NHTSA evaluates the impact of CAFE standards on all manufacturers, 

based on a forecast of specific vehicle models each manufacturer will produce for sale in 

the U.S. in the future. An analysis for MY 2011 can involve thousands of unique vehicle 

models, hundreds of unique engines, and hundreds of unique transmissions. Model-bymodel representation, as used in the analysis for this final rule, allows the agency to, 

among other things, account for technologies expected to be present on each vehicle 

under “business as usual” conditions, thereby avoiding errors regarding the potential to 

add further technologies. 

Because of the intense informational and computational requirements, industry-wide 

studies that rely on vehicle simulation reduce the fleet to a limited number of 

“representative” vehicles. This reduction limits the ability to account for technological 

and other heterogeneity of the fleet, virtually ensuring the overestimation of 

improvements available to some vehicles (e.g., vehicles that begin with a great deal of 

technology) and some manufacturers (e.g., manufacturers that sell many high-technology 

vehicles). AVL’s analysis for NESCCAF and Ricardo’s analysis for EPA, each of which 

considered only five vehicle models, are both, therefore, of severely limited use for the 

kind of fleetwide analysis used in this final rule, although both provide useful information 

regarding the range of fuel savings achieved by specific technologies and “packages” of 

technologies. 

The analysis conducted by Sierra Research for the Alliance considers a significantly 

greater number (25) of “representative” vehicles, drawing important distinctions between 

similarly-sized cars based on performance. Sierra was able to do so in part because it 

analyzed historical vehicles. For example, Sierra indicates that model year 1998 engines 

were used to supply VEHSIM with baseline, “blended” engine maps applied universally 

(rather than specific maps for each manufacturer and vehicle model) for vehicle model 

years out to 2020. Considering that, even without increases in CAFE standards, many 

vehicles produced for sale in the U.S. during the time period considered in a CAFE 

rulemaking are likely to have technologies such as VVLT and cylinder deactivation, 

NHTSA doubts “blended” 1998 engines are as representative as implied by Sierra’s 

analysis. 

Although NHTSA could, in principle, integrate full vehicle simulation of every vehicle 

model into its analysis of the future fleet, the agency expects that manufacturers would be 

unable to provide much of the required information for future vehicles. Even if 

manufacturers were to provide such information, using full vehicle simulation to estimate 

the effect of further technological improvements to future vehicles would involve 
V-69

uncertain detailed estimates, such as valve timing, cylinder deactivation operating 

conditions, transmission shift points, and hybrid vehicle energy management strategies 

for each specific vehicle, engine, and transmission combination. Even setting aside the 

vast increases in computational demands that would accompany the use of full vehicle 

simulation in model-by-model analysis of the entire fleet, the agency remains convinced 

that the availability of underlying information and data would be too limited for this 

approach to be practical. 

As a third alternative, one that might be more explicitly “physics-based” than the use of 

synergy factors and vastly more practical than full vehicle simulation, NHTSA requested 

comment on the use of partitioned fuel consumption accounting. Aside from GM’s 

nonspecific recommendation that the Volpe model be modified to account for the “basic 

physics of vehicles,” NHTSA did not receive comments regarding the relative merits of 

partitioning fuel consumption into several energy loss mechanisms for purposes of 

estimating the effects of fuel-saving technologies, even though the concept is similar to 

that proposed by Patton, et al. in 2002.132 Some manufacturers provided some of the 

information that would have been necessary for the implementation of this approach. 

However, as a group, manufacturers that submitted product plan information to the 

agency provided far too little disaggregated fuel consumption information to support the 

development of this approach. Although NHTSA continues to believe that partitioning 

fuel consumption into various loss mechanisms could provide a practical and sound basis 

for future analysis, the information required to support this approach is not available at 

this time. 

In conclusion, NHTSA observes that with respect to the CAFE analysis prepared for this 

final rule, full vehicle simulation could theoretically be used at three different levels. 

First, full vehicle simulation could be used only to provide specific estimates, that, 

combined with other data (e.g., from bench testing) would provide a basis for estimates 

of the effectiveness of specific individual technologies. While NHTSA will continue 

considering this type of analysis, the agency anticipates that it will continue to be feasible 

and informative to make somewhat greater use of full vehicle simulation. Second, full 

vehicle simulation could be fully integrated into NHTSA’s model-by-model analysis of 

the entire fleet to be projected to be produced in future model years. NHTSA expects, 

however, that this level of integration will remain infeasible considering the size and 

complexity of the fleet. Also, considering the forward-looking nature of NHTSA’s 

analysis, and the amount of information required to perform full vehicle simulation, 

NHTSA anticipates that this level of integration would involve misleadingly precise 

estimates of fuel consumption, even for MY 2011. Finally, full vehicle simulation can be 

used to develop less complex representations of interactions between technologies (such 

as was done using the lumped parameter model to develop the synergies for the final 

rule), and to perform reference points to which vehicle-specific estimates may be 

compared. NHTSA views this as a practical and productive potential use of full vehicle 

 

132 Patton, et al., present an energy balance calculation that disaggregates fuel consumption into six energy 

loss categories, indicating that “an accounting of the effects of individual technologies on energy losses 

within these categories provides a practical, physically-based means to evaluate and compare the fuel 

consumption effects of the various technologies.” (Patton, et. al., (2002), op. cit., p. 11.) 
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simulation, and will consider following this approach in the future. NHTSA has 

contracted with NAS to, among other things, evaluate the potential use of full vehicle 

simulation and other fuel consumption estimation methodologies. Nevertheless, in 

addition to considering further modifications to the Volpe model, NHTSA will continue 

to consider other methods for evaluating the cost and effect of adding technology to 

manufacturers’ fleets. 

9. Refresh and redesign schedule

In addition to, and as discussed below, developing analytical methods that address 

limitations on overall rates at which new technologies can be expected to feasibly 

penetrate manufacturers’ fleets, the agency has also developed methods to address the 

feasible scheduling of changes to specific vehicle models. In the Volpe model, which the 

agency has used to support the current rulemaking, these scheduling-related methods 

were first applied in 2003, in response to concerns that an early version of the model 

would sometimes add and then subsequently remove some technologies.133 By 2006, 

these methods were integrated into a new version of the model, one which explicitly 

“carried forward” technologies added to one vehicle model to succeeding vehicle models 

in the next model year, and which timed the application of many technologies to coincide 

with the redesign or freshening of any given vehicle model.134

Even within the context of the phase-in caps discussed below, NHTSA considers these 

model-by-model scheduling constraints necessary in order to produce an analysis that 

reasonably accounts for the need for a period of stability following the redesign of any 

given vehicle model. If engineering, tooling, testing, and other redesign-related resources 

were free, every vehicle model could be redesigned every year. In reality, however, 

every vehicle redesign consumes resources simply to address the redesign. Phase-in 

caps, which are applied at the level of manufacturer’s entire fleet, do not constrain the 

scheduling of changes to any particular vehicle model. Conversely, scheduling 

constraints to address vehicle freshening and redesign do not necessarily yield realistic 

overall penetration rates (e.g., for strong hybrids). 

In the automobile industry there are two terms that describe when changes to vehicles 

occur: redesign and refresh (i.e., freshening). Vehicle redesign usually encompasses 

changes to a vehicle’s appearance, shape, dimensions, and powertrain, and is traditionally 

associated with the introduction of “new” vehicles into the market, which is often 

characterized as the next generation of a vehicle. In contrast, vehicle refresh usually 

encompasses only changes to a vehicle’s appearance, and may include an upgraded 

powertrain. Refresh is traditionally associated with mid-cycle cosmetic changes to a 

vehicle, within its current generation, to make it appear “fresh.” Vehicle refresh 

traditionally occurs no earlier than two years after a vehicle redesign or at least two years 

before a scheduled redesign. In the NPRM, NHTSA tied the application of the majority 

of the technologies to a vehicle’s refresh/redesign cycle, because their application was 

significant enough that it could involve substantial engineering, testing, and calibration 

work. 

 

133 68 FR 16874 (Apr. 7, 2003). 134 71 FR 17582 (Apr. 6, 2006). 
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NHTSA based the redesign and refresh schedules used in the NPRM as inputs to the 

Volpe model on a combination of manufacturers’ confidential product plans and 

NHTSA’s engineering judgment. In most instances, NHTSA reviewed manufacturers’ 

planned redesign and refresh schedules and used them in the same manner it did in past 

rulemakings. However, in NHTSA’s judgment, manufacturers’ planned redesign and 

refresh schedules for some vehicle models were unrealistically slow considering overall 

market trends. In these cases, the agency re-estimated redesign and refresh schedules 

more consistent with the agency’s expectations, as discussed below. Also, if companies 

did not provide product plan data, NHTSA used publicly available data about vehicle 

redesigns to project the redesign and refresh schedules for the vehicles produced by these 

companies.135

Unless a manufacturer submitted plans for a more rapid redesign and refresh schedule, 

NHTSA assumed that passenger cars would normally be redesigned every 5 years, based 

on the trend over the last 10-15 years showing that passenger cars are typically 

redesigned every 5 years. These trends were reflected in the manufacturer product plans 

that NHTSA used in the NPRM analysis, and were also confirmed by many automakers 

in meetings held with NHTSA to discuss various general issues regarding the 

rulemaking. 

NHTSA explained that it believes that the vehicle design process has progressed and 

improved rapidly over the last decade and that these improvements have made it possible 

for some manufacturers to shorten the design process for some vehicles in order to 

introduce vehicles more frequently in response to competitive market forces. Although 

manufacturers have likely already taken advantage of most available improvements, 

according to public and confidential data available to NHTSA, almost all passenger cars 

will be on a 5-year redesign cycle by the end of the decade, with the exception being 

some high performance vehicles and vehicles with specific market niches. 

NHTSA also stated in the NPRM that light trucks are currently redesigned every 5 to 7 

years, with some vehicles (like full-size vans) having longer redesign periods. In the 

most competitive SUV and crossover vehicle segments, the redesign cycle currently 

averages slightly above 5 years. NHTSA explained that it is expected that the light truck 

redesign schedule will be shortened in the future due to competitive market forces Thus, 

for almost all light trucks scheduled for a redesign in model year 2014 and later, NHTSA 

projected a 5-year redesign cycle. Exceptions were made for high performance vehicles 

and other vehicles that traditionally had longer than average design cycles. For those 

vehicles, NHTSA attempted to preserve their historical redesign cycle rates. 

NHTSA discussed these assumptions with several manufacturers at the NPRM stage, 

before the current economic crisis. Two manufacturers indicated at that time that their 

vehicle redesign cycles take at least five years for cars and 6 years and longer for trucks 

because they rely on those later years to earn a profit on the vehicles. They argued that 

 

135 Sources included, but were not limited to manufacturers’ web sites, industry trade publications (e.g., 

Automotive News), and commercial data sources (e.g., Wards Automotive, etc.). 
V-72

they would not be able to sustain their business if forced by CAFE standards to a shorter 

redesign cycle. The agency recognizes that some manufacturers are severely stressed in 

the current economic environment, and that some manufacturers may be hoping to delay 

planned vehicle redesigns in order to conserve financial resources. However, consistent 

with its forecast of the overall size of the light vehicle market from MY 2011 on, the 

agency currently expects that the industry’s status will improve, and that manufacturers 

will typically redesign both car and truck models every 5 years in order to compete in that 

market. 

NHTSA received relatively few comments regarding its refresh/redesign schedule 

assumptions. UCS commented that redesign schedules should be shortened to 3 years, 

based on recent public statements by Ford that they intended to move to that cycle, and 

based on other recent manufacturer behavior. 

Although NHTSA agrees with UCS that remarks by one Ford official at a January 2008 

conference suggest that that company was then hoping to accelerate its vehicle “cycle 

time” to 3 years, the agency questions the context, intended meaning and scope, and 

representation of those remarks.136 Further, the agency notes that the article referenced 

by UCS also indicates that “most manufacturers make changes to their vehicle lines every 

four years or more, depending on the segment of the market, with mid-cycle freshenings 

every two years or so.”137 Although some manufacturers have, in their product plans, 

indicated that they plan to redesign some vehicle models more frequently than has been 

the industry norm, all manufacturers have also indicated that they expect to redesign 

some other vehicle models considerably less frequently. The CAR report submitted by 

the Alliance, prepared by the Center for Automotive Research and EDF, states that “For a 

given vehicle line, the time from conception to first production may span two and onehalf to five years,” but that “The time from first production (“Job #1”) to the last vehicle 

off the line (“Balance Out”) may span from four to five years to eight to ten years or 

more, depending on the dynamics of the market segment.” The CAR report then states 

that “At the point of final production of the current vehicle line, a new model with the 

same badge and similar characteristics may be ready to take its place, continuing the 

cycle, or the old model may be dropped in favor of a different product.”138

NHTSA believes that this description, which states that a vehicle model will be 

redesigned or dropped after 4-10 years, is consistent with other characterizations of the 

redesign and freshening process, and supports its 5-year redesign assumption and its 2-3 

year refresh cycle assumptions.139 Thus, for purposes of the final rule, NHTSA is 

retaining the 5-year redesign/2-3 year refresh assumptions employed in the NPRM. 

However, NHTSA will continue to monitor manufacturing trends and will reconsider 

these assumptions in subsequent rulemakings if warranted.

 

136 Zoia, D.E. 2008. Ford to cut cycle times to three years. Online at http://www.wardsauto.com. January 

24. 

137 Id. 138 See NHTSA-2008-0089-0170.1, Attachment 16, at 8 (393 of pdf). 139 See id., at 9 (394 of pdf). 
V-73

For purposes of the final rule, NHTSA has also considered confidential product plans 

where applicable and industry trends on refresh and redesign timing as discussed above, 

to apply specific technologies at redesign, refresh, or any model years as shown in Table 

V-7 below. 
V-74

Table V-7. Technology Refresh and Redesign Application

Technology 

Redesign 

only 

Redesign or 

Refresh Anytime

Low Friction Lubricants X 

Engine Friction Reduction X 

VVT - Coupled Cam Phasing (CCP) on SOHC X 

Discrete Variable Valve Lift (DVVL) on SOHC X 

Cylinder Deactivation on SOHC X 

VVT - Intake Cam Phasing (ICP) X 

VVT – Dual Cam Phasing (DCP) X 

Discrete Variable Valve Lift (DVVL) on DOHC X 

Continuously Variable Valve Lift (CVVL) X 

Cylinder Deactivation on DOHC X 

Cylinder Deactivation on OHV X 

VVT - Coupled Cam Phasing (CCP) on OHV X 

Discrete Variable Valve Lift (DVVL) on OHV X 

Conversion to DOHC with DCP X 

Stoichiometric Gasoline Direct Injection (GDI) X 

Combustion Restart X 

Turbocharging and Downsizing X 

Exhaust Gas Recirculation (EGR) Boost X 

Conversion to Diesel following CBRST X 

Conversion to Diesel following TRBDS X 

Electric Power Steering X 

Improved Accessories X 

12V Micro-Hybrid X 

Higher Voltage/Improved Alternator X 

Integrated Starter Generator X 

6-Speed Manual/Improved Internals X 

Improved Auto. Trans. Controls/Externals X 

Continuously Variable Transmission X 

6/7/8-Speed Auto. Trans with Improved Internals X 

Dual Clutch or Automated Manual Transmission X 

Power Split Hybrid X 

2-Mode Hybrid X 

Plug-in Hybrid X 

Material Substitution (1%) X 

Material Substitution (2%) X 

Material Substitution (5%) X 

Low Rolling Resistance Tires X 

Low Drag Brakes X 

Secondary Axle Disconnect X 

Aero Drag Reduction X 
V-75

As the table shows, most technologies are applied by the Volpe model when a specific 

vehicle is due for a redesign or refresh. However, for low friction lubricants, the model is 

not restricted to applying it during a refresh/redesign year and thus it was made available 

for application at any time. Low friction lubricants are very cost-effective, can apply to 

multiple vehicle models/platforms and can be applied across multiple vehicle 

models/platforms in one year. Although they can also be applied during a 

refresh/redesign year, they are not restricted to that timeframe because their application is 

not viewed as necessitating a major engineering redesign and associated 

testing/calibration. 

For several technologies estimated in the NPRM to be available for application during 

any model year, NHTSA now estimates that these technologies will be available only at 

refresh or redesign. Those technologies include aggressive shift logic, improved 

accessories, low rolling resistance tires and low drag brakes. Aggressive shift logic is 

now one of the technologies included under improved automatic transmission controls. 

This technology requires a recalibration specific to each vehicle, such that it can therefore 

be applied only at refresh or redesign model years. The “improved accessories” 

technology has been redefined to include intelligent engine cooling systems, which 

require a considerable change to the vehicle and engine cooling system; therefore, 

improved accessories also can be applied only at refresh or redesign model years. Also, 

NHTSA concurs with manufacturers’ confidential statements that indicating that low 

drag brakes and low rolling resistance tires can be applied only at refresh or redesign 

model years due to the need for vehicle testing and calibration (e.g., to ensure safe 

handling and braking) when these technologies are applied. 

10. Phase-in caps

In 2002, NHTSA proposed the first increases in CAFE standards in six years due to a 

previous statutorily-imposed prohibition on setting new standards. That proposal, for 

MY 2005-2007 light truck standards, relied, in part, on a precursor to the current Volpe 

model. This earlier model used a “technology application algorithm” to estimate the 

technologies that manufacturers could apply in order to comply with new CAFE 

standards. 

NHTSA received more than 65,000 comments on that proposal. Among those were 

many manufacturer comments concerning lead time and the potential for rapid 

widespread use of new technologies. The agency noted that DaimlerChrysler and Ford 

“argued that the agency had underestimated the lead time necessary to incorporate fuel 

economy improvements in vehicles, as well as the difficulties of introducing new 

technologies across a high volume fleet.” Specific to Volpe’s technology application 

algorithm, the agency noted that General Motors took issue with the algorithm’s 

“application of technologies to all truck lines in a single model year.”140

In response to those concerns, Volpe’s algorithm was modified “to recognize that capital 

costs require employment of technologies for several years, rather than in a single 

 

140 68 FR 16874 (Apr. 7, 2003). 
V-76

year.”141 Those changes moderated the rates at which technologies were estimated to 

penetrate manufacturers’ fleets in response to the new (MY 2005-MY 2007) CAFE 

standards. These changes produced more realistic estimates of the technologies 

manufacturers could apply in response to the new standards, and thereby produced more 

realistic estimates of the costs of those standards. 

Prior to the next rulemaking, the Volpe model underwent significant integration and 

improvement, including the accommodation of explicit “phase-in caps” to constrain the 

rates at which each technology would be estimated to penetrate each manufacturer’s fleet 

in response to new CAFE standards.142 As documented in 2006, the agency’s final 

standards for light trucks sold in MY 2008-MY 2011 were based on phase-in caps 

ranging from 17 percent to 25 percent (corresponding to full penetration of the fleet 

within 4 to 6 years) for most technologies, and from 3 percent to 10 percent (full 

penetration within 10 to 33 years) for more advanced technologies such as hybrid electric 

vehicles.143 The agency based these rates on consideration of comments and on the 2002 

NAS Committee’s findings that “widespread penetration of even existing technologies 

will probably require 4 to 8 years” and that for emerging technologies “that require 

additional research and development, this time lag can be considerably longer”.144

In its 2008 NPRM proposing new CAFE standards for passenger cars and light trucks 

sold during MY 2011-MY 2015, NHTSA considered manufacturers’ planned product 

offerings and estimates of technology availability, cost, and effectiveness, as well as 

broader market conditions and technology developments. The agency concluded that 

many technologies could be deployed more rapidly than it had estimated during the prior 

rulemaking.145 For most engine technologies, the agency increased these caps from 17 

percent to 20 percent, equivalent to reducing the estimated time for potential fleet 

penetration from 6 years to 5 years. For stoichiometric gasoline direct injection (GDI) 

engines, the agency increased the phase-in cap from 3 percent to 20 percent, equivalent to 

estimating that such engines could potentially penetrate a given manufacturer’s fleet in 5 

years rather than the previously-estimated 33 years. However, as in its earlier CAFE 

rulemakings, the agency continued to recognize that myriad constraints prohibit most 

technologies from being applied across an entire fleet of vehicles within a year, even if 

those technologies are available in the market. 

In addition to requesting further explanation of NHTSA’s use of phase-in caps, 

commenters addressing phase-in caps generally asserted one of three themes: (1) that 

hybrid phase-in caps were much lower than market trends or manufacturer 

 

141 Id., at 16885. 142 These caps constrain the extent to which additional technology is applied by the model, beyond the 

levels projected in each manufacturer’s baseline fleet. Also, because manufacturers’ fleets are comprised 

of vehicles, engines, and transmissions sold in discrete volumes, phase-in caps cannot be applied as precise 

limits. In some cases (when a phase-in cap is small or a manufacturer has a limited product line), doing so 

would prevent the technology from being applied at all. Therefore, the Volpe model enforces each phasein cap constraint as soon as it has been exceeded by application of technologies to manufacturers. 

143 71 FR 17572, 17679 (Apr. 6, 2006). 144 Id. at. 17572. See also 2002 NAS Report, at 5. 145 73 FR 24387-88 (May 2, 2008). 
V-77

announcements would otherwise suggest; (2) that the phase-in caps proposed in the 

NPRM were too high in the early years of the rulemaking and did not reflect the very 

small (from a manufacturing perspective) amount of lead-time between the final rule and 

the MY 2011 standards, and/or were too low in the later years of the rulemaking given 

the relatively-increased amount of lead-time for those model years; (3) that there are 

insufficient resources (either in terms of capital or engineering) to implement the number 

of technologies implied by the phase-in caps simultaneously. 

Agency response: NHTSA continues to recognize that many factors constrain the rates 

at which manufacturers will be able to feasibly add fuel-saving technologies to the fleets 

they will sell in the United States. For a given technology, examples of these factors may 

include, but would not be limited to the following: 

• Is the technology ready for commercial use? For example, can it operate safely 

and reliably under real-world driving conditions for several years and many 

miles? 

• If the technology requires special infrastructure (e.g., new electrical generation 

and charging facilities), how quickly will that be put in place? 

• How quickly can suppliers ramp up to produce the technology in mass quantities? 

For example, how quickly can they obtain the materials, tooling, and engineering 

resources they will need? 

• Are original equipment manufacturers (OEMs) ready to integrate the technology 

into vehicles? For example, how quickly can they obtain the necessary tooling 

(e.g., retool factories), engineering, and financial resources? 

• How long will it take to establish failure and warranty data, and to make sure 

dealers and maintenance and repair businesses have any new training and tooling 

required in order to work with the new technology? 

• Will OEMs be able to reasonably recoup prior investments for tooling and other 

capital? 

• To what extent are suppliers and OEMs constrained by preexisting contracts? 

NHTSA cannot explicitly and quantitatively evaluate every one of these and other factors 

with respect to each manufacturer’s potential deployment of each technology available 

during the production intent or emerging technology framework. Attempting to do so 

would require an extraordinary effort by the agency, and would likely be subject to 

tremendous uncertainties. For example, in the current economic and market 

environment, the agency expects that it would be impossible to reliably predict specific 

characteristics of future supply chains. Therefore, the agency has concluded that it is 

appropriate to continue using phase-in caps to apply the agency’s best judgment of the 

extent to which such factors combine to constrain the rates at which technologies may 

feasibly be deployed. We note, however, that many of the assumptions about phase-in 

caps made in this final rule apply to years beyond MY 2011, because as the NAS 

Committee and commenters indicated, technologies are phased in over several years, so 
V-78

the agency evaluated the phasing-in of technologies over the five-year period proposed in 

the NPRM. NHTSA provides these assumptions both in response to comments and to 

provide context for the agency’s decisions regarding MY 2011 phase-in caps. We 

emphasize that all assumptions for years other than MY 2011 will be reconsidered for 

future rulemakings and may be subject to change at that time. 

Considering the above-mentioned comments, NHTSA has concluded that the phase-in 

caps it applied during its analysis documented in the 2008 NPRM resulted in technology 

penetration rates that were unrealistically high in the earlier model years covered by its 

proposal, particularly for MY 2011. This was a significant basis for the proposed 

standards’ “front loading” about which manufacturers expressed serious concerns. In 

response, and based on this conclusion, the Volpe model was modified for purposes of 

the final rule analysis to use phase-in caps for each technology that vary from one year to 

the next, and that in many cases would have increased more rapidly in the later years of 

the agency’s analysis than in earlier years. In making these changes, particularly to the 

MY 2011 phase-in caps, the agency has been mindful of the need to provide 

manufacturers sufficient lead time to add technologies to their fleets. In the agency’s 

judgment, its revised approach more realistically represents manufacturers’ capabilities 

and therefore produces more realistic estimates of the costs of new CAFE standards. 

For some technologies, NHTSA also concluded that slower overall rates of fleet 

penetration are more likely than the rates shown in the NPRM. The agency estimates that 

cylinder deactivation, stoichiometric GDI, and turbocharging with downsizing would be 

able to potentially be added to 12-14 percent of the fleet per year on average, rather than 

the 20 percent phase-in caps used in the NPRM for these technologies. Considering 

manufacturers’ comments and some aspects of its reevaluation of the incremental 

benefits of available engine technologies, the agency has concluded that these 

technologies will, for some engines, require more significant hardware changes and 

certification burden than previously recognized, such that feasible deployment is likely to 

be somewhat slower than estimated in the NPRM. 

NHTSA has also concluded, considering the complexities involved in deploying strongly 

hybridized vehicles (i.e., power split, two mode, and plug-in hybrids), it is unrealistic to 

expect that, in response to new CAFE standards, manufacturers can produce more of such 

vehicles in MY 2011 than they are already planning. Therefore, NHTSA has set the MY 

2011 phase-in cap for strong hybrids to zero in that model year. Based on new 

information regarding engineering resources entailed in developing new power split and 

two-mode hybrid vehicles, the agency estimated in its analysis that these technologies 

could be added to up to 11 percent and 8 percent, respectively, of a given manufacturer’s 

long run fleet, rather than the 15 percent the agency estimated for the NPRM. The 

agency also considered a less aggressive 1 percent longer run phase-in cap for plug-in 

hybrids, in part because although the agency expects that plug-in hybrids will rely on 

lithium-ion batteries, it is not clear whether and, if so, how the supply chain for large and 

robust lithium-ion batteries will develop. 
V-79

On the other hand, NHTSA has also concluded that some technologies can potentially be 

deployed more widely than estimated in the NPRM. For example, the agency estimates 

that 6/7/8-speed transmissions, dual clutch or automated manual transmissions, secondary 

axle disconnect, and aerodynamic improvements can potentially (notwithstanding 

engineering constraints that, for example, preclude the application of aerodynamic 

improvements to some performance vehicles) be added at an average rate of 20 percent 

per year of a given manufacturer’s fleet rather than the 14-17 percent average annual 

phase-in caps used in the NPRM for these technologies. In the agency’s judgment, 

increased phase-in caps are appropriate for these transmission technologies, in part 

because the agency’s review of confidential product plans which indicated a higher than 

anticipated application rate of these technologies than existed at the time of the NPRM. 

Additionally, several manufacturers indicated a high likelihood of significant usage of 

dual clutch transmissions across their fleet of vehicles. The secondary axle disconnect 

technology was redefined for the final rule to consist of a somewhat basic, existing 

technology applicable only to 4 wheel-drive vehicles (a smaller population) rather than 

the NPRM-defined technology (which was applicable to both 4 and all wheel drive 

vehicles). The agency has also concluded that, because it has identified performance 

vehicles as such, and has estimated that aerodynamic improvements are not applicable to 

these vehicles, aerodynamic dynamic improvements can be applied more widely as long 

as they are applied consistent with vehicle redesign schedules. Furthermore, considering 

changes in manufacturers’ stated expectations regarding prospects for diesel engines, the 

agency estimates that diesel engines could be added to as much as 4 percent of a 

manufacturer’s light truck fleet each year on average, rather than the 3 percent estimated 

in the NPRM. These changes in NHTSA’s estimates stem from the agency’s 

reevaluation of the status of these technologies, as revealed by manufacturers’ plans and 

confidential statements, as well as other related comments submitted in response to the 

NPRM. 

Regarding comments that manufacturers’ public statements reflect the ability to deploy 

technology more rapidly than reflected in the phase-in caps NHTSA applied in the 

NPRM, NHTSA notes that it did consider such statements. Combined with other 

information, these led the agency to conclude that, as mentioned above, some 

technologies could, particularly in later years, be applied more widely than the agency 

had previously estimated. However, in their confidential statements to NHTSA, 

manufacturers are typically more candid about factors—both positive and negative—that 

affects their ability to deploy new technologies than they are in public statements 

available to their competitors. Therefore, NHTSA places greater weight on 

manufacturers’ confidential statements, especially when they are consistent with 

statements made by other manufacturers and/or suppliers. NHTSA also observes that 

some organizations have exhibited a tendency to take manufacturers’ statements out of 

context, or overlook important caveats included in such statements, which are largely 

used for marketing purposes. 

Table V-8 below outlines the phase-in caps for each discrete technology for MY 2011. 

These phase-in caps, along with the expanded number and types of vehicle subclasses, 

address the concerns raised by commenters and represent a substantial improvement in 
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terms of consideration of the factors affecting technology penetration rates over those 

used in the NPRM. Additional considerations regarding specific phase-in caps, including 

nonlinear increases in these caps, are presented in the more detailed technology-bytechnology analysis summarized below. 

For some of the technologies applied in the final rule, primarily the valvetrain and diesel 

engine technologies, NHTSA has utilized combined phase-ins caps since the technologies 

are effectively the same from the standpoints of engineering and implementation. The 

final rule represented diesel engines as two technologies that both result in the conversion 

of gasoline engine vehicles. The annual phase-in caps for these two technologies, which 

are both set to a maximum of 3 percent for passenger cars (4 percent for light trucks) 

have been combined so that the maximum total application of either or both technologies 

to any manufacturers’ passenger car fleet is limited to 3 percent (not 6 percent). For 

example, if 3 percent of a manufacturers’ passenger car fleet has received diesel 

following combustion restart in a given year, diesel following turbocharging and 

downsizing will not be applied because the phase-in cap for diesels would have been 

reached. These combined phase-in caps are discussed below where applicable to each 

technology. 

 Table V-8a. Phase in caps from 2006 rule, 2008 NPRM, and current rule

Final Rule

MY2011

Low Friction Lubricants 25% 50% 50%

Engine Friction Reduction 17% 20% 20%

VVT - Coupled Cam Phasing (CCP) on SOHC 17% 20% 15%

Discrete Variable Valve Lift (DVVL) on SOHC 17% 20% 15%

Cylinder Deactivation on SOHC 17% 20% 9%

VVT - Intake Cam Phasing (ICP) 17% 20% 15%

VVT - Dual Cam Phasing (DCP) 17% 20% 15%

Discrete Variable Valve Lift (DVVL) on DOHC 17% 20% 15%

Continuously Variable Valve Lift (CVVL) 17% 20% 15%

Cylinder Deactivation on DOHC 17% 20% 9%

Cylinder Deactivation on OHV 17% 20% 9%

VVT - Coupled Cam Phasing (CCP) on OHV 17% 20% 15%

Discrete Variable Valve Lift (DVVL) on OHV 10% 20% 15%

Conversion to DOHC with DCP n.a n.a 9%

Stoichiometric Gasoline Direct Injection (GDI) 3% 20% 3%

Combustion Restart n.a n.a. 0%

Turbocharging and Downsizing 17% 20% 9%

Exhaust Gas Recirculation (EGR) Boost n.a n.a. 0%

Conversion to Diesel following CBRST 3% 3% 3%

Conversion to Diesel following TRBDS 3% 3% 3%

 * Increased annually (in a linear manner) at the rate indicated

Technology

2006

Rule*

2008

NPRM*
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Table V-8b. Phase in caps from 2006 rule, 2008 NPRM, and current rule 

Final Rule

MY2011

Electric Power Steering 17% 25% 10%

Improved Accessories 25% 25% 10%

12V Micro-Hybrid n.a. n.a. 3%

Higher Voltage/Improved Alternator 17% 25% 10%

Integrated Starter Generator 5% 3% 3%

6-Speed Manual/Improved Internals n.a. 17% 33%

Improved Auto. Trans. Controls/Externals n.a. 25% 33%

Continuously Variable Transmission 17% 17% 5%

6/7/8-Speed Auto. Trans with Improved Internals 17% 17% 50%

Dual Clutch or Automated Manual Transmission 17% 17% 20%

Power Split Hybrid 5% 3% 0%

2-Mode Hybrid 5% 3% 0%

Plug-in Hybrid n.a. 3% 0%

Material Substitution (1%) 17% 17% 5%

Material Substitution (2%) 17% 17% 5%

Material Substitution (5%) 17% 17% 5%

Low Rolling Resistance Tires 25% 25% 20%

Low Drag Brakes 17% 25% 20%

Secondary Axle Disconnect 17% 17% 17%

Aero Drag Reduction 17% 17% 17%

 * Increased annually (in a linear manner) at the rate indicated

Technology

2006

Rule*

2008

NPRM*
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D. Specific technologies considered for application and NHTSA’s estimates of 

their incremental costs and effectiveness 

1. What data sources did NHTSA evaluate?

In developing the technology assumptions in the final rule, NHTSA, working with 

Ricardo, examined a wide range of data sources and comments. We reexamined the 

sources we relied on for the NPRM such as the 2002 NAS Report, the 2004 NESCCAF 

report developed for CARB by AVL and Martec, the 2006 EEA report and the EPA 

certification data. We also considered more recent and updated sources of information 

and reports submitted to the NPRM docket, including the (1) Sierra Research report 

submitted by the Alliance as an attachment to its comments as another set of estimates for 

fuel economy cost and effectiveness,146 (2) CARB’s response to aspects of that report, 

which was filed as supplemental comment on October 14, 2008, (3) the 2008 Martec 

Report,147 which updated the Martec report on which the 2004 NESCCAF study was 

based, and the EPA Staff Technical Report,148 which largely mirrored NHTSA’s NPRM 

estimates. 

The agency also evaluated confidential data from a number of vehicle manufacturers and 

technology component suppliers.149 We note that vehicle manufacturers updated their 

product plans in response to NHTSA’s May 2008 Request for Comment.150 

 2. Individual technology descriptions and cost/effectiveness estimates 

(a) Gasoline Engine Technologies 

(i) Overview 

Most passenger cars and light trucks in the U.S. have gasoline-fueled spark ignition 

internal combustion engines. These engines move the vehicle by converting the chemical 

energy in gasoline fuel to useful mechanical work output as shaft torque and power 

delivered to the transmission and to the vehicle’s driving wheels. Vehicle fuel economy 

is directly proportional to the efficiency of the engine. Two common terms are used to 

define the efficiency of an engine are (1) Brake Specific Fuel Consumption (BSFC), 

which is the ratio of the mass of fuel used to the output mechanical energy; and (2) Brake 

Thermal Efficiency (BTE), which is the ratio of the fuel chemical energy, known as 

calorific value, to the output mechanical energy. 

 

146 Sierra Research, “Attachment to Comment Regarding the NHTSA Proposal for Average Fuel Economy 

Standards Passenger Cars and light Trucks Model Years 2011-2015,” June 27, 2008. Available at Docket 

No. NHTSA-2008-0089-0179.1. 

147 Martec, “Variable Costs of Fuel Economy Technologies,” June 1, 2008. Available at Docket No. 

NHTSA-2008-0089-0169.1.

148 EPA Staff Technical Report: Cost and Effectiveness Estimates of Technologies Used to Reduce LightDuty Vehicle Carbon Dioxide Emissions. EPA420-R-08-008, March 2008. 

149 The major suppliers that provided NHTSA with fuel economy cost and effectiveness estimates in 

response to our request for comments included Borg-Warner, Cummins, and Delphi, while Borg-Warner, 

Bosch, Coring, Cummins, Delphi, and Siemens also provided NHTSA with fuel economy cost and 

effectiveness estimates during confidential meetings. 

150 Manufacturers that provided NHTSA with fuel economy cost and effectiveness estimates in response to 

our request for comments include BMW, Chrysler, Daimler, Ford, GM, Honda, Nissan, and Toyota. 
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The efficiency of an automotive spark ignition engine varies considerably with the 

rotational speed and torque output demanded from the engine. The most efficient 

operating condition for most current engine designs occurs around medium speed (30-50 

percent of the maximum allowable engine rpm) and typically between 70-85 percent of 

maximum torque output at that speed. At this operating condition, BTE is typically 33-

36 percent. However, at lower engine speeds and torque outputs, at which the engine 

operates in most consumer vehicle use and on standardized drive cycles, BTE typically 

drops to 20-25 percent. 

Spark ignition engine efficiency can be improved by reducing the energy losses that 

occur between the point of combustion of the fuel in the cylinders to the point where that 

energy reaches the output crankshaft. Reduction in this energy loss results in a greater 

proportion of the chemical energy of the fuel being converted into useful work. For 

improving engine efficiency at lighter engine load demand points, which are most 

relevant for CAFE fuel economy, the technologies that can be added to a given engine 

may be characterized by which type of energy loss is reduced, as shown in Table V-9 

below. 

Table V-9. Technology Characterization by Type of Loss Reduced 

Technology

 Heat Loss 

Reduction 

Exhaust 

Energy 

Reduction

Gas 

Exchange 

Reduction

 Friction 

Reduction 

Low Friction Lubricants 9

Engine Friction Reduction 9

VVT - Coupled Cam Phasing (CCP) on SOHC 9

Discrete Variable Valve Lift (DVVL) on SOHC 9

Cylinder Deactivation on SOHC 9

VVT - Intake Cam Phasing (ICP) 9

VVT - Dual Cam Phasing (DCP) 9

Discrete Variable Valve Lift (DVVL) on DOHC 9

Continuously Variable Valve Lift (CVVL) 9

Cylinder Deactivation on DOHC 9

Cylinder Deactivation on OHV 9

VVT - Coupled Cam Phasing (CCP) on OHV 9

Discrete Variable Valve Lift (DVVL) on OHV 9

Conversion to DOHC with DCP 9

Stoichiometric Gasoline Direct Injection (GDI) 9

Combustion Restart 9

Turbocharging and Downsizing 9 9

Exhaust Gas Recirculation (EGR) Boost 999

Conversion to Diesel 9 99

9 Represents area of primary influence 

As Table V-9 shows, the main types of energy losses that can be reduced in gasoline 

engines to improve fuel economy are exhaust energy losses, engine friction losses, and 
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gas exchange losses. Converting the gasoline engine to a diesel engine can also reduce 

heat losses. 

Exhaust Energy Loss Reduction 

Exhaust energy includes the kinematic and thermal energy of the exhaust gases, as well 

as the wasted chemical energy of unburned fuel. These losses represent approximately 

32 percent of the initial fuel chemical energy and can be reduced in three ways: first, by 

recovering mechanical or electrical energy from the exhaust gases; second, by improving 

the hydrocarbon fuel conversion; and third, by improving the cycle thermodynamic 

efficiency. The thermodynamic efficiency can be improved by either increasing the 

engine’s compression ratio or by operating with a lean air/fuel ratio. The latter is not 

considered to be at the emerging technology point yet due to the non-availability of lean 

NOx aftertreatment, as discussed below. However, the compression ratio may potentially 

be raised by 1 to 1.5 ratios using stoichiometric direct fuel injection. 

Engine Friction Loss Reduction 

Friction losses can represent a significant proportion of the global losses at low load. 

These losses are dissipated through the cooling system in the form of heat. Besides via 

direct reduction measures, friction can also be reduced through downsizing the engine by 

means of increasing the engine-specific power output. 

Gas Exchange Loss Reduction 

 The energy expended while delivering the combustion air to the cylinders and expelling 

the combustion products is known as gas exchange loss, commonly referred to as 

pumping loss. The main source of pumping loss in a gasoline engine is the use of an inlet 

air throttle, which regulates engine output by controlling the pre-combustion cylinder air 

pressure, but is an inefficient way to achieve this pressure control. A more efficient way 

of controlling the cylinder air pressure is to modify the valve timing or lift. Another way 

to reduce the average pumping losses is to “downsize” the engine, making it run at higher 

loads or higher pressures. 

As illustrated in Table V-9, several different technologies target pumping loss reduction, 

but it is important to note that the fuel consumption reduction from these technologies is 

not necessarily cumulative. Once most of the pumping work has been eliminated, adding 

further technologies that also target reduced pumping loss will have little additional 

effectiveness. Thus, in the revised decision trees, the effectiveness value shown for 

additional technologies targeting pumping loss depends on the existing technology 

combination already present on the engine. 

(ii) Low Friction Lubricants (LUB)

One of the most basic methods of reducing fuel consumption in gasoline engines is the 

use of lower viscosity engine lubricants. More advanced multi-viscosity engine oils are 

available today with improved performance in a wider temperature band and with better 

lubricating properties. CAFE standards notwithstanding, the trend towards lower friction 

lubricants is widespread. Within the next several year, most vehicles are likely to use 
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5W-30 motor oil, and some will use even less viscous oils, such as 5W-20 or possibly 

even 0W-20, to reduce cold start friction. 

The NPRM reflected NHTSA’s belief that manufacturer estimates are the most accurate, 

and it estimated that low friction lubricants could reduce fuel consumption by 0.5 percent 

for all vehicle types at an incremental cost of $3, which represented the mid-point of 

manufacturer estimates range, rounded up to the next dollar. For the final rule NHTSA 

used the $3 cost from the NPRM, updated it to 2007 dollars, and marked it up to a retail 

price equivalent (RPE) of $5. Several manufacturers commented confidentially that low 

friction lubricants could reduce fuel consumption by 0 to 1 percent, and the Alliance 

suggested 0.5 percent relative to the baseline fleet. These comments confirm NHTSA’s 

NPRM effectiveness estimate, so NHTSA has retained it for the final rule. 

Low friction lubricants may be applied to any class of vehicles. The phase-in for low 

friction lubricants is capped at 50 percent for MY 2011. Honda commented that low 

friction lubricants cannot be applied to engines that have not been developed specifically 

for them.151 NHTSA understands that in some cases there could be a need for design 

changes and durability verification to implement low friction lubricants in existing 

engines. However, aftermarket low friction lubricant products already exist, and have 

been approved for use in existing engines. 

(iii) Engine Friction Reduction (EFR)

Besides low friction lubricants, manufacturers can also reduce friction and improve fuel 

economy by improving the design of engine components and subsystems. Examples 

include improvements in low-tension piston rings, roller cam followers, improved 

crankshaft design and bearings, material coatings, material substitution, more optimal 

thermal management, and piston and cylinder surface treatments.

In the NPRM, based on confidential manufacturer data and the NAS, NESCCAF, and 

EEA reports, NHTSA estimated that friction reduction could incrementally reduce fuel 

consumption for all vehicles by 1 to 3 percent at a cost of $0 to $21 per cylinder resulting 

in cost estimates of $0-$84 for a 4-cylinder, $0-$126 for a V-6, and $0-$168 for a V-8. 

For the final rule, NHTSA assumed there would be some cost associated with reducing 

engine friction, since at a minimum engineering and validation testing is required, in 

addition to any new components required such as roller followers or improved bearings. 

Additionally some revised components, such as improved surface materials/treatments, 

piston rings, etc., have costs that vary by component size which need to account for the 

full range of engines under consideration in the rulemaking, from small displacement 

gasoline to large displacement diesel engines. 

Considering the above, NHTSA relied on confidential manufacturer comments in 

response to the NPRM to determine a lower technology cost bound of $35 for a 4-

cylinder engine and an upper cost of $195 for a 6 cylinder engine. These costs were 

marked up by a 1.5 RPE factor to arrive at per-cylinder costs of $13 to $49 which were 

used to establish costs based on cylinder count. Costs of $52 to $196 for a 4-cylinder 

 

151 Docket NHTSA-2008-0089-0191.1. 
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engine, $78 to $294 for a 6-cylinder engine, and $104 to $392 for an 8-cylinder engine 

were used in the final rule. 

Confidential manufacturer comments submitted in response to the NPRM showed an 

effectiveness range of 0.3 to 2 percent for engine friction reduction. Besides the 

comments received another effectiveness estimate, a November 2007 press release from 

Renault, claimed a gain of 2 percent over the NEDC cycle152 from engine friction 

reduction.153 Based on the available sources, NHTSA established the fuel consumption 

effectiveness estimate for the final rule as 1 to 2 percent. 

Engine friction-reducing technologies are available from model year 2011 and may be 

applied to all vehicle subclasses. No learning factors were applied to costs as the 

technology has a loosely defined BOM which may in part consist of materials (surface 

treatments, raw materials) that are commodity based. As was the case in the NPRM, an 

average of 20 percent year-over-year phase-in rate starting in 2011 was adopted. As 

confirmed by manufacturers’ comments, NHTSA has maintained the NPRM position that 

engine friction reduction may only be applied in conjunction with a refresh cycle. 

(iv) Variable Valve Timing (VVT)

Variable valve timing (VVT) is a classification of valve-train designs that alter the timing 

of the intake valve, exhaust valve, or both, primarily to reduce pumping losses, increase 

specific power, and control the level of residual gases in the cylinder. VVT reduces 

pumping losses when the engine is lightly loaded by positioning the valve at the optimum 

position needed to sustain horsepower and torque. VVT can also improve thermal 

efficiency at higher engine speeds and loads. Additionally, VVT can be used to alter 

(and optimize) the effective compression ratio where it is advantageous for certain engine 

operating modes. 

VVT has now become a widely adopted technology: for the 2007 model year, over half 

of all new cars and light trucks have engines with some method of variable valve timing. 

Therefore, the degree of further improvement across the fleet is limited by the level of 

valvetrain technology already implemented on the vehicles. Comments from Ford 

received in response to the NPRM indicate that many of its new and upgraded engines 

during the specified time period will launch with or upgrade to advanced forms of VVT, 

which are discussed below.154 Information found in the submitted product plans is used 

 

152 Due to the advanced nature of many of the technologies discussed in the NPRM, and in an effort to find 

broad based rationale for the specific benefits of each technology type, reference data has been gathered 

that specifies fuel consumption benefits as measured on the NEDC test cycle. To make this conversion, 

data from the International Council on Clean Transportation (ICCT) showed excellent correlation between 

CAFE test cycle results and NEDC test cycle results. While there was an offset in the linear best fit, the 

slope was nearly equal to 1; therefore, for this report, any percentage improvement found on the NEDC 

cycle will be assumed to be equivalent to gains found on the CAFE test cycle. 153 Renault press release, “Renault Introduces The Ecological, Economical Logan ‘Renault Eco2’ Concept 

At The Michelin Organized Challenge Bibendum, November 14, 2007. Available at 

http://www.renault.com/renault_com/en/images/15181%2015181_DP_logan_eco2_Shanghai_14_nov_DE

F_GB_2_tcm1120-686305.pdf (last accessed October 27, 2008 ) 154 Docket No. NHTSA-2008-0089-0202.1, at 4. 
V-87

to determine the degree to which VVT technologies have already been applied to 

particular vehicles to ensure the proper level of VVT technology, if any, is applied. 

There are three different implementation classifications of variable valve timing: ICP 

(Intake Cam Phasing), where a cam phaser is used to adjust the timing of the inlet valves 

only; CCP (Coupled Cam Phasing), where a cam phaser is used to adjust the timing of 

both the inlet and exhaust valves equally; and DCP (Dual Cam Phasing), where two cam 

phasers are used to control the inlet and exhaust valve timing independently. 

Each of these three implementations of VVT uses a cam phaser to adjust the camshaft 

angular position relative to the crankshaft position, referred to as “camshaft phasing.” 

This phase adjustment results in changes to the pumping work required by the engine to 

accomplish the gas exchange process. The majority of current cam phaser applications 

use hydraulically actuated units, powered by engine oil pressure and managed by a 

solenoid that controls the oil pressure supplied to the phaser. Electrically actuated cam 

phasers are relatively new, but are now in volume production with Toyota, which 

suggests that technical issues have been resolved. 

Honda commented that VVT is not applicable on existing engine designs that do not 

already contain these technologies due to durability, noise-vibration-harshness (NVH), 

thermal, packaging, and other constraints that require engine redesign. 

1. Intake Cam Phasing (ICP)

Valvetrains with ICP can modify the timing of the inlet valves by phasing the intake 

camshaft while the exhaust valve timing remains fixed. This requires the addition of a 

cam phaser on each bank of intake valves on the engine. An in-line 4-cylinder engine has 

one bank of intake valves, while V-configured engines have two banks of intake valves. 

In the NPRM, NHTSA and EPA estimated that ICP would cost $59 per cam phaser or 

$59 for an in-line 4 cylinder engine and $119 for a V-type, for an overall cost estimate of 

$59 to $119, based on the NAS, NESCCAF, and EEA reports and confidential 

manufacturer data. NHTSA received several updated cost estimates confidentially from 

manufacturers for ICP costs in response to the NPRM that varied over a wide range from 

$35 to $300, and additionally looked to the 2008 Martec report for costing guidance. 

According to the 2008 Martec report, content assumptions for ICP costing include the 

addition of a cam phaser and oil control valves at $25 and $10 respectively, per bank, 

which agreed with confidential manufacturer data received in response to the NPRM. 

These figures were then adjusted to include an incremental camshaft sensor per bank at 

$4, and an additional $2 increase to account for an ECU upgrade as shown by 

confidential data. Using a markup of 1.5 to yield a RPE value, the incremental cost for 

ICP in the final rule is estimated to be $61 per bank, resulting in a $61 charge for in-line 

engine configurations and $122 for V-engine configurations. 

For fuel economy effectiveness values, NHTSA tentatively concluded in the NPRM that 

the incremental gain in fuel consumption for ICP would be 1 to 2 percent depending on 

engine configuration, in agreement with the NESCCAF study. Confidential manufacturer 

data submitted in response to the NPRM showed a larger effectiveness range of 1.0 to 3.4 
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percent, although the majority of those estimates fell at the lower end of that range. 

Based on the comments received, NHTSA retained the NPRM estimates of 1 to 2 percent 

incremental improvement in fuel consumption due to ICP. 

ICP is applicable to all vehicle classes and can be applied at the refresh cycle. For the 

final rule, NHTSA has combined the phase-in caps for ICP, CCPS, CCPO and DCP and 

capped the joint penetration allowed at 15 percent in MY 2011 with time-based learning 

applied. 

2. Coupled Cam Phasing (CCPS and CCPO)

Valvetrains with coupled (or coordinated) cam phasing can modify the timing of both the 

inlet valves and the exhaust valves an equal amount by phasing the camshaft of a single 

overhead cam (SOHC) engine or an overhead valve (OHV) engine.155 For overhead cam 

engines, this requires the addition of a cam phaser on each bank of the engine. Thus, an 

in-line 4-cylinder engine has one cam phaser, while V-engines have two cam phasers. 

For overhead valve (OHV) engines, which have only one camshaft to actuate both inlet 

and exhaust valves, CCP is the only VVT implementation option available.156

In the NPRM, NHTSA explained that for an OHV engine, the same phaser added for ICP 

would be used for CCP control, so the cost for CCP should be identical to that for ICP. 

For an OHV, since only one phaser would be required since only camshaft exists, 

NHTSA estimated the cost for CCP at $59 regardless of engine configuration, using the 

logic provided for ICP. For purposes of the final rule, the logic for ICP also carries over 

to the cost estimates for CCP. Cost assumptions for CCP are the same as ICP resulting in 

RPE-adjusted costs of $61 for in-line SOHC or OHV engines and $122 for SOHC Vengine configurations, incremental to an engine without VVT.

For fuel economy effectiveness, NHTSA estimated in the NPRM that the incremental 

gain in fuel consumption for CCP is 1 to 3 percent above that obtained by ICP, in 

agreement with the NESCCAF report and confidential manufacturer data. Confidential 

manufacturer data submitted in response to the NPRM also showed an effectiveness 

range of 1 to 3 percent for CCP, although Ford has publicly reported a 3.3 percent 

improvement for CCP when applied to its 5.4 liter 3-valve V8 engine (which has high 

EGR tolerance due to the valve-masking effect with the 3-valve design).157 Most engines 

are not as EGR-tolerant and so will not achieve as much effectiveness from CCP as the 

Ford engine. For purposes of the final rule, NHTSA essentially carried over the NPRM 

incremental effectiveness of applying the CCP technologies to be 1 to 3 percent. 

 

155 Although CCP appears only in the SOHC and OHV branches of the decision tree, it is noted that a 

single phaser with a secondary chain drive would allow CCP to be applied to DOHC engines. Since this 

would potentially be adopted on a limited number of DOHC engines NHTSA did not include it in that 

branch of the decision tree. 

156 It is also noted that coaxial camshaft developments would allow other VVT options to be applied to 

OHV engines. However, since they would potentially be adopted on a limited number of OHV engines 

NHTSA did not include them in the decision tree. 

157 Robert Stein, Tachih Chou, and Jeffrey Lyjak, “The Combustion System Of The Ford 5.4 L 3 Valve 

Engine,” Global Powertrain Congress 2003 - Advanced Engine Design & Performance, Sep 2003, Volume 

24. Available at http://www.gpc-icpem.org/pages/publications.html (last accessed Nov. 8, 2008)
V-89

CCP can be applied to any class of vehicles at refresh. For the final rule, NHTSA has 

combined the phase-in caps for ICP, CCPS, CCPO and DCP and capped the joint 

penetration at 15 percent in NY 2011. Since these technologies are mature and in high 

volume, time-based learning factors are applied. CCP can be applied to any class of 

vehicles. 

3. Dual Cam Phasing (DCP)

The most flexible VVT design is dual (independent) cam phasing, where the intake and 

exhaust valve opening and closing events are controlled independently. This option 

allows the option of controlling valve overlap, which can be used as an internal EGR 

strategy. At low engine loads, DCP creates a reduction in pumping losses, resulting in 

improved fuel consumption. Additionally, increased internal EGR results in lower 

engine-out NOX emissions and improved fuel consumption. This fuel economy 

improvement depends on the residual tolerance of the combustion system, as noted in the 

CCP section above. Additional improvements are observed at idle, where low valve 

overlap can result in improved combustion stability, potentially reducing idle fuel 

consumption. 

In the NPRM, NHTSA estimated costs for DCP by building upon the cost estimates for 

ICP, where an additional cam phaser is added to control each bank of exhaust valves less 

the cost of the EGR valve which can be deleted. This resulted in an NPRM cost range of 

$89 to $209. For purposes of the final rule, cost assumptions for DCP, which included 

inflation, were determined by essentially doubling the ICP hardware, yielding an 

incremental cost of $61 per engine cylinder bank, over ICP. This translates to a cost of 

$61 for in-line engines and $122 for V-engine configurations, incremental to ICP 

technology. 

For fuel economy effectiveness, NHTSA estimated in the NPRM that the incremental 

gain in fuel consumption for DCP is 1 to 3 percent, in agreement with the NESCCAF 

report and confidential manufacturer data. Confidential manufacturer data received in 

response to the NPRM showed an effectiveness range of 0.5 to 3.4 percent for DCP. 

Publicly available data from BMW158 and Ford159 show an effectiveness of 5 percent for 

DCP over engines without VVT, agreeing with the upper bounds for ICP and DCP 

combined. For purposes of the final rule, NHTSA concluded that the effectiveness for 

DCP should be at the upper end of the CCP range due to the additional flexibility gained 

through independent control of intake and exhaust valve timing, and therefore estimated 

an incremental fuel consumption reduction of 2 to 3 percent for DCP incremental to the 1 

to 2 percent for ICP. 

 

158 Meyer, BMW, “Turbo-Charging BMW’s Spray-Guided DI Combustion System – Benefits and 

Challenges,” Global Powertrain Congress, September, 2005, vol. 33. Available at http://www.gpcicpem.org/pages/publications.html (last accessed Nov. 8, 2008)

159 Ulrich Kramer and Patrick Phlips, “Phasing Strategy For An Engine With Twin Variable Cam Timing,” 

SAE Technical Paper 2002-01-1101, 2002. Available at http://www.sae.org/technical/papers/2002-01-

1101. (last accessed Nov. 9, 2008)
V-90

There are no class-specific applications of this technology and DCP can be applied at the 

refresh cycle. For the final rule, NHTSA has combined the annual average phase-in caps 

for ICP, CCPS, CCPO and DCP and capped the joint penetration at 15 percent in MY 

2011. The DCP technology is assumed to be produced at high volume, thus time-based 

learning is applied. 

(v) Discrete Variable Valve Lift (DVVLS, DVVLD, DVVLO)

DVVL systems allow the selection between two or three separate cam profiles by means 

of a hydraulically actuated mechanical system. By optimizing the cam profile for 

specific engine operating regions, the pumping losses can be reduced by reducing the 

amount of throttling required to produce the desired engine power output. This increases 

the efficiency of the engine. DVVL is normally applied together with VVT control. 

DVVL is also known as Cam Profile Switching (CPS). DVVL is a mature technology 

with low technical risk. 

In the NPRM, based on the NESCCAF report and confidential manufacturer data, 

NHTSA estimated the incremental cost for DVVL at $169 to $322 compared to VVT 

depending on engine size, which included $25 for controls and associated oil supply 

needs. In response to the NPRM, confidential manufacturer comments noted a cost range 

of $150 to $600 for DVVL on OHC engines. Sierra Research has noted costs ranging 

from $518 to $656 for DVVL including dual cam phasers on a mid-size car and $634 to 

$802 on trucks.160 For purposes of the final rule, NHTSA has changed the order of the 

technologies in the decision trees which has changed how the DVVL costs are handled. 

For the overhead cam engines, SOHC and DOHC, the costs were derived by taking $30 

per cylinder for lost motion devices, adding a $4 incremental cost for a camshaft position 

sensor upgrade and $10 for an oil control valve on each engine cylinder bank, as 

indicated by the 2008 Martec report. This assumes that one lost motion device is used to 

control either a single intake valve on an SOHC engine or a pair of intake valves on a 

DOHC engine, as was done in the NPRM. NHTSA’s independent review concurred with 

data in the 2008 Martec report because it contained the most complete published 

description of DVVL costs and it agreed with confidential manufacturer data received in 

response to the NPRM NHTSA adopted these cost estimates for the final rule, such that 

incremental costs for DVVLS and DVVLD, including a 1.5 RPE markup, are $201 for an 

in-line 4-cylinder engine, $306 for V-6 engines, and $396 for V-8 engines. For overhead 

valve engines, OHV, the costs for V6 and V8 engines do not include the lost motion 

devices and control hardware since DVVLO follows cylinder deactivation on the OHV 

decision tree path and employs similar lost motion devices. Rather, the DVVLO cost is 

for active engine mounts on V6 and V8 OHV engines which was based on $50 variable 

cost from Martec, adjusted to 2007 dollars and marked up with a 1.5 RPE factor to $76. 

For in-line 4-cylinder engines cylinder deactivation is not allowed so the cost for 

DVVLO is the same as for DVVLS and DVVLD at $201.

For fuel economy effectiveness, in the NPRM NHTSA estimated that DVVL could 

incrementally reduce fuel consumption by 0.5 to 3 percent compared to VVT. 

 

160 Docket no. NHTSA-2008-0089-0179.1, p 59 and Docket no. NHTSA-2008-0089-0046, p. 52. 
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Confidential manufacturer comments received in response to the NPRM indicated a 2 

percent effectiveness for DVVL, while the Alliance commented that a two-step system 

with dual cam phasing could reduce fuel consumption by 6.3 percent, with 1.3 percent 

attributable to DVVL. Publicly-available estimates suggest an improvement over the 

NEDC test cycle of 8 percent for DCP with 2 stage inlet DVVL applied to a 1.6 liter 

DOHC 4 cylinder engine in a 1500 kg vehicle.161 With the DCP system expected to 

deliver 5 percent effectiveness, this suggests the DVVL system is giving approximately 3 

percent. The comments received from manufacturers and publicly available data are in 

alignment with independent review suggesting a range of 1 to 3 percent for overhead cam 

engines with VVT. NHTSA has therefore estimated an incremental reduction in fuel 

consumption for DVVLS and DVVLD of 1 to 3 percent for purposes of the final rule. On 

OHV engines, DVVLO is applied following both VVT and cylinder deactivation, 

therefore the fuel consumption effectiveness has been reduced from 1 to 3 percent for 

OHC engines to 0.5 to 2.6 percent. 

This technology may be applied to any class of vehicles with any kind of engine at the 

redesign cycle. For the final rule, NHTSA has combined the phase-in caps for DVVLS, 

DVVLD, DVVLO and CVVL and capped the joint penetration allowed at 15 percent in 

MY 2011 with time-based learning applied. Other technologies, such as continuously 

variable valve lift (CVVL), described below, will be implemented in place of DVVL in 

some applications where the fuel economy requirements dictate further optimization of 

the engine’s breathing characteristics to improve efficiency.

(vi) Continuously Variable Valve Lift (CVVL) 

In CVVL systems, maximum valve lift is varied by means of a mechanical linkage, 

driven by an actuator controlled by the engine control unit. The valve opening and 

phasing vary as the maximum lift is changed; the relation depends on the geometry of the 

mechanical system. BMW has the most production experience with CVVL systems and 

has sold port-injected “Valvetronic” engines since 2001. CVVL allows the airflow into 

the engine to be regulated by means of inlet valve opening reduction, which improves 

engine efficiency by reducing pumping losses from throttling the intake system further 

upstream as with a normally throttled engine. 

Variable valve lift gives a further reduction in pumping losses compared to that which 

can be obtained with cam phase control only, with CVVL providing greater effectiveness 

than DVVL, since it can be fully optimized for all engine speeds and loads, and is not 

limited to a two or three step compromise. There may also be a small reduction in 

valvetrain friction when operating at low valve lift. This results in improved low load 

fuel consumption for cam phase control with variable valve lift as compared to cam phase 

control only. Most of the fuel economy effectiveness is achieved with variable valve lift 

on the inlet valves only. 

 

161 Mark Sellnau and Eric Rask, “Two-Step Variable Valve Actuation For Fuel Economy, Emissions, and 

Performance, Delphi Research Labs, SAE 2003-01-0029. Available at 

http://www.sae.org/technical/papers/2003-01-0029. (last accessed Nov. 9, 2008)
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It is generally more difficult to achieve good cylinder-to-cylinder airflow balance at low 

load with a CVVL valve-throttled engine due to the sensitivity of airflow to small 

differences in lift caused by manufacturing tolerances. BMW has reported mixture 

quality issues with CVVL and port fuel injection, requiring a compromise on pumping 

work reduction to ensure good mixture quality. In addition, a small amount of throttling 

is necessary with CVVL to maintain the vacuum required for power brake assist, unless a 

separate vacuum pump is used. BMW calibrations maintain a small amount of inlet 

manifold depression on their “Valvetronic” engines to allow the brake servo to function, 

which reduces the efficiency gain from the system somewhat. Tumble air motion 

generated by the inlet port is not available in the cylinder at low valve lift, which has an 

effect on combustion characteristics. The high gas velocities at the valve seat generate 

high turbulence levels, but most of this has decayed by the time of ignition. This 

phenomenon could potentially lead to sub-optimal combustion characteristics, which 

would reduce the fuel consumption effectiveness of the technology. 

In the NPRM, NHTSA estimated the cost for CVVL of $254 to $508 compared to VVT, 

with cost estimates varying from $254 for a 4-cylinder engine, $466 for a 6-cylinder 

engine, and $508 for an 8-cylinder engine, based on confidential manufacturer data and 

the NESCCAF report, with more weight given to the manufacturer data. As for DVVL, 

for purposes of the final rule, NHTSA relied primarily on the 2008 Martec report, 

because it contained the most complete published description of CVVL costs and agreed 

with confidential manufacturer data received in response to the NPRM. The system 

consists of 1 stepper motor per bank to control an eccentric shaft and the costs as 

described by Martec include dual cam phasing are $285 for an in-line 4-cylinder engine, 

$450 for a V-6 engine, and $550 for a V-8 engine. Applying a 1.5 RPE markup factor to 

these variable costs, and then deducting $122 for the incremental cost of both ICP and 

DCP per bank, the incremental RPE cost is $306 for a 4-cylinder engine, $432 for a 6-

cylinder engine and $582 for an 8-cylinder engine. 

For fuel economy effectiveness, in the NPRM NHTSA estimated that CVVL could 

incrementally reduce fuel consumption by 1.5 to 4 percent compared to VVT, based on 

confidential manufacturer data and the NESCCAF report. Confidential manufacturer 

comments received in response to the NPRM suggested a range of 3 to 7.4 percent 

incremental fuel consumption savings. NHTSA also found several sources reporting a 5 

percent additional fuel consumption effectiveness over the NEDC cycle when applying 

CVVL to an engine with dual cam phasers.162 For purposes of the final rule, NHTSA has 

estimated the reduction in fuel consumption for CVVL at 1.5 to 3.5 percent over an 

engine with DCP. This estimate is lower that the effectiveness reported by BMW and 

allows the application of CVVL without the need for the high level of manufacturing 

complexity inherent in BMW’s “Valvetronic” engines.

 

162 See Johannes Liebl, Manfred Kluting, Jurgen Poggel, and Stephen Missy, BMW, “The New BMW 4-

Cylinder Engine with Valvetronic Part 2: Thermodynamics and Functional Features,” MTZ Worldwide, 

July/Aug 2001, pp 26-29. See also Meyer, BMW, “Turbo-Charging BMW’s Spray-Guided DI Combustion 

System – Benefits and Challenges,” Global Powertrain Congress, Sept. 2005, vol. 33. Available at 

http://www.gpc-icpem.org/pages/publications.html (last accessed Nov. 8, 2008). See also Rainer Wurms, 

Philipp Lobbert, Stefan Dengler, Ralf Budack, and Axel Eiser, Audi, “How Much VVT Makes Sense?” 

Haus der Technik Conference on Variable Valve Control, Essen, Feb. 2007.
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There are no class specific applications of this technology, although it appears in only the 

DOHC portion of the decision tree. Due to the changes required to implement DVVL on 

an engine the Volpe model allows it to be applied at redesign model years only with timebased learning applied. For the final rule, NHTSA has combined the phase-in caps for 

DVVLS, DVVLD, DVVLO and CVVL and capped the joint penetration allowed at 20 

percent per year on average (15 percent in year one). There is no technical reason this 

technology could not be applied to all DOHC engines, but due to engineering resource 

limitations it is unlikely that CVVL will be applied to all engines, and that other 

technologies such as DVVL will be used in some instances. 

(vii) Cylinder Deactivation (DEACS, DEACD, DEACO)

In conventional spark-ignited engines, combustion occurs in all cylinders of the engine 

(i.e., the engine is “firing on all cylinders”), and throttling the airflow controls the engine 

output, or load. This is an inefficient method of operating the engine at low loads as 

pumping losses result from throttling. Cylinder deactivation (DEAC) can improve engine 

efficiency by disabling or deactivating half of the cylinders when the load is less than half 

of the engine’s total torque capability, allowing the active cylinders to operate at roughly 

twice the load level, and thereby incur roughly half the pumping losses. 

Simplistically, cylinder deactivation control strategy relies on setting maximum and 

minimum manifold absolute pressures (which are directly proportional to load) within 

which it can deactivate the cylinders. The engine operating range over which cylinder 

deactivation may be enabled is restricted by other factors as well, with noise, vibration, 

and harshness (NVH) being the primary concern; these restrictions all reduce the fuel 

economy effectiveness achievable with cylinder deactivation. In general, DEAC has very 

high sensitivity of efficiency gain relative to vehicle application, according to comments 

from Ford, Chrysler, the Alliance, and in confidential comments submitted in response to 

the NPRM. 

Manufacturers have stated that use of DEAC on 4 cylinder engines would cause 

unacceptable NVH; therefore NHTSA has not applied cylinder deactivation to 4-cylinder 

engines. In addition, to address NVH issues for V6 and V8 engines, active engine 

mounts are included in the content list. Noise quality from both intake and exhaust 

systems has been problematic on some vehicle applications, and in some cases, has 

resulted in active exhaust systems solutions with an ECU-controlled valve. 

The NPRM reported an incremental cost range for DEAC at $203 to $229, citing 

manufacturer data as the most credible, with the bill of materials including lost motion 

devices for each cylinder. The 2008 Martec report estimated the additional hardware 

necessary for cylinder deactivation ranging between $50 for the addition of two active 

engine mounts ($75 RPE using 1.5 RPE factor) where DVVL already exists. This value 

has been adopted by NHTSA in the final rule so DEACS and DEACD costs are $75. For 

OHV engines NHTSA estimates the costs for DEACO as being $306 for V6 engines and 

$400 for V8 engines that are not already equipped with DVVL using assumptions for lost 
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motion devices plus incremental costs for oil control valves and camshaft position 

sensors as noted in the DVVL section. 

For fuel economy effectiveness, in the NPRM NHTSA estimated that cylinder 

deactivation could reduce fuel consumption by 4.5 to 6 percent. As noted, DEAC has 

very high sensitivity of efficiency gain relative to vehicle application. Chrysler, for 

example, stated that the effectivenesss could range from 3 to 10 percent on the same 

engine depending on the specific vehicle application.163 Confidential manufacturer 

comments received in response to the NPRM reported a range of 3 to 7.5 percent. For 

the final rule, the incremental fuel consumption effectiveness varies depending on which 

branch of the decision tree it is on: for DOHC engines which are already equipped with 

DCP and DVVLD there is little benefit that can be achieved since the pumping work has 

already been minimized and internal EGR rates are maximized, so the effectiveness 

ranges from 0 to 0.5 percent for DEACD; for SOHC engines which have CCP and 

DVVLS applied, NHTSA estimates a 2.5 to 3 percent effectiveness for DEACS; and for 

OHV engines, which do not have VVT or VVL technologies, the effectiveness for 

DEACO ranges from 3.9 to 5.5 percent. 

This technology may be applied only to V-6 and V-8 engines, as discussed above, and so 

does not apply to vehicle classes with I-4 engines. DEAC can be applied during a 

redesign or refresh model year with time-based learning. NHTSA proposed to raise the 

phase-in cap for this technology to 20 percent per year in the NPRM. For the final rule, 

NHTSA has combined the phase-in caps for DEACS, DEACD and DEACO and capped 

the joint average annual penetration allowed at 9 percent in MY 2011. 

(viii) Conversion to Double Overhead Camshaft Engine with Dual Cam Phasing 

(CDOHC)

This technology was named “Multi-valve Overhead Camshaft Engine” in the NPRM. 

Engines with overhead cams (OHC) and more than two valves per cylinder achieve 

increased airflow at high engine speeds and reductions of the valvetrain’s moving mass 

and enable central positioning of the spark plug. Such engines typically develop higher 

power at high engine speeds. In the NPRM, the model was generally not allowed to 

apply multivalve OHC technology to OHV engine, except where continuous variable 

valve timing and lift (CVVL) is applied to OHV engine. In that case, the model assumed 

conversion to a DOHC valvetrain, because a DOHC valvetrain is a prerequisite for the 

application of any advanced engine technology over and above CVVL. Since applying 

CVVL to an OHV engine is the last improvement that could be made, it was assumed 

that manufacturers would redesign that engine as a DOHC and include CVVL as part of 

that redesign. 

However, it appears likely that vehicles will still use overhead valve (OHV) engine with 

pushrods and one intake and one exhaust valve per cylinder into the next decade. For the 

final rule, NHTSA assumed that conversion of an OHV engine to a DOHC engine would 

more likely be accompanied by dual cam phasing (DCP) than by CVVL, since DCP 

application rates are higher than CVVL rates. 

 

163 Docket No. NHTSA-2008-0089-0215.1. 
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For V8 engines, the incremental cost to redesign an OHV engine as a DOHC with DCP 

was estimated as $746 which includes $415 for the engine conversion to DOHC per the 

2008 Martec report and a 1.5RPE factor, plus $122 for an incremental cam phasing 

system (reflecting the doubling of cam shafts). For a V6 engine we estimated 75 percent 

of the V8 engine cost to convert to DOHC plus the same incremental coupled cam 

phasing cost to arrive at $590. For inline 4-cylinder engines, 50 percent of the V8 engine 

conversion costs were assumed and one additional cam phasing system yielding an 

incremental cost including a 1.5 RPE factor of $373. 

For fuel economy effectiveness, NHTSA estimated in the NPRM that the incremental 

gain in fuel consumption for conversion of an OHV engine with cylinder deactivation 

and CCP to a DOHC engine with CVVL at 1 to 4 percent, in agreement with the 

NESCCAF report and confidential manufacturer data. The fuel consumption benefit for 

converting an OHV engine to a DOHC engine with DCP is due largely to friction 

reduction according to a confidential manufacturer comment. For the final rule the upper 

bound stated in the NPRM was reduced because DCP will give less improvement than 

CVVL compared to an engine that already has cylinder deactivation and CCP applied. 

NHTSA estimates the incremental fuel consumption effectiveness at 1 to 2.6 percent 

independent of the number of engine cylinders. 

There are no class-specific applications of this technology. In the NPRM, NHTSA 

proposed raising the phase-in cap to 20 percent per year, but has concluded for the final 

rule that a 9 percent phase-in cap for MY 2011 is more consistent with manufacturers’ 

comments. No comments were received regarding phase-in rates of converting OHV 

engines to DOHC. The conversion from OHV to DOHC engine architecture with DCP is 

a major engine redesign that can be applied at redesign model years only with time-based 

learning applied. 

(ix) Stoichiometric Gasoline Direct Injection (SGDI)

In gasoline direct injection (GDI) engines, fuel is injected into the cylinder rather than 

into the inlet manifold or inlet port. GDI allows for the compression ratio of the engine 

to be increased by up to 1.5 units higher than a port-injected engine at the same fuel 

octane level. As a result of the higher compression ratio, the thermodynamic efficiency is 

improved, which is the primary reason for the fuel economy effectiveness with 

stoichiometric DI systems. The compression ratio increase comes about as a result of the 

in-cylinder air charge cooling that occurs as the fuel, which is sprayed directly into the 

combustion chamber, evaporates. 

Volumetric efficiency in naturally-aspirated GDI engines can also be improved by up to 2 

percent, due to charge cooling, which improves the full load torque. The improved full 

load torque capability of GDI engines can have a secondary effect on fuel economy by 

enabling engine downsizing, thereby reducing fuel consumption. 

Two operating strategies can be used in gasoline DI engines, characterized by the mixture 

preparation strategy. One strategy is to use homogenous charge where fuel is injected 
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during the intake stroke with a single injection. The aim is to produce a homogeneous 

air-fuel-residual mixture by the time of ignition. In this mode, a stoichiometric air/fuel 

ratio can be used and the exhaust aftertreatment system can be a relatively low cost, 

conventional three-way catalyst. Another strategy is to use stratified charge where fuel is 

injected late in the compression stroke with single or multiple injections. The aim here is 

to produce an overall lean, stratified mixture, with a rich area in the region of the spark 

plug to enable stable ignition. Multiple injections can be used per cycle to control the 

degree of stratification. Use of lean mixtures significantly improves efficiency by 

reducing pumping work, but requires a relatively high cost lean NOx trap in the exhaust 

aftertreatment system. 

For purposes of this rulemaking, only homogeneous charge stoichiometric DI systems 

were considered, due to the anticipated unavailability of low sulfur gasoline during the 

time period considered. This decision was supported by comments from Mercedes, 

which sells lean burn DI engines in other world markets, stating that lean burn DI engines 

cannot function in the absence of ultra-low sulfur gasoline. Lean NOx trap technologies 

require ultra-low sulfur gasoline to function at high conversion efficiency over the entire 

life cycle of a vehicle. 

Gasoline DI systems effectiveness from the increased efficiency of the thermodynamic 

cycle. The fuel consumption effectiveness from DI technology is therefore cumulative to 

technologies that target pumping losses, such as the VVT and VVLT technologies. The 

Sierra Research report stated that Sierra Research could not determine from the NPRM 

decision trees if VVLT technologies were retained when SGDI was applied. To clarify, 

as the model progresses through the decision trees, technologies preceding SGDI are 

retained in the cumulative effectiveness and cost. 

In the NPRM, NHTSA estimated the incremental fuel consumption effectiveness for 

naturally aspirated SGDI164 to be 1 to 2 percent. The Alliance commented that it 

estimated 3 percent gains in fuel efficiency, as well as a 7 percent improvement in torque, 

which can be used to mildly downsize the engine and give up to a 5.8 percent increase in 

efficiency. Other published literature reports a 3 percent effectiveness for SGDI,165 and 

another source reports a 5 percent improvement on the NEDC drive cycle.166 

Confidential manufacturer data submitted in response to the NPRM reported an 

efficiency effectiveness range of 1 to 2 percent. For the final rule NHTSA has estimated, 

following independent review of all the sources referenced above, the incremental gain in 

fuel consumption for SGDI to be approximately 2 to 3 percent. 

 

164 SGDI was referred to as GDI or SIDI in the NPRM. 165 Paul Whitaker, Ricardo, Inc., “Gasoline Engine Performance And Emissions – Future Technologies and 

Optimization,” ERC Symposium, Low Emission Combustion Technologies for Future IC Engines, 

Madison, WI, June 8-9, 2005. Available at 

http://www.erc.wisc.edu/symposiums/2005_Symposium/June%208%20PM/Whitaker_Ricardo.pdf (last 

accessed Nov. 9, 2008).

166 Stefan Trampert, FEV Motorentechnik GmbH, “Engine and Transmission Development Trends - Rising 

Fuel Cost Pushes Technology,” Symposium on International Automotive Technology, Pune, India, January 

2007.
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Content assumptions for cost estimating of SGDI include no major changes to engine 

architecture compared to a port fuel injection engine, although cylinder head casting 

changes are required to incorporate the fuel injection system and the piston must change 

as well to suit the revised combustion chamber geometry. The fuel injection system 

utilizes an electrically-driven low pressure fuel pump to feed a high pressure mechanical 

pump, supplying fuel at pressures up to 200 Bar. A common fuel rail supplies the 

injectors, which produce a highly atomized spray with a Sauter Mean Diameter (SMD) of 

15-20 microns, which compares to approximately 50 microns for a port injector. 

In the NPRM, NHTSA estimated the following incremental cost ranges for applying 

SGDI: $122 to $420 for an inline 4-cylinder engine, $204 to $525 for a V6 engine, and 

$228 to $525 for a V8 engine. The Alliance commented that NHTSA had not accounted 

for the costs required to address NVH concerns associated with the implementation of 

SGDI. For purposes of the final rule, all costs have been based upon side mount DI 

technology as these costs were determined in the 2008 Martec Report to be lower than 

center mount DI systems. An applied RPE factor of 1.5 was used in all cases, and a NVH 

package was added to all engines in response to Alliance comments, providing 

incremental costs that ranged from $293 to $440 for an I4 engine, to $384 to $558 for a 

V6 engine and $512 to $744 for a V8 engine. 

Homogeneous, stoichiometric DI systems are regarded as mature technology with 

minimal technical risk and are expected to be increasingly incorporated into 

manufacturers’ product lineups. Time-based learning has been applied to this technology 

due to the fact that over 1.5 million vehicles containing this technology are now produced 

annually. Due to the changes to the cylinder head and combustion system and the control 

system development required to adopt SGDI technology, which are fairly extensive, 

SGDI can be applied only at redesign model years. There are no limitations on applying 

SGDI to any vehicle class. The phase-in cap for SGDI is applied at a 3 percent rate for 

MY 2011 in order to account for the lead time required to incorporate SGDI engines. 

(x) Combustion Restart (CBRST) 

Combustion restart allows “start-stop” functionality of DI engines through the 

implementation of an upgraded starter with bi-directional rotation to allow precise 

crankshaft positioning prior to subsequent fuel injection and spark ignition, allowing 

engine restart. This method of implementing engine stop/start functionality allows not 

only the fuel savings from not idling the engine, but also reduces fuel consumption as the 

engine speeds up to its operational speed. A Direct Injection (DI) fuel system is required 

for implementation of this technology. 

NHTSA has determined, upon independent review, combustion restart to be a high 

technical risk due to the following unresolved issues. First, very high or very low 

ambient air temperatures may limit the ability to start the engine in the described manner. 

Although the starter motor can provide fail-safe starting capability in these temperature 

limited areas, strategies must be developed to manage the transitions. Additionally, a failsafe start strategy that recognizes failed attempts and responds quickly enough has yet to 

be demonstrated. The risk of missed start events is currently relatively high, which is 
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unacceptable from a production implementation perspective. As a result, availability of 

this technology was assessed as beyond the emerging technology time frame for MY 

2011. 

(xi) Turbocharging and Downsizing (TRBDS)

Forced induction in the form of turbocharging and supercharging has been used on 

internal combustion engines for many years. Their traditional role has been to provide 

enhanced performance for high-end or sports car applications. However, turbocharging 

and downsizing can also be used to improve fuel economy. There is a natural friction 

reduction with a boosted downsized engine, because engine friction torque is primarily a 

function of engine displacement. When comparing FMEP (Friction Mean Effective 

Pressure – friction torque normalized by displacement) there is very little difference 

between the full size naturally-aspirated engine and the boosted downsized engine despite 

the higher cylinder pressure associated with higher BMEP. Turbocharging and 

downsizing can also reduce pumping losses (PMEP), because a turbocharged downsized 

engine runs at higher BMEP (Brake Mean Effective Pressure) levels, and therefore higher 

manifold pressures, than a naturally aspirated engine. The upper limit of BMEP level 

that can be expected from a naturally aspirated engine is approximately 13.5 Bar, 

whereas a turbocharged engine can produce BMEP levels in excess of 20 Bar. Engines 

that are not downsized and boosted use a throttle to regulate load, but this causes 

pumping losses as discussed previously. Thus, by using a small displacement engine 

with a turbocharger, the smaller engine works harder (higher cylinder load), which results 

in lower pumping loss since the throttle must be further open to produce the same road 

power output. 

Due to the incremental nature of the decision tree, engines having turbocharging and 

downsizing applied are assumed to have SGDI already applied. In boosted engines, 

SGDI allows improved scavenging of the cylinder, which reduces the internal exhaust 

gas residual level and the charge temperature. This in turn allows a higher compression 

ratio to be used for a given fuel octane rating and can therefore improve the fuel 

consumption of boosted SGDI engines. 

In most cases, a boosted downsized engine can replace a conventional naturally aspirated 

engine and achieve equivalent or greater (albeit at the expense of fuel economy) power 

and torque. However, there are some challenges associated with acceptance of a down 

sized boosted engine, including: 

• Achievement of “seamless” power delivery compared to the naturally 

aspirated engine (no perceptible turbo lag); 

• A complication in emissions regulatory compliance, because the addition 

of a turbocharger causes additional difficulty with catalyst light off due to 

the thermal inertia of the turbo itself; 

• Potential issue with customer acceptance of smaller-displacement engines, 

given a common perception that only larger-displacement engines can be 

high-powered; and 

• Additional base engine cost and vehicle integration costs. 
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Manufacturers’ structural changes to the base engine are generally focused on increasing 

the structure’s capacity to tolerate higher cylinder pressures. NHTSA believes that it is 

reasonable to expect that the maximum cylinder pressure would increase by 25 to 30 

percent over those typical of a naturally aspirated engine. Another consideration is that 

higher pressures lead to higher thermal loads. 

One potential disadvantage of downsized and boosted engines is cost. Turbocharging 

systems can be expensive and are best combined with direct injection and other engine 

technologies. The Alliance expressed a related concern that the fuel economy 

effectiveness was based on the use of premium grade fuel in direct injection turbocharged 

engines, and argued that as the baseline vehicles were not fueled with premium gasoline, 

this gave the direct injection turbocharged engines an unrealistic advantage.167 However, 

CARB stated in its comments that premium fuel is not necessary for use with 

turbocharged downsized engines and that substantial effectiveness are still available with 

regular fuel.168 In fact, most turbocharged direct injection engines will have a 

compression ratio and calibration designed to give best performance on premium fuel, 

although they are safe to operate on regular fuel. On regular fuel, the knock sensor 

output is used to allow the ECU to keep the engine safe by controlling boost and ignition 

timing. Maximum torque is reduced on the lower octane fuel due to the ECU 

intervention strategy, but at part load, where knock is not an issue, the fuel economy will 

not be affected adversely relative to the estimated effectiveness. Additionally, the driver 

retains the choice of obtaining more performance by paying more for premium fuel and 

will still obtain stated fuel consumption effectiveness. 

Nevertheless, the case for using downsized boosted engines has strengthened with the 

wider introduction of direct injection gasoline engines. Downsized boosted engines with 

stoichiometric direct injection present minimal technical risk, although there have been 

only limited demonstrations of this technology achieving SULEV emission levels. 

In the NPRM, NHTSA estimated that downsized and turbocharged engines could 

incrementally reduce fuel consumption from 5 to 7.5 percent. CARB commented that 

Sierra Research in its presentation to the NAS committee on January 24, 2008, suggested 

there is no carbon dioxide reduction potential for turbocharging and downsizing, but 

argued that this is not supported by other vehicle simulation efforts nor by manufacturer 

plans to release systems such as the Ford EcoBoost.169 The Alliance and Sierra Research, 

in contrast, commented that turbocharged and downsized engines do not improve fuel 

economy unless they are also equipped with DI fuel systems and using premium fuel.170 

NHTSA believes that turbocharging and downsizing, when combined with SGDI, offers 

benefits without the use of premium fuel as noted above. Confidential manufacturer data 

suggests an incremental range of fuel consumption reduction of 4.8 to 7.5 percent for 

turbocharging and downsizing. Other publicly-available sources suggest a fuel 

consumption benefit of 8 to 13 percent compared to current-production naturally-

 

167 Docket No. NHTSA-2008-0089-0179.1. 168 Docket No. NHTSA-2008-0089-0173. 169 Docket no. NHTSA-2008-0089-0173.4. 170 Docket no. NHTSA-2008-0089-0046, Docket no. NHTSA-2008-0089-0179.1. 
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aspirated engines without friction reduction or other fuel economy technologies: a joint 

technical paper by Bosch and Ricardo suggesting an EPA fuel economy gain of 8 to 10 

percent for downsizing from a 5.7 liter port injection V8 to a 3.6 liter V6 with direct 

injection;171 a Renault report suggesting a 11.9 percent NEDC fuel consumption gain for 

downsizing from a 1.4 liter port injection in-line 4-cylinder engine to a 1.0 liter in-line 4-

cylinder engine with direct injection;172 and a Robert Bosch paper suggesting a 13 

percent NEDC gain for downsizing to a turbocharged DI engine.173 These reported fuel 

economy benefits show a wide range in large part due to the degree of vehicle attribute 

matching (such as acceleration performance) that was achieved. 

For purposes of the final rule, NHTSA estimated a net fuel consumption reduction of 

approximately 14 percent for a turbocharged downsized DOHC engine with direct 

injection and DCP over a baseline fixed-valve engine that does not incorporate friction 

reducing technologies. This equates to an incremental fuel consumption reduction of 2.1 

to 5.2 percent for TRBDS, which is incremental to an engine with SGDI and previously 

applied technologies (e.g., VVT and VVL) as defined by the decision tree. This wide 

range is dependent upon the decision tree path that is followed or the configuration of the 

engine prior to conversion to TRBDS. The incremental fuel consumption benefit for 

TRBDS is estimated to range from 2.1 to 2.2 percent for V6 and V8 engines and from 4.5 

to 5.2 percent for inline 4-cylinder engines. As explained, the incremental improvement 

from TRBDS must be added to the previous technology point on the decision tree. In the 

case of SOHC and OHV engines, for example, moving to the TRBDS technology also 

assumes implementation of DOHC engine architecture in addition to DCP and SGDI. 

In the NPRM, NHTSA estimated that the cost for a boosted/downsized engine system 

would be $690 for small cars, $810 for large trucks, and $120 for all other vehicle 

classes, based on the NAS report, the EEA report, and confidential manufacturer data, 

which assumed downsizing allowed the removal to two cylinders in most cases, except 

for small cars and large trucks. CARB questioned Martec’s cost estimates for 

turbocharging and downsizing, specifically the credit for downsizing a V6 engine to an 

in-line 4 cylinder dropped from their estimate used in the NESCCAF report of $700 to 

$310 and the use of more expensive hardware than some manufacturers use. In response, 

NHTSA’s independent review of the cost to downsize a V6 DOHC engine to a I4 DOHC 

engine closely aligned with the 2008 Martec credit of $310, while the report for 

NESCCAF was not specific with regard to the assumptions used to construct that 

estimate. Additionally, confidential manufacturer data submitted in response to the 

NPRM provided a range for TRBDS with SGDI of $600 to $1,400 variable cost or $900 

to $2100 RPE assuming a 1.5 markup factor. When comparing the confidential 

 

171 David Woldring and Tilo Landenfeld of Bosch, and Mark J. Christie of Ricardo, “DI Boost: 

Application of a High Performance Gasoline Direct Injection Concept,” SAE 2007-01-1410. Available at

http://www.sae.org/technical/papers/2007-01-1410 (last accessed Nov. 9, 2008) 172 Yves Boccadoro, Loïc Kermanac’h, Laurent Siauve, and Jean-Michel Vincent, Renault Powertrain 

Division, “The New Renault TCE 1.2L Turbocharged Gasoline Engine,” 28th Vienna Motor Symposium, 

April 2007.

173 Tobias Heiter, Matthias Philipp, Robert Bosch, “Gasoline Direct Injection: Is There a Simplified, CostOptimal System Approach for an Attractive Future of Gasoline Engines?” AVL Engine & Environment 

Conference, September 2005.
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manufacturer cost range and the incremental RPE cost estimates for the final rule, it is 

important to realize the incremental cost for TRBDS does not include SGDI since it is 

considered a separate technology.174

Some of the costs included in turbocharging and downsizing come from structural 

changes due to the higher cylinder pressures and increased cylinder temperatures, which 

also drive additional cooling requirements (e.g. water-cooled charge air cooler, 

circulation pump, and thermostats) and require improved exhaust valve materials. High 

austenitic stainless steel exhaust manifolds and upgraded main bearings are some of the 

other hardware upgrades required. For purposes of the final rule, NHTSA used cost data 

from the 2008 Martec report, but constructed a bill of materials consistent with the 

incremental TRBDS technology as shown in the decision trees and based on confidential 

manufacturer data. For the vehicle subclasses which have a baseline gasoline V8 engine, 

two turbochargers rated for 1050°C at $250 each were added, $270 was deducted for 

downsizing to a V6 from a V8 engine, $217 was added for engine upgrades to handle 

higher operating pressures and temperatures at, and a water-cooled charge air cooler was 

added at $280. The baseline SOHC engine was converted to a DOHC engine with 4 

valves per cylinder at a variable incremental cost of $92. The total variable costs summed 

to $819 and a 1.5 RPE factor was applied to arrive at $1,229 incremental cost to 

turbocharging and downsizing. 

For the vehicle subclasses which have a baseline gasoline V6 engine, a twin-scroll 

turbocharger rated for 1050°C was added at a cost of $350, $310 was deducted for 

downsizing to an I4 from a V6 engine, $160 was added for engine upgrades to handle 

higher operating pressures and temperatures, and a water-cooled charge air cooler was 

added at $259. The baseline SOHC engine was converted to a DOHC engine with 4 

valves per cylinder at a variable incremental cost of $87. The total variable costs 

summed to $548 and a 1.5 RPE factor was applied to arrive at $822 incremental cost to 

turbocharging and downsizing. 

For the vehicle subclasses which have a baseline gasoline I4 engine, a twin-scroll 

turbocharger rated for 1050°C was added at a cost of $350, $160 was added for engine 

upgrades to handle higher operating pressures and temperatures, and a water-cooled 

charge air cooler was added at $259. The baseline SOHC engine was converted to a 

DOHC engine with 4 valves per cylinder at a variable incremental cost of $46. The total 

variable costs summed to $815 and a 1.5 RPE factor was applied to arrive at $1,223 

incremental cost for turbocharging and downsizing. 

 In summary, for the final rule NHTSA estimated TRBDS to have an incremental RPE 

cost of $1,223 for vehicle classes with a baseline in-line 4-cylinder engine downsized to a 

 

174 NHTSA also examined the Jetta TDI as an example of a current vehicle model that comes in both diesel 

and gasoline-engine form, but in attempting to do an apples-to-apples comparison with the nonturbocharged/downsized version , the SE, found indications that VW appears to be keeping the cost of the 

TDI down by removing other content (e.g., the SE has a sunroof, which normally costs around $1,000, 

while the TDI does not). Thus, NHTSA did not find VW’s price differential for the two versions of the 

Jetta to be convincing evidence of the actual cost of turbocharging and downsizing an engine. 
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smaller I-4 engine which are: Subcompact, Performance Subcompact, Compact and 

Midsize Car, and Small Truck. For vehicle classes with a baseline V6 engine that was 

downsized to an I4 engine the RPE cost is estimated at $822; these classes are the 

Performance Compact, Performance Midsize and Large Car, Minivan and Midsize Truck. 

The two vehicle classes with baseline V8 engines, Performance Large Car and Large 

Truck, were downsized to V6 turbocharged engines at an incremental RPE cost of 

$1,229. 

Time-based learning has been applied to TRBDS because submitted product plan data 

indicated turbocharging and downsizing would already be at high volume in 2011. Due to 

the fact that a turbocharged and downsized engine is entirely different than the baseline 

engine it can be applied only at redesign model years. The phase-in cap for TRBDS is 

applied at a 9 percent rate for MY 2011 in order to account for the lead time required to 

incorporate TRBDS engines. 

(xii) Cooled Exhaust Gas Recirculation Boost (EGRB)

EGR Boost is a combustion concept that involves utilizing EGR as a charge dilutant for 

controlling combustion temperatures. Fuel economy is therefore increased by operating 

the engine at or near the stoichiometric air/fuel ratio over the entire speed and load range 

and using higher exhaust gas residual levels at part load conditions. Further fuel 

economy increases can be achieved by increased compression ratio enabled by reduced 

knock sensitivity, which enables higher thermal efficiency from more advanced spark 

timing. Currently available turbo, charge air cooler, and EGR cooler technologies are 

sufficient to demonstrate the feasibility of this concept. 

However, this remains a technology with a number of issues that still need to be 

addressed and for which there is no production experience. EGR system fouling 

characteristics could be potentially worse than diesel EGR system fouling, due to the 

higher HC levels found in gasoline exhaust. Turbocharger compressor contamination 

may also be an issue for low pressure EGR systems. Additionally, transient controls of 

boost pressure, EGR rate, cam phasers and intake charge temperature to exploit the 

cooled EGR combustion concept fully will require development beyond what has already 

been accomplished by the automotive industry. These are all “implementation readiness” 

issues that must be resolved prior to putting EGR Boost into volume production. 

Because of these issues NHTSA did not consider EGR Boost in the NPRM, and 

consequently had no tentative conclusions with regard to its cost or fuel economy 

effectiveness. For purposes of the final rule, NHTSA found no evidence from 

commenters or elsewhere that these implementation readiness issues could be resolved 

prior to MY 2011. Therefore, in the final rule, the phase-in cap for MY 2011 is zero. 

(b) Diesel Engine Technologies

Diesel engines, which currently make up about 0.27 percent of engines in the MY 2008 

U.S. fleet, have several characteristics that give them superior fuel efficiency compared 

to conventional gasoline, spark-ignited engines. Pumping losses are much lower due to 

lack of (or greatly reduced) throttling. The diesel combustion cycle operates at a higher 
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compression ratio, with a very lean air/fuel mixture, and turbocharged light-duty diesels 

typically achieve much higher torque levels at lower engine speeds than equivalentdisplacement naturally-aspirated gasoline engines. Additionally, diesel fuel has higher 

energy content per gallon.175

However, diesel engines, including those on the many diesel vehicles sold in Europe, 

have emissions characteristics that present challenges to meeting federal Tier 2 emissions 

standards. It is a significant systems-engineering challenge to maintain the fuel 

consumption advantage of the diesel engine while meeting U.S. emissions regulations, 

since fuel consumption is negatively impacted by emissions reduction strategies. 

Emission compliance strategies for diesel vehicles sold in the U.S. are expected to 

include a combination of combustion improvements and aftertreatment. These emission 

control strategies are currently widely used in Europe, but will have to be modified due to 

the fact that U.S. emission standards, especially for NOx, are much tighter than 

corresponding European standards. To achieve U.S. Tier 2 emissions limits, roughly 45 

to 65 percent more NOx reduction is required compared to the Euro VI standards. 

Additionally, as discussed below, there may be a fuel consumption penalty associated 

with diesel aftertreatment since extra fuel is needed for the aftertreatment, subsequently 

this extra fuel is not used in the combustion process of the engine that provides torque to 

propel the vehicle. 

Nevertheless, emissions control technologies do exist, and will enable diesel engines to 

make considerable headway in the U.S. fleet in coming years. Several key advances in 

diesel technology have made it possible to reduce emissions coming from the engine 

prior to aftertreatment. These technologies include improved fuel systems (higher 

pressures and more responsive injectors), advanced controls and sensors to optimize 

combustion and emissions performance, higher EGR levels and EGR cooling to reduce 

NOx, lower compression ratios, and advanced turbocharging systems. 

The fuel systems on advanced diesel engines are anticipated to be of a High-Pressure 

Common Rail (HPCR) type with piezoelectric injectors that operate at pressures up to 

1800 Bar or greater and provide fast response to allow multiple injections per cycle. The 

air systems will include a variable geometry turbocharger for 4-cylinder inline engines 

with charge-air cooling and high-pressure and low-pressure EGR loops with EGR 

coolers. For V-6 or V-8 engines the air systems will employ series sequential turbocharging with one variable geometry turbocharger and one fixed geometry turbocharger. 

As suggested above, the traditional 3-way catalyst aftertreatment found on gasolinepowered vehicles is ineffective due to the lean-burn combustion of a diesel. All diesels 

will require a diesel particulate filter (DPF), a diesel oxidation catalyst (DOC), and a NOx

reduction strategy to comply with Tier 2 emissions standards. The most common NOx

reduction strategies include the use of lean NOx traps (LNT) or selective catalytic 

reduction (SCR), which are outlined below. 

 

175 Burning one gallon of diesel fuel produces about 11 percent more carbon dioxide than gasoline due to 

the higher density and carbon to hydrogen ratio. 
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(i) Diesel Engine with Lean NOx Trap (LNT) Catalyst After-Treatment

A lean NOx trap operates, in principle, by storing NOx (NO and NO2) when the engine is 

running in its normal (lean) state. When the control system determines (via mathematical 

model or a NOx sensor) that the trap is saturated with NOx, it switches the engine into a 

rich operating mode or may in some cases inject fuel directly into the exhaust stream to 

produce excess hydrocarbons that act as a reducing agent to convert the stored NOx to N2

and water, thereby “regenerating” the LNT and opening up more locations for NOx to be 

stored. LNTs are sensitive to sulfur deposits that can reduce catalytic performance, but 

periodically undergo a desulfurization engine-operating mode to clean it of sulfur 

buildup. 

The fuel consumption penalty associated with aftertreatment systems, including both 

DPF and LNT, is taken into account in the reported values. In the case of the DPF, extra 

fuel is needed to raise the temperature of the DPF above approximately 550°C to enable 

active regeneration. A similar process is needed to regenerate the LNT, but instead of 

being used to remove particulates and raise the temperature, the excess fuel is used to 

provide a fuel-rich condition at the LNT to convert the trapped NOx on the LNT to 

nitrogen gas. The estimated fuel consumption penalty on the CAFE test cycle associated 

with the LNT aftertreatment system is 5 percent on the EPA city cycle and 3 percent on 

the highway cycle, as described in the report to the EPA.176

In order to maintain equivalent performance to comparable gasoline-engine vehicles, an 

inline 4-cylinder (I-4) diesel engine with displacement varying around 2 liters to meet 

vehicle performance requirements was assumed for Subcompact, Performance 

Subcompact, Compact, and Midsize Passenger Car and Small Truck vehicle subclasses, 

and it was also assumed that these vehicles would utilize LNT aftertreatment systems. 

In the NPRM, NHTSA estimated that LNT-based diesels could incrementally reduce fuel 

consumption by 8 to 15 percent at an incremental RPE cost of $1,500 to $1,600 

compared to a direct injected turbocharged and downsized spark-ignition engine, in 

agreement with confidential manufacturer data. These costs were based on a “bottom up” 

cost analysis that was performed with EPA, which then subtracted the costs of all 

previous steps on the decision tree prior to diesel engines. 

Comments submitted in response to the NPRM including both manufacturers’ 

confidential data and non-confidential data sources for diesel engines was in the range of 

16.7 percent to 26.7177 percent fuel consumption benefit over a baseline gasoline engine 

at a variable cost of $2,000 to $11,200. Confidentially submitted diesel cost and 

effectiveness estimates generally did not differentiate between car and truck applications, 

engine size and aftertreatement systems leading to large ranges for both cost and 

 

176 Ricardo, “A Study of Potential Effectiveness of Carbon Dioxide Reducing Vehicle Technologies, 

Revised Final Report,” at 62. Available at http://www.epa.gov/otaq/technology/420r08004a.pdf (last 

accessed Oct. 4, 2008). 

177 The 26.7 percent fuel consumption reduction is a maximum estimate cited in a June 2008 Sierra 

Research report (Docket No. NHTSA-2008-089-0179.1) for a CAFE estimate in a midsize car, whereas an 

April 2008 Sierra report (Docket No. NHTSA-2008-089-0046) cites a maximum estimate of 22.4 percent 

for the same vehicle class; NHTSA was unable to discern why the estimates differed. 
V-105

effectiveness estimates. Additionally, most of the costs appeared to be stated as variable 

costs not RPE but this was not always completely discernible. 

For purposes of the final rule, NHTSA estimated the net fuel consumption benefit for an 

I-4 diesel engine with LNT aftertreatment to be approximately 20 to 26 percent 

improvement over a baseline gasoline engine. This equates to a 5.3 to 7.7 percent 

improvement for DSLT, which is incremental to a turbocharged downsized gasoline 

engine (TRBDS) with EGRB, and a 15.0 to 15.3 percent incremental improvement for 

DSLC, which is incremental to a gasoline engine with combustion restart (CBRST.) The 

2008 Martec report was relied upon for cost estimates and the diesel cost was adjusted by 

removing the downsizing credit and applying a 1.5 RPE marked up factor to arrive at a 

cost of $4007 compared to a baseline gasoline engine. This results in an incremental 

RPE cost of $1,567 to $1,858 for DSLT and $2,963 to $3,254 for DSLC. NHTSA’s 

independent review concurred with all the costs in this bill-of-material-based cost 

analysis. 

A large part of the explanation for the cost increase since the NPRM is the dramatic 

increase in commodity costs for the aftertreatment systems, namely the platinum group 

metals. The updated cost estimates of Martec 2008 and others reflect the rise of global 

costs for raw materials since Martec 2004 and other prior referenced cost estimates were 

conducted. As described in Martec 2008, engine technologies employing high 

temperature steels or catalysts with considerable platinum group metals usage have 

experienced tremendous inflation of raw material prices. These updated estimates 

account for current spot prices of platinum and rhodium which have demonstrated cost 

inflation amounting to between 300 and 750 percent of global prices.178 

(ii) Diesel Engine with Selective Catalytic Reduction (SCR) After-Treatment

An SCR aftertreatment system uses a reductant (typically, ammonia derived from urea) 

that is continuously injected into the exhaust stream ahead of the SCR catalyst. 

Ammonia combines with NOx in the SCR catalyst to form N2 and water. The hardware 

configuration for an SCR system is more complicated than that of an LNT, due to the 

onboard urea storage and delivery system (which requires a urea pump and injector into 

the exhaust stream). While a rich engine-operating mode is not required for NOx

reduction, the urea is typically injected at a rate of 3 to 4 percent of the fuel consumed. 

Manufacturers designing SCR systems intend to align urea tank refills with standard 

maintenance practices such as oil changes. 

The fuel consumption penalty associated with the SCR aftertreatment system is taken into 

account in the values reported here. Similar to the LNT system, extra fuel is needed to 

warm up the SCR system to an effective operating temperature. The estimated fuel 

consumption penalty on the CAFE test cycle associated with the SCR aftertreatment 

system is 5 percent on the EPA city cycle and none on the highway cycle, as described in 

 

178 Martec, “Variable Costs of Fuel Economy Technologies,” June 1, 2008, at 13-20. Docket No. NHTSA2008-0089-0169.1.
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the report to the EPA.179 A recent report, however, suggests a fuel economy benefit 

associated with the use of a SCR system, based on the supposition that the engine 

calibration is shifted towards improved fuel consumption and more of the NOx reduction 

is being handled by the SCR system.180 Nevertheless, since this benefit is not yet proven 

for high-volume production, it has not been applied for purposes of the final rule. 

In order to maintain equivalent performance to comparable gasoline-engine vehicles, a V6 diesel engine, with displacement varying around 3 liters was assumed for Performance 

Compact, Performance Midsize, Large Passenger Car, Minivan, and Midsize Truck. A V8 diesel engine, with displacement varying around 4.5 liters to meet vehicle performance 

requirements, was assumed for Large Truck and Performance Large Car vehicle classes. 

It was also assumed that these classes with V-6 and V-8 diesel engines utilize SCR 

aftertreatment systems instead of LNT. 

In the NPRM, NHTSA estimated incremental fuel consumption reduction for diesel 

engines with an SCR system to range from 11 to 20 percent at an incremental RPE cost 

of $2,051 to $2,411 compared to a direct injected turbocharged and downsized sparkignition engine. These costs were based on a “bottom up” cost analysis that was 

performed with EPA, which then subtracted the costs of all previous steps on the decision 

tree prior to diesel engines. 

As explained above for LNT, confidential manufacturer and non-confidential comment 

data submitted in response to the NPRM for diesel engines was in the range of 16.7 

percent to 26.7 percent fuel consumption benefit over a baseline gasoline engine at 

variable cost of $2,000 to $11,200 with no detail about the aftertreatment, engine size or 

application. Additionally, Ricardo’s vehicle simulation work for EPA found an 

incremental fuel economy benefit of 19 percent for a 4.8L diesel in a Large Truck.181

However, when the baseline 4-speed automatic transmission shift and torque converter 

lockup scheduling was optimized for the diesel engine, an additional 5 percent fuel 

economy benefit was obtained to yield an incremental benefit for a diesel of 24 percent. 

As noted in the report on page 84, however, this does not represent an optimized result, 

as only the final packages complete with all technologies were optimized. Nevertheless, 

this is a reasonable estimate for diesel engine fuel economy benefit over a baseline 

gasoline engine with coordinated cam phasing (CCP). This estimate did not have the 

aftertreatment penalty, however, so applying the 5 percent penalty associated with diesel 

oxidation catalyst, diesel particulate filter, and SCR aftertreatment brings the fuel 

 

179 Ricardo, “A Study of Potential Effectiveness of Carbon Dioxide Reducing Vehicle Technologies, 

Revised Final Report,” at 62. Available at http://www.epa.gov/otaq/technology/420r08004a.pdf (last 

accessed Oct. 4, 2008). 

180 Timothy V. Johnson, “Diesel Emission Control in Review,” Society of Automotive Engineers Technical 

Series, 2008-01-0069, 2008. Available at http://www.sae.org/technical/papers/2008-01-0069 (last accessed 

Nov. 9, 2008).

181 Ricardo, “A Study of Potential Effectiveness of Carbon Dioxide Reducing Vehicle Technologies, 

Revised Final Report,” Table 7-9 shows incremental fuel economy and CO2 benfits for Truck with 

technology package 11, p. 87. Available at http://www.epa.gov/otaq/technology/420r08004a.pdf (last 

accessed Oct. 4, 2008). 
V-107

economy benefit for diesel engine with aftertreatment down to 19 percent, which is equal 

to a 16 percent fuel consumption benefit. 

For purposes of the final rule, NHTSA estimated the net fuel consumption benefit for a 

V-6 diesel engine with SCR aftertreatment to be approximately 20 to 26 percent 

improvement over a baseline gasoline engine. This equates to a 4.0 to 7.7 percent 

improvement for DSLT, which is incremental to a turbocharged downsized gasoline 

engine (TRBDS) with EGRB, and a 9.9 to 13.1 percent incremental improvement for 

DSLC, which is incremental to a gasoline engine with combustion restart (CBRST.) The 

2008 Martec report was relied upon for cost estimates and the diesel cost was adjusted by 

removing the downsizing credit and applying a 1.5 RPE marked up factor to arrive at a 

cost of $5,603 compared to a baseline gasoline engine. This results in an incremental 

RPE cost of $3,110 to $3,495 for DSLT and $4,105 to $4,490 for DSLC. NHTSA’s 

independent review concurred with all the costs in this bill-of-material-based cost 

analysis for V-6 engines. 

NHTSA estimated the net fuel consumption benefit for a V-8 diesel engine with SCR 

aftertreatment to be approximately 19 to 25 percent improvement over a baseline gasoline 

engine. This equates to a 4.0 to 6.5 percent improvement for DSLT, which is incremental 

to a turbocharged downsized gasoline engine (TRBDS) with EGRB, and a 10.0 to 12.0 

percent incremental improvement for DSLC, which is incremental to CBRST. The 2008 

Martec report was relied upon for cost estimates and the diesel cost was adjusted by 

removing the downsizing credit and applying a 1.5 RPE marked up factor to arrive at a 

cost of $7,002 compared to a baseline gasoline engine. This results in an incremental 

RPE cost of $3,723 to $4,215 for DSLT and $5,125 to $5,617 for DSLC. NHTSA’s 

independent review concurred with all the costs in this bill-of-material-based cost 

analysis for V-8 engines. 

The diesel engine with SCR has an incremental cost that is significantly higher for the 

final rule than the NPRM. NHTSA believes the increase is explained by the improved 

accuracy of the final rule analysis which relied on the updated cost estimates from the 

2008 Martec Report as described previously182. In addition, comments from the Alliance 

suggested that the incremental diesel cost for a midsize car was $6,198 and $7,581183 for 

a pickup truck. 

The economic breakeven point for diesel engine aftertreatment options is based on public 

information184 and on recent discussions that NHTSA and EPA have had with auto 

 

182 Martec, “Variable Costs of Fuel Economy Technologies,” June 1, 2008, at 13-20. Docket No. NHTSA2008-0089-0169.1. 

183 These cost estimates are taken from the April 2008 Sierra Research report (Docket No. NHTSA-2008-

089-0046). A June 2008 Sierra Research report (Docket No. NHTSA-2008-089-0179.1) contained lower 

estimates of $5,947 and $7,271 for the same vehicles; NHTSA was unable to discern the reason for the 

difference. 

184 Timothy V. Johnson, “Diesel Emission Control in Review,” Diesel Engine-Efficiency and Emissions 

Research (DEER) Conference, Detroit, MI, August 20-24, 2006. Available at 

http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2006/session2/2006_deer_johnson.pdf (last 

accessed Nov. 9, 2008). See also Tim Johnson, “Diesel Engine Emissions and Their Control,” Platinum 
V-108

manufacturers and aftertreatment device manufacturers. NHTSA explained in the NPRM 

that it had received strong indications that LNT systems would probably be used on 

smaller vehicles while the SCR systems would be used on larger vehicles and trucks. The 

economic break-even point between LNT and SCR is dependent on the quantity of 

catalyst used, the market price for the metals in those catalysts, and the cost of the urea 

injection system. The NPRM estimated that the breakeven point would occur around 3 

liters engine displacement, based on discussions with auto manufacturers and 

aftertreatment device manufacturers. Thus, NHTSA tentatively concluded that it would 

be cheaper to manufacturer diesel engines smaller than 3 liters with an LNT system, and 

that conversely, it would be cheaper to manufacturer diesel engines larger than 3.0 liters 

with a SCR system. No comments were submitted to NHTSA regarding the breakeven 

point between a LNT and SCR system. However, according to one source of recently 

published data the breakeven point occurs between 2.0 to 2.5L.185 Considering that 

continuing developments are being made in this area and the wide range of precious 

metal content required, NHTSA believes that an economic breakeven point of 2 to 3 liters 

is reasonable and that other factors will strongly influence which system is chosen by any 

given vehicle manufacturer. 

Cummins commented that LNT systems should be considered for more than just the 

compact and subcompact vehicles, and stated that a number of large vehicles and trucks 

currently use LNT. Cummins argued that a LNT after-treatment system can be a costeffective technology on both small and larger engines. For the final rule, NHTSA 

assumed the use of a LNT after-treatment system for three additional vehicle subclasses 

compared to the NPRM. However, following the rationale explained in the preceding 

paragraph, the SCR type after-treatment system is assumed for larger vehicle subclasses. 

As is the case with all technologies in the analysis, technology application assumptions 

are based on the general understanding of what a manufacturer could do in response to 

meeting emissions compliance but other manufacturer specific factors will dictate the 

actual technology applications. 

In the NPRM, NHTSA assumed a 3 percent phase in rate per year for diesel technologies. 

For the final rule, passenger cars, as defined by the technology class, retained the 3 

percent combined (for DSLT and DSLC) phase-in cap. However, diesel technologies for 

truck technology classes were allowed to be applied at a 4 percent combined (for DSLT 

and DSLC) phase-in cap to account for the higher application rates observed in the 

submitted product plans and diesel’s favorable characteristics in truck applications. 

Volume-based learning was assumed for the NPRM, however, confidential product plans 

indicated that this technology would be in high-volume in the 2011 time frame, thus 

time-based learning was assumed for the final rule. For the final rule, diesel technologies 

can only be applied at redesign, which is consistent with the NPRM. 

(c) Transmission Technologies 

 Metals Review, 52, at 23-37 (2008). Available at

http://www.platinummetalsreview.com/dynamic/article/view/52-1-23-37 (last accessed Nov. 9, 2008) 185 Id.
V-109

NHTSA has also reconsidered the way it applies transmission technologies in the Volpe 

model to obtain increased fuel savings. The revised decision tree for transmission 

technologies reflects the fact that baseline vehicles now include either 4- or 5-speed 

automatic transmissions, given that many manufacturers are already employing 5-speed 

automatic transmissions or are going directly to 6-speed automatics.186 The decision tree 

in the final rule also combines “aggressive shift logic” and “early torque converter 

lockup,” although the NPRM considered them separately, because NHTSA concluded 

upon further review that the two technologies could be optimized simultaneously due to 

the fact that adding both of them primarily required only minor modifications to the 

transmission or calibration software. Cost and effectiveness numbers have also been 

thoroughly reexamined, as have learning rates and phase-in caps, based on comments 

received. The section below describes each of the transmission technologies considered. 

(i) Improved Transmission Controls and Externals (IATC)

During operation, an automatic transmission’s controller manages the operation of the 

transmission by scheduling the upshift or downshift, and locking or allowing the torque 

converter to slip based on a preprogrammed shift schedule. The shift schedule contains a 

number of lookup table functions, which define the shift points and torque converter 

lockup based on vehicle speed and throttle position, and other parameters such as 

temperature. Aggressive shift logic (ASL) can be employed in such a way as to 

maximize fuel efficiency by modifying the shift schedule to upshift earlier and inhibit 

downshifts under some conditions, which reduces engine pumping losses and engine 

friction as noted in the gas engine section. Early torque converter lockup187 in 

conjunction with ASL can further improve fuel economy by locking the torque converter 

sooner, thus reducing inherent torque converter slippage or losses. As discussed above, 

the NPRM separated these two technologies, but they are combined for purposes of the 

final rule since the calibration software can be optimized for both functions 

simultaneously. 

Calibrating the transmission shift schedule to improve fuel consumption reduces the 

average engine speed and increases the average engine load, which can lead to a 

perceptible increase in engine harshness. The degree to which the engine harshness can 

be increased before it becomes noticeable to the driver is strongly influenced by 

characteristics of the vehicle, and although it is somewhat subjective, it always places a 

limit on how much fuel consumption can be improved by transmission control changes. 

The Alliance agreed in its comments that ASL can be used effectively to reduce throttling 

losses, but at the expense of noise-vibration-harshness (NVH) and drivability concerns. 

The Alliance also commented that losses in the torque converter typically make 

automatic transmissions less efficient than manual transmissions, and suggested that 

efficiency can be improved by mechanically “locking up” the torque converter earlier or 

 

186 Confidential product plans indicate that future products manufactured within the rulemaking period may 

not go from 4- or 5-speed transmission, but will instead introduce 6- or 7-speed automatic transmissions as 

replacements. 

187 Although only modifications to the transmission calibration software are considered as part of this 

technology, very aggressive early torque converter lock up may require an adjustment to damper stiffness 

and hysteresis inside the torque converter. Internal transmission hardware changes associated with this 

technology are addressed in 6/7/8-Speed Automatic Transmission with Improved Internals section. 
V-110

replacing the torque converter with a friction clutch of the type used on a manual 

transmission. Simply replacing a torque converter with a friction clutch, however, 

ignores the torque multiplication that torque converters provide at vehicle launch. 

In the NPRM, NHTSA estimated that aggressive shift logic could incrementally reduce 

fuel consumption by 1 to 2 percent at an incremental cost of $38 and early torque 

converter lockup could incrementally reduce fuel consumption by 0.5 percent at a $30 

cost for the calibration effort. Confidential manufacturer comments suggested that less 

aggressive shift logic must be employed on vehicles with low acceleration reserve, but 

that a 1-3 percent improvement in fuel economy was attainable on vehicles with adequate 

acceleration reserve. 

For the final rule, NHTSA combined aggressive shift logic and early torque converter 

lockup into the IATC technology with an effectiveness estimate of 1.5 to 2.5 percent in 

agreement with most confidential manufacturer estimates. As aggressive shift logic and 

early torque converter lockup are both achievable with a similar calibration effort, the 

incremental cost for improved automatic transmission controls used the higher value of 

$38, converted this value to 2007 dollars, and applied a 1.5 RPE markup factor to arrive 

at an incremental cost estimate of $59 for the final rule.

The IATC technology is considered to be available at the start of the 2011 model year, 

and as was the case in the NPRM, NHTSA considers that it can be applied during a 

refresh model year since NVH concerns must be addressed. The technology is applicable 

to all vehicle subclasses and NHTSA determined IATC type technologies will be high 

volume within the 2011 time frame so time-based learning is assumed, with a phase-in 

cap for MY 2011 of 33 percent. 

(ii) Automatic 6-, 7- and 8-Speed Transmissions (NAUTO)

Having more “speeds” on a transmission (i.e., having more gear ratios on the 

transmission) gives three effects in terms of vehicle performance and fuel economy. 

First, more gear ratios allow deeper 1st and 2nd gear ratios for improved launch 

performance, or increased acceleration. Second, a wider ratio spread also offers the 

ability to reduce the steps between gear ratios, which allows the engine to operate closer 

to optimum speed and load efficiency region. And third, a reduction in gear ratio step 

size improves internal transmission losses by reducing the sliding speeds across the 

clutches, thus reducing the viscous drag loss generated between two surfaces rotating at 

different speeds. Bearing spin losses are also reduced as the differential speed across the 

two bearing surfaces is reduced. This allows the engine to operate at a reduced load level 

to improve fuel economy.

Although the additional gear ratios improve shift feel, they also introduce more frequent 

shifting between gears, which can be perceived by consumers as bothersome. 

Additionally, package space limitations prevent 7- and 8-speed automatics from being 

applicable to front wheel drive vehicles. 
V-111

Comparison between NPRM and final rule cost and effectiveness estimates are somewhat 

complicated by the revisions in the decision trees and technology assumptions. In the 

NPRM, NHTSA estimated that 6-, 7- and 8-speed transmissions could incrementally 

reduce fuel consumption by 0.5 to 2.5 percent at an incremental cost of $76 to $187, 

relative to a 5-speed automatic transmission, a technology not used in the final rule 

decision tree, and the incremental cost for a 4-speed to a 5-speed automatic transmission 

(again no longer considered in the final rule) was estimated to be $76 to $167. 

In response to NHTSA’s request for information, confidential manufacturer data 

projected that 6-speed transmissions could incrementally reduce fuel consumption by 0 to 

5 percent from a baseline 4-speed automatic transmission, while an 8-speed transmission 

could incrementally reduce fuel consumption by up to 6 percent from a baseline 4-speed 

automatic transmission. The 2008 Martec report estimated a cost of $323 (RPE adjusted) 

for converting a 4-speed to a 6-speed transmission and a cost of $638 (RPE adjusted) for 

converting a 4-speed to an 8-speed transmission. GM has publicly claimed a fuel 

economy improvement of up to 4 percent for its new 6-speed automatic transmissions.188 

The 2008 EPA Staff Technical Report found a 4.5 to 6.5 percent fuel consumption 

improvement for a 6-speed over a 4-speed automatic transmission.189

For the final rule, NHTSA estimated that the conversion to a 6-,7- and 8-speed 

transmission (NAUTO) from a 4 or 5-speed automatic transmission with IATC would 

have an incremental fuel consumption benefit of 1.4 percent to 3.4 percent, for all vehicle 

subclasses. The 2008 Martec report, which quoted high volume, fully learned costs, was 

relied on to develop the final rule cost estimates. Subcompact, Compact, Midsize, Large 

Car and Minivan subclasses, which are typically considered normal performance 

passenger cars, are assumed to utilize a 6-speed automatic transmission only (as opposed 

to 7 or 8 speeds) resulting in an incremental RPE cost of $323 from Martec 2008. For 

Performance Subcompact, Performance Compact, Performance Midsize, Performance 

Large car and Small, Midsize and Large truck, where performance and or payload/towing 

may be a larger factor, NHTSA assumed that 6-, 7- or 8-speed transmissions are 

applicable thus the incremental RPE cost range of $323-$638 was established which used 

the Martec 2008 six speed cost and 8-speed costs for the estimates.

This technology will be available from the start of the rulemaking period. Confidential 

manufacturer data indicates the widespread use of 6-speed or greater automatic 

transmissions and introductions into the fleet occur primarily at vehicle redesign cycles. 

This prompted NHTSA to set the phase-in rate at 50 percent for MY 2011, but also to 

consider that the technology can only be applied at a redesign cycle, as opposed to the 

refresh cycle application of the NPRM. The technology is determined to be at high 

 

188 General Motors, news release, “From Hybrids to Six-Speeds, Direct Injection And More, GM’s 2008 

Global Powertrain Lineup Provides More Miles with Less Fuel” (released Mar. 6, 2007). Available at 

http://www.gm.com/experience/fuel_economy/news/2007/adv_engines/2008-powertrain-lineup-082707.jsp 

(last accessed Sept. 18, 2008). 

189 Page 17, “EPA Staff Technical Report: Cost and Effectiveness Estimates of Technologies Used to 

Reduce Light-duty Vehicle Carbon Dioxide Emissions” Environmental Protection Agency, EPA420-R-08-

008, March 2008.
V-112

volume in the 2011 timeframe, and since these are mature and stable technologies, timebased learning factors are applied. 

(iii) Dual Clutch Transmissions / Automated Manual Transmissions (DCTAM)

An automated manual transmission (AMT) is similar in architecture to a conventional 

manual transmission, but shifting and launch functions are performed through hydraulic 

or electric actuation. There are two basic types of AMTs, single-clutch and dual-clutch 

transmission (DCT), both of which were considered in the NPRM. Upon further 

consideration and in response to manufacturer comments to only include dual-clutch 

AMTs, single-clutch AMTs are not applied in the analysis for the final rule. 

Single clutch transmissions exhibit a torque interruption when changing gears because 

the clutch has to be disengaged. In a conventional manual transmission vehicle, the 

driver has initiated the gear change, and so expects to feel the resulting torque 

interruption. With an AMT, in contrast, a control system initiates the shift, which is 

unexpected and can be disconcerting to the driver. Comments from Ford in response to 

the NPRM indicated that the acceptability of this torque interruption among U.S. drivers 

is poor, although Ford also commented that DCTs do not have the risk of customer 

acceptance that AMTs do. BorgWarner, a DCT supplier, echoed these comments. DCTs 

do not display the torque interrupt characteristic due to their use of two clutch 

mechanisms which allow for uninterrupted power transmission. To assist with launch of 

a DCT equipped vehicle, the first gear ratio can be deepened to gain back some of the 

performance advantage an automatic transmission possesses due to the torque converter’s 

torque multiplication factor. 

There are two types of DCT systems, wet clutch and dry clutch, which are used for 

different types of vehicles. Wet clutch DCTs offer a higher torque capacity that comes 

from the use of a hydraulic system that cools the clutches, but that are less efficient than 

the dry clutch type due to the losses associated with hydraulic pumping. Additionally, 

wet DCTs have a higher cost due to the additional hydraulic hardware required. Wet 

clutch DCT systems have been available in the U.S. market on imported products since 

2005, and Chrysler has publicly stated that it will have a DCT transmission in its 2010 

model year vehicle line-up.190

Consistent with manufacturers’ confidential comments and based on its own analysis, 

NHTSA determined that dry clutch DCTs are applicable to smaller front wheel drive 

cars, due to their lower vehicle weight and torque production, and wet clutch DCTs are 

more applicable to higher torque applications with higher power requirements. Therefore 

lower cost, higher efficiency dry clutch DCTs are specified for the Subcompact and 

Compact Car vehicle classes, while all other classes required wet clutch DCTs. 

In the NPRM, NHTSA estimated that the incremental cost for DCTs was $141, 

independent of vehicle class, which was the midpoint of the NESCCAF estimates and 

within the range provided confidential manufacturer data. CARB commented that 

 

190 Chrysler blog, “Dual-Clutch Transmissions Explained” (released October 3, 2007) available at

http://blog.chryslerllc.com/blog.do?p=entry&id=113, last accessed September 18, 2008. 
V-113

NHTSA had incorrectly cited the cost of AMTs from the NESCCAF study in the NPRM, 

stating that AMTs had been determined to be cost neutral (zero cost) relative to baseline 

transmission, as opposed to a $0-$240 cost justification. Confidential manufacturer data 

suggest additional DCT costs from $80 to $740, with dry clutch DCT costs being 

approximately $100 less due to reduced hydraulic system content. The 2008 Martec 

study also reported variable costs for AMTs. 

In the NPRM, NHTSA cited the NESCCAF study as projecting that AMTs could 

incrementally reduce fuel consumption by 5 to 8 percent and confidential manufacturer 

data projected that AMTs could incrementally reduce fuel consumption by 2 to 5 percent. 

On the basis of these estimates, NHTSA concluded in the NPRM that AMTs could 

incrementally reduce fuel consumption by 4.5 to 7.5 percent. Confidential manufacturer 

data received in response to the NPRM suggest a benefit of 2 to 12 percent for DCTs 

over a 6-speed planetary automatic, and one confidential manufacturer estimates a benefit 

of 1 to 2 percent for a dry clutch DCT over a wet clutch DCT. The 2008 EPA Staff 

Technical Report also indicates a benefit of 9.5 to 14.5 percent for a DCT (wet or dry was 

not specified) over a 4-speed planetary automatic transmission. 

For the final rule, NHTSA estimated a 5.5 to 9.5 percent improvement in fuel 

consumption over a baseline 4/5-speed automatic transmission for a wet clutch DCT, 

which was assumed for all vehicle subclasses except Subcompact and Compact Car. This 

results in an incremental effectiveness estimate of 2.7 to 4.1 percent over the NAUTO 

technology. For Subcompact and Compact Cars, which were assumed to use a dry clutch 

DCT, NHTSA estimated an 8 to 13 percent fuel consumption improvement over a 

baseline 4/5-speed automatic transmission, which equates to a 5.5 to 7.5 percent 

incremental improvement over the NAUTO technology.

The 2008 Martec report was utilized to develop the cost estimates for the final rule; it 

estimated an RPE cost of $450 for a dry clutch DCT, and $600 for a wet clutch DCT, 

both relative to a baseline 4/5-speed. In the transmission decision tree for the final rule, 

this yielded a dry clutch DCT incremental cost estimate of $68 for the Subcompact and 

Compact Cars relative to the NAUTO technology. For Midsize, Large Car and Minivan 

classes the wet clutch DCT incremental cost over NAUTO is $218, which reflects the 

lower, 6-speed only cost of the NAUTO technology applied to these vehicles. The 

average incremental cost for wet DCT for the four Performance classes and the Small, 

Midsize and Larger truck is $61, which is lower than the other vehicle subclasses due to 

the higher cost NAUTO technology (up to 8-speeds) that the DCTAM technology 

supersedes. 

NHTSA relied upon confidential manufacturer product plans showing DCT production 

will be readily available and at high volume by 2011. Therefore volume-based learning 

is not applicable, and since this is a mature and stable technology, time-based learning is 

applied. As production facility conversion or construction may be required to facilitate 

required capacity, NHTSA limited the production phase-in caps in MY 2011 to 20 

percent. As with other transmission technologies, application was allowed at redesign 

only due to the vehicle changes required to adapt a new type transmission. 
V-114

(iv) Continuously Variable Transmission (CVT)

A continuously variable transmission (CVT) is unique in that it does not use gears to 

provide ratios for operation. Most CVTs use either a belt or chain on a system of two 

pulleys (the less common toroidal CVTs replace belts and pulleys with discs and rollers) 

that progressively vary the ratio, thus permitting an infinite number of effective gear 

ratios between a maximum and minimum value, and often a wider range of ratios than 

conventional automatic transmissions. This enables even finer optimization of the 

transmission ratio under different operating conditions and, therefore, some reduction of 

engine pumping and friction losses. In theory, the CVT has the ability to be the most 

fuel-efficient kind of transmission due to the infinite ability to optimize the ratio and 

operate the engine at its most efficient point. However, this effectiveness is reduced by 

the significant internal losses from high-pressure, high-flow-rate hydraulic pump, 

churning, friction loss, and bearing losses required to generate the high forces needed for 

traction.191 

Some U.S. car manufacturers have abandoned CVT applications because they failed to 

deliver fuel economy improvements over automatic transmissions. GM abandoned the 

use of CVT before 2006.192 Ford offered a CVT in the Five Hundred and Freestyle from 

MYs 2005-2007 and discontinued it thereafter. However, Chrysler offers CVTs in the 

Dodge Caliber, the Jeep Compass, and the Jeep Patriot. Nissan was using CVTs in many 

vehicles, but appears to be restricting the use of this technology to passenger cars only. 

In the NPRM, NHTSA estimated a CVT effectiveness of approximately 6 percent over a 

4-speed automatic, which was above the NESCCAF value but in the range of NAS. For 

costs, NHTSA concluded in the NPRM that the adjusted costs presented in the 2002 

NESCCAF study represent the best available estimates, and thus estimated that CVTs 

could incrementally reduce fuel consumption by 3.5 percent when compared to a 

conventional 5-speed automatic transmission (which cost an incremental $76 - $167), a 

technology which is considered a baseline transmission option on the final rule decision 

tree, at an incremental cost of $100 to $139. After reviewing confidential manufacturer 

data and the Martec report, for the final rule NHTSA is now estimating the incremental 

cost of CVTs to be $300 for all vehicle subclasses, except for large performance cars, 

midsize light trucks and large light trucks for which the technology is incompatible. 

Confidential manufacturer data in response to the NPRM suggested that the incremental 

effectiveness estimate from CVTs may be 2 to 8 percent over 4-speed planetary 

transmissions in simulation (however one commenter reported a zero percent 

improvement in dynamometer testing) at a cost of $140 to $800. Considering the NPRM 

conclusion and confidential data together with independent review, NHTSA has 

 

191 “Transmission and Driveline – Major contributors to FUEL efficiency, safety, fun to drive and brand 

differentiation”, Car Training Institute Symposium, May 6-7, 2008- Plenary Speech, Robert Lee, Vice 

President, Mircea Gradu, Director Transmission and Driveline, Chrysler LLC, USA. Available from the 

Car Training Institute, for contact information see http://www.car-traininginstitute.com/cti_en/html/kontakt.html (last accessed Nov. 9, 2008). 192 See http://car-reviews.automobile.com/news/general-motors-to-kill-continually-variabletransmission/166/ (last accessed Oct. 23, 2008).
V-115

estimated the fuel consumption effectiveness for CVTs at 2.2 to 4.5 percent over a 4/5-

speed automatic transmission, which translates into a 0.7 to 2.0 incremental effectiveness 

improvement over the IATC technology. NHTSA estimated the CVT incremental cost to 

be $300 for the final rule, noting that the NPRM costs were incremental to a 5-speed 

technology that is no longer represented in the decision tree, hence the higher final rule 

cost.193

CVTs are currently available, but due to their limited torque-carrying capability, they are 

not applied to Performance Large cars and Midsize and Large trucks. There is limited 

production capability for CVTs, so the phase-in cap for MY 2011 is limited to 5 percent 

to account for new plants and tooling to be prepared. CVTs can be introduced at product 

redesign intervals only based on confidential manufacturer data and consistent with the 

NPRM approach (since it requires vehicle attribute prove-out, test and certification prior 

to introduction). Confidential manufacturer data indicates that CVTs will be at high 

volumes by 2011, and this is a mature and stable technology, therefore NHTSA applied 

time-based learning factors. 

(v) 6-Speed Manual Transmissions (6MAN)

Manual transmissions are entirely dependent upon driver input to change gear ratio: the 

driver selects when to perform the shift and which gear ratio to select. This is the most 

efficient transfer of energy of all transmission layouts, because it has the lowest internal 

gear losses, with a minimal hydraulic system, and the driver provides the energy to 

actuate the clutch. From a systems viewpoint, however, vehicles with manual 

transmissions have the drawback that the driver may not always select the optimum gear 

ratio for fuel economy. Nonetheless, increasing the number of available ratios in a 

manual transmission can improve fuel economy by allowing the driver to select a ratio 

that optimizes engine operation more often. Typically, this is achieved through adding 

overdrive ratios to reduce engine speed at cruising velocities (which saves fuel through 

reduced pumping losses) and pushing the torque required of the engine towards the 

optimum level. However, if the gear ratio steps are not properly designed, this may 

require the driver to change gears more often in city driving resulting in customer 

dissatisfaction. Additionally, if gear ratios are selected to achieve improved launch 

performance instead of to improve fuel economy, then no fuel saving effectiveness is 

realized. 

NHTSA recognizes that while the manual transmission is very efficient, its effect on fuel 

consumption relies heavily upon driver input. In driving environments where little 

shifting is required, the manual transmission is the most efficient because it has the 

lowest internal losses of all transmissions. However, the manual transmission may have 

lower fuel efficiency on a drive cycle when drivers shift at non-optimum points. 

In the NPRM, NHTSA estimated that a 6-speed manual transmission could incrementally 

reduce fuel consumption by 0.5 percent when compared to a 5-speed manual 

transmission, at an incremental cost of $107. Confidential manufacturer data received in 

 

193 Since the decision trees are configured differently, the net cost to CVT in the NPRM included 5-speed 

automatic transmission technology costs that are not applied in the final rule. 
V-116

response to the NPRM suggests that manual transmissions could incrementally reduce 

fuel consumption by 0 to 1 percent over a base 5-speed manual transmission at an 

incremental cost of $40 to $900. Most confidential comments suggested that the 

incremental cost was within the lower quartile of the full range, thus $225 (the lower 

quartile upper-bound) was multiplied by the 1.5 RPE markup factor for a total of $338. 

Therefore, the final rule states that the incremental fuel consumption effectiveness for a 

6-speed manual transmission over a 5-speed manual transmission is 0.5 percent at a RPE 

cost of $338. 

This technology is applicable to all vehicle classes considered and can be introduced at 

product redesign intervals, consistent with the NPRM and other final rule transmission 

technologies. Six-speed manuals are already in production at stable and mature high 

volumes so time-based learning is applied with a 33 percent phase-in rate for MY 2011. 

(d) Hybrid and Electrification/Accessory Technologies

(i) Overview 

A hybrid describes a vehicle that combines two or more sources of energy, where one is a 

consumable energy source (like gasoline) and one is rechargeable (during operation, or 

by another energy source). Hybrids reduce fuel consumption through three major 

mechanisms: (1) by turning off the engine when it is not needed, such as when the 

vehicle is coasting or when stopped; (2) by recapturing lost braking energy and storing it 

for later use; and by (3) optimizing the operation of the internal combustion engine to 

operate at or near its most efficient point more of the time. A fourth mechanism to 

reduce fuel consumption, available only to plug-in hybrids, is by substituting the fuel 

energy with energy from another source, such as the electric grid. 

Engine start/stop is the most basic of hybrid functions, and as the name suggests, the 

engine is shut off when the vehicle is not moving or when it is coasting, and restarted 

when needed. This saves the fuel that would normally be utilized to spin the engine 

when it is not needed. Regenerative braking is another hybrid function which allows 

some of the vehicle’s kinetic energy to be recovered and later reused, as opposed to being 

wasted as heat in the brakes. The reused energy displaces some of the fuel that would 

normally be used to drive the vehicle, and thus results in reduced fuel consumption. 

Operating the engine at its most efficient operating region more of the time is made 

possible by adding electric motor power to the engine’s power so that the engine has a 

degree of independence from the power required to drive the vehicle. Fuel consumption 

is reduced by more efficient engine operation, the degree of which depends heavily on 

the amount of power the electric motor can provide. Hybrid vehicles with large electric 

motors and battery packs can take this to an extreme and drive the wheels with electric 

power only and the engine consuming no fuel. Plug-in hybrid vehicles can substitute fuel 

energy with electrical energy, further reducing the fuel consumption.194

 

194 Substituting fuel energy with electrical energy may not actually save total overall energy used, when 

considering the inefficiencies of creating the electricity at a power plant and storing it in a battery pack, but 

it does enable use of other primary energy sources, and reduces the vehicle’s fuel consumption. Plug-in 

hybrids are also receiving increasing attention because of their ability to use “clean energy” from the 

electric grid, such as that solar or wind, which can reduce the overall greenhouse gas output. 
V-117

Hybrid vehicles utilize some combination of the above mechanisms to reduce fuel 

consumption. The effectiveness of a hybrid, and generally the complexity and cost, 

depends on the utilization of the above mechanisms and how aggressively they are 

pursued. 

In addition to the purely hybrid technologies, which decrease the proportion of 

propulsion energy coming from the fuel by increasing the proportion of that energy 

coming from electricity, there are other steps that can be taken to improve the efficiency 

of auxiliary functions (e.g., power-assisted steering or air-conditioning) which also 

reduce fuel consumption. These steps, together with the hybrid technologies, are 

collectively referred to as “vehicle electrification” because they generally use electricity 

instead of engine power. Three “electrification” technologies are considered in this 

analysis along with the hybrid technologies: electrical power steering (EPS), improved 

accessories (IACC), and high voltage or improved efficiency alternator (HVIA). 

(ii) Hybrid System Sizing and Cost Estimating Methodology 

Estimates of cost and effectiveness for hybrid and related electrical technologies have 

been adjusted from those described in the NPRM to address commenters’ concerns that 

NHTSA considered technologies not likely to be adopted by automakers (e.g., 42V 

electrical systems) or did not scale the costs for likely technologies across the range of 

vehicle subclasses considered. To address these concerns, the portfolio of vehicle 

electrification technologies has been refined based on commenter data as described below 

in the individual hybrid technologies sections. Ricardo and NHTSA have also developed 

a “ground-up” hybrid technology cost estimating methodology and, where possible, 

validated it to confidential manufacturer data. The hybrid technology cost method 

accounts for variation in component sizing across both the hybrid type and the vehicle 

platform. The method utilizes four pieces of data: (1) key component sizes for a midsize 

car by hybrid system type; (2) normalized costs for each key component; (3) component 

scaling factors that are applied to each vehicle subclass by hybrid system type; and (4) 

vehicle characteristics for the subclasses which are used as the basis for the scaling 

factors. 

Component sizes were estimated for a midsize car using publicly available vehicle 

specification data and commenter data for each type of hybrid system as shown in Table 

V-10. 
V-118

Table V-10. Component Sizes by Hybrid Type for a Midsize Car

Component MHEV ISG PSHEV 2MHEV PHEV

Primary Motor power, continuous (kW) 3 11 45 45 45

Secondary Motor power, continuous (kW) na na 30 45 30

Primary Inverter power, continuous (kW) 3 11 45 45 45

Secondary Inverter power, continuous (kW) na na 30 45 30

Controls complexity (relative to strong hybrid) 25% 50% 100% 100% 100%

NiMH Battery Pack capacity (kW-hr) na 1 2 2 na

Li-Ion Battery Pack capacity (kW-hr) na na na na 15

DC/DC Converter power (kW) 0.7 3 3 3 3

High Voltage Wiring (relative to strong hybrid) na 50% 100% 100% 100%

Supplemental heating Yes Yes Yes Yes Yes

Mechanical Transmission (relative to baseline vehicle) 100% 100% 50% 100% 25%

Electric AC No No Yes Yes Yes

Blended Brakes No No Yes Yes Yes

Charger power, continuous (kW) na na na na 3

Hybrid Type

In developing Table V-10, NHTSA made several assumptions: 

1) Hybrid controls hardware varies with the level of functionality offered by the 

hybrid technology. Assumed hybrid controls complexity for a 12V micro 

hybrid (MHEV) was 25 percent of a strong hybrid controls system and the 

complexity for an Integrated Starter Generator (ISG) was 50 percent. These 

ratios were estimates based on the directional need for increased functionality 

as system complexity increases. 

2) In the time frame considered, Li-ion battery packs will have limited market 

penetration, with a majority of hybrid vehicles using NiMH batteries. One 

estimate from Anderman indicates that Li-ion market penetration will achieve 

35 percent by 2015.195 For the purposes of this analysis, it was assumed that 

mild and strong hybrids will use NiMH batteries and plug-in hybrids will use 

Li-ion batteries. 

3) The plug-in hybrid battery pack was sized for a mid-sized car by assuming: 

the vehicle has a 20 mile all electric range and consumes an average of 300 

W-hr per mile; the battery pack can be discharged down to 50 percent depth of 

discharge; and the capacity of a new battery pack is 20 percent greater than at 

end of life (i.e., range on a new battery pack is 24 miles). 

4) All hybrid systems included a DC/DC converter which was sized to 

accommodate vehicle electrical loads appropriate for increased vehicle 

electrification in the time frame considered. 

5) High voltage wiring scaled with hybrid vehicle functionality and could be 

represented as a fraction of strong hybrid wiring. These ratios were estimates 

based on the directional need for increased functionality as system complexity 

increases. 

6) All hybrid systems included a supplemental heater to provide vehicle heating 

when the engine is stopped, however, only stronger hybrids included electric 

air conditioning to enable engine stop/start when vehicle air conditioning was 

requested by the operator. 

 

195 Anderman, Advanced Automotive Battery Conference, May 2008. Proceedings available for purchase 

at http://www.advancedautobat.com/Proceedings/index.html (last accessed October 17, 2008).
V-119

In the hybrid technology cost methodology developed for cost-scaling purposes, several 

strong hybrid systems replaced a conventional transmission with a hybrid-specific 

transmission, resulting in a cost offset for the removal of a portion of the clutches and 

gear sets within the transmission. The transmission cost in Table V-11 below expresses 

hybrid transmission costs as a percentage of traditional automatic transmission cost, as 

described in the 2008 Martec Report, at $850. The method assumed that the mechanical 

aspect of a power-split transmission with a reduced number of gear sets and clutches 

resulted in a cost savings of 50 percent of a conventional transmission with torque 

converter. For a 2-mode hybrid, the mechanical aspects of the transmission are similar in 

complexity to a conventional transmission with a torque converter, thus no mechanical 

cost savings was appropriate. The plug-in hybrid assumed a highly simplified 

transmission for electric motor drive, thus 25 percent of the base vehicle transmission 

cost was applied. 

Estimates for the cost basis of each key component are shown in Table V-11 below along 

with the sources of those estimates. The cost basis estimates assume fully learned, highvolume (greater than 1.2 million units per annum) production. The costs shown are 

variable costs that are not RPE adjusted. 
V-120

Table V-11. Component Cost Basis at High Volumes and Data Sources 

Component Cost 

Basis Data Source

Primary Motor ($/kW) 15 $ 

Secondary Motor ($/kW) 15 $ 

Primary Inverter ($/kW) 10 $ 

Secondary Inverter ($/kW) 10 $ 

Controls 100 $ 

NiMH Battery Pack ($/kW-hr.) 50 $ Attorneys General/Anderman comments 

(NHTSA-2008-089-0199.5) 

Li-Ion Battery Pack ($/kW-hr.) 600 $ Anderman, AABC 2008 ($900/kW-hr @ 

2000 units/yr learned and rounded)

DC/DC Converter 100 $ Confidential business information 

High Voltage Wiring 250 $ 

Supplemental heating 84 $ 

Mechanical Transmission 850 $ Martec 2008 (to 4-spd. Auto.) 

Electric AC 450 $ Confidential business information 

Blended Brakes 400 $ Martec 2008 

Charger 100 $ Confidential business information 

Automatic Transmission pump 75 $ Martec 2008 

 Martec 2008 

 Martec 2008 

 Confidential business information 

Component scaling factors were determined based on vehicle characteristics for 

each type of hybrid system as shown in Table V-12 below. 
V-121

Table V-12. Component Scaling Factors applied to Vehicle Class for each Hybrid 

System Type 

Component MHEV ISG PSHEV 2MHEV PHEV

Primary Motor Engine 

displacement Curb weight Engine power

Secondary Motor na na Vehicle 

mass2

Primary Inverter

Secondary Inverter na na

Controls

NiMH Battery Pack na na

Li-Ion Battery Pack na na na na Vehicle 

mass

DC/DC Converter

High Voltage Wiring na

Supplemental heating

Mechanical Transmission

Electric AC na na

Blended Brakes na na

Charger na na na na

Same for all 

vehicle 

classes

(1) For all vehicle classes except for performance classes which use Engine Torque

(2) Vehicle mass used as surrogate for vehicle road load

(3) Vehicle mass used as surrogate for vehicle electrical load

Hybrid Type

Engine displacement

Curb weight1

Vehicle mass3

Vehicle footprint

Primary motor power

Secondary motor power

Complexity

Vehicle mass

Same for all vehicle classes

Vehicle footprint

Vehicle footprint

Same for all vehicle classes

NHTSA’s CAFE database was used to define the average vehicle characteristics for each 

vehicle subclass as shown in Table V-13 below, and these attributes were used as the 

basis of the scaling factors. 
V-122

Table V-13. Key Vehicle Characteristics For Each Vehicle Class 

Vehicle Subclass

Curb 

Weight

(lbs)

Footprint

(ft2)

Engine 

Disp. (L)

Power

(hp)

Torque

(ft-lb)

Subcompact Car 2795 41 1.9 134 133

Compact Car 3359 44 2.2 166 167

Midsize Car 3725 47 2.9 205 206

Large Car 4110 50 3.4 258 248

Performance Subcompact Car 3054 40 2.7 260 260

Performance Compact Car 3516 44 3.0 269 260

Performance Midsize Car 3822 47 3.9 337 318

Performance Large Car 4189 51 4.8 394 388

Minivan 4090 50 3.3 247 242

Small Truck 3413 45 2.6 178 185

Medium Truck 4260 50 3.6 250 256

Large Truck 5366 63 5.0 323 352

Table V-14 shows the costs for the different types of hybrid systems on a midsize 

vehicle. The individual component costs were scaled from the normalized costs shown in 

Table V-11 according to the component size shown in Table V-10 and adjusted to a low 

volume cost by backing out volume-based learning reductions.196 These component costs 

were summed to get the total low volume cost for each hybrid type, and a 1.5 RPE 

adjustment was applied. The ISG technology replaces the MHEV technology on the 

Electrification/Accessory technology decision tree, therefore the MHEV technology costs 

must be subtracted to reflect true costs ($2,898 - $707 = $2,191 in this example). 

Wherever possible, the results of the hybrid technology cost method were compared with 

values as previously described in the NPRM and the results generally matched prior 

estimates. Additionally, the results from the hybrid technology cost method were 

validated with public literature and confidential manufactures test data as allowed. 

Elements of the 2008 Martec report identified cost data and a detailed bill of materials for 

several comparable hybrid technologies (Micro-hybrid systems and Full Hybrid systems), 

and the hybrid technology cost model agreed well with this data. The scalable bill of 

material based methodology described above was determined to offer the best solution 

for estimating component sizes and costs across a range of hybrid systems and vehicle 

platforms and the validation of these cost outputs with other data sources suggests that 

this approach is a reasonable approach. 

 

196 High volume costs are multiplied by a factor of 1.56, which represents two cycles of 20 percent reverse 

learning, to determine the appropriate low volume, or unlearned costs. 
V-123

Table V-14. Hybrid System - Midsize Vehicle Low Volume Costs 

(iii) Electrical Power Steering (EPS) 

Electrical Power Steering (EPS) is advantageous over conventional hydraulic powerassisted steering in that it only draws power when the vehicle is being steered, which is 

typically a small percentage of the time a vehicle is operating. In fact, on the EPA test 

cycle no steering is done, so the CAFE fuel consumption effectiveness comes about by 

eliminating the losses from driving the hydraulic steering pump at engine speed. EPS 

systems use either an electric motor driving a hydraulic pump (this is a subset of EPS 

systems known as electro-hydraulic power steering) or an electric motor directly assisting 

in turning the steering column. EPS is seen as an enabler for all vehicle hybridization 

technologies, since it provides power steering when the engine is off. This was a primary 

consideration in placing EPS at the top of the Electrification/Accessory decision tree. 

In the NPRM, NHTSA estimated the fuel consumption effectiveness for EPS at 1.5 to 2 

percent at an incremental cost of $118 to $197, believing confidential manufacturer data 

most accurate. In response to the NPRM Sierra Research suggested EPS and high 

MHEV ISG* PSHEV 2MHEV PHEV

Primary Motor [Example: MHEV = 3KW * 

15$/KW * 1.56 (vol uplift)] $ 263 70 $ 1,053 $ 1,053 $ 1,755 $ 

Secondary Motor - $ - $ 702 $ 1,053 $ 702 $ 

Primary Inverter 47 $ 176 $ 702 $ 702 $ 1,170 $ 

Secondary Inverter - $ - $ 468 $ 702 $ 468 $ 

Controls 39 $ 78 $ 156 $ 156 $ 156 $ 

NiMH Battery Pack - $ 546 $ 1,092 $ 1,092 $ - $ 

Li-Ion Battery Pack - $ - $ - $ - $ 14,040 $ 

DC/DC Converter 109 $ 468 $ 468 $ 468 $ 468 $ 

High Voltage Wiring - $ 195 $ 390 $ 390 $ 390 $ 

Supplemental heating 131 $ 131 $ 131 $ 131 $ 131 $ 

Mechanical Transmission - $ - $ (663) $ - $ (995) $ 

Electric AC - $ - $ 702 $ 702 $ 702 $ 

Blended Brakes - $ - $ 624 $ 624 $ 624 $ 

Charger - $ - $ - $ - $ 468 $ 

Automatic transmission pump 75 $ 75 $ - $ - $ - $ 

Total Hybrid System Cost @ Low Volume 471 $ 1,932 $ 5,825 $ 7,073 $ 20,080 $ 

 RPE (1.5) System Cost @ Low Volume $ 2,898 707 $ 8,738 $ 10,610 $ 30,119 $ 

Component

Hybrid Type 

Low Volume (Unlearned) Costs

 * ISG replaces the MHEV technology on the Accessory/Electrification Decision Tree
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efficiency alternators combined is worth 1 to 1.8 percent on the CAFE test cycle,197 and 

confidential manufacturer data indicated a 0.7 to 2.9 percent fuel consumption reduction. 

The cost range from confidential manufacturer data was $70 to $300. Sierra estimated 

EPS for cars at $82 and $150 for trucks.198 A market study by Frost & Sullivan indicated 

the cost of an EPS system at roughly $65 more than a conventional hydraulic (HPS) 

system.199 Because there is a wide range in the effectiveness for EPS depending on the 

vehicle size, NHTSA has increased the range from the NPRM to incorporate the lower 

ranges suggested by most manufacturers and estimates the fuel consumption 

effectiveness for EPS at 1 to 2 percent for the purpose of the final rule. The incremental 

costs are also estimated on range below the Sierra value for cars but above the Frost & 

Sullivan estimate at a piece cost range of $70 to $80 and included a 1.5 RPE uplift to 

$105 to $120 for the final rule. 

EPS is currently in volume production in small to mid-sized vehicles with a standard 12V 

electrical system; however, heavier vehicles may require a higher voltage system, which 

adds cost and complexity. The Chevy Tahoe Hybrid, for example, uses a higher voltage 

EPS system. For purposes of the final rule, NHTSA has applied EPS to all vehicle 

subclasses except for Large trucks. 

In the NPRM, NHTSA assumed a 25 percent phase in rate of EPS technologies. For the 

purposes of the final rule, EPS phase-in caps were limited to 10 percent in MY 2011 to 

address confidential manufacturer concerns over lead time. In the NPRM, NHTSA 

assumed a volume-based learning effect for EPS. For the final rule, however, NHTSA 

applied time-based learning for EPS since NHTSA’s analysis indicated that this 

technology would be in high-volume use at the beginning of its first year of availability. 

NHTSA also assumed in the NPRM that EPS could be applied during refresh model 

years, which was consistent with information provided in confidential product plans, 

therefore for the purpose of the final rule, NHTSA again applied EPS at refresh timing. 

(iv) Improved Accessories (IACC) 

Improved accessories (IACC) was defined in the NPRM as improvements in accessories 

such as the alternator, coolant and oil pumps that are traditionally driven by the engine. 

Improving the efficiency or outright electrification of these accessories would provide 

opportunity to reduce the accessory loads on the engine. However, as the oil pump 

provides lubrication to the engine’s sliding surfaces such as bearings pistons, and 

camshafts and oil flow is always required when the engine is spinning, and it is only 

supplied when the engine is spinning, there is no efficiency to be gained by electrifying 

the oil pump.200

 

197 Docket No. NHTSA-2008-0089-0179.1, Attachment 2, at 53. 198 Docket No. NHTSA-2008-0089-0179.1, Attachment 2, at 59. 199 Cost for EPS quoted at 48 Euros, at $1.35 per Euro exchange rate (Oct. 7, 2008) equates to $65, from 

Frost & Sullivan, Feb. 9, 2006 “Japanese Steering System Market Moves Into High Gear,” 

http://www.theautochannel.com/news/2006/02/09/210036.html (last accessed Nov. 2, 2008). 200 Oil pump electrification comes with an additional potential technical and financial risk (to warranty and 

consumer), in that significant engine damage can occur should the system fail to provide engine lubrication, 

even on a momentary basis. 
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Electrical air conditioning (EAC) could reduce fuel consumption by allowing the engine 

to be shut off when it is not needed to drive the vehicle. For this reason EAC is often 

used on hybrid vehicles. In highway driving, however, there is little opportunity to shut 

the engine off; furthermore EAC is less efficient when the engine is running because it 

requires mechanical energy from the engine to be converted to electrical energy and then 

back again to mechanical. Since air conditioning is not required on the EPA city or 

highway test cycles, there is no CAFE fuel consumption effectiveness from EAC. 

Therefore, EAC does not improve accessory efficiency apart from the hybrid 

technologies. For the purposes of the final rule, IACC refers strictly to improved engine 

cooling, since electrical lubrication and air conditioning are not effective stand-alone fuel 

saving technologies and improved alternator is considered as a separate technology given 

its importance to vehicle electrification. 

Improved engine cooling, or intelligent cooling, can save fuel through two mechanisms: 

by reducing engine friction as the engine warms up faster; and by operating an electric 

coolant pump at a lower speed than the engine would (i.e., independent of engine speed). 

Intelligent cooling can be applied to vehicles that do not typically carry heavy payloads. 

Larger vehicles with towing capacity present a challenge for electrical intelligent cooling 

systems, as these vehicles have high cooling fan loads. Therefore NHTSA did not apply 

IACC to the Large Truck and SUV class. 

In the NPRM, NHTSA estimated the fuel consumption effectiveness for improved 

accessories at 1 to 2 percent at an incremental cost of $124 to $166 based on the 2002 

NAS Report and confidential manufacturer data. Confidential manufacturer data 

received in response to the NPRM and Sierra Research both suggested a range for fuel 

consumption effectiveness from 0.5 to 2 percent. A comment from MEMA suggested 

that improved thermal control of the engine could produce between 4 and 8 percent fuel 

economy improvement;201 however, NHTSA’s independent review of intelligent cooling 

suggests this estimate is high and concurs with the estimates from NAS. Independent 

review found the cost for IACC at low volumes, assuming the base vehicle already has an 

electric fan, to be $180 to $220. These costs were adjusted to account for volume-based 

learning and then marked up to account for the 1.5 RPE factor. For the purposes of the 

final rule, NHTSA retained the fuel consumption effectiveness at 1 to 2 percent and 

estimated the incremental costs to be $173 to $211. 

MEMA also suggested that NHTSA consider solar glass technology to reduce cabin 

thermal loading; however, air conditioning technologies were not considered as part of 

this technology. 

In the NPRM, NHTSA proposed a 25 percent phase-in cap for Improved Accessories. To 

address manufacturer concerns over lead time in the early years, the IACC phase-in cap 

was limited to 10 percent for MY 2011for the final rule. In the NPRM, NHTSA assumed 

for improved accessories a volume-based learning curve. For the final rule, however, 

NHTSA applied time-based learning for IACC since NHTSA’s analysis indicated that 

this technology would be in high-volume use at the beginning of its first year of 

 

201 Docket No. NHTSA-2008-0089-0193.1. 
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availability. NHTSA assumed in the NPRM that improved accessories could be applied 

during any model year. For the purpose of the final rule, NHTSA applied intelligent 

cooling at refresh model years due to the significant changes required to the vehicle 

cooling system that necessitate recertification testing. 

(v) 12V Micro Hybrid (MHEV) 

12V Micro-Hybrid (MHEV) systems are the most basic of hybrid systems and offer 

mainly idle-stop capability. Their low cost and easy adaptability to existing powertrains 

and platforms can make them attractive for some applications. The conventional beltdriven alternator is replaced with a belt-driven, enhanced power starter-alternator and a 

redesigned front-end accessory drive system that facilitates bi-directional torque 

application. Also, during idle-stop, some functions such as power steering and 

automatic transmission hydraulic pressure are lost with conventional arrangements; so 

electric power steering and an auxiliary transmission pump are needed. These 

components are similar to those that would be used in other hybrid designs. Also 

included in this technology is the Smart Starter Motor. This system is comprised of an 

enhanced starter motor, along with some electronic control that monitors the 

accelerator, brake, clutch positions, and the battery voltage as well as low-noise gears to 

provide fast and quiet engine starts. Despite its extended capabilities, the starter is 

compact and thus relatively easy to integrate in the vehicle. 

12V micro hybrid was added to the technology list to address concerns from CARB and 

Delphi that the hybrid classifications used in the NPRM did not adequately represent 

these technologies.202

The effectiveness estimates by NHTSA for this technology are based on confidential 

manufacturer data and independent source data. For the vehicles equipped with 

(baseline) inline 4, those with smaller displacements, the effectiveness is between 1 and 

2.9 percent, and for those equipped with V-6 or V-8, the effectiveness is between 3.4 and 

4 percent. The 1 to 2.9 percent incremental fuel consumption savings applies to the SubCompact Car, Performance Sub-Compact Car, Compact Car, Midsized Car, and Small 

Truck/SUV variants. The 3.4 to 4 percent incremental fuel consumption applies to the 

remaining classes with the exception of Large Truck/SUV where MHEV is not applied 

due to payload and towing requirements for this class. 

Confidential manufacturer comments submitted in response to the NPRM indicated a 

$200 to $1000 cost for the MHEV. The 12V micro-hybrid does not have a high voltage 

battery, and thus does not have a high-voltage wire cost. The 12V micro-hybrid system 

for the midsize vehicle has a 3kW electric motor. This agrees well with two 

commercially available systems used on smaller engines.203 The value used for the 

DC/DC converter represents the cost for a 12V power conditioning circuit to allow 

uninterrupted power to the radio and a limited number of other accessories when the 

 

202 Docket Nos. NHTSA-2008-0089-0173 and -0144.1, respectively. 203 Citroen uses a 2kW system for a 1.4L diesel engine, and Valeo has a 1.6kW system applicable for 

engines up to 2L in displacement. The midsize vehicle class has an average engine size of 2.9L, and thus a 

3kW starter is appropriate.
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engine starter is engaged. The sizing for the rest of the components is shown in Table V9. 

The MHEV technology, which will be available from the 2011 model year, is projected 

to be in high volume use at the beginning of its first year of availability according to 

NHTSA’s analysis, therefore volume based learning reductions (two cycles at 20 percent) 

were applied to “learn” the hybrid method costs and time based learning factors were 

applied throughout the remaining years. For the final rule, NHTSA established 

incremental costs ranging from $372 to $549 with the highest cost applying to the 

Performance Large Car class. 

The 12V micro hybrid technology is applicable across all the vehicle segments except for 

the Large Truck/SUV class. Although this technology was not specifically stated in the 

NPRM, a phase-in cap of 3 percent for MY 2011 was assumed for hybrid technologies. 

For the final rule, this figure was retained since it is generally supportable within the 

industry as expressed at the SAE HEV Symposium in San Diego in Feb 2008.

The NPRM proposed that all of the hybrid technologies could be introduced during the 

redesign model year only. This view is consistent with manufacturer’s views, therefore, 

for this rule making, NHTSA has assumed that 12V micro hybrids can only be introduced 

at the redesign model years. 

(vi) High Voltage / Improved Alternator (HVIA) 

In the NPRM, a 42V accessory technology was identified in the decision tree for Other 

Technologies. Several confidential manufacturer comments received by NHTSA related 

to 42V technology, and indicated that the effectiveness of 42V system were not realized 

when electrical conversion efficiencies were considered, and the cost of transitioning the 

industry from a 12V to 42V system made the technology unreasonable for deployment in 

the emerging technology time frame. As a result of these comments, NHTSA revised the 

technology from 42V technology to High Voltage / Improved Alternator (HVIA). 

The “High Voltage/Improved Efficiency Alternator” technology block represents 

technologies associated with increased alternator efficiency. As most alternators in 

production vehicles today are optimized for cost and the process for increasing the 

efficiency of an alternator is well understood by the industry, this technology is 

applicable to all vehicle subclasses except Midsize and Large Truck and SUV where it is 

not considered applicable due to the high utility of these classes. 

The NPRM identified fuel economy effectiveness that were based on 42V accessory 

systems, and are not directly applicable for this current technology definition. 

Confidential manufacturer data indicates that a midsized car with an improved efficiency 

alternator provided 0.2 to 0.9 percent fuel consumption effectiveness over the CAFE 

drive cycles, and a pickup truck provided 0.6 percent fuel consumption effectiveness over 

the same cycles. As this technology can be applied over a range of vehicles, NHTSA 

believes the fuel consumption effectiveness for larger vehicles will be biased downward. 
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For purposes of this final rule, NHTSA estimates the fuel consumption effectiveness for 

High Voltage/Improved Efficiency Alternator” technology at 0.2 to 0.9 percent. 

The NPRM identified several sources for high voltage / improved efficiency alternators 

incremental costs, but focused this technology on 42V systems, thus making some of 

these references not representative of the current technology description. The NPRM 

“Engine accessory improvement” technology discussion, however, did quote the 

NESCCAF study that indicated a $56 cost for a high efficiency generator. An 

independent confidential study estimated that the incremental cost increase for a high 

efficiency generator at high volume was similar to the NESCCAF quoted cost, thus 

NHTSA concludes that the NESCCAF study cost of $56 is still a representative cost for 

this technology. At a 1.5 RPE value, this cost equates to $84. 

As the definition of the technology has been revised from the NPRM, phase-in rates 

identified in the NPRM are not applicable. NHTSA believes the High voltage / Improved 

Efficiency Alternator technology represents an adjustment to the alternator 

manufacturing industry infrastructure, so for purposes of this final rule, phase-in caps for 

this technology were estimated at 10 percent for MY 2011. 

Also, as the definition of the technology has been revised from the NPRM, learning curve 

assumptions from the NPRM are not applicable. The high voltage / improved alternator 

technology costs were based on high volume estimates, thus, for purposes of the final 

rule, NHTSA assumed time-based learning (3 percent YOY) for High Voltage Systems / 

Improved Alternator technology. For purposes of the final rule, NHTSA assumed the 

technology can be introduced during refresh or redesign model changes only. 

(vii) Integrated Starter Generator (ISG)

The next hybrid technology that is considered is the Integrated Starter Generator (ISG) 

technology. There are 2 types of integrated starter generator hybrids that are considered: 

the belt mounted type and the crank mounted type. 

A Belt Mounted Integrated Starter Generator (BISG) system is similar to a microhybrid system, except that here it is defined as a system with a 110 to 144V battery 

pack which thus can perform some regenerative braking, whereas the 12V micro-hybrid 

system cannot. The larger electric machine and battery enables additional hybrid 

functions of regenerative braking and a very limited degree of operating the engine 

independently of vehicle load. While having a larger electric machine and more battery 

capacity than a MHEV, this system has a smaller electric machine than stronger hybrid 

systems because of the limited torque capacity of the belt driven design. 

BISG systems replace the conventional belt-driven alternator with a belt-driven, 

enhanced power starter-alternator and a redesigned front-end accessory drive system that 

facilitates bi-directional torque application utilizing a common electric machine. Also, 

during idle-stop, some functions such as power steering and automatic transmission 

hydraulic pressure are lost with conventional arrangements; so electric power steering 
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and an auxiliary transmission pump need to be added. These components are similar to 

those that would be used in other hybrid designs. 

A Crank Mounted Integrated Starter Generator (CISG) hybrid system, also called an 

Integrated Motor Assist (IMA) system, utilizes a thin axial electric motor (100-144V) 

bolted to the engine’s crankshaft. The electric machine acts as both a motor for helping 

to launch the vehicle and a generator for recovering energy while slowing down. It also 

acts as the starter for the engine and is a higher efficiency generator. An example of this 

type of a system is found in the Honda Civic Hybrid. For purposes of the final rule, 

NHTSA assumed the electric machine is rigidly fixed to the engine crankshaft, thus 

making electric-only drive not practical.204 

The fuel consumption effectiveness of the ISG systems are greater than those of microhybrids, because they are able to perform the additional hybrid function of regenerative 

braking and able to utilize the engine more efficiently because some transient power 

demands from the driver can be separated from the engine operation. Their transient 

performance can be better as well, because the larger electric machine can provide torque 

boost. The ISG systems are more expensive than the micro hybrids, but have lower cost 

than the strong hybrids described below because the electrical component sizes (batteries, 

electric machines, power electronics, etc.) are sized in between the micro-hybrid and the 

strong hybrid components. The engineering effort required to adapt conventional 

powertrains to these configurations is also in between that required for micro-hybrid and 

strong hybrid configurations. Packaging is a greater concern due to the fact that the 

engine-motor-transmission assembly is physically longer, and the battery pack, high 

voltage cabling and power electronics are larger. 

The hybrid decision tree was modified to address several manufacturer comments and 

comments from CARB and Delphi asking for more appropriate separation of hybrid 

technology classifications (i.e., 12V versus higher voltage Integrated Starter Generators, 

etc.). The inclusion of the ISG technology in the final rule is in response to these 

comments and those from subject matter experts.

The NPRM had proposed a fuel consumption savings of between 5 and 10 percent for 

ISG systems, and between 3.5 and 8.5 percent for the Honda IMA system, both of which 

fall in the ISG category described above. Confidential manufacturer comments submitted 

in response to the NPRM indicated an incremental 3.8 to 7.4 percent fuel consumption 

effectiveness and a $1,500 to $2,400 cost as compared to the baseline vehicle. 

The incremental fuel consumption savings for the Compact Car variant for ISG over a 

12V Micro-hybrid with start/stop was calculated using published data and confidential 

manufacturer data, while published Honda Civic Hybrid data was used to calculate the 

fuel consumption gains due to the hybrid system. For the final rule, gains for the other 

 

204 A clutch between the engine and the electric motor would enable pure electric drive, but the Porsche 

Cayenne is the only example of such a system that is planned in the rulemaking time frame. Because of 

limited expected volumes of this type of system, and in the interest of reducing complexity, that variant is 

not included here. 
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technologies also included on this vehicle were subtracted out to give an incremental 

effectiveness of 5.7 to 6.5 percent for ISG. Data for these individual gains was taken 

from confidential manufacturer data. The 5.7 to 6.5 percent incremental fuel 

consumption savings was carried over from the Compact Car to all other vehicle 

subclasses. A 2 percent incremental effectiveness was subtracted from the Performance 

subclasses to allow for the improved baseline performance 

The NPRM proposed a cost of $1,636 to $2,274 for these systems. For the final rule, 

NHTSA determined the cost for the ISG system using system sizing data for different 

available ISG hybrids. The 2006 Honda Civic has a Crank Mounted ISG and uses a 0.87 

kW-hr battery pack. In light of the potential growth of vehicle electrification, a 1 kW-hr 

pack size was chosen for both the belt and crank mounted ISG systems. The crank 

mounted ISG was sized as 11kW continuous (15kW peak). This is an average of the 

10kW system on the 2003 Honda Civic and the 12kW system on the 2005 Honda Accord. 

The 2006 Civic has a 15kW system. The belt mounted ISG has a slightly smaller electric 

machine (7.5kW continuous and 10kW peak) due to power transmission limitations of 

the belt. 

For the final rule, the hybrid technology cost method projected costs ranging from $2,475 

to $3,290 for the Sub-Compact car class through the Midsize Truck classes as compared 

to the conventional baseline vehicle and the incremental costs of $1,713 to $2,457 were 

calculated by backing out the prior hybrid technology costs. The ISG technology is 

projected to be in low volume use at the beginning of the rulemaking period therefore 

low volume costs are used and volume-based learning factors are applied. 

Integrated starter generator systems are applicable to all vehicle subclasses except Large 

Truck. In the NPRM, a phase-in cap of 3 percent was assumed for both the “ISG with 

idle off” and “IMA” technologies. For the final rule, NHTSA has retained the phase-in 

cap of 3 percent. These values are generally supportable within the industry as expressed 

at the SAE HEV Symposium in San Diego in February 2008. 

The NPRM proposed that all of the hybrid technologies could be introduced during the 

redesign model year only. This view is consistent with manufacturer’s views as well, 

because all of the hybrid technologies under consideration require redesign of the 

powertrain (ranging from engine accessory drive to transmission redesign) and vehicle 

redesign to package the hybrid components (from high voltage cabling to the addition of 

large battery packs). Given this, for purposes of the final rule, they can only be 

introduced in redesign model years. 

(viii) Power Split Hybrid 

The Power Split hybrid (PSHEV) is described as a full or a strong hybrid since it has the 

ability to move the vehicle on electric power only. It replaces the vehicle’s transmission 

with a single planetary gear and a motor/generator. A second, more powerful 

motor/generator is directly connected to the vehicle’s final drive. The planetary gear 

splits the engine’s torque between the first motor/generator and the final drive. The first 

motor/generator uses power from the engine to either charge the battery or supply power 
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to the wheels. The speed of the first motor/generator determines the relative speed of the 

engine to the wheels. In this way, the planetary gear allows the engine to operate 

independently of vehicle speed, much like a CVT. The Toyota Prius and the Ford Hybrid 

Escape are two examples of power split hybrid vehicles. 

In addition to providing the functions of idle engine stop and subsequent restart, 

regenerative braking, this hybrid system allows for pure EV operation. The two 

motor/generators are bigger and more powerful than those in an ISG hybrid, allowing the 

engine to be run in efficient operating zones more often. For these reasons, the power 

split system provides very good fuel consumption in city driving. During highway 

cycles, the hybrid functions of regenerative braking, engine start/stop and optimal engine 

operation cannot be applied as often as in city driving, and so the effectiveness in fuel 

consumption are less. Additionally, it is less efficient at highway speeds due to the fact 

that the first motor/generator must be spinning at a relatively high speed and therefore 

incurs losses. 

The battery pack for PSHEV is assumed to be 300V NiMH for the time period 

considered in this rulemaking, as is used in current PSHEV systems today. Their 

reliability is proven (having been in hybrids for over 10 years) and their cost is lower than 

Li Ion, so it is likely that the battery technology used in HEVs will continue to be NiMH 

for the near future for hybrids that do not require high energy storage capability like a 

plug-in hybrid does. 

The Power Split hybrid also reduces the cost of the transmission, replacing a 

conventional multi-speed unit with a single planetary gear. The electric components are 

bigger than those in an ISG configuration so the costs are correspondingly higher. 

However, the Power Split system is not planned for use on full-size trucks and SUVs due 

to its limited ability to efficiently provide the torque needed by these vehicles. The drive 

torque is limited to the first motor/generator’s capacity to resist the torque of the engine. 

It is anticipated that Large Trucks would use the 2-mode hybrid system. 

In the NPRM, a phase-in rate of 3 percent was assumed for the power split technology. 

Although this system has been engineered for some vehicles by a couple of 

manufacturers, the required engineering resources both at OEMs and Tier 1 suppliers are 

high . and most importantly, require long product development lead times. Thus 

NHTSA believes it would be extremely difficult for manufacturers to implement in levels 

greater than that of the submitted product plans for MY 2011. For the final rule, NHTSA 

limited the volumes of power split hybrids to zero percent in MY 2011. Power split 

hybrid cost and effectiveness estimates will not be discussed here, given that the 

technology is not applied in MY 2011 beyond product plan levels in NHTSA’s analysis, 

and NHTSA will consider them further in its future rulemaking actions. 

The NPRM proposed that all of the hybrid technologies could be introduced during the 

redesign model year only, consistent with manufacturer’s views. Given this, for this final 

rule NHTSA has retained the redesign application timing. 
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(ix) 2-Mode Hybrid 

The 2-mode hybrid (2MHEV) is another strong hybrid system that has all-electric drive 

capability. The 2MHEV uses an adaptation of a conventional stepped-ratio automatic 

transmission by replacing some of the transmission clutches with two electric motors, 

which makes the transmission act like a CVT. Like the Power Split hybrid, these motors 

control the ratio of engine speed to vehicle speed. But unlike the Power Split system, 

clutches allow the motors to be bypassed, which improves both the transmission’s torque 

capacity and efficiency for improved fuel economy at highway speeds. This type of 

system is used in the Chevy Tahoe Hybrid. 

In addition to providing the hybrid functions of engine stop and subsequent restart and 

regenerative braking, the 2MHEV allows for pure EV operation. The two 

motor/generators are bigger and more powerful than those in an ISG hybrid, allowing the 

engine to be run in efficient operating zones more often. For these reasons, the 2-mode 

system also provides very good fuel economy in city driving. The primary 

motor/generator is comparable in size to that in the PSHEV system, but the secondary 

motor/generator is larger. The 2-mode system cost is greater than that for the power split 

system due to the additional transmission complexity and secondary motor sizing. 

The battery pack for 2MHEV is assumed to be 300V NiMH for the time period 

considered in this rulemaking, as is used in current 2MHEV systems today. Their 

reliability is proven (having been in hybrids for over 10 years) and their cost is lower than 

Li Ion, so it is likely that the batteries will continue to be NiMH for the near future for 

hybrids that do not require high energy storage capability like a plug-in hybrid does.

Given the relatively large size of the 2 mode powertrain, this technology was assumed to 

be applicable to the Small through Large Truck/SUV classes. In the NPRM, a phase-in 

rate of 3 percent was assumed for 2 mode hybrids. The 2-modes have recently been 

introduced in the marketplace on a few vehicle platforms. The engineering resources that 

are needed both at the OEMs and Tier 1s to develop this across many more platforms are 

considerable, as discussed above for power split hybrids. For purposes of the final rule, 

the phase-in rate has been set to zero percent in MY 2011. 2 mode hybrid cost and 

effectiveness estimates will not be discussed here, given that the technology is not 

applied in MY 2011 beyond product plan levels in NHTSA’s analysis, and NHTSA will 

consider them further in its future rulemaking actions. 

The NPRM proposed that all of the hybrid technologies could be introduced during the 

redesign model year only, consistent with manufacturer’s views. Given this, for this final 

rule NHTSA has retained the redesign application timing. 

(x) Plug-In Hybrid 

Plug-In Hybrid Electric Vehicles (PHEV) are very similar to other strong hybrid electric 

vehicles, but with significant functional differences. The key distinguishing feature is the 

ability to charge the battery pack from an outside source of electricity (usually the electric 

grid). A PHEV would have a larger battery pack with greater energy capacity, and an 
V-133

ability to be discharged further (referred to as “depth of discharge”). No major 

manufacturer currently has a PHEV in production, although both GM and Toyota have 

publicly announced that they will launch plug-in hybrids in limited volumes by 2010. 

PHEVs offer a significant opportunity to displace petroleum-derived fuels with electricity 

from the electrical grid. The reduction in petroleum use depends on the electric-drive 

range capability and the vehicle usage (i.e., trip distance between recharging, ambient 

temperature, etc.). PHEVs can have a wide variation in the All Electric Range (AER) 

that they offer. Some PHEVs are of the “blended” type where the engine is on during 

most of the vehicle operation, but the proportion of electric energy that is used to propel 

the vehicle is significantly higher than that used in a PSHEV or 2MHEV. 

PHEVs were not projected to be in volume use in the NPRM, but due to confidential 

manufacturer product plans, PHEVs do, in fact, appear in limited volumes in the final 

rule analysis, and therefore low volume, unlearned costs are assumed. However, the 

manufacturer-stated production volumes of PHEVs are very low, so the phase-in cap for 

MY 2011 is zero—given the considerable engineering hurdles, the low availability of LiIon batteries in the MY 2011 time frame and the reasons discussed above for power split 

and 2 mode hybrids, NHTSA did not believe that PHEVs could be applied to more MY 

2011 vehicles beyond what was indicated in the product plans. Additionally, plug-in 

hybrid cost and effectiveness estimates will not be discussed here, given that the 

technology is not applied in MY 2011 beyond product plan levels in NHTSA’s analysis, 

and NHTSA will consider them further in its future rulemaking actions. The NPRM 

proposed that all of the hybrid technologies could be introduced during the redesign 

model year only, consistent with manufacturer’s views. Given this, for this final rule 

NHTSA has allowed application of PHEVs in redesign model years only. 

(e) Vehicle Technologies 

(i) Material Substitution (MS1, MS2, MS5)

The term “material substitution” encompasses a variety of techniques with a variety of 

costs and lead times. These techniques may include using lighter-weight and/or higherstrength materials, redesigning components, and size matching of components. Lighterweight materials involve using lower-density materials in vehicle components, such as 

replacing steel parts with aluminum or plastic. The use of higher-strength materials 

involves the substitution of one material for another that possesses higher strength and 

less weight. An example would be using high strength alloy steel versus cold rolled steel. 

Component redesign is an ongoing process to reduce costs and/or weight of components, 

while improving performance and reliability. The Aluminum Association commented 

that lightweight structures are a significant enabler for the new powertrain technologies. 

Smaller and less expensive powertrains are required and the combination of reduced 

power and weight reduction positively reinforce and result in optimal fuel economy 

performance. An example would be a subsystem replacing multiple components and 

mounting hardware. 

However, the cost of reducing weight is difficult to determine and depends upon the 

methods used. For example, a change in design that reduces weight on a new model may 
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or may not save money. On the other hand, material substitution can result in an increase 

in price per application of the technology if more expensive materials are used. As 

discussed further below, for purposes of this final rule, NHTSA has considered only 

vehicles weighing greater than 5,000 lbs (curb weight) for weight reduction through 

materials substitution. A typical BOM for Material Substitution would include primarily 

substitution of high strength steels for heavier steels or other structural, materials on a 

vehicle. This BOM was established for each class but was not adjusted for each class due 

to the fact that the vehicle technology of Material Substitution is already scaled by it 

being based on percent of curb weight at or over 5,000 lbs. 

In the NPRM, NHTSA estimated fuel economy effectiveness of a 2 percent incremental 

reduction in fuel consumption per each 3 percent reduction in vehicle weight. Nissan 

commented that NHTSA’s modeling of material substitution application was overly 

optimistic, but did not elaborate further. Confidential manufacturer comments in 

response to the NPRM did not provide standardized effectiveness estimates, but ranged 

from 3.3 to 3.9 percent mpg improvement for a 10 percent reduction in mass, to 0.20 to 

0.75 percent per 1 percent weight reduction, to 1 percent reduction on the FTP city cycle 

per 100 lbs reduced, with a maximum possible weight reduction of 5 percent. 

Bearing in mind that NHTSA only assumes material substitution for vehicles at or above 

5,000 lbs curb weight and based on manufacturer comments which together suggest an 

incremental improvement in fuel consumption of approximately 0.60 percent to 0.9 

percent per 3 percent reduction in material weight, NHTSA has estimated an incremental 

improvement in fuel consumption of 1 percent (corresponding to a 3 percent reduction in 

vehicle weight, or roughly 0.35 percent fuel consumption per 1 percent reduction in 

vehicle weight). This estimate is consistent with the majority of the manufacturer 

comments.

As for costs, in the NPRM NHTSA estimated incremental costs of $0.75 to $1.25 per 

pound reduced through material substitution. The costs for material substitution were not 

clearly commented on in the confidential manufacturer responses. Confidential 

manufacturer estimates ranged from $50 to $511 for 1 percent reduction, although in 

most cases the cost estimates were not for the entire range of substitution (1-5 percent) 

and did not provide any additional clarification on how they specifically applied to the 

material substitution technology. Consequently, for purposes of the final rule NHTSA 

retained the existing NPRM cost estimates with adjustments to 2007 dollar levels 

resulting in an incremental $1 to $2 per pound of substituted material, which applies to 

the MS1 and MS2 technology, and $2 to $4 per pound for the MS5 technology. Costs for 

material substitution are not adjusted by vehicle subclass, as the technology costs are 

based on a percentage of the vehicle weight (per pound) and limited to Medium and 

Large Truck/SUV Van subclasses above 5,000 lbs curb weight. 

The agency notes that comments from the Alliance and the Aluminum Association 

associated engine downsizing with weight reduction/material substitution and quoted 

effectiveness for this action as well. NHTSA considers engine downsizing separately 
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from typical material substitution efforts, and consequently did not include those cost and 

fuel economy effectiveness for this technology. 

In the NPRM, NHTSA assumed a 17 percent phase-in rate for material substitution. 

NHTSA received only one confidential manufacturer comment regarding material 

substitution phase-in percentage, suggesting 17 to 30 percent, but the agency notes that it 

generally received comments suggesting a non-linear phase-in rate for this technology, 

that would start at a rate lower than the current NPRM value and increase over time. In 

response to these comments, NHTSA revised the MY 2011 phase-in percentage to 5 

percent to account for lead time limitations. 

For material substitution technologies, neither volume-based cost reductions nor timebased cost reductions are applied. This technology does not employ a particular list of 

components to employ credible cost reduction.

In the NPRM, NHTSA assumed that material substitution (1 percent) could be applied 

during a redesign model year only. For this final rule, based on confidential 

manufacturer comments, NHTSA estimated that material substitution (1 percent) could 

be applied during either a refresh or a redesign model year, due to minimal design 

changes with minimal component or vehicle-level testing required. However, NHTSA 

retained the assumption that material substitution (2 percent and 5 percent) could be 

applied during redesign model year only, as in the NPRM, because the agency neither 

received comments to contradict this assumption nor found other data to substantiate a 

change. The technology title was changed from Material Substitution (3 percent) to 

Material Substitution (5 percent) to more accurately represent the cumulative amount for 

the technology.

(ii) Low Drag Brakes (LDB)

Low drag brakes reduce the sliding friction of disc brake pads on rotors when the brakes 

are not engaged because the brake pads are pulled away from the rotating rotor. A 

typical BOM for Low Drag Brakes would typically include changes in brake caliper 

speed by changing the brake control system, springs, etc. on a vehicles brake system. 

This BOM was established for each class and was not adjusted for each class due to the 

fact that the vehicle technology BOM would not change by class across vehicle classes. 

Confidential manufacturer comments in response to the NPRM indicated that most 

passenger cars have already adopted this technology, but that ladder frame trucks have 

not yet adopted this technology. Consequently, in the final rule this technology was 

assumed to be applicable only to the Large Performance Passenger Car and Medium and 

Large Truck classes. 

In the NPRM, NHTSA assumed an incremental improvement in fuel consumption of 1 to 

2 percent for low drag brakes. Confidential manufacturer comments submitted in 

response to the NPRM indicated an effective range of 0.5-1.0 percent for this technology 

and this range was applied in the final rule. As for costs, NHTSA assumed in the NPRM 

incremental costs of $85 to $90 for the addition of low drag brakes. For the final rule, 
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NHTSA took the average and adjusted it to 2007 dollars to establish an $89 final rule 

cost. 

The NPRM assumed an annual average phase-in rate for low drag brakes of 25 percent. 

For the final rule, the phase-in cap is 20 percent. No learning curve was applied in the 

NPRM but for the final rule, low drag brakes were considered a high volume, mature and 

stable technology, and thus time-based learning was applied. Low drag brakes are 

assumed in the final rule to be applicable at refresh cycle only. 

(iii) Low Rolling Resistance Tires (ROLL)

Tire rolling resistance is the frictional loss associated mainly with the energy dissipated 

in the deformation of the tires under load – and thus, influence fuel economy. Other tire 

design characteristics (e.g., materials, construction, and tread design) influence durability, 

traction control (both wet and dry grip), vehicle handling, and ride comfort in addition to 

rolling resistance. A typical low rolling resistance tires BOM would include: tire 

inflation pressure, material change, and constructions with less hysteresis, geometry 

changes (e.g., reduced aspect ratios), reduction in sidewall and tread deflection, potential 

spring and shock tuning. Low rolling resistance tires are applicable to all classes of 

vehicles, except for ladder frame light trucks and performance vehicles. NHTSA assumed 

that this technology should not be applied to vehicles in the Large truck class due to the 

increased traction and handling requirements for off-road and braking performance at 

payload and towing limits which cannot be met with low resistance tire designs. 

Likewise, this technology was not applied to vehicles in the Performance Car classes due 

to increased traction requirements for braking and handling which cannot be met with 

low roll resistance tire designs. Confidential manufacturer comments received regarding 

applicability of this technology to particular vehicle classes confirmed NHTSA’s 

assumption. 

In the NPRM, NHTSA assumed an incremental reduction in fuel consumption of 1 to 2 

percent for application of low rolling resistance tires. Confidential manufacturer 

comments varied widely and addressed the conflicting objectives of increasing safety by 

increasing rolling resistance for better tire traction, and improving fuel economy with 

lower rolling resistance tires that provide reduced traction. Confidential manufacturer 

comments suggested fuel consumption effectiveness of negative impact to a positive 0.1 

percent per year over the next five years from 2008, while other confidential 

manufacturer comments indicate that the percentage effectiveness of low rolling 

resistance tires would increase each year, although it would apply differently for 

performance classes. Confidential manufacturer comments also indicated that some 

manufacturers have already applied this technology and consequently would receive no 

further effectiveness from this technology. The 2002 NAS Report indicated that an 

assumed 10 percent rolling resistance reduction would provide an increase in fuel 

economy of 1 to 2 percent. NHTSA believes the NAS effectiveness is still valid and used 

1 to 2 percent incremental reduction in fuel consumption for application of low rolling 

resistance tires in the final rule.
V-137

NHTSA estimated the incremental cost of four low rolling resistance tires to be $6 per 

vehicle in the NPRM, independent of vehicle class, although not applicable to large 

trucks. NHTSA received few specific comments on the costs of applying low rolling 

resistance tires however confidential manufacturer comments that were received provided 

widely ranging and higher costs. NHTSA increased the range from the NPRM cost 

estimates to $6 to $9 per vehicle in the final rule. 

In the NPRM, NHTSA assumed an annual phase-in rate of 25 percent for low rolling 

resistance tires. Confidential manufacturer comments on the phase-in rate for low rolling 

resistance tires varied, with some suggesting that many vehicle classes already had high 

phase-in rates planned or accomplished. As discussed above, the comments also 

suggested a non-linear phase-in plan over the 5-year period. Confidential manufacturer 

data was in the 25-30 percent range. Based on confidential manufacturer comments 

received and NHTSA’s analysis, the final rule includes a phase-in cap for low rolling 

resistance tires with a phase-in rate of 20 percent for MY 2011. 

For low rolling resistant tire technology, neither volume-based cost reductions nor timebased cost reductions are applied. This technology is presumed to be significantly 

dependent on commodity raw material prices and to be priced independent of particular 

design or manufacturing savings.

In the NPRM, NHTSA assumed that low rolling resistance tires could be applied during 

any model year. However, based on confidential manufacturer comments NHTSA 

recognizes that there are some vehicle attribute impacts which may result from 

application of low rolling resistance tires, such as changes to vehicle dynamics and 

braking. Vehicle validation testing for safety and vehicle attribute prove-out is not 

usually planned for every model year, so NHTSA assumed that this technology can be 

applied during a redesign or refresh model year for purposes of the final rule. 

(iv) Front or Secondary Axle Disconnect for Four-Wheel Drive Systems (SAX)

To provide shift-on-the-fly capabilities, reduce wear and tear on secondary axles, and 

improve performance and fuel economy, many part-time four-wheel drive (4WD) 

systems use some type of axle disconnect. Axle disconnects are typically used on 4WD 

vehicles with two-wheel drive (2WD) operating modes. When shifting from 2WD to 

4WD “on the fly” (while moving), the front axle disconnect couples the front driveshaft

to the front differential side gear only when the transfer case’s synchronizing mechanism 

has spun the front driveshaft, transfer case chain or gear set and differential carrier up to 

the same speed as the rear driveshaft. 4WD systems that have axle disconnect typically 

do not have either manual- or automatic-locking hubs. For example, to isolate the front 

wheels from the rest of the front driveline, front axle disconnects use a sliding sleeve to 

connect or disconnect an axle shaft from the front differential side gear. The 

effectiveness to fuel efficiency is created by reducing inertial, chain, bearing and gear 

losses (parasitic losses). 

Full time 4WD or all-wheel-drive (AWD) systems used for on-road performance and 

safety do not use axle disconnect systems due to the need for instantaneous activation of 
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torque to wheels, and the agency is not aware of any manufacturer or suppliers who are 

developing a system to allow secondary axle disconnect suitable for use on AWD 

systems at this time. Secondary axle disconnect technology is primarily found on solid 

axle 4WD systems and not on the transaxle and/or independent axle systems typically 

found in AWD vehicles; thus, the application of this technology to AWD systems has not 

been considered for purposes of this rulemaking. The technology will be evaluated in 

future rulemakings. 

Vehicle technology BOM information was not adjusted by vehicle classes due to the fact 

that the vehicle technology is limited to transfer case and front axle design changes. 

Scaling of components might be impacted but the components themselves will be the 

same. This is consistent with NHTSA’s assumptions in the NPRM, and is supported by 

comments from confidential supplier and manufacturers. Secondary Axle Disconnect 

BOM typically involves a transfer case which includes electronic solenoid with clutch 

system to disconnect front drive and using axle mounted vacuum or electric disconnect 

that still allows driveshaft rotation without connection to wheel ends. 

In the NPRM, NHTSA employed “unibody” and “ladder frame” terms to differentiate 

application of this technology, and had suggested “unibody” AWD systems could apply 

this same technology. In actuality, most 4WD vehicles are “ladder frame” technology 

and AWD are “unibody” designs (which for the reasons stated above will not be 

considered for this technology). Ladder frame technology is typically associated with 

greater payload, towing, and off-road capability, whereas unibody designs are typically 

used in smaller, usually front-wheel drive vehicles, and are typically not associated with 

higher payload, towing, and off-road use. For the final rule, NHTSA removed these 

vehicle design criteria since it is not a requirement to incorporate axle disconnect 

technology, only a historical design point and vehicle manufacturers should not be 

limited to a specific vehicle or chassis configuration to apply this technology. Therefore, 

this technology is applicable to 4WD vehicles in all vehicle classes (independent of 

chassis or frame design). 

In the NPRM, NHTSA estimated an incremental reduction in fuel consumption of 1 to 

1.5 percent for axle disconnect. Confidential manufacturer comments suggested an 

incremental effectiveness of 1 to 1.5 percent. Supported by this confidential 

manufacturer data, NHTSA maintained an incremental effectiveness of 1 to 1.5 percent 

for axle disconnect for the final rule. 

As for costs, the NPRM estimated the incremental cost for adding axle disconnect 

technology at $114 for 4WD systems and the $676 estimate was for the AWD systems 

which are not applied in the final rule. NHTSA received no specific comments on costs 

for this technology and found no additional sources to support a change from this value 

for the 4WD value of $114, so for purposes of the final rule, NHTSA revised the $114 

figure to 2007 dollars to establish a $117 final rule cost. 

In the NPRM, NHTSA assumed a phase-in cap of 17 percent for secondary axle 

disconnect for each model year covered by the rulemaking. No specific comments were 
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received regarding the phase-in rate for this technology, but as discussed above, 

manufacturers generally argued for a non-linear phase-in plan over the 5-year period 

covered by the rulemaking. Based on general comments received and NHTSA’s analysis, 

the final rule includes an average annual phase-in rate for secondary axle disconnect of 

17 percent for MY 2011. 

In the NPRM, NHTSA assumed a volume-based learning curve factor of 20 percent for 

secondary axle disconnect. For the final rule, secondary axle disconnect learning was 

established as time-based due to confidential manufacturer data demonstrating that this is 

a mature technology, such that additional volumes will provide no additional advantage 

for incorporation by manufacturers.

In the NPRM, NHTSA assumed that secondary axle disconnect could be applied to a 

vehicle either during refresh or redesign model years. NHTSA received no comments 

and found no sources to disagree with this assumption, and since testing to validate the 

functional requirements and vehicle attribute prove-out testing is usually not planned for 

every model year, NHTSA has retained this assumption for the final rule. 

(v) Aerodynamic Drag Reduction (AERO)

Several factors affect a vehicle’s aerodynamic drag and the resulting power required to 

move it through the air. While these values change with air density and the square and 

cube of vehicle speed, respectively, the overall drag effect is determined by the product 

of its frontal area and drag coefficient. Reductions in these quantities can therefore 

reduce fuel consumption. While frontal areas tend to be relatively similar within a 

vehicle class (mostly due to market-competitive size requirements), significant variations 

in drag coefficient can be observed. Significant fleet aerodynamic drag reductions may 

require incorporation into a manufacturer’s new model phase-in schedules depending on 

the mix of vehicle classes distributed across the manufacturer’s lineup. However, 

shorter-term aerodynamic reductions, with less of a fuel economy effectiveness, may be 

achieved through the use of revised exterior components (typically at a model refresh in 

mid-cycle) and add-on devices that are in general circulation today. The latter list would 

include revised front and rear fascias, modified front air dams and rear valances, addition 

of rear deck lips and underbody panels, and more efficient exterior mirrors. 

Vehicle technology BOM information was not adjusted by vehicle classes due to the fact 

that Aero Drag Reductions are already scaled based on percent overall vehicle coefficient 

of drag CdA. Aero Drag Reduction BOM could include (but would not be limited to) the 

following components or subsystems: underbody covers, front lower air dams, overall 

front fascia changes, headlights, hood, fenders, grill, windshield angle, A-Pillar angle, 

door seal gaps, roof (which would both be high impact and very high cost), side view 

mirrors, door handles (low impact), ride height, rear deck lip, wheels, wheel covers, and 

optimizing the cooling flow path. 

In the NPRM, NHTSA estimated an incremental aerodynamic drag reduction of 20 

percent for cars, and 10 percent for trucks. Confidential manufacturer comments 

received indicated that the 20 percent reduction for cars in the NPRM may have been 
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overly optimistic, as significant changes in aero drag have already been applied to those 

vehicle classes. However, confidential manufacturer comments agreed with the 10 

percent aerodynamic drag reduction for trucks, since there are still significant 

opportunities to improve aero drag in trucks designed for truck-related utility. The Sierra 

Research study submitted by the Alliance concluded that a 10 percent incremental 

aerodynamic drag reduction for mid-size cars gives a 1.5 percent improvement in vehicle 

fuel economy. Thus, for purposes of the final rule, NHTSA has estimated that a fleet 

average of 10 percent total aerodynamic drag reduction is attainable (with a caveat for 

“high-performance” vehicles described below), which equates to incremental reductions 

in fuel consumption of 2 percent and 3 percent for cars and trucks, respectively. These 

numbers are in agreement with publicly-available technical literature205 and are supported 

by confidential manufacturer information. Performance car classes are excluded from 

this technology improvement because they have largely applied this technology already. 

As for costs, in the NPRM NHTSA assumed an incremental cost of $0 to $75 for aero 

drag reduction on both cars and trucks. After reviewing the 2008 Martec Report, 

however, NHTSA concluded that a lower-bound cost of $0 was not supportable. NHTSA 

replaced the lower-bound cost with $40 (non-RPE) based on the assumptions that the 

underbody cover and acoustic covers described in the Martec report approximates the 

cost for one large underbody cover as might be required for minimal aero drag reduction 

actions.206 The upper limit was determined by updating the NPRM upper cost to 2007 

dollars and applying an RPE uplift thereby establishing the incremental cost, independent 

of vehicle class, to range from $60 to $116 (RPE) for the final rule 

In the NPRM, NHTSA assumed a 17 percent phase-in rate for aero drag reduction for 

each model year covered by the rulemaking. No specific comments were received 

regarding the phase-in rate for this technology, but as discussed above, manufacturers 

generally argued for a non-linear phase-in plan over a 5-year period. Based on comments 

received and NHTSA’s analysis, the final rule includes an phase-in rate for aero drag 

reduction of 17 percent in MY 2011. Neither volume-based cost reductions nor timebased cost reductions are applied. In the NPRM, NHTSA assumed that aero drag 

reduction could be applied in either a refresh or a redesign model year and that 

assumption has been retained for the final rule. 

(f) Technologies considered but not included in the final rule analysis

Although discussed and considered as potentially viable in the NPRM, NHTSA has 

determined that three technologies will be unavailable in the time frame considered. 

These technologies have been identified as either pre-emerging or not technologically 

feasible. Pre-emerging technologies are those that are still in the research phase at this 

time, and which are not expected to be under development for production vehicles for 

 

205 Sue Elliott-Sink, “Improving Aerodynamics to Boost Fuel Economy,” May 2, 2006. Available at

http://www.edmunds.com/advice/fueleconomy/articles/106954/article.html (last accessed Oct. 5, 2008). 198 2008 Martec Report, at 25. NHTSA also assumed that the cost of fuel pulsation dampening technology 

noted in the Martec report grouped with the underbody cover and acoustic covers does not significantly 

impact the $40 cost as fuel pulsation dampening technology is very low in cost relative to the other actions. 

Therefore NHTSA did not modify the $40 estimate.
V-141

several years. In another case, the technology depends on a fuel that is not readily 

available. Thus, for the reasons discussed below, these technologies were not considered 

in NHTSA’s analysis for the final rule. The technologies are camless valve actuation 

(CVA), lean burn gasoline direct injection (LBDI), homogeneous charge compression 

ignition (HCCI), and electric assist turbocharging. Although not applied in this 

rulemaking, NHTSA will continue to monitor the industry and system suppliers for 

progress on these technologies, and should they become available, consider them for use 

in any future rulemaking activity. 

(i) Camless Valve Actuation

Camless valve actuation relies on electromechanical actuators instead of camshafts to 

open and close the cylinder valves. When electromechanical actuators are used to replace 

cams and coupled with sensors and microprocessor controls, valve timing and lift can be 

optimized over all conditions. An engine valvetrain that operates independently of any 

mechanical means provides the ultimate in flexibility for intake and exhaust timing and 

lift optimization. With it comes infinite valve overlap variability, the rapid response 

required to change between operating modes (such as HCCI and GDI), intake valve 

throttling, cylinder deactivation, and elimination of the camshafts (reduced friction). This 

level of control can enable even further incremental reductions in fuel consumption. 

As noted in the NPRM, this technology has been under research for many decades and 

although some progress is being made, NHTSA has found no evidence to support that the 

technology can be successfully implemented, costed, or have defined fuel consumption 

effectiveness at this time. 

(ii) Lean-Burn Gasoline Direct Injection Technology

One way to improve an engine’s thermodynamic efficiency dramatically is by operating 

at a lean air-fuel mixture (excess air). Fuel system improvements, changes in combustion 

chamber design and repositioning of the injectors have allowed for better air/fuel mixing 

and combustion efficiency. There is currently a shift from wall-guided injection to spray 

guided injection, which improves injection precision and targeting towards the spark 

plug, increasing lean combustion stability. Combined with advances in NOx aftertreatment, lean-burn GDI engines may eventually be a possibility in North America. 

However, as noted in the NPRM, a key technical requirement for lean-burn GDI engines 

to meet EPA’s Tier 2 NOx emissions levels is the availability of low-sulfur gasoline, 

which is projected to be unavailable during the time frame considered. Therefore the 

technology was not applied in the final rule 

(iii) Homogeneous Charge Compression Ignition

Homogeneous charge compression ignition (HCCI), also referred to as controlled auto 

ignition (CAI), is an alternate engine operating mode that does not rely on a spark event 

to initiate combustion. The principles are more closely aligned with a diesel combustion 

cycle, in which the compressed charge exceeds a temperature and pressure necessary for 

spontaneous ignition. The resulting burn is much shorter in duration with higher thermal 

efficiency. Shorter combustion times and higher EGR tolerance permit very high 
V-142

compression ratios (which also increase thermodynamic efficiency), and additionally, 

pumping losses are reduced because the engine can run unthrottled. 

NHTSA noted in the NPRM that several manufacturers had made public statements about 

the viability of incorporating HCCI into production vehicles over the next 10 years. 

Upon further review of confidential product plan information, and reviewing comments 

received in response to the NPRM, NHTSA has determined the technology will not be 

available within the time frame considered. Consequently, the technology was not 

applied in the final rule. 

(iv) Electric Assist Turbocharging

The Alliance commented that global development of electric assist turbocharging has not 

demonstrated the fuel efficiency effectiveness of a 12V EAT up to 2kW power levels 

since the 2004 NESCCAF study, and stated that it saw remote probability of its 

application over the next decade.207 While hybrid vehicles lower the incremental 

hardware requirements for higher-voltage, higher-power EAT systems, NHTSA believes 

that significant development work is required to demonstrate effective systems and that 

implementation in significant volumes will not occur in the time frame considered. Thus, 

this technology was not included on the decision trees. 

E. Cost and effectiveness tables

The tables representing the Volpe model input files for incremental technology costs by 

vehicle subclass are presented below. The tables have been divided into passenger cars, 

performance passenger cars, and light trucks to make them easier to read.

 

207 NHTSA-2008-0089-0169.1, at 41. 
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Table V-15. Technology Incremental Cost Estimates, Passenger Cars 

Subcompac Compact Midsize Large

Car Car Car Car

Inline 4 Inline 4 Inline 4 V6

Low Friction Lubricants LUB 5 5 5 5

Engine Friction Reduction EFR 52 - 196 52 - 196 52 - 196 78 - 294

VVT - Coupled Cam Phasing (CCP) on SOHC CCPS 61 61 61 122

Discrete Variable Valve Lift (DVVL) on SOHC DVVLS 201 201 201 306

Cylinder Deactivation on SOHC DEACS n.a. n.a. n.a. 75

VVT - Intake Cam Phasing (ICP) ICP 61 61 61 122

VVT - Dual Cam Phasing (DCP) DCP 61 61 61 122

Discrete Variable Valve Lift (DVVL) on DOHC DVVLD 201 201 201 306

Continuously Variable Valve Lift (CVVL) CVVL 306 306 306 432

Cylinder Deactivation on DOHC DEACD n.a. n.a. n.a. 75

Cylinder Deactivation on OHV DEACO n.a. n.a. n.a. 306

VVT - Coupled Cam Phasing (CCP) on OHV CCPO 61 61 61 122

Discrete Variable Valve Lift (DVVL) on OHV DVVLO 201 201 201 76

Conversion to DOHC with DCP CDOHC 373 373 373 590

Stoichiometric Gasoline Direct Injection (GDI) SGDI 293 - 440 293 - 440 293 - 440 384 - 558

Turbocharging and Downsizing TRBDS 1223 1223 1223 822

Conversion to Diesel following CBRST DSLC 2,963 - 

3,254

2,963 - 

3,254

2,963 - 

3,254

4,105 - 

4,490

Conversion to Diesel following TRBDS DSLT 1,567 - 

1,858

1,567 - 

1,858

1,567 - 

1,858

3,110 - 

3,495

Electric Power Steering EPS 105 - 120 105 - 120 105 - 120 105 - 120

Improved Accessories IACC 173 - 211 173 - 211 173 - 211 173 - 211

12V Micro-Hybrid MHEV 372 408 453 490

Higher Voltage/Improved Alternator HVIA 84 84 84 84

Integrated Starter Generator (Belt/Crank) ISG 1713 2019 2190 2386

6-Speed Manual/Improved Internals 6MAN 338 338 338 338

Improved Auto. Trans. Controls/Externals IATC 59 59 59 59

Continuously Variable Transmission CVT 300 300 300 300

6/7/8-Speed Auto. Trans with Improved Internals NAUTO 323 323 323 323

Dual Clutch or Automated Manual Transmission DCTAM 68 68 218 218

Material Substitution (1%) MS1 n.a. n.a. n.a. n.a.

Material Substitution (2%) MS2 n.a. n.a. n.a. n.a.

Material Substitution (5%) MS5 n.a. n.a. n.a. n.a.

Low Rolling Resistance Tires ROLL 6 - 9 6 - 9 6 - 9 6 - 9

Low Drag Brakes LDB n.a. n.a. n.a. n.a.

Secondary Axle Disconnect SAX 117 117 117 117

Aero Drag Reduction AERO 60 - 116 60 - 116 60 - 116 60 - 116

Nominal Baseline Engine (For Cost Basis)

VEHICLE TECHNOLOGY RETAIL PRICE EQUIVALENT INCREMENTAL COSTS PER VEHICLE 

($) BY VEHICLE TECHNICAL CLASS - PASSENGER CARS
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Table V-16. Technology Incremental Cost Estimates, Performance Passenger Cars 

Perform. Perform. Perform. Perform.

Subcomp. Compact Midsize Large

Car Car Car Car

Inline 4 V6 V6 V8

Low Friction Lubricants LUB 5555

Engine Friction Reduction EFR 52 - 196 78 - 294 78 - 294 104 - 392

VVT - Coupled Cam Phasing (CCP) on SOHC CCPS 61 122 122 122

Discrete Variable Valve Lift (DVVL) on SOHC DVVLS 201 306 306 396

Cylinder Deactivation on SOHC DEACS n.a. 75 75 75

VVT - Intake Cam Phasing (ICP) ICP 61 122 122 122

VVT - Dual Cam Phasing (DCP) DCP 61 122 122 122

Discrete Variable Valve Lift (DVVL) on DOHC DVVLD 201 306 306 396

Continuously Variable Valve Lift (CVVL) CVVL 306 432 432 582

Cylinder Deactivation on DOHC DEACD n.a. 75 75 75

Cylinder Deactivation on OHV DEACO n.a. 306 306 400

VVT - Coupled Cam Phasing (CCP) on OHV CCPO 61 122 122 122

Discrete Variable Valve Lift (DVVL) on OHV DVVLO 201 76 76 76

Conversion to DOHC with DCP CDOHC 373 590 590 746

Stoichiometric Gasoline Direct Injection (GDI) SGDI 293 - 440 384 - 558 384 - 558 512 - 744

Turbocharging and Downsizing TRBDS 1,223 822 822 1,229

Conversion to Diesel following CBRST DSLC 2,963 - 

3,254

4,105 - 

4,490

4,105 - 

4,490

5,125 - 

5,617

Conversion to Diesel following TRBDS DSLT 1,567 - 

1,858

3,110 - 

3,495

3,110 - 

3,495

3,723 - 

4,215

Electric Power Steering EPS 105 - 120 105 - 120 105 - 120 105 - 120

Improved Accessories IACC 173 - 211 173 - 211 173 - 211 173 - 211

12V Micro-Hybrid MHEV 406 443 494 549

Higher Voltage/Improved Alternator HVIA 84 84 84 84

Integrated Starter Generator (Belt/Crank) ISG

1,789 - 

1,864 2,054 2,183 2,351

6-Speed Manual/Improved Internals 6MAN 338 338 338 338

Improved Auto. Trans. Controls/Externals IATC 59 59 59 59

Continuously Variable Transmission CVT 300 300 300 n.a.

6/7/8-Speed Auto. Trans with Improved Internals NAUTO 323 - 638 323 - 638 323 - 638 323 - 638

Dual Clutch or Automated Manual Transmission DCTAM (97) - 218 (97) - 218 (97) - 218 (97) - 218

Material Substitution (1%) MS1 n.a. n.a. n.a. n.a.

Material Substitution (2%) MS2 n.a. n.a. n.a. n.a.

Material Substitution (5%) MS5 n.a. n.a. n.a. n.a.

Low Rolling Resistance Tires ROLL n.a. n.a. n.a. n.a.

Low Drag Brakes LDB n.a. n.a. n.a. n.a.

Secondary Axle Disconnect SAX 117 117 117 117

Aero Drag Reduction AERO 60 - 116 60 - 116 60 - 116 60 - 116

Nominal Baseline Engine (For Cost Basis)

VEHICLE TECHNOLOGY RETAIL PRICE EQUIVALENT INCREMENTAL COSTS PER VEHICLE 

($) BY VEHICLE TECHNICAL CLASS - PERFORMANCE CARS
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Table V-17. Technology Incremental Cost Estimates, Light Trucks 

Minivan Small Midsize Large

LT LT LT LT

V6 Inline 4 V6 V8

Low Friction Lubricants LUB 5 5 5 5

Engine Friction Reduction EFR 78 - 294 52 - 196 78 - 294 104 - 392

VVT - Coupled Cam Phasing (CCP) on SOHC CCPS 122 61 122 122

Discrete Variable Valve Lift (DVVL) on SOHC DVVLS 306 201 306 396

Cylinder Deactivation on SOHC DEACS 75 n.a. 75 75

VVT - Intake Cam Phasing (ICP) ICP 122 61 122 122

VVT - Dual Cam Phasing (DCP) DCP 122 61 122 122

Discrete Variable Valve Lift (DVVL) on DOHC DVVLD 306 201 306 396

Continuously Variable Valve Lift (CVVL) CVVL 432 306 432 582

Cylinder Deactivation on DOHC DEACD 75 n.a. 75 75

Cylinder Deactivation on OHV DEACO 306 n.a. 306 400

VVT - Coupled Cam Phasing (CCP) on OHV CCPO 122 61 122 122

Discrete Variable Valve Lift (DVVL) on OHV DVVLO 76 201 76 76

Conversion to DOHC with DCP CDOHC 590 373 590 746

Stoichiometric Gasoline Direct Injection (GDI) SGDI 384 - 558 293 - 440 384 - 558 512 - 744

Turbocharging and Downsizing TRBDS 822 1223 822 1229

Conversion to Diesel following CBRST DSLC 4,105 - 

4,490

2,963 - 

3,254

4,105 - 

4,490

5,125 - 

5,617

Conversion to Diesel following TRBDS DSLT 3,110 - 

3,495

1,567 - 

1,858

3,110 - 

3,495

3,723 - 

4,215

Electric Power Steering EPS 105 - 120 105 - 120 105 - 120 n.a.

Improved Accessories IACC 173 - 211 173 - 211 n.a. n.a.

12V Micro-Hybrid MHEV 490 427 502 n.a.

Higher Voltage/Improved Alternator HVIA 84 84 84 n.a.

Integrated Starter Generator (Belt/Crank) ISG 2386 2029 2457 n.a.

6-Speed Manual/Improved Internals 6MAN 338 338 338 338

Improved Auto. Trans. Controls/Externals IATC 59 59 59 59

Continuously Variable Transmission CVT 300 300 n.a. n.a.

6/7/8-Speed Auto. Trans with Improved Internals NAUTO 323 323 - 638 323 - 638 323 - 638

Dual Clutch or Automated Manual Transmission DCTAM 218 (97) - 218 (97) - 218 (97) - 218

Material Substitution (1%) MS1 n.a. n.a. 1 - 2 1 - 2

Material Substitution (2%) MS2 n.a. n.a. 1 - 2 1 - 2

Material Substitution (5%) MS5 n.a. n.a. 2 - 4 2 - 4

Low Rolling Resistance Tires ROLL 6 - 9 6 - 9 6 - 9 n.a.

Low Drag Brakes LDB n.a. n.a. 89 89

Secondary Axle Disconnect SAX 117 117 117 117

Aero Drag Reduction AERO 60 - 116 60 - 116 60 - 116 60 - 116

Nominal Baseline Engine (For Cost Basis)

VEHICLE TECHNOLOGY RETAIL PRICE EQUIVALENT INCREMENTAL COSTS PER VEHICLE 

($) BY VEHICLE TECHNICAL CLASS - LIGHT TRUCKS
V-146

The tables representing the Volpe model input files for incremental technology 

effectiveness values by vehicle subclass are presented below. The tables have been 

divided into passenger cars, performance passenger cars, and light trucks to make them 

easier to read.
Table V-18. Technology Incremental Effectiveness Estimates, Passenger Cars 

Subcompact Compact Midsize Large

Car Car Car Car

Inline 4 Inline 4 Inline 4 V6

Low Friction Lubricants LUB 0.5 0.5 0.5 0.5

Engine Friction Reduction EFR 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

VVT - Coupled Cam Phasing (CCP) on SOHC CCPS 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0

Discrete Variable Valve Lift (DVVL) on SOHC DVVLS 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0

Cylinder Deactivation on SOHC DEACS n.a. n.a. n.a. 2.5 - 3.0

VVT - Intake Cam Phasing (ICP) ICP 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

VVT - Dual Cam Phasing (DCP) DCP 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0

Discrete Variable Valve Lift (DVVL) on DOHC DVVLD 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0

Continuously Variable Valve Lift (CVVL) CVVL 1.5 - 3.5 1.5 - 3.5 1.5 - 3.5 1.5 - 3.5

Cylinder Deactivation on DOHC DEACD n.a. n.a. n.a. 0 - 0.5

Cylinder Deactivation on OHV DEACO n.a. n.a. n.a. 3.9 - 5.5

VVT - Coupled Cam Phasing (CCP) on OHV CCPO 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5

Discrete Variable Valve Lift (DVVL) on OHV DVVLO 0.5 - 2.6 0.5 - 2.6 0.5 - 2.6 0.5 - 2.6

Conversion to DOHC with DCP CDOHC 1.0 - 2.6 1.0 - 2.6 1.0 - 2.6 1.0 - 2.6

Stoichiometric Gasoline Direct Injection (GDI) SGDI 1.9 - 2.9 1.9 - 2.9 1.9 - 2.9 1.9 - 2.9

Turbocharging and Downsizing TRBDS 4.5 - 5.2 4.5 - 5.2 4.5 - 5.2 2.1 - 2.2

Conversion to Diesel following CBRST DSLC 15.0 - 15.3 15.0 - 15.3 13.8 - 14.2 11.1 - 12.0

Conversion to Diesel following TRBDS DSLT 6.6 - 7.7 6.6 - 7.7 5.3 - 6.5 5.3 - 6.5

Electric Power Steering EPS 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

Improved Accessories IACC 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

12V Micro-Hybrid MHEV 1.0 - 2.9 1.0 - 2.9 3.4 - 4.0 3.4 - 4.0

Higher Voltage/Improved Alternator HVIA 0.2 - 0.9 0.2 - 0.9 0.2 - 0.6 0.2 - 0.6

Integrated Starter Generator (Belt/Crank) ISG 5.7 - 6.5 5.7 - 6.5 5.7 - 6.5 5.7 - 6.5

6-Speed Manual/Improved Internals 6MAN 1 1 1 1

Improved Auto. Trans. Controls/Externals IATC 1.5 - 2.5 1.5 - 2.5 1.5 - 2.5 1.5 - 2.5

Continuously Variable Transmission CVT 0.7 - 2.0 0.7 - 2.0 0.7 - 2.0 0.7 - 2.0

6/7/8-Speed Auto. Trans with Improved Internals NAUTO 1.4 - 3.4 1.4 - 3.4 1.4 - 3.4 1.4 - 3.4

Dual Clutch or Automated Manual Transmission DCTAM 5.5 - 7.5 5.5 - 7.5 2.7 - 4.1 2.7 - 4.1

Material Substitution (1%) MS1 n.a. n.a. n.a. n.a.

Material Substitution (2%) MS2 n.a. n.a. n.a. n.a.

Material Substitution (5%) MS5 n.a. n.a. n.a. n.a.

Low Rolling Resistance Tires ROLL 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

Low Drag Brakes LDB n.a. n.a. n.a. n.a.

Secondary Axle Disconnect SAX 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5

Aero Drag Reduction AERO 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0

Nominal Baseline Engine (For Cost Basis)

VEHICLE TECHNOLOGY INCREMENTAL FUEL CONSUMPTION REDUCTION (-%) BY VEHICLE 

TECHNOLOGY CLASS - PASSENGER CARS
Table V-19. Technology Incremental Effectiveness Estimates, 

Performance Cars 

Perform. Perform. Perform. Perform.

Subcomp. Compact Midsize Large

Car Car Car Car

Inline 4 V6 V6 V8

Low Friction Lubricants LUB 0.5 0.5 0.5 0.5

Engine Friction Reduction EFR 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

VVT - Coupled Cam Phasing (CCP) on SOHC CCPS 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0

Discrete Variable Valve Lift (DVVL) on SOHC DVVLS 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0

Cylinder Deactivation on SOHC DEACS n.a. 2.5 - 3.0 2.5 - 3.0 2.5 - 3.0

VVT - Intake Cam Phasing (ICP) ICP 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

VVT - Dual Cam Phasing (DCP) DCP 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0

Discrete Variable Valve Lift (DVVL) on DOHC DVVLD 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0

Continuously Variable Valve Lift (CVVL) CVVL 1.5 - 3.5 1.5 - 3.5 1.5 - 3.5 1.5 - 3.5

Cylinder Deactivation on DOHC DEACD n.a. 0 - 0.5 0 - 0.5 0 - 0.5

Cylinder Deactivation on OHV DEACO n.a. 3.9 - 5.5 3.9 - 5.5 3.9 - 5.5

VVT - Coupled Cam Phasing (CCP) on OHV CCPO 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5

Discrete Variable Valve Lift (DVVL) on OHV DVVLO 0.5 - 2.6 0.5 - 2.6 0.5 - 2.6 0.5 - 2.6

Conversion to DOHC with DCP CDOHC 1.0 - 2.6 1.0 - 2.6 1.0 - 2.6 1.0 - 2.6

Stoichiometric Gasoline Direct Injection (GDI) SGDI 1.9 - 2.9 1.9 - 2.9 1.9 - 2.9 1.9 - 2.9

Turbocharging and Downsizing TRBDS 4.5 - 5.2 2.1 - 2.2 2.1 - 2.2 2.1 - 2.2

Conversion to Diesel following CBRST DSLC 15.0 - 15.3 12.3 - 13.1 11.1 - 12.0 11.1 - 12.0

Conversion to Diesel following TRBDS DSLT 6.6 - 7.7 6.6 - 7.7 5.3 - 6.5 5.3 - 6.5

Electric Power Steering EPS 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

Improved Accessories IACC 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

12V Micro-Hybrid MHEV 1.0 - 2.9 1.2 - 2.9 3.4 - 4.0 3.4 - 4.0

Higher Voltage/Improved Alternator HVIA 0.2 - 0.9 0.2 - 0.9 0.2 - 0.6 0.2 - 0.6

Integrated Starter Generator (Belt/Crank) ISG 1.8 - 2.6 1.8 - 2.6 1.8 - 1.9 1.8 - 2.6

6-Speed Manual/Improved Internals 6MAN 0.5 0.5 0.5 0.5

Improved Auto. Trans. Controls/Externals IATC 1.5 - 2.5 1.5 - 2.5 1.5 - 2.5 1.5 - 2.5

Continuously Variable Transmission CVT 0.7 - 2.0 0.7 - 2.0 0.7 - 2.0 n.a.

6/7/8-Speed Auto. Trans with Improved Internals NAUTO 1.4 - 3.4 1.4 - 3.4 1.4 - 3.4 1.4 - 3.4

Dual Clutch or Automated Manual Transmission DCTAM 2.7 - 4.1 2.7 - 4.1 2.7 - 4.1 2.7 - 4.1

Material Substitution (1%) MS1 n.a. n.a. n.a. n.a.

Material Substitution (2%) MS2 n.a. n.a. n.a. n.a.

Material Substitution (5%) MS5 n.a. n.a. n.a. n.a.

Low Rolling Resistance Tires ROLL n.a. n.a. n.a. n.a.

Low Drag Brakes LDB n.a. n.a. n.a. n.a.

Secondary Axle Disconnect SAX 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5

Aero Drag Reduction AERO 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0

Nominal Baseline Engine (For Cost Basis)

VEHICLE TECHNOLOGY INCREMENTAL FUEL CONSUMPTION REDUCTION (-%) BY VEHICLE 

TECHNOLOGY CLASS - PERFORMANCE CARS
Table V-20. Technology Incremental Effectiveness Estimates, Light Trucks 

Minivan Small Midsize Large

LT LT LT LT

V6 Inline 4 V6 V8

Low Friction Lubricants LUB 0.5 0.5 0.5 0.5

Engine Friction Reduction EFR 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

VVT - Coupled Cam Phasing (CCP) on SOHC CCPS 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0

Discrete Variable Valve Lift (DVVL) on SOHC DVVLS 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0

Cylinder Deactivation on SOHC DEACS 2.5 - 3.0 n.a. 2.5 - 3.0 2.5 - 3.0

VVT - Intake Cam Phasing (ICP) ICP 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0

VVT - Dual Cam Phasing (DCP) DCP 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0

Discrete Variable Valve Lift (DVVL) on DOHC DVVLD 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0 1.0 - 3.0

Continuously Variable Valve Lift (CVVL) CVVL 1.5 - 3.5 1.5 - 3.5 1.5 - 3.5 1.5 - 3.5

Cylinder Deactivation on DOHC DEACD 0 - 0.5 n.a. 0 - 0.5 0 - 0.5

Cylinder Deactivation on OHV DEACO 3.9 - 5.5 n.a. 3.9 - 5.5 3.9 - 5.5

VVT - Coupled Cam Phasing (CCP) on OHV CCPO 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5

Discrete Variable Valve Lift (DVVL) on OHV DVVLO 0.5 - 2.6 0.5 - 2.6 0.5 - 2.6 0.5 - 2.6

Conversion to DOHC with DCP CDOHC 1.0 - 2.6 1.0 - 2.6 1.0 - 2.6 1.0 - 2.6

Stoichiometric Gasoline Direct Injection (GDI) SGDI 1.9 - 2.9 1.9 - 2.9 1.9 - 2.9 1.9 - 2.9

Turbocharging and Downsizing TRBDS 2.1 - 2.2 4.5 - 5.2 2.1 - 2.2 2.1 - 2.2

Conversion to Diesel following CBRST DSLC 11.1 - 12.0 13.8 - 14.2 9.9 - 12.0 10.0 - 10.9

Conversion to Diesel following TRBDS DSLT 5.3 - 6.5 5.3 - 6.5 4.0 - 6.5 4.0 - 5.3

Electric Power Steering EPS 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 n.a.

Improved Accessories IACC 1.0 - 2.0 1.0 - 2.0 n.a. n.a.

12V Micro-Hybrid MHEV 3.4 - 4.0 1.0 - 2.9 3.4 - 4.0 n.a.

Higher Voltage/Improved Alternator HVIA 0.2 - 0.6 0.2 - 0.9 0.2 - 0.6 n.a.

Integrated Starter Generator (Belt/Crank) ISG 5.7 - 6.5 5.7 - 6.5 5.7 - 6.5 n.a.

6-Speed Manual/Improved Internals 6MAN 0.5 0.5 0.5 0.5

Improved Auto. Trans. Controls/Externals IATC 1.5 - 2.5 1.5 - 2.5 1.5 - 2.5 1.5 - 2.5

Continuously Variable Transmission CVT 0.7 - 2.0 0.7 - 2.0 n.a. n.a.

6/7/8-Speed Auto. Trans with Improved Internals NAUTO 1.4 - 3.4 1.4 - 3.4 1.4 - 3.4 1.4 - 3.4

Dual Clutch or Automated Manual Transmission DCTAM 2.7 - 4.1 2.7 - 4.1 2.7 - 4.1 2.7 - 4.1

Material Substitution (1%) MS1 n.a. n.a. 0.4 0.4

Material Substitution (2%) MS2 n.a. n.a. 0.4 0.4

Material Substitution (5%) MS5 n.a. n.a. 1.0 1.0

Low Rolling Resistance Tires ROLL 1.0 - 2.0 1.0 - 2.0 1.0 - 2.0 n.a.

Low Drag Brakes LDB n.a. n.a. 0.5 - 1.0 0.5 - 1.0

Secondary Axle Disconnect SAX 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5 1.0 - 1.5

Aero Drag Reduction AERO 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0 2.0 - 3.0

Nominal Baseline Engine (For Cost Basis)

VEHICLE TECHNOLOGY INCREMENTAL FUEL CONSUMPTION REDUCTION (-%) BY VEHICLE 

TECHNOLOGY CLASS - LIGHT TRUCKS
The tables representing the Volpe model input files for approximate net (accumulated) 

technology costs by vehicle subclass are presented below. The tables have been divided 

into passenger cars, performance passenger cars, and light trucks to make them easier to 

read.
V-151

Table V-21. Approximate Net (Accumulated) Technology Costs, 

Passenger Cars 

Subcompact Compact Midsize Large

Car Car Car Car

Stoichiometric Gas Direct Injection (SGDI) 600 - 1,100 600 - 1,100 600 - 1,100 1,000 - 1,900

Turbocharge and Downsize (TRBDS) 2,000 - 2,600 2,000 - 2,600 2,000 - 2,600 1,900 - 2,700

Diesel Engine (DSLT/DSLC) 4,000 4,000 4,000 5,600

Dual Clutch Transmission (DCTAM) 500 500 600 600

Integrated Starter Generator Mild-hybrid (ISG) 2,400 - 2,500 2,800 3,000 - 3,100 3,200 - 3,300

APPROXIMATE RETAIL PRICE EQUIVALENT NET COSTS PER VEHICLE ($) BY VEHICLE 

CLASS TO KEY TECHNOLOGIES (Rounded to nearest $100)

Final Technology (As compared to baseline 

vehicle before any technologies are applied)

Table V-22. Approximate Net (Accumulated) Technology Costs, 

Performance Passenger Cars 

Performance Performance Performance Performance

Subcompact Compact Midsize Large

Car Car Car Car

Stoichiometric Gas Direct Injection (SGDI) 600 - 1,100 1,000 - 1,700 1,000 - 1,900 1,200 - 2,400

Turbocharge and Downsize (TRBDS) 2,000 - 2,600 1,900 - 2,700 1,900 - 2,700 2,600 - 3,700

Diesel Engine (DSLT/DSLC) 4,000 5,600 5,600 7,000

Dual Clutch Transmission (DCTAM) 600 600 600 600

Integrated Starter Generator Mild-hybrid (ISG) 2,500 - 2,700 2,900 3,000 - 3,100 3,300

APPROXIMATE RETAIL PRICE EQUIVALENT NET COSTS PER VEHICLE ($) BY VEHICLE 

CLASS TO KEY TECHNOLOGIES (Rounded to nearest $100)

Final Technology (As compared to baseline 

vehicle before any technologies are applied)

Table V-23. Approximate Net (Accumulated) Technology Costs, Light Trucks 

Minivan Small Midsize Large

LT LT LT LT

Stoichiometric Gas Direct Injection (SGDI) 1,000 - 1,900 600 - 1,100 1,000 - 1,900 1,200 - 2,400

Turbocharge and Downsize (TRBDS) 1,900 - 2,700 2,000 - 2,600 1,900 - 2,700 2,600 - 3,700

Diesel Engine (DSLT/DSLC) 5,600 4,000 5,600 7,000

Dual Clutch Transmission (DCTAM) 600 600 600 600

Integrated Starter Generator Mild-hybrid (ISG) 3,200 - 3,300 2,800 - 2,900 3,200 n.a.

APPROXIMATE RETAIL PRICE EQUIVALENT NET COSTS PER VEHICLE ($) BY VEHICLE 

CLASS TO KEY TECHNOLOGIES (Rounded to nearest $100)

Final Technology (As compared to baseline 

vehicle before any technologies are applied)
V-152

The tables representing the Volpe model input files for approximate net (accumulated) 

technology effectiveness values by vehicle subclass are presented below. The tables have been 

divided into passenger cars, performance passenger cars, and light trucks to make them easier to 

read. 

Table V-24. Approximate Net Technology Effectiveness, Passenger Cars 

Subcompact Compact Midsize Large

Car Car Car Car

Stoichiometric Gas Direct Injection (SGDI) 4.8 - 13.1 4.8 - 13.1 4.8 - 13.1 7.2 - 14.1

Turbocharge and Downsize (TRBDS) 11.2 - 17.4 11.2 - 17.4 11.2 - 17.4 11.2 - 17.4

Diesel Engine (DSLT/DSLC) 21.2 - 25.9 21.2 - 25.9 20.2 - 24.9 20.2 - 24.9

Dual Clutch Transmission (DCTAM) 8.2 - 12.9 8.2 - 12.9 5.5 - 9.7 5.5 - 9.7

Integrated Starter Generator Mild-hybrid (ISG) 8.7 - 13.6 8.7 - 13.6 10.9 - 14.3 10.9 - 14.3

NET EFFECTIVENESS ESTIMATES FUEL CONSUMPTION REDUCTION PER VEHICLE

(-%) BY VEHICLE CLASS TO KEY TECHNOLOGIES 

Final Technology (As compared to baseline 

vehicle before any technologies are applied)

Table V-25. Approximate Net Technology Effectiveness, 

Performance Passenger Cars 

Performance Performance Performance Performance

Subcompact Compact Midsize Large

Car Car Car Car

Stoichiometric Gas Direct Injection (SGDI) 4.8 - 13.1 7.2 - 14.1 7.2 - 14.1 7.2 - 14.1

Turbocharge and Downsize (TRBDS) 11.2 - 17.4 11.2 - 17.4 11.2 - 17.4 11.2 - 17.4

Diesel Engine (DSLT/DSLC) 21.2 - 25.9 21.2 - 25.9 20.2 - 24.9 20.2 - 24.9

Dual Clutch Transmission (DCTAM) 5.5 - 9.7 5.5 - 9.7 5.5 - 9.7 5.5 - 9.7

Integrated Starter Generator Mild-hybrid (ISG) 4.9 - 10.0 5.1 - 10.0 7.2 - 10.1 7.2 - 10.7

NET EFFECTIVENESS ESTIMATES FUEL CONSUMPTION REDUCTION PER VEHICLE 

(-%) BY VEHICLE CLASS TO KEY TECHNOLOGIES 

Final Technology (As compared to baseline vehicle 

before any technologies are applied)

Table V-26. Approximate Net Technology Effectiveness, Light Trucks 

Minivan Small Midsize Large

LT LT LT LT

Stoichiometric Gas Direct Injection (SGDI) 7.2 - 14.1 4.8 - 13.1 7.2 - 14.1 7.2 - 14.2

Turbocharge and Downsize (TRBDS) 11.2 - 17.4 11.2 - 17.4 11.2 - 17.4 11.2 - 17.4

Diesel Engine (DSLT/DSLC) 20.2 - 24.9 20.2 - 24.9 20.2 - 23.9 19.2 - 23.9

Dual Clutch Transmission (DCTAM) 5.5 - 9.7 5.5 - 9.7 5.5 - 9.7 5.5 - 9.7

Integrated Starter Generator Mild-hybrid (ISG) 10.9 - 14.3 8.7 - 13.6 10.0 - 12.6 n.a.

NET EFFECTIVENESS ESTIMATES FUEL CONSUMPTION REDUCTION PER VEHICLE 

(-%) BY VEHICLE CLASS TO KEY TECHNOLOGIES 

Final Technology (As compared to baseline vehicle 

before any technologies are applied)
V-153

C. Penetration of Technologies by Alternative 

Tables V-27 shows the penetration of technologies by alternative for passenger cars and Tables V-28 

shows the penetration of technologies for light trucks for the alternatives. These tables are for the 

whole fleet combined, not by specific manufacturers. They allow the reader to see the progression of 

technologies applied as the alternatives get stricter. 
V-154

Table V-27 

Penetration Rate of New Technologies to Passenger Cars 

Technology 

25% 

Below 

Opt. 

7% 

25% 

Above 

50% 

Above 

Opt. 

3% 

TC = 

TB 

Tech 

Ex. 

Low Friction Lubricants 59% 59% 59% 59% 71% 71% 96% 

Engine Friction Reduction 5% 7% 11% 11% 15% 19% 33% 

VVT - Coupled Cam Phasing (CCP) on SOHC 9% 9% 10% 10% 10% 10% 10% 

Discrete Variable Valve Lift (DVVL) on SOHC 0% 0% 0% 0% 0% 0% 4% 

Cylinder Deactivation on SOHC 0% 0% 0% 0% 0% 0% 0% 

VVT - Intake Cam Phasing (ICP) 37% 35% 34% 34% 34% 33% 25% 

VVT - Dual Cam Phasing (DCP) 38% 41% 42% 42% 42% 43% 52% 

Discrete Variable Valve Lift (DVVL) on DOHC 0% 1% 4% 4% 4% 6% 12% 

Continuously Variable Valve Lift (CVVL) 0% 0% 0% 0% 0% 0% 1% 

Cylinder Deactivation on DOHC 3% 3% 3% 3% 3% 3% 1% 

Cylinder Deactivation on OHV 1% 1% 1% 1% 2% 2% 0% 

VVT - Coupled Cam Phasing (CCP) on OHV 4% 4% 4% 4% 4% 3% 4% 

Discrete Variable Valve Lift (DVVL) on OHV 0% 0% 0% 1% 1% 1% 2% 

Conversion to DOHC with DCP 0% 0% 0% 0% 0% 0% 0% 

Stoichiometric Gasoline Direct Injection (GDI) 12% 12% 12% 13% 13% 15% 13% 

Combustion Restart 0% 0% 0% 0% 0% 0% 11% 

Turbocharging and Downsizing 7% 7% 7% 9% 9% 9% 8% 

Exhaust Gas Recirculation (EGR) Boost 0% 0% 0% 0% 0% 0% 2% 

Conversion to Diesel following TRBDS 0% 0% 1% 1% 1% 2% 16% 

Conversion to Diesel following CBRST 0% 0% 0% 0% 0% 0% 0% 

6-Speed Manual/Improved Internals 5% 5% 6% 6% 6% 6% 6% 

Improved Auto. Trans. Controls/Externals 6% 6% 6% 4% 4% 4% 9% 

Continuously Variable Transmission 11% 11% 11% 11% 11% 11% 11% 

6/7/8-Speed Auto. Trans with Improved Internals 36% 36% 36% 34% 34% 34% 33% 

Dual Clutch or Automated Manual Transmission 7% 7% 7% 12% 13% 13% 13% 

Electric Power Steering 36% 37% 37% 39% 42% 40% 45% 

Improved Accessories 36% 37% 37% 39% 39% 38% 44% 

12V Micro-Hybrid 0% 1% 2% 1% 1% 3% 0% 

Higher Voltage/Improved Alternator 1% 1% 3% 5% 5% 8% 11% 

Integrated Starter Generator 0% 0% 0% 1% 1% 1% 4% 

Power Split Hybrid 5% 5% 5% 5% 5% 5% 12% 

2-Mode Hybrid 0% 0% 0% 0% 0% 0% 0% 

Plug-in Hybrid 0% 0% 0% 0% 0% 0% 0% 

Material Substitution (1%) 0% 0% 0% 0% 0% 0% 0% 

Material Substitution (2%) 0% 0% 0% 0% 0% 0% 0% 

Material Substitution (5%) 0% 0% 0% 0% 0% 0% 0% 

Low Rolling Resistance Tires 32% 34% 34% 34% 34% 34% 53% 

Low Drag Brakes 4% 5% 5% 5% 6% 7% 7% 

Secondary Axle Disconnect – Unibody 0% 0% 0% 0% 0% 0% 0% 

Secondary Axle Disconnect - Ladder Frame 1% 1% 1% 1% 1% 1% 1% 

Aero Drag Reduction 11% 11% 11% 11% 12% 12% 27% 
V-155

 

Table V-28 

Penetration Rate of New Technologies to Light Trucks 

Technology 

25% 

Below 

Opt. 

7% 

25% 

Above 

50% 

Above 

Opt. 

3% 

TC = 

TB 

Tech 

Ex. 

Low Friction Lubricants 80% 80% 80% 80% 80% 80% 96% 

Engine Friction Reduction 25% 25% 26% 26% 25% 26% 34% 

VVT - Coupled Cam Phasing (CCP) on SOHC 6% 6% 6% 6% 6% 6% 6% 

Discrete Variable Valve Lift (DVVL) on SOHC 0% 0% 0% 0% 0% 0% 2% 

Cylinder Deactivation on SOHC 0% 0% 0% 0% 0% 0% 1% 

VVT - Intake Cam Phasing (ICP) 25% 25% 25% 25% 25% 25% 23% 

VVT - Dual Cam Phasing (DCP) 36% 36% 36% 36% 36% 36% 37% 

Discrete Variable Valve Lift (DVVL) on DOHC 0% 0% 1% 1% 0% 1% 4% 

Continuously Variable Valve Lift (CVVL) 0% 0% 2% 2% 0% 2% 0% 

Cylinder Deactivation on DOHC 1% 1% 1% 1% 1% 1% 6% 

Cylinder Deactivation on OHV 11% 11% 11% 11% 11% 10% 12% 

VVT - Coupled Cam Phasing (CCP) on OHV 13% 13% 13% 13% 13% 13% 17% 

Discrete Variable Valve Lift (DVVL) on OHV 2% 2% 2% 2% 2% 2% 2% 

Conversion to DOHC with DCP 0% 0% 0% 0% 0% 0% 0% 

Stoichiometric Gasoline Direct Injection (GDI) 10% 10% 12% 12% 10% 10% 9% 

Combustion Restart 1% 1% 1% 1% 1% 1% 19% 

Turbocharging and Downsizing 5% 5% 7% 7% 5% 7% 6% 

Exhaust Gas Recirculation (EGR) Boost 0% 0% 0% 0% 0% 0% 0% 

Conversion to Diesel following TRBDS 1% 1% 1% 1% 1% 2% 8% 

Conversion to Diesel following CBRST 3% 3% 3% 3% 3% 3% 3% 

6-Speed Manual/Improved Internals 0% 0% 0% 0% 0% 0% 0% 

Improved Auto. Trans. Controls/Externals 14% 14% 14% 14% 14% 15% 15% 

Continuously Variable Transmission 3% 3% 3% 3% 3% 3% 3% 

6/7/8-Speed Auto. Trans with Improved Internals 39% 39% 39% 39% 39% 39% 38% 

Dual Clutch or Automated Manual Transmission 10% 10% 10% 10% 10% 10% 12% 

Electric Power Steering 34% 34% 34% 34% 34% 34% 33% 

Improved Accessories 19% 19% 19% 19% 19% 19% 22% 

12V Micro-Hybrid 2% 2% 2% 2% 2% 2% 0% 

Higher Voltage/Improved Alternator 5% 5% 5% 5% 5% 5% 10% 

Integrated Starter Generator 1% 1% 1% 1% 1% 1% 7% 

Power Split Hybrid 1% 1% 1% 1% 1% 1% 2% 

2-Mode Hybrid 1% 1% 1% 1% 1% 1% 1% 

Plug-in Hybrid 0% 0% 0% 0% 0% 0% 0% 

Material Substitution (1%) 3% 3% 3% 3% 3% 3% 6% 

Material Substitution (2%) 1% 1% 1% 1% 1% 1% 2% 

Material Substitution (5%) 0% 0% 1% 1% 0% 1% 2% 

Low Rolling Resistance Tires 39% 39% 39% 39% 39% 41% 49% 

Low Drag Brakes 17% 17% 17% 17% 17% 17% 28% 

Secondary Axle Disconnect - Unibody 0% 0% 0% 0% 0% 0% 0% 

Secondary Axle Disconnect - Ladder Frame 25% 25% 25% 25% 25% 25% 27% 

Aero Drag Reduction 18% 18% 18% 18% 18% 18% 27% 
VI-1

VI. MANUFACTURER SPECIFIC CAFE CAPABILITIES

Table VI-1 shows the CAFE product plans for each of the manufacturers, based on the 

manufacturer’s plans without taking into account any alternative or dual fuel vehicle attributes. 

Table VI-2 shows the ADJUSTED BASELINE. Note that when we do cost and benefit 

analyses, we use the ADJUSTED BASELINE throughout the analysis. The adjusted baseline is 

essentially the higher of the manufacturer’s plans or the MY 2010 fuel economy standard. The 

adjusted baseline assumes for the analysis that each manufacturer, below the MY 2010 standard 

applicable to that manufacturer, (except Ferrari, Maserati, Daimler, Porsche and Volkswagen) 

would apply technology to achieve the MY 2010 standard. Those mpg levels of those 

manufacturers with product plans above the MY 2010 standard, or above their required reform 

level standard in any model year, are retained for the adjusted baseline. Our rationale for this 

adjustment of the baseline is that the costs and benefits of achieving MY 2010 mpg levels for 

light trucks have already been analyzed and estimated in previous analyses. The methodology in 

this analysis is to apply technologies to the manufacturers’ plans and increase them to the 

adjusted baseline. The costs of these technologies are estimated, but they are not considered part 

of this rule. We then estimate the costs and benefits of going from the adjusted baseline to the 

level of the alternatives.208 

The required standard levels are shown in Table VI-3 for passenger cars and for light trucks. 

Table VI-4 provides the estimated achieved levels for passenger cars and light trucks. All of the 

analyses compared the estimated achieved levels versus the adjusted baseline. Table VI-5 for 

passenger cars and Table VI-6 for light trucks shows what we believe the manufacturers’ fuel 

economy could be for “meeting” the alternative levels analyzed in this analysis. They include in 

some cases manufacturers’ plans at levels higher than the alternative standards would require. 

Note that not all manufacturers are assumed to attempt to “meet” the alternatives. We assume 

that Ferrari, Maserati, Daimler, Porsche and Volkswagen would not meet these levels because, 

for them, the cost of meeting these levels is more than the cost of paying penalties. These 

manufacturers have shown, in the past, the willingness to pay penalties rather than spend more 

money to improve the fuel economy of their products. 

The agency has performed an analysis of how manufacturers could respond to changes in the 

proposed CAFE levels. The “Technology Application Analysis” (or the “Volpe Analysis”) uses 

a technology application algorithm to systematically apply consistent cost and performance 

assumptions to the entire industry, as well as consistent assumptions regarding economic 

decision-making by manufacturers. The resulting computer model (the CAFE Compliance and 

Effects Model), developed by technical staff of the DOT Volpe National Transportation Systems 

Center in consultation with NHTSA staff, is used to help estimate the overall economic impact of 

the alternative CAFE standards. The Volpe analysis shows the economic impact of the standards 

in terms of increases in new vehicle prices on a manufacturer-wide, industry-wide, and average 

 

208 Some manufacturer’s plans are above the level of the standard already and are assumed to remain at that level. 

Some manufacturer’s levels go slightly above the proposed mark for them since some technologies are applied to all 

models of a particular manufacturer so that the exact level for each manufacturer may be slightly higher than the 

level of the standard and costs and benefits are estimated to that level. 
VI-2

per-vehicle basis. Based on these estimates and corresponding estimates of net economic and 

other benefits, the agency is able to consider alternatives that are economically practicable and 

technologically feasible. 

We note that the Volpe model has been updated and refined with respect to its representation of 

some fuel-saving technologies, but the model remains fundamentally unchanged. The model has 

been peer reviewed. The model documentation, including a description of the input assumptions 

and process, as well as peer review reports, was made available in the rulemaking docket for the 

August 2005 NPRM.209

Our analyses of the potential effects of alternative CAFE standards were founded on two major 

elements: (1) projections of the technical characteristics and sales volumes of future product 

offerings and (2) estimates of the applicability and incremental cost and fuel savings associated 

with different hardware changes—technologies—that might be utilized in response to alternative 

CAFE standards. 

 

 

209 See Docket Nos. NHTSA-20005-22223-3, 4, 5. 
VI-3

Table VI-1 

Manufacturers Production Plans – MY 2011 

Estimated mpg 

Manufacturer Passenger Cars Light Trucks 

BMW 27.0 23.0 

Chrysler 28.2 23.1 

Daimler 25.2 20.6 

Ferrari 16.2 N.A. 

Ford 29.3 22.5 

General Motors 30.3 21.4 

Honda 32.3 25.2 

Hyundai 31.7 26.0 

Maserati 18.2 N.A. 

Mitsubishi 29.3 26.7 

Nissan 31.3 21.4 

Porsche 27.2 20.0 

Subaru 28.6 28.6 

Suzuki 28.7 24.0 

Tata 24.7 23.9 

Toyota 33.2 22.7 

Volkswagen 28.5 20.1 

Total/Average 30.4 22.6 
VI-4

Table VI-2 

Adjusted Baseline – MY 2011 

 Estimated mpg 

Manufacturer Passenger Cars Light Trucks 

BMW 27.5 23.9 

Chrysler 28.2 23.3 

Daimler 25.9 20.6 

Ferrari 16.2 N.A. 

Ford 29.3 22.6 

General Motors 30.3 22.2 

Honda 32.3 25.2 

Hyundai 31.7 26.0 

Maserati 18.2 N.A. 

Mitsubishi 29.3 26.7 

Nissan 31.3 21.8 

Porsche 27.5 20.0 

Subaru 28.6 28.6 

Suzuki 28.7 24.0 

Tata 26.0 24.9 

Toyota 33.2 23.1 

Volkswagen 28.5 20.1 

Total/Average 30.5 23.0 
VI-5

Table VI-3 

Estimated Required Levels by Final Rule MY 2011 

Estimated mpg 

Manufacturer Passenger Cars Light Trucks 

BMW 30.2 25.7 

Chrysler 28.6 24.2 

Daimler 28.9 24.5 

Ferrari 30.7 NA 

Ford 30.1 23.6 

General Motors 30.0 23.3 

Honda 30.6 25.4 

Hyundai 30.3 25.3 

Maserati 27.5 NA 

Mitsubishi 30.9 26.7 

Nissan 30.5 24.0 

Porsche 31.2 25.5 

Subaru 30.9 26.6 

Suzuki 31.0 26.4 

Tata 27.5 26.1 

Toyota 30.6 24.8 

Volkswagen 30.9 24.9 

Total/Average 30.2 24.1 
VI-6

Table VI-4 

Estimated Achievable Levels – MY 2011 

 Estimated mpg 

Manufacturer Passenger Cars Light Trucks 

BMW 27.7 23.9 

Chrysler 28.6 24.2 

Daimler 25.9 20.6 

Ferrari 16.2 NA 

Ford 30.1 22.6 

General Motors 30.3 22.2 

Honda 32.3 25.5 

Hyundai 31.7 26.0 

Maserati 18.2 NA 

Mitsubishi 31.2 26.7 

Nissan 31.3 21.8 

Porsche 28.2 20.0 

Subaru 30.0 28.6 

Suzuki 29.5 24.0 

Tata 26.1 25.9 

Toyota 33.2 23.1 

Volkswagen 29.0 20.1 

Total/Average 30.7 23.2 
VI-7

Table VI-5 

Estimated Achievable Fuel Economy Levels 

By Alternative – MY 2011 

Passenger Cars 

(mpg) 

Manufacturer 

25% 

Below 

Opt. 

7% 

25% 

Above 

50% 

Above 

Opt. 

3% 

TC = 

TB 

Tech 

Ex. 

BMW 27.7 27.7 27.7 27.7 27.7 27.7 27.9 

Chrysler 28.4 28.6 28.9 29.5 29.5 29.8 31.5 

Daimler 25.9 25.9 25.9 25.9 25.9 25.9 25.9 

Ferrari 16.2 16.2 16.2 16.2 16.2 16.2 16.2 

Ford 29.9 30.1 30.4 30.5 30.5 30.5 31.2 

General 

Motors 30.3 30.3 30.3 30.6 31.0 31.3 32.0 

Honda 32.3 32.3 32.3 32.3 32.3 32.3 36.0 

Hyundai 31.7 31.7 31.7 31.7 31.7 31.7 35.4 

Maserati 18.2 18.2 18.2 18.2 18.2 18.2 18.2 

Mitsubishi 30.6 31.2 31.2 31.2 31.2 31.2 31.9 

Nissan 31.3 31.3 31.3 31.3 31.6 31.9 32.1 

Porsche 28.2 28.2 28.2 28.2 28.2 28.2 28.4 

Subaru 30.0 30.0 30.0 30.0 30.0 30.0 30.5 

Suzuki 29.5 29.5 29.5 29.5 29.5 29.5 29.7 

Tata 26.1 26.1 26.1 26.1 26.1 26.1 27.2 

Toyota 33.2 33.2 33.2 33.2 33.2 33.2 33.9 

Volkswagen 29.0 29.0 29.0 29.0 29.0 29.0 29.1 

Total/Average 30.7 30.7 30.8 31.0 31.0 31.2 32.4 
VI-8

Table VI-6 

Estimated Achievable Fuel Economy Levels 

By Alternative – MY 2011 

Light Trucks 

(mpg) 

Manufacturer 

25% 

Below 

Opt. 

7% 

25% 

Above 

50% 

Above 

Opt. 

3% 

TC = 

TB 

Tech 

Ex. 

BMW 23.9 23.9 23.9 23.9 23.9 23.9 23.9 

Chrysler 24.2 24.2 24.3 24.3 24.2 24.5 25.4 

Daimler 20.6 20.6 20.6 20.6 20.6 20.6 20.6 

Ferrari NA NA NA NA NA NA NA 

Ford 22.6 22.6 22.6 22.6 22.6 22.6 22.6 

General 

Motors 22.2 22.2 22.2 22.2 22.2 22.2 22.6 

Honda 25.5 25.5 25.5 25.5 25.5 25.6 28.0 

Hyundai 26.0 26.0 26.0 26.0 26.0 26.0 28.2 

Maserati NA NA NA NA NA NA NA 

Mitsubishi 26.7 26.7 27.2 27.2 26.7 27.2 32.1 

Nissan 21.8 21.8 21.8 21.8 21.8 21.8 21.9 

Porsche 20.0 20.0 20.0 20.0 20.0 20.0 20.0 

Subaru 28.6 28.6 28.6 28.6 28.6 28.6 28.7 

Suzuki 24.0 24.0 24.0 24.0 24.0 24.0 24.0 

Tata 25.9 25.9 25.9 25.9 25.9 25.9 27.8 

Toyota 23.1 23.1 23.1 23.1 23.1 23.1 23.2 

Volkswagen 20.1 20.1 20.1 20.1 20.1 20.1 20.1 

Total/Average 23.2 23.2 23.2 23.2 23.2 23.2 23.7 
VII-1

VII. COST IMPACTS 

Technology Costs 

Table V-1 provides the technology cost estimates used in this analysis. These are meant to 

represent consumer costs for high-volume production of these technologies after sufficient 

experience with their application have resulted in all “learning curve” effects being fully 

realized. The method taken to get to this consumer cost estimate starts with an initial estimate of 

the incremental manufacturers’ direct costs (or variable costs) for high-volume production of 

these technologies. In the case of some very new technologies, the agency may have only had 

cost estimates from low volume products and has assumed that the products have not matured in 

the development production cycle and that a “learning curve” will result in a reduction in the 

variable cost of the product. The variable costs are marked up by a factor of 1.5 to take into 

account fixed costs of R&D, burden, manufacturer’s profits, and dealer’s profits. The final 

results are shown in Table V1. 

The variable costs are incremental costs in material, labor, and variable burden for the product. 

For example, if a vehicle already has a 4-speed automatic transmission, the cost of applying a 5-

speed transmission is assumed to be the incremental cost, calculated as the cost of applying a 5-

speed transmission less the cost of applying the previously applied 4-speed automatic 

transmission. 

Manufacturers’ actual costs for applying these technologies to specific vehicle models are likely 

to include significant additional outlays for accompanying design or engineering changes to each 

model, development and testing of prototype versions, recalibrating engine operating parameters, 

and integrating the technology with other attributes of the vehicle. Manufacturers may also incur 

additional corporate overhead, marketing, or distribution and selling expenses as a consequence 

of their efforts to improve the fuel economy of individual vehicle models and their overall 

product lines. 

In order to account for these additional costs, the agency applies an indirect cost multiplier of 1.5 

to its estimate of the vehicle manufacturers’ direct costs for producing or acquiring each fuel 

economy-improving technology to arrive at a consumer cost. This estimate was developed by 

Argonne National Laboratory in a recent review of vehicle manufacturers’ indirect costs. The 

Argonne study was specifically intended to improve the accuracy of future cost estimates for 

production of vehicles that achieve high fuel economy by employing many of the same advanced 

technologies considered in the agency’s analysis.210 Thus, its recommendation that a multiplier 

of 1.5 be applied to direct manufacturing costs to reflect manufacturers’ increased indirect costs 

for deploying advanced fuel economy technologies appears to be appropriate for use in the 

agency’s current analysis. Historically, NHTSA has used almost the exact same multiplier, a 

multiplier of 1.51211, as the markup from variable costs or direct manufacturing costs to 

 

210 Vyas, Anant, Dan Santini, and Roy Cuenca, Comparison of Indirect Cost Multipliers for Vehicle 

Manufacturing, Center for Transportation Research, Argonne National Laboratory, April 2000. 

211 Spinney, Bruce C., CPA, NHTSA “Advanced Air Bag System Cost Weight and Leadtime Analysis Summary 

Report” Docket No. 2007-27453-10. 
VII-2

consumer costs. This markup takes into account fixed costs, burden, manufacturer’s profit, and 

dealers profit. NHTSA’s methodology for developing this markup factor was recently peer 

reviewed (see Docket No.27453-4). 

Potential opportunity costs of improved fuel economy 

An important concern is whether achieving the fuel economy improvements required by 

alternative CAFE standards would require manufacturers to compromise the performance, 

carrying capacity, safety, or comfort of their vehicles. If it did so, the resulting sacrifice in the 

value of these attributes to vehicle buyers would represent an additional cost of achieving the 

required improvements in fuel economy, and thus of manufacturers’ compliance with stricter 

CAFE standards. While exact dollar values of these attributes to buyers are extremely difficult 

to infer from vehicle purchase prices, it is nevertheless clear that changes in these attributes can 

affect the utility that vehicles provide to their owners, and thus their value to potential buyers. 

The agency has approached this potential problem by developing cost estimates for fuel 

economy-improving technologies that include any additional manufacturing costs that would be 

necessary to maintain the performance, comfort, capacity, or safety of any vehicle to which those 

technologies are applied. Theoretically, opportunity costs could also include any foregone 

opportunities to enhance these products for consumers. However, estimating values for foregone 

opportunities is an even tougher task. So, the agency followed the precedent established by NAS 

in its 2002 analysis of the costs and benefits of improving fuel economy by raising CAFE 

standards.212 The NAS study estimated “constant performance and utility” costs for fuel 

economy technologies, and the agency has used these as the basis for developing the technology 

costs it employed in analyzing manufacturer’s costs for complying with alternative standards. 

NHTSA fully acknowledges the difficulty of estimating technology costs that include costs for 

the accompanying changes in vehicle design that are necessary to maintain performance, 

capacity, and utility. However, the agency believes its cost estimates for fuel economy 

technologies are generally sufficient to prevent significant reductions in consumer welfare. 

The technology application algorithm implemented with the Volpe model was used as the basis 

for estimating costs for the fleet. The agency did estimate the costs or fines to bring passenger 

car manufacturers up to the 27.5 mpg level in place for MY 2010 as shown in Table VII-2. 

Table VII-3 shows the estimates for those light truck manufacturers that are not planning on 

meeting the CAFE reform level for MY 2011, without using fuel economy adjustments for 

alternative fueled vehicles, up to the level required for them for MY 2011. These costs have 

been estimated, but they are not considered to be part of the costs of meeting the proposed 

requirements. Those costs, and commensurate benefits, are considered part of the costs and 

benefits of complying with previously issued rules. 

 

212 National Academy of Sciences, Costs and Effectiveness of Increasing Corporate Average Fuel Economy 

Standards, 2002. 
VII-3

Tables VII-4a through 4n for passenger cars and Tables VII-5a through 5n show the costs for 

light trucks (on an average cost-per-vehicle basis and on a total cost basis) of applying 

technology necessary to move each manufacturer’s planned fuel economy levels up to the level 

of the alternative. Thus, if a manufacturer’s product plans resulted in a fuel economy level of 

22.2 mpg during each model year, the cost represents the cumulative cost of technologies 

necessary to bring that manufacturer’s fleet average up to the levels of the alternative. The costs 

for several manufacturers are the fines that these manufacturers would have to pay on an average 

vehicle basis. We assume that the costs of fines will be passed on to consumers. The second 

part of each of these tables shows the estimated total manufacturer costs in millions of dollars. 

Fines are not included in the second part of these tables, since these are transfer payments and 

not technology costs. 
VII-4

Table VII-1 

Estimated Incremental Costs or Fines over Manufacturer’s Plans 

To get to Adjusted Baseline – MY 2011 

Average Cost per Vehicle (2007$) 

Manufacturer Passenger Cars Light Trucks 

BMW (64.6) (215.8) 

Chrysler - (19.0) 

Daimler (300.6) (137.5) 

Ferrari (621.5) 

Ford - (67.0) 

General Motors - (529.8) 

Honda - - 

Hyundai - - 

Maserati (511.5) 

Mitsubishi - - 

Nissan - (269.8) 

Porsche (80.7) (214.5) 

Subaru - - 

Suzuki - (88.0) 

Tata (1,112.9) (355.0) 

Toyota - (137.4) 

Volkswagen - (181.5) 

Total/Average (8.8) (205.1) 
VII-5

Table VII-2 

Estimated Incremental Costs or Fines over Adjusted Baseline 

Average Cost per Vehicle (2007$) 

MY 2011 Passenger Cars 

Manufacturer 

25% 

Below 

Opt. 

7% 

25% 

Above 

50% 

Above 

Opt. 

3% 

TC = 

TB 

Tech 

Ex. 

BMW 200 217 233 255 272 288 536 

Chrysler 16 44 140 425 425 642 3,440 

Daimler 66 77 94 110 127 143 341 

Ferrari 160 176 193 215 237 253 479 

Ford 70 119 391 633 655 666 1,661 

General 

Motors 0 0 0 29 118 396 1,727 

Honda 0 0 0 0 0 0 1,427 

Hyundai 0 0 0 0 0 0 2,260 

Maserati 0 0 11 28 39 55 231 

Mitsubishi 280 787 787 872 894 910 1,767 

Nissan 0 0 0 0 47 265 847 

Porsche 441 458 474 496 518 535 763 

Subaru 343 360 376 398 420 437 810 

Suzuki 233 250 261 283 305 321 572 

Tata 0 0 11 28 44 55 231 

Toyota 0 0 0 0 0 0 388 

Volkswagen 186 203 219 241 258 274 516 

Total/Average 40 64 120 193 220 310 1,445 
VII-6

Table VII-3 

Estimated Incremental Costs or Fines over Adjusted Baseline 

Average Cost per Vehicle (2007$) 

MY 2011 Light Trucks 

Manufacturer 

25% 

Below 

Opt. 

7% 

25% 

Above 

50% 

Above 

Opt. 

3% 

TC = 

TB 

Tech 

Ex. 

BMW 72 72 77 77 72 83 380 

Chrysler 473 473 690 690 473 1,079 2,919 

Daimler 77 77 83 83 77 88 358 

Ferrari 0 0 0 0 0 0 0 

Ford 33 33 39 39 33 44 292 

General 

Motors 44 44 50 50 44 55 739 

Honda 35 35 35 35 35 42 2,912 

Hyundai 0 0 0 0 0 0 2,602 

Maserati 0 0 0 0 0 0 0 

Mitsubishi 0 0 54 54 0 54 3,915 

Nissan 44 44 50 50 44 55 314 

Porsche 88 88 94 94 88 99 391 

Subaru 0 0 0 0 0 0 225 

Suzuki 44 44 50 50 44 55 369 

Tata 2,274 2,274 2,279 2,279 2,274 2,285 7,220 

Toyota 55 55 61 61 55 66 336 

Volkswagen 83 83 88 88 83 94 374 

Total/Average 126 126 169 169 126 242 1,177 
VII-7

Table VII-4 

 Estimated Incremental Costs or Fines over Adjusted Baseline 

Total Incremental Costs in Millions (2007$) 

MY 2011 Passenger Cars 

Manufacturer 

25% 

Below 

Opt. 

7% 

25% 

Above 

50% 

Above 

Opt. 

3% 

TC = 

TB 

Tech 

Ex. 

BMW 68 74 79 87 93 98 183 

Chrysler 11 31 99 300 300 454 2,433 

Daimler 3 4 5 6 7 8 18 

Ferrari 0 0 0 0 0 0 1 

Ford 114 192 632 1,022 1,058 1,076 2,683 

General 

Motors 0 0 0 49 201 674 2,936 

Honda 0 0 0 0 0 0 1,783 

Hyundai 0 0 0 0 0 0 1,480 

Maserati 0 0 0 0 0 0 1 

Mitsubishi 59 165 165 183 188 191 371 

Nissan 0 0 0 0 37 210 669 

Porsche 6 6 6 7 7 7 10 

Subaru 32 33 35 37 39 40 75 

Suzuki 24 26 27 29 32 33 59 

Tata 0 0 0 1 2 2 8 

Toyota 0 0 0 0 0 0 545 

Volkswagen 58 63 68 75 80 85 160 

Total/Average 375 595 1,117 1,796 2,042 2,878 13,415 
VII-8

Table VII-5 

Estimated Incremental Costs or Fines over Adjusted Baseline 

Total Incremental Costs in Millions (2007$) 

MY 2011 Light Trucks 

Manufacturer 

25% 

Below 

Opt. 

7% 

25% 

Above 

50% 

Above 

Opt. 

3% 

TC = 

TB 

Tech 

Ex. 

BMW 7 7 7 7 7 8 37 

Chrysler 575 575 839 839 575 1,312 3,549 

Daimler 2 2 2 2 2 2 8 

Ferrari 0 0 0 0 0 0 0 

Ford 38 38 44 44 38 50 333 

General 

Motors 81 81 91 91 81 101 1,363 

Honda 16 16 16 16 16 20 1,367 

Hyundai 0 0 0 0 0 0 576 

Maserati 0 0 0 0 0 0 0 

Mitsubishi 0 0 1 1 0 1 66 

Nissan 21 21 24 24 21 26 150 

Porsche 2 2 2 2 2 3 10 

Subaru 0 0 0 0 0 0 29 

Suzuki 1 1 1 1 1 1 8 

Tata 58 58 58 58 58 59 185 

Toyota 60 60 66 66 60 72 367 

Volkswagen 4 4 4 4 4 4 17 

Total/Average 865 865 1,157 1,157 865 1,660 8,065 
VII-9

Financial Impacts of Raising CAFE Standards 

As has been widely reported in the public domain throughout this rulemaking, and as shown in 

public comments, the national and global economies are in crisis. Even before those recent 

developments, the automobile manufacturers were already facing substantial difficulties. 

Together, these problems have made NHTSA’s economic practicability analysis particularly 

important and challenging in this rulemaking. 

Automobile sales have dropped significantly. U.S. motor vehicle sales in 2008 were 18 percent 

below 2007 levels. January 2009 industry sales were 37 percent lower than in January 2008.213 

The sales of every major manufacturer declined. Vehicle manufacturers have not been able to 

raise prices to offset declining unit sales.214

The financial state of the major U.S. automotive manufacturers is particularly difficult.. General 

Motors’ 2008 U.S. vehicle sales were down 23 percent, and January 2009 sales were down 51 

percent.215 GM last earned an accounting profit in 2004, and has lost a cumulative $72 billion 

between 2005 and the third quarter of 2008.216 GM has a negative net worth of $60 billion, and 

consumed more than $3.5 billion in cash in the third quarter. GM is largely unable to borrow 

additional funds in capital markets, and must rely on a dwindling pool of cash to fund any further 

operating losses and capital investments. 

Ford Motor Company’s 2008 sales declined 20 percent.217 The firm has lost nearly $30 billion 

since 2006. The firm has a negative net worth of $2 billion, and consumed some $5.5 billion in 

cash in the fourth quarter of 2008.218 Ford is also largely unable to borrow additional funds in 

capital markets, and must also rely on a dwindling pool of cash to fund any further operating 

losses and capital investments. 

Chrysler is closely held, and consequently does not publish financial statements. However, 

Chrysler’s 2008 unit sales were 30 percent below last year’s sales, and January 2009 sales were 

off 55 percent.219 In a report to submitted to the Senate Banking Committee in December 2008, 

Chrysler indicated that, if the Federal Government provided $13 billion in financing, Chrysler 

 

213 Ward’s Automotive, “Ward’s U.S. Light Vehicle Sales Summary,” December 2008. Available at: 

http://wardsauto.com/keydata/USSalesSummary0812.xls / (Last accessed February 6, 2008). 214 Commerce Department data indicates no apparent change in nominal prices of new vehicle sales over the past 

few years. 

215 General Motors Corp, monthly sales report for December 2008. Available at: 

http://www.gm.com/corporate/investor_information/sales_prod/hist_sales.jsp 

(last accessed February 6, 2009). 

216 General Motors Corp. annual report for 2007, quarterly earnings announcement for the third quarter of 2008. 

Available at http://www.gm.com/corporate/investor_information/earnings/index.jsp (last accessed November 12, 

2008). 

217 Ford Motor Company, Fourth quarter 2008 financial results. Available at: http://www.ford.com/aboutford/investor-relations/company-reports/financial-results (last accessed February 6, 2009). 218 Ford Motor Company, Annual Report 2007, p. 121 and fourth quarter 2008 earning release, Slide 26.. 219 Ward’s Automotive, op. cit. 
VII-10

expected to end 2009 with some $6.7 billion in net cash.220 However, absent federal 

intervention, it is not clear that Chrysler would be able to survive 2009 in one piece. 

As the figures set forth above demonstrate, the automobile industry is already experiencing 

substantial economic hardship, even in the absence of new fuel economy standards. All three 

firms have announced a steady stream of plant closings, layoffs, and employment of new 

employees at reduced wages. 

NHTSA believes these hardships have much to do with the condition of the national economy 

and perhaps the price of gasoline, and little, if anything, to do with the stringency of CAFE 

standards for the current or recent model years. We believe that given the scale of the recent 

decline in industry sales, and the restrictiveness of private credit markets, that near-term 

developments will be compelled by the industry’s immediate financial situation, rather than by 

the long-term financial consequences of this rulemaking. 

Market forces are already requiring manufacturers to improve the fuel economy of their vehicles, 

as shown both by changes in product plans reported to NHTSA, and by automaker 

announcements in recent weeks. The improvements in fleet fuel economy required by this rule 

are consistent with the pressure induced by changing consumer preferences. 

The various compliance flexibility mechanisms permitted by EISA, including flexible and 

alternative fuel vehicles, banking, averaging, and trading of fuel economy credits will also 

reduce compliance costs to some degree. By statute, NHTSA is not permitted to consider the 

benefits of flexibility mechanisms in assessing the costs and benefits of the rule. 

On the other hand, the agency is mindful that CAFE standards do affect the relative 

competitiveness of different vehicle manufacturers, and recognizes that standards more stringent 

than those promulgated here could have a more detrimental effect. 

 However, the core of the problem for the agency is to determine what new standards might be 

economically practicable within the MY 2011 time frame, given the state of both the domestic 

and the international auto industries. The complexity of an economic practicability 

determination has been materially increased by the decision of GM and Chrysler to seek, and the 

U.S. Government to provide, substantial financial assistance. Congress has appropriated $7.5 

billion (to support a maximum of $25 billion in loans under Section 136 of EISA to support the 

development of advanced technology vehicles and components in the United States.221 DOE 

reports that 75 requests for funding, totaling some $38 billion have been received by the deadline 

date, of which 23 requests were deemed “substantially complete,” and hence eligible for further 

consideration among the initial tranche of projects. 

 

220 Robert Nardelli, “Chrysler’s Plan for Short-Term and Long-Term Viability,” submitted to Senate Committee on 

Banking, Housing, and Urban Affairs, December 2, 2008. Available at: 

http://banking.senate.gov/public/files/ChryslerUSSenateViabilityPlan.pdf (last accessed February 6, 2009). 221221 The authorizing language for this provision is in Section 136 of EISA. This language is amended and funds 

are appropriated in the Emergency Economic Stabilization Act of 2008 (H.R. 1424, Pub.L. 110-343). See also the 

DOE Advanced Technology Vehicle Manufacturing Loan Program website: http://www.atvmloan.energy.gov/ (last 

accessed February 6, 2009). 
VII-11

The Treasury Department has also advanced substantial funding to GM, Chrysler and GMAC 

under the Troubled Asset Relief Program (TARP). (Ford elected not to accept public funding 

under the TARP). GM received a loan of $13.4 billion, while Chrysler received $4 billion.222 

GM and Chrysler have also submitted restructuring plans to the Treasury Department in 

February 2009 requesting additional Federal assistance to “achieve and sustain long-term 

viability” while “comply[ing] with applicable Federal fuel efficiency and emission 

requirements.” Since this rule had not been promulgated at the time the report was submitted, 

GM and Chrysler were left with a degree of doubt about exactly what CAFE standards would 

apply to MYs 2011 and thereafter. 

Given the foregoing, therefore, the agency has decided that in this exceptional situation, 

economic practicability must be determined based on whether the expenditures needed to 

achieve compliance with the final MY 2011 standards are “within the financial capability of the 

industry, but not so stringent as to threaten substantial economic hardship for the industry,” no 

matter who contributes the funds. This is an operational definition of a standard set using costbenefit analysis. We have attempted to set the MY 2011 CAFE standards so that they are both 

technologically and economically feasible while providing the maximum national public social 

benefit. In principle, most vehicles meeting the standard will provide social benefits to the 

public at large and private benefits to automobile owners greater than their extra cost. 

One of the primary ways in which the agency seeks to ensure that its standards are within the 

financial capability of the industry is to attempt to ensure that manufacturers have sufficient lead 

time to modify their manufacturing plans to comply with the final standards in the model years 

covered by them. Employing appropriate assumptions about lead time in our analysis helps to 

avoid applying technologies before they are ready to be applied, or when their benefits are 

insufficient to justify their costs. It also helps avoid basing standards on the assumption that 

technologies could be applied more rapidly than practically achievable by manufacturers. 

NHTSA considers these matters in its analysis of issues including refresh and redesign 

schedules, phase-in caps, and learning rates. 

A number of manufacturers commented that the proposed standards were too stringent in the 

early years and were therefore not economically practicable. In reevaluating the range of fuelsaving technologies expected to be available in MY 2011, the agency has developed more 

realistic estimates of the set of technologies available, the extent to which these technologies are 

most likely to be applied either at a vehicle freshening or redesign, and the limits (i.e., caps) that 

should be applied to the rates at which these technologies can be phased in. NHTSA believes the 

resultant MY 2011 standards, which also reflect all other inputs to NHTSA analysis, are not 

inappropriately “front loaded,” particularly given that they cover only one model year. 

NHTSA further considers the sales and employment impacts of the final standards on individual 

manufacturers as part of its efforts to determine whether the standards are economically 

practicable. The sales analysis looks at a purchasing decision from the eyes of a knowledgeable 

and rational consumer, comparing the estimated cost increase versus the payback in fuel savings 

 

222U.S. Department of the Treasury, “Indicative Summary of Terms for Secured Term Loan Facility,” December 19, 

2008, for Chrsyler and GM. Available at http://www.treasury.gov/press/releases/hp1333.htm (last accessed 

February 6, 2009). 
VII-12

over 5 years (the average new vehicle loan) for each manufacturer. This relationship depends on 

the cost-effectiveness of technologies available to each manufacturer. Overall, based on a 7 

percent discount rate for future fuel savings, while the sales and employment impacts estimated 

from the final standards are higher than those estimated in the NPRM, they are still relatively 

small compared to the impacts estimated from the higher alternatives discussed above, such as 

the standards set such that total costs equal total benefits. 

The agency does not have the capability to predict the capital investment needs of the automobile 

industry to install fuel economy technologies, nor the capability to determine the level of capital 

investments available to specific manufacturers in the future. The agency asked for comments to 

provide us with information about the ability of manufacturers to provide the capital investment 

needs for the various alternatives. However, no responses were provided. 

The Impact of Higher Prices on Sales 

Higher fuel economy standards are expected to increase the price of passenger cars and light 

trucks. The potential impact of higher vehicle prices on sales was examined on a manufacturerspecific basis, since the estimated cost of improving fuel economy and the fuel economy 

improvement is different for each manufacturer. There is a broad consensus in the economic 

literature that the price elasticity for demand for automobiles is approximately –1.0.223,224,225

Thus, every one percent increase in the price of the vehicle would reduce sales by one percent. 

Elasticity estimates assume no perceived change in the quality of the product. However, in this 

case, vehicle price increases result from adding technologies that improve fuel economy. If 

consumers do not value improved fuel economy at all, and consider nothing but the increase in 

price in their purchase decisions, then the estimated impact on sales from price elasticity could 

be applied directly. However, we believe that consumers do value improved fuel economy, 

because they reduce the operating cost of the vehicles. We also believe that consumers consider 

other factors that affect their costs and have included these in the analysis. 

One issue that significantly affects this sales analysis is: How much of the retail price increase 

needed to cover the fuel economy technology investments will manufacturers be able to pass on 

to consumers? The estimates reported above assume that manufacturers will be able to pass all 

of their costs to improve fuel economy on to consumers. However, the ability of manufacturers 

to pass the compliance costs on to consumers will depend upon how consumers value the fuel 

economy improvements. Consumer valuation of fuel economy improvements often depends 

upon the price of gasoline, which has recently been very volatile. To the extent that we have 

accurately predicted the price of gasoline and consumers reactions, and manufacturers can pass 

on all of the costs to consumers, then the sales and employment impact analyses are reasonable. 

If manufacturers only increase retail prices to the extent that consumers value these fuel 

economy improvements, then there would be no impact on sales. 

 

223 Kleit, A.N. (1990). “The Effect of Annual Changes in Automobile Fuel Economy Standards.” Journal of Regulatory 

Economics, vol. 2, pp 151-172. 224 Bordley, R. (1994). “An Overlapping Choice Set Model of Automotive Price Elasticities,” Transportation Research B, vol 

28B, no 6, pp 401-408. 

225 McCarthy , P.S. (1996). “Market Price and Income Elasticities of New Vehicle Demands,” The Review of 

Economics and Statistics, vol. LXXVII, no. 3, pp. 543-547. 
VII-13

Sales losses are predicted to occur only if consumers fail to value fuel economy improvements at 

least as much as they pay in higher prices. Our analysis indicates that during the first 5 years, on 

average initial purchasers will not yet recoup their added investment and this leads to our 

prediction of sales losses. If manufacturers are unable to raise prices beyond the level of 

consumer's valuation of fuel savings, then manufacturer's profit levels would fall but there would 

be no impact on sales. Likewise, if fuel prices rise beyond levels used in this analysis, 

consumer's valuation of improved fuel economy could increase to match or exceed their initial 

investment, resulting in no impact or even an increase in sales levels. 

 

To estimate the average value consumers place on fuel savings at the time of purchase, we 

assume that the average purchaser considers the fuel savings they would receive over a 5 year 

timeframe. We chose 5 years because this is the average length of time of a financing 

agreement. 226 The present values of these savings were calculated using a 7 percent discount 

rate for those alternatives that were based on a 7 percent discount rate and using a 3 percent 

discount rate for the one alternative based on a 3 percent discount rate. We used a fuel price 

forecast (see Table VIII-3) that included taxes, because this is what consumers must pay. Fuel 

savings were calculated over the first 5 years and discounted back to a present value. 

The agency believes that consumers may consider several other factors over the 5 year horizon 

when contemplating the purchase of a new vehicle. The agency added these factors into the 

calculation to represent how an increase in technology costs might affect consumers’ buying 

considerations. 

First, consumers might consider the sales taxes they have to pay at the time of purchasing the 

vehicle. We took sales taxes in 2007 by state and weighted them by population by state to 

determine a national weighted-average sales tax of 5.5 percent. 

Second, we considered insurance costs over the 5 year period. More expensive vehicles will 

require more expensive collision and comprehensive (e.g., theft) car insurance. According to the 

National Association of Insurance Commissioners (NAIC) the national average premium for 

collision + comprehensive insurance in 2000 was $389 while the average new car transaction 

price was $20,600. If we assume that this premium is proportional to the new car price, it 

represents about 1.9 percent of the new car price and insurance is paid each year for the five year 

period we are considering for payback. Discounting that stream of insurance costs back to 

present value indicates that the present value of the component of insurance costs that vary with 

vehicle price is equal to 8.7 percent of the vehicle’s price at a 3 percent discount rate and 8.0 

percent of the vehicle’s price at a 7 percent discount rate. 

Third, we considered that 70 percent of new vehicle purchasers take out loans to finance their 

purchase. The average new vehicle loan is for 5 years at a 6 percent rate227. At these terms the 

average person taking a loan will pay 16 percent more for their vehicle over the 5 years than a 

 

226 National average financing terms for automobile loans are available from the Board of Governors of the Federal 

Reserve System G.19 “Consumer Finance” release. See: http://www.federalreserve.gov/releases/g19/ 227 New car loan rates in 2007 average about 7.8 percent at commercial banks and 4.5 percent at auto finance 

companies, so their average is close to 7 percent 
VII-14

consumer paying cash for the vehicle at the time of purchase228. Discounting the additional 3.2 

percent (16 percent / 5 years) per year over the 5 years using a 3 percent mid-year discount 

rate229 results in a discounted present value of 14.87 percent higher for those taking a loan, and at 

a 7 percent discount rate results in a 13.58 percent higher for those taking a loan. Multiplying 

that by the 70 percent that take a loan, means that the average consumer would pay 10.4 percent 

more than the retail price for loans the consumer discounted at a 3 percent discount rate and 9.5 

percent more than the retail price for loans the consumer discounted at a 7 percent discount rate. 

Fourth, we considered the residual value (or resale value) of the vehicle after 5 years and 

expressed this as a percentage of the new vehicle price. In other words, if the price of the vehicle 

increases due to fuel economy technologies, the resale value of the vehicle will go up 

proportionately. To estimate that value, we looked at 138 model year 2002 vehicles to compare 

their original MSRP values (based on www.nadaguides.com) to their current trade-in values (5 

years later in 2007 based on www.edmunds.com). The sales weighted average residual value for 

this group of vehicles was 37.5 percent. Discounting the residual value back 5 years using a 3 

percent discount rate (37.5 percent * .8755) gives an effective residual value at new of 32.8 

percent. Discounting the residual value back 5 years using a 7 percent discount rate (37.5 

percent * 0.7375) gives an effective residual value at new of 27.7 percent. 

We add these four factors together. At a 3 percent discount rate, the consumer considers he 

could get 32.8 percent back upon resale in 5 years, but will pay 10.4 percent more for loans, 5.5 

percent more for taxes and 8.7 percent more in insurance, results in a 8.2 percent return on the 

increase in price for fuel economy technology (32.8 percent – 10.4 percent - 5.5 percent – 8.7 

percent). Thus, the increase in price per vehicle is multiplied by 0.918 (1 – 0.082) before 

subtracting the fuel savings to determine the overall net consumer valuation the increase of costs 

on his purchase decision. At a 7 percent discount rate, the consumer considers he could get 27.7 

percent back upon resale in 5 years, but will pay 9.5 percent more for loans, 5.5 percent more for 

taxes and 8.0 percent more in insurance, results in a 4.7 percent return on the increase in price for 

fuel economy technology (27.7 percent – 9.5 percent - 5.5 percent – 8.0 percent). Thus, the 

increase in price per vehicle is multiplied by 0.953 (1 – 0.047) before subtracting the fuel savings 

to determine the overall net consumer valuation the increase of costs on his purchase decision. 

Using sales volumes from Ward’s Automotive Yearbook 2008 for MY 2007 sales and the MY 

2008 base vehicle average prices, we determined an average passenger car and an average light 

truck price per manufacturer. The average base price for all passenger cars using this method 

was $26,201 and for all light trucks was $29,678. While this method does not give an exact 

price, the results are reasonable and specific to individual manufacturers230. These prices are in 

 

228 Based on www.bankrate.com auto loan calculator for a 5 year loan at 6 percent. 229 For a 3 percent discount rate, the summation of 3.2 percent x 0.9853 in year one, 3.2 x 0.9566 in year two, 3.2 x 

0.9288 in year three, 3.2 x 0.9017 in year 4, and 3.2 x 0.8755 in year five. For a 7 percent discount rate, the 

summation of 3.2 percent x 0.9667 in year one, 3.2 x 0.9053 in year two, 3.2 x 0.8444 in year 3, 3.2 x 0.7891 in year 

4, and 3.2 x 0.7375 in year 5. 

230 The base price does not include the more expensive lines of a model or purchased optional equipment; nor does 

it count discounts given. Thus, it is not an average light truck purchase transaction price, but a price that we can 

track. 
VII-15

2007 dollars. Average prices and estimated sales volumes are needed because price elasticity is 

an estimate of how a percent increase in price affects the percent decrease in sales. 

A sample calculation for Ford passenger cars under the Optimized 7% alternative in MY 2011 is 

an estimated retail price increase of $119 which is multiplied by 0.953 to get a residual price 

increase of $113. The estimated fuel savings over the 5 years of $176 at a 7 percent discount rate 

results in a net benefit to consumers of $63. Comparing that to the $25,373 average price is a 

0.247 percent price decrease. Ford sales were estimated to be about 1,615,000 passenger cars for 

MY 2011. With a price elasticity of –1.0, a 0.247 percent decrease in net cost to consumers 

could result in an estimated increase in sales of 3,997 passenger cars. 

Combined passenger car and light truck sales decreases are estimated for every alternative. As 

the alternatives get stricter, there are progressively larger losses in sales. Table VII-6 shows the 

estimated impact on sales for passenger cars and light trucks combined. 

Our projections indicate that CAFE standards will result in sales increases for some 

manufacturers under some scenarios, but overwhelmingly decreases for the industry total. As 

the alternatives get progressively more stringent, the projected sales loss increases. For the TC = 

TB alternative the MY 2011 sales loss is projected to be 86,000 or 0.5 percent and for the 

Technology Exhaustion alternative the sales loss is projected to be 585,000 or 3.6 percent of the 

total sales of 16.136 million light vehicles. 

Note that there is no feedback loop between this sales analysis and the Volpe model. These sales 

estimates are not used to determine additional or less mileage traveled or fuel consumed. The 

Volpe model does not attempt to estimate the extent to which the sales volumes of different 

vehicle models might change in response to fuel economy increases, financial outlays for 

additional technology, and increases in civil penalties that could all result from increased CAFE 

standards. As NHTSA explained in the NPRM, (1) Volpe Center staff tested many potential 

specifications of multinomial logit model that could be used to estimate such effects, but none 

produced plausible coefficients, (2) NHTSA and Volpe Center staff were not confident that 

baseline vehicle transaction prices could be reliably predicted, and (3) NHTSA and Volpe Center 

staff were not confident a basis would be available to estimate manufacturers’ decisions 

regarding the allocation of compliance costs.231

As NHTSA further acknowledged in the NPRM, Resources for the Future (RFF) has, under 

contract to EPA, been working toward the development of a market share model. Although RFF 

did not complete this work in time for consideration as part of this rulemaking, depending on the 

extent to which these efforts are eventually successful, the Volpe model could at some point be 

modified to include cost allocation and market share models. 

Among the attachments to its comments, the Alliance of Automobile Manufacturers submitted a 

study prepared by NERA, which used its model of the vehicle market “to estimate the value that 

consumers place on reductions in fuel operating cost while controlling for other factors.”232 

 

231 Federal Register / Vol. 73, No. 86 / Friday, May 2, 2008 / Proposed Rules, p. 24394. 232 NERA Economic Consulting, “Evaluation of NHTSA’s Benefit-Cost Analysis of 2011-2015 CAFE Standards”, 

2008, p. 18. 
VII-16

NERA states that its model “operates at the level of individual vehicle models” and “utilizes data 

on transaction prices (as distinct from manufacturers’ suggested retail prices), sales volumes, and 

detailed vehicle characteristics for model years 2001 through 2007.”233 With such a model, 

NERA may, in principle, have had the ability to estimate shifts in the market shares of individual 

vehicle models from these model years, if NERA had also been able to estimate how 

manufacturers would allocate overall compliance costs. Of course, representing only past model 

years, such an analysis would have had uncertain relevance to future model years. In any event, 

NERA apparently did not attempt to do so, but instead used NHTSA’s estimate of the own-price 

elasticity of demand for new vehicles to estimate the overall change in sales of new vehicles.234

NHTSA and Volpe Center staff will continue to consider the potential to integrate a market share 

model into the Volpe model, and will give careful consideration to the above-mentioned RFF 

effort when that work is complete. However, NHTSA received no concrete recommendations in 

response to its request for comments regarding the formulation and calibration of a market share 

model, the estimation of future vehicle prices (i.e., transaction prices), and the estimation of 

manufacturers’ decisions regarding the allocation of compliance costs. The Agency does not 

have a sufficient basis to include a market share model into its Volpe model and analysis at this 

time. 

 

233 Ibid., p. 18. 234 Ibid., p. 27. 
VII-17

 

Table VII-6 

Potential Impact on Sales by Manufacturer 

MY 2011 Passenger Cars and Light Trucks Combined 

Manufacturer 25% Below 

Opt. 

7% 

25% 

Above 

50% 

Above 

Opt. 

3% TC = TB 

Tech 

Ex. 

BMW -1,123 -1,246 -1,381 -1,545 -1,529 -1,803 -3,934

Chrysler -3,232 -2,530 -10,394 -14,330 -3,892 -29,894 -156,924

Daimler -87 -97 -115 -130 -137 -162 -452

Ferrari -1 -1 -1 -2 -2 -2 -4

Ford 3,055 2,805 -9,883 -23,010 -21,059 -25,210 -85,413

General Motors -2,560 -2,560 -2,876 -924 186 -15,661 -123,844

Honda 818 818 818 818 963 1,360 -70,331

Hyundai 0 0 0 0 0 0 -71,561

Maserati 0 0 0 -1 -1 -2 -8

Mitsubishi 85 -3,156 -3,105 -3,731 -3,336 -4,063 -11,798

Nissan -661 -661 -744 -744 78 -4,936 -24,752

Porsche -88 -92 -98 -102 -96 -113 -263

Subaru -81 -136 -190 -263 -185 -390 -2,058

Suzuki -338 -443 -517 -657 -608 -906 -2,515

Tata -688 -688 -694 -701 -662 -713 -2,221

Toyota -1,993 -1,993 -2,192 -2,192 -1,920 -2,392 -24,986

Volkswagen -601 -777 -957 -1,191 -1,122 -1,547 -4,208

Total/Average -7,496 -10,757 -32,329 -48,704 -33,323 -86,434 -585,272
VII-18
VII-19

Potential Impact on Employment 

There are three potential areas of employment that fuel economy standards could impact. The 

first is the hiring of additional engineers by automobile companies and their suppliers to do 

research and development and testing on new technologies to determine their capabilities, 

durability, platform introduction, etc. The agency does not anticipate a huge number of 

incremental jobs in the engineering field. Often people would be diverted from one area to 

another and the incremental number of jobs might be a few thousand. 

The second area is the impact that new technologies would have on the production line. Again, 

we don’t anticipate a large number of incremental workers, as for the most part you are replacing 

one engine with another or one transmission with another. In some instances the technology is 

more complex, requiring more parts and there would be a small increase in the number of 

production employees, but we don’t anticipate a large change. 

The third area is the potential impact that sales gains or losses could have on production 

employment. This area is potentially much more sensitive to change than the first two areas 

discussed above. In the past, the agency and others have made estimates of the impact of sales 

losses on employment. In the final rule reducing the light truck fuel economy standard for MY 

1985, the agency concluded that sales losses of 100,000 to 180,000 would result in employment 

losses of 12,000 to 23,000 (49 FR 41252, October 22, 1984).235 In the final rule reducing the 

MY 1986 passenger car fuel economy standard, the agency concluded that while it was difficult 

to precisely estimate the impacts, “there would be a likelihood of sales losses well into the 

hundreds of thousands of units and job losses well into the tens of thousands. Sales and 

employment losses of these magnitudes would have significant adverse effects on the economy 

... ” (50 FR 40538, October 4, 1985). In the final rule amending the passenger car standards for 

MY 1987 and 1988, the agency said that “... domestic car production may fall by more than 

900,000 units. The short employment effects are substantial: over 130,000 jobs...” (51 FR 

35598, October 6, 1986). These estimates imply a ratio between the number of vehicles sales 

lost and the number of employees laid off in the 1980s of between 6.9 (900,000/130,000) and 8.3 

(100,000/12,000). 

Certainly productivity has increased since that time. In order to get an estimate of potential job 

losses per sales loss, we examined more recent U.S. employment (original equipment 

manufacturers and suppliers) and U.S. production. Total employment in 2000 reached a peak in 

the Motor Vehicle and Equipment Manufacturing sector of the economy at 1,313,600. Since 

then there has been a decline to 1,108,000 in 2003 and to 1,098,000 in 2005236. Averaging those 

three years, the average U.S. domestic employee produces 10.5 vehicles. Thus, one could 

assume that projected sales loss divided by 10.5 would give an estimate of the potential 

employment loss. 

 

235 The agency’s decision to lower standards based on that amount of impacts identified in the 1985 rule was upheld 

by the DC Circuit in Public Citizen v. NHTSA, 848 F.2d 256. 

236 Based on “U.S. Automotive Industry Employment Trends”, Office of Aerospace and Automotive Industries, U.S. 

Department of Commerce, March 30, 2005, and Ward’s Automotive Yearbook, 2006, pgs. 215, 222, and 270. 
VII-20

Table VII-7 

U.S. Light Duty Vehicle Production and Employment 

U.S. Light Vehicle Production 

U.S. Employment 

Production per Employee 

2000 12,773,714 1,313,600 9.7 

2003 12,087,028 1,108,000 10.9 

2005 11,946,653 1,098,000 10.9 

Total/Average 36,807,396 3,519,600 10.5 

 

At this time, the agency considers these effects to occur in the short to medium term (meaning up 

to 5 years). Over the next few years, consumers can elect to defer vehicle purchases by 

continuing to operate existing vehicles. Eventually, however, the rising maintenance costs for 

aging vehicles will make replacements look more attractive. 

However, vehicle owners may also react to persistently higher vehicle costs by permanently 

owning fewer vehicles, and keeping existing vehicles in service for somewhat longer. In this 

case, the possibility exists that there may be permanent sales losses, compared with a situation in 

which vehicle prices are lower. 
VII-21

Table VII-8 

Impact on Auto Industry Employment by Alternative 

(Jobs) 

MY 2011 

 Passenger Cars Light Trucks Passenger Cars and 

Light Trucks 

Combined 

25% Below Optimized (7%) 272 -986 -714 

Optimized (7%) -39 -986 -1,024 

25% Above Optimized (7%) -1,336 -1,743 -3,079 

50% Above Optimized (7%) -2,896 -1,743 -4,638 

Optimized (3%) -2,419 -755 -3,174 

TC = TB (7%) -5,375 -2,857 -8,232 

Technology Exhaustion (7%) -37,260 -18,481 -55,740 

Table VII-9 provides further information relating to the stringency of the different alternatives. 

It looks at the largest 17 passenger car manufacturers and the 15 light truck manufacturers and 

examines whether or not they run out of technologies that the agency believes they have 

available. As the alternatives get more stringent, more manufacturers run out of technologies. 

It should be noted that Table VII-9 does not take into account any of the flexibilities that 

manufacturers have available to comply with a standard. It does not consider credits, credit 

trading, etc. 

Table VII-9 

Number of Manufacturers That Run Out of Technology 

 Cars Light Trucks 

25% Below Optimized (7%) 7 10 

Optimized (7%) 7 10 

25% Above Optimized (7%) 9 10 

50% Above Optimized (7%) 11 10 

Optimized (3%) 11 10 

TC = TB (7%) 11 10 

Technology Exhaustion (7%) 16 15 
VIII-1 

VIII. BENEFITS

Economic Impacts from Higher CAFE Standards 

Economic impacts from adopting a more stringent CAFE standard for passenger cars and light 

trucks were estimated separately for each model year over the lifespan of those vehicles in the 

U.S. vehicle fleet, extending from the initial year when a model is offered for sale through the 

year when nearly all vehicles from that model year have been retired or scrapped (assumed to be 

26 years for passenger cars and 36 years for light trucks in this analysis). The principal source of 

the economic and environmental impacts considered in this analysis is the reduction in gasoline 

use resulting from the improvement in fuel economy of new light-duty vehicles produced. 

Reducing gasoline consumption provides consumer benefits through decreased fuel costs, 

through reduced costs for externalities such as demand price inflation, economic disruption, and 

military security, through reduced economic and health impacts from criteria pollutants and 

green house gas emissions, through increased driving ranges for vehicles, and through consumer 

surplus from added driving. Offsetting a part of these benefits are added costs from congestion, 

crashes, and noise, as well as some offset to fuel consumption and pollution savings, all due to an 

increase in driving that results from lower driving costs (the rebound effect). Each of these 

impacts is measured by comparing their value under each alternative approach to their value 

under the adjusted baseline. Future impacts are estimated after discounting to the year the 

vehicle is sold to determine their present value.237 

Basic Inputs for Analysis of Economic Impacts 

The variety of impacts discussed above are a function of basic factors which determine their 

magnitude and define their value. These include the discount rate, the level of vehicle sales, the 

magnitude of the rebound effect, and the relationship between EPA measured fuel efficiency and 

actual on-road fuel efficiency. 

The Discount Rate

Discounting future fuel savings and other benefits is intended to account for the reduction in 

their value to society when they are deferred until some future date rather than received 

immediately. The discount rate expresses the percent decline in the value of these benefits – as 

viewed from today’s perspective – for each year they are deferred into the future. In setting the 

standards using a marginal cost/marginal benefit methodology we used two different discount 

rates. The inter-generational discount rate used for the long term social cost of carbon benefits is 

3 percent and the conventional discount rate used for the fuel and other savings over the next 36 

year is 7 percent. See the discussion in Chapter I on docket comments for the basis for selecting 

these rates. 

 

237 Discounting to the year when each model year was produced allows future economic benefits from improving 

each model year’s fuel economy to be compared to added production costs for making those vehicles more fuelefficient, which are assumed to be incurred at the time those vehicles are manufactured. 
VIII-2 

Vehicle Classification

Passenger automobiles were defined in EPCA as “any automobile (other than an automobile 

capable of off-highway operation) which the Secretary [i.e., NHTSA] decides by rule is 

manufactured primarily for use in the transportation of not more than 10 individuals.” Thus, 

under EPCA, there are two general groups of automobiles that qualify as non-passenger 

automobiles or light trucks: (1) those defined by NHTSA in its regulations as other than 

passenger automobiles due to their having not been manufactured “primarily” for transporting up 

to ten individuals; and (2) those expressly excluded from the passenger category by statute due to 

their capability for off-highway operation, regardless of whether they were manufactured 

primarily for passenger transportation. NHTSA’s classification rule directly tracks those two 

broad groups of non-passenger automobiles in subsections (a) and (b), respectively, of 49 CFR 

Part 523.5. 

In the NPRM, NHTSA took a fresh look at the regulatory definitions in light of its desire to 

ensure clarity in how vehicles are classified, the passage of EISA, and the Ninth Circuit’s 

decision in CBD. The NPRM proposed to tighten the coverage of its regulatory definition of 

“light truck” to ensure that, starting in MY 2011, 2WD versions of SUVs are no longer classified 

as off-highway capable light trucks under 49 CFR Part 523.5(b), simply because the SUV also 

comes in a 4WD version. 

NHTSA has tightened the coverage of its regulatory definition of “light truck” to ensure that 2 

wheel drive (2WD) versions of an SUV are not classified as light trucks under Part 523.5(b) 

simply because the SUV also comes in a 4WD version. In order to be properly classifiable as a 

light truck under Part 523, a 2WD SUV must either be over 6,000 lbs GVWR and meet 4 out of 

5 ground clearance characteristics to make it off-highway capable under Part 523.5(b), or meet 

one of the functional characteristics under Part 523.5(a) (e.g., greater cargo carrying capacity 

than passenger carrying capacity). In other words, a 2WD vehicle of 6,000 lbs GVWR or less, 

even if it has a sufficient number of clearance characteristics, cannot be considered off-highway 

capable. This is based on the plain meaning of Part 523.5(b) (which refers to a vehicle that “has” 

4WD) and the statute (49 U.S.C. § 32901(a)(18)(b) speaks of a vehicle that “is a 4-wheel drive 

automobile”). Additionally, 2WD SUVs may not be properly classified as light trucks simply 

because a manufacturer asserts that their base form has no back seat and thus would “provide 

greater cargo-carrying than passenger-carrying volume” according to Part 523.5(a)(4). No 

change in the regulatory definition is needed. The clarification accomplishes NHTSA’s purpose. 

This clarification, which the vehicle manufacturers largely supported, resulted in the reclassification of an average of 1,400,000 2WD SUVs from light trucks to passenger cars in each 

of the five model years covered by the standards. 

Additional discussion of vehicle classification is contained in the preamble to the final rule.. 

Sales Estimates

A critical variable affecting the total economic benefits from improving light truck fuel economy 

is the number of vehicles likely to be produced under stricter fuel economy. Projections of total 

passenger cars and light truck sales for future years (see Table VIII-1a and VIII-1b) were 

obtained from the Energy Information Administration’s (EIA) Annual Energy Outlook 2008 
VIII-3 

(AEO 2008), a standard government reference for projections of energy production and 

consumption in different sectors of the U.S. economy.238 These values will be used as 

multipliers to estimate the overall impacts (both costs and benefits) of changes in fuel economy 

standards. 

In all cases, manufacturers’ respective sales volumes were normalized to produce 

passenger car and light truck fleets which reflected manufacturers’ respective MY 2008 market 

shares within the construct of the projected aggregate vehicle sales volumes that were forecasted 

in EIA’s 2008 Annual Energy Outlook. NHTSA does so in order to develop a market forecast 

that is realistic in terms of both its overall size and manufacturers’ market shares. The product 

mix for each manufacturer that submitted product plans was preserved and in the case of those 

than did not submit plans, the product mix was the same as indicated in their pre-model year 

2008 CAFE data. 

NHTSA has relied on product plans from manufacturers to help the agency determine the 

composition of the future fleets. The product plans are provided in response to NHTSA’s 

request for information from the manufacturers, and respond to very detailed questions about 

vehicle model characteristics that influence fuel economy.239 The baseline market forecast mix 

of products (make/model, engines, transmissions, etc.) that NHTSA has used in its analysis is 

based significantly on the confidential product plan information manufacturers submit to the 

agency. See the preamble to the final rule for more information on how we used the 

manufacturers’ confidential product plans. 

 

238 U.S. Department of Energy, Energy Information Administration, Annual Energy Outlook 2007, Supplemental 

Table 47, http://www.eia.doe.gov/oiaf/aeo/supplement/suptab_47.xls. 

239 Id.
VIII-4 

Table VIII-1 

Sales Projections – MY 2011 

(1,000s of vehicles) 

Manufacturer 

 Passenger 

Cars Light Trucks Combined 

BMW 340.9 96.2 437.1 

Chrysler 707.3 1,215.9 1,923.2 

Daimler 52.9 23.0 75.9 

Ferrari 1.9 1.9 

Ford 1,615.0 1,143.9 2,759.0 

General 

Motors 1,700.1 1,844.1 3,544.2 

Honda 1,249.9 469.5 1,719.5 

Hyundai 655.1 221.3 876.4 

Maserati 4.4 4.4 

Mitsubishi 209.8 16.9 226.8 

Nissan 789.4 479.3 1,268.7 

Porsche 13.5 25.8 39.3 

Subaru 92.1 126.7 218.8 

Suzuki 103.8 21.6 125.5 

Tata 35.0 25.7 60.7 

Toyota 1,405.1 1,094.5 2,499.6 

Volkswagen 310.7 45.2 355.9 

Total/Average 9,286.9 6,849.7 16,136.7 
VIII-5 

The “Rebound Effect”

The rebound effect refers to the tendency for owners to increase the number of miles they drive a 

vehicle in response to an increase in its fuel economy, as would result from more stringent fuel 

economy standards. The rebound effect occurs because an increase in a vehicle’s fuel economy 

reduces its owner’s fuel cost for driving each mile, which is typically the largest single 

component of the cost of operating a vehicle. Even with the vehicle’s higher fuel economy, this 

additional driving uses some fuel, so the rebound effect will reduce the net fuel savings that 

result when the fuel economy standards require manufacturers to increase fuel economy. The 

rebound effect is usually expressed as the percentage by which annual vehicle use increases 

when average fuel cost per mile driven decreases in response to a change in the marginal cost of 

driving an extra mile, due either an increase in fuel economy or a reduction in the price of fuel. 

The magnitude of the rebound effect is one of the determinants of the actual fuel savings that are 

likely to result from adopting stricter standards, and thus an important parameter affecting 

NHTSA’s evaluation of alternative standards for future model years. The rebound effect can be 

measured directly by estimating the elasticity of vehicle use with respect to fuel economy itself, 

or indirectly by the elasticity of vehicle use with respect to fuel cost per mile driven.240 When 

expressed as a positive percentage, either of these parameters gives the fraction of fuel savings 

that would otherwise result from adopting stricter standards, but is offset by the increase in fuel 

consumption that results when vehicles with increased fuel economy are driven more. 

Research on the magnitude of the rebound effect in light-duty vehicle use dates to the early 

1980s, and almost unanimously concludes that a statistically significant rebound effect occurs 

when vehicle fuel efficiency improves.241 The most common approach to estimating its 

magnitude has been to analyze statistically household survey data on vehicle use, fuel 

consumption, fuel prices (often obtained from external sources), and other determinants of 

household travel demand to isolate the response of vehicle use to higher fuel economy. Other 

studies have relied on econometric analysis of annual U.S. data on vehicle use, fuel economy, 

fuel prices, and other variables to identify the response of total or average vehicle use to changes 

in fleet-wide average fuel economy and its effect of fuel cost per mile driven. Two recent studies 

analyzed yearly variation in vehicle ownership and use, fuel prices, and fuel economy among 

individual states over an extended time period in order to measure the response of vehicle use to 

changing fuel economy.242 

An important distinction among studies of the rebound effect is whether they assume that the 

effect is constant, or varies over time in response to the absolute levels of fuel costs, personal 

income, or household vehicle ownership. Most studies using aggregate annual data for the U.S. 

 

240 Fuel cost per mile is equal to the price of fuel in dollars per gallon divided by fuel economy in miles per gallon, 

so this figure declines when a vehicle’s fuel economy increases. 

241 Some studies estimate that the long-run rebound effect is significantly larger than the immediate response to 

increased fuel efficiency. Although their estimates of the adjustment period required for the rebound effect to reach 

its long-run magnitude vary, this long-run effect is most appropriate for evaluating the fuel savings and emissions 

reductions resulting from stricter standards that would apply to future model years. 

242 In effect, these studies treat U.S. states as a data “panel” by applying appropriate estimation procedures to data 

consisting of each year’s average values of these variables for the separate states. 
VIII-6 

assume a constant rebound effect, although some of these studies test whether the effect can vary 

as changes in retail fuel prices or average fuel economy alter fuel cost per mile driven. Many 

studies using household survey data estimate significantly different rebound effects for 

households owning varying numbers of vehicles, although they arrive at differing conclusions 

about whether the rebound effect is larger among households that own more vehicles. One 

recent study using state-level data concludes that the rebound effect varies directly in response to 

changes in personal income and the degree of urbanization of U.S. cities, as well as fuel costs. 

In order to arrive at an estimate of the rebound effect for use in assessing the fuel savings, 

emissions reductions, and other impacts of alternative standards, NHTSA reviewed 22 studies of 

the rebound effect conducted from 1983 through 2005. We then conducted a detailed analysis of 

the 66 separate estimates of the long-run rebound effect reported in these studies, which is 

summarized in the table below.243 As the table indicates, these 66 estimates of the long-run 

rebound effect range from as low as 7 percent to as high as 75 percent, with a mean value of 23 

percent. 

Limiting the sample to 50 estimates reported in the 17 published studies of the rebound effect 

yields the same range but a slightly higher mean (24 percent), while focusing on the authors’ 

preferred estimates from published studies narrows this range and lowers its average only 

slightly. The median estimate of the rebound effect in all three samples, which is generally 

regarded as a more reliable indicator of their central tendency than the average because it is less 

influenced by unusually small and large estimates, is 22 percent. As Table VIII-2 indicates, 

approximately two-thirds of all estimates reviewed, of all published estimates, and of authors’ 

preferred estimates fall in the range of 10-30 percent. 

Table VIII-2 

Summary of Rebound Effect Estimates 

Category of Estimates Number of Range Distribution 

Studies 

Number of 

Estimates 

Low High Median Mean Std. Dev.

All Estimates 22 66 7% 75% 22% 23% 14% 

Published Estimates 17 50 7% 75% 22% 24% 14% 

Authors' Preferred Estimates 17 17 9% 75% 22% 22% 15% 

U.S. Time-Series Estimates 7 34 7% 45% 14% 18% 9% 

Household Survey Estimates 13 23 9% 75% 31% 31% 16% 

Pooled U.S. State Estimates 2 9 8% 58% 22% 25% 14% 

Constant Rebound Effect (1) 15 37 7% 75% 20% 23% 16% 

Variable Rebound Effect: (1) 

Reported Estimates 10 29 10% 45% 23% 23% 10% 

Updated to 2006 (2) 10 29 6% 46% 16% 19% 12% 

(1) Three studies estimate both constant and variable rebound effects. 

 

243 In some cases, NHTSA derived estimates of the overall rebound effect from more detailed results reported in the 

studies. For example, where studies estimated different rebound effects for households owning different numbers 

of vehicles but did not report an overall value, we computed a weighted average of the reported values using the 

distribution of households among vehicle ownership categories. 
VIII-7 

(2) Reported estimates updated to reflect 2006 values of vehicle use, fuel prices, fleet 

fuel efficiency, household income, and household vehicle ownership. 

The type of data used and authors’ assumption about whether the rebound effect varies over time 

have important effects on its estimated magnitude. The 34 estimates derived from analysis of 

U.S. annual time-series data produce a median estimate of 14 percent for the long-run rebound 

effect, while the median of 23 estimates based on household survey data is more than twice as 

large (31 percent), and the median of 9 estimates based on pooled state data matches that of the 

entire sample (22 percent). The 37 estimates assuming a constant rebound effect produce a 

median of 20 percent, while the 29 originally reported estimates of a variable rebound effect 

have a slightly higher median value (23 percent). 

In selecting a single value for the rebound effect to use in analyzing alternative standards for 

future model years, NHTSA attaches greater significance to studies that allow the rebound effect 

to vary in response to changes in the various factors that have been found to affect its magnitude. 

However, it is also important to update authors’ originally-reported estimates of variable rebound 

effects to reflect current conditions. Recalculating the 29 original estimates of variable rebound 

effects to reflect current (2006) values for retail fuel prices, average fuel economy, personal 

income, and household vehicle ownership reduces their median estimate to 16 percent.244 

NHTSA also tentatively attaches greater significance to the recent study by Small and Van 

Dender (2005), which finds that the rebound effect tends to decline as average fuel economy, 

personal income, and suburbanization of U.S. cities increase, but – in accordance with previous 

studies – rises with increasing fuel prices.245

Considering the empirical evidence on the rebound effect as a whole, but according greater 

importance to the updated estimates from studies allowing the rebound effect to vary – 

particularly the Small and Van Dender study – NHTSA has selected a rebound effect of 15 

percent to evaluate the fuel savings and other effects of alternative standards for the time period 

 

244 As an illustration, Small and Van Dender (2005) allow the rebound effect to vary over time in response to 

changes in real per capita income as well as average fuel cost per mile driven. While their estimate for the entire 

interval (1966-2001) they analyze is 22 percent, updating this estimate using 2006 values of these variables reduces 

the rebound effect to approximately 10 percent. Similarly, updating Greene’s 1992 original estimate of a 15 percent 

rebound effect to reflect 2006 fuel prices and average fuel economy reduces it to 6 percent. See David L. Greene, 

“Vehicle Use and Fuel Economy: How Big is the Rebound Effect?” The Energy Journal, 13:1 (1992), 117-143. In 

contrast, the distribution of households among vehicle ownership categories in the data samples used by Hensher et 

al. (1990) and Greene et al. (1999) are nearly identical to the most recent estimates for the U.S., so updating their 

original estimates to current U.S. conditions changes them very little. See David A. Hensher, Frank W. Milthorpe, 

and Nariida C. Smith, “The Demand for Vehicle Use in the Urban Household Sector: Theory and Empirical 

Evidence,” Journal of Transport Economics and Policy, 24:2 (1990), 119-137; and David L. Greene, James R. Kahn, 

and Robert C. Gibson, “Fuel Economy Rebound Effect for Household Vehicles,” The Energy Journal, 20:3 (1999), 

1-21. 

245 In the most recent light truck CAFE rulemaking, NHTSA chose not to preference the Small and Van Dender 

study over other published estimates of the value of the rebound effect, stating that since it “remains an unpublished 

working paper that has not been subjected to formal peer review, ...the agency does not yet consider the estimates it 

provides to have the same credibility as the published and widely-cited estimates it relied upon.” See 71 FR 17633 

(Apr. 6, 2006). The study has subsequently been published and peer-reviewed, so NHTSA is now prepared to 

“consider it in developing its own estimate of the rebound effect for use in subsequent CAFE rulemakings.” 
VIII-8 

covered by this rulemaking. However, we do not believe that evidence of the rebound effect’s 

dependence on fuel prices or household income is sufficiently convincing to justify allowing its 

future value to vary in response to forecast changes in these variables. A range extending from 

10 percent to at least 20 percent appears to be appropriate for the required analysis of the 

uncertainty surrounding these estimates. 

NHTSA has updated the 29 estimates from studies that allowed the rebound effect to vary to 

reflect current (2008 to date) fuel prices, fuel economy, vehicle ownership levels, and household 

income. The resulting updated estimates are significantly higher than those reported in the 

NPRM, primarily because of the large increase in fuel prices since 2006 (the date to which the 

estimates reported in the NPRM were updated). The updated 2008 estimates of the fuel 

economy rebound effect range from 8 percent to 46 percent, with a median value of 19 percent. 

Using the average retail gasoline price forecast for 2011-30 from the AEO 2008 High Price case, 

the projected estimates of the rebound effect for those years would range from 7 percent to 46 

percent, with a median value of 19 percent. Finally, NHTSA notes that the forecast of fuel prices 

used to develop its adopted CAFE standards for model years 2011 projects that retail gasoline 

prices will continue to rise by somewhat more than 1 percent annually over the lifetimes of 

vehicles affected by those standards. At the same time, real household incomes are projected to 

grow by about 2 percent annually over this same period. Given the relative sensitivity of the 

Small and Van Dender rebound effect estimate to changes in fuel prices and income, these 

forecasts suggest that future growth in fuel prices is likely to offset a significant fraction of the 

projected decline in the rebound effect that would result from income growth. 

In light of these results, NHTSA has elected to continue to use a 15 percent rebound effect in its 

analysis of fuel savings and other benefits from higher CAFE standards for this final rule. 

Recognizing the uncertainty surrounding this estimate, the agency has analyzed the sensitivity of 

its benefits estimates to a range of values for the rebound effect from 10 percent to 20 percent. 

In its future CAFE rulemaking activities, NHTSA plans to prepare detailed year-by-year 

forecasts of the magnitude of the rebound effect using the published studies it regards as most 

reliable, in conjunction with forecasts of fuel prices, household income growth, and vehicle 

ownership levels. This analysis will indicate whether the combined effect of future changes in 

the factors that past research has shown to influence the rebound effect is likely to be an increase 

or a reduction in its future magnitude. NHTSA will base the estimate of the rebound effect it 

employs in analyzing future CAFE standards on the projected future values of the rebound effect 

over the lifetimes of vehicles affected by those standards. 

On-Road Fuel Economy Adjustment

Actual fuel economy levels achieved by vehicles in on-road driving fall significantly short of 

their levels measured under the laboratory-like test conditions used by EPA to establish its 

published fuel economy ratings for different models. In analyzing the fuel savings from 

alternative passenger car and light truck CAFE standards, the agency adjusts the actual fuel 

economy performance of each passenger car and light truck model downward from its rated 

value to reflect the expected size of this on-road fuel economy “gap.” In December 2006, EPA 
VIII-9 

adopted changes to its regulations on fuel economy labeling, which were intended to bring 

vehicles’ rated fuel economy levels closer to their actual on-road fuel economy levels.246 

Supplemental analysis reported by EPA as part of its Final Rule indicates that actual on-road fuel 

economy for light-duty vehicles averages 20 percent lower than published fuel economy 

levels.247 For example, if the overall EPA fuel economy rating of a light truck is 20 mpg, the onroad fuel economy actually achieved by a typical driver of that vehicle is expected to be 16 mpg 

(20*.80). The agency has employed EPA’s revised estimate of this on-road fuel economy gap in 

its analysis of the fuel savings resulting from alternative CAFE standards for MY 2011-2018 

passenger cars and MY 2012-18 light trucks. 

Benefits from Fuel Savings 

The main source of economic benefits from a fuel economy standard is the value of the resulting 

fuel savings over the lifetimes of vehicles that are required to comply with the stricter standards. 

These fuel savings for each scenario are measured by the difference between the adjusted 

baseline fuel economy for each model year and the fuel economy levels corresponding to that 

alternative. The sum of these annual fuel savings over each calendar year that a vehicle remains 

in service represents the cumulative fuel savings resulting from applying the alternative to 

vehicles produced during that model year. 

As previously noted, actual fuel economy levels achieved by vehicles in on-road driving fall 

significantly short of their levels measured under the laboratory-like test conditions used by EPA 

to establish its published fuel economy ratings for different models. In analyzing the fuel 

savings from alternative passenger car and light truck CAFE standards, the agency adjusts the 

actual fuel economy performance of each passenger car and light truck model downward from its 

rated value to reflect the expected size of this on-road fuel economy “gap.” In December 2006, 

EPA adopted changes to its regulations on fuel economy labeling, which were intended to bring 

vehicles’ rated fuel economy levels closer to their actual on-road fuel economy levels.248 

Supplemental analysis reported by EPA as part of its Final Rule indicates that actual on-road fuel 

economy for light-duty vehicles averages 20 percent lower than published fuel economy 

levels.249 The agency has employed EPA’s revised estimate of this on-road fuel economy gap in 

 

246 EPA, Fuel Economy Labeling of Motor Vehicles: Revisions To Improve Calculation of Fuel Economy Estimates; Final Rule, 40 CFR Parts 

86 and 600, Federal Register, December 27, 2006, pp. 77872-77969, http://www.epa.gov/fedrgstr/EPA-AIR/2006/December/Day27/a9749.pdf. 

247 EPA, Final Technical Support Document: Fuel Economy Labeling of Motor Vehicle Revisions to Improve 

Calculation of Fuel Economy Estimates, Office of Transportation and Air Quality EPA420-R-06-017 December 

2006, Chapter II, http://www.epa.gov/fueleconomy/420r06017.pdf. 248 EPA, Fuel Economy Labeling of Motor Vehicles: Revisions To Improve Calculation of Fuel Economy Estimates; Final Rule, 40 CFR Parts 

86 and 600, Federal Register, December 27, 2006, pp. 77872-77969, http://www.epa.gov/fedrgstr/EPA-AIR/2006/December/Day27/a9749.pdf. 

249 EPA, Final Technical Support Document: Fuel Economy Labeling of Motor Vehicle Revisions to Improve 

Calculation of Fuel Economy Estimates, Office of Transportation and Air Quality EPA420-R-06-017 December 

2006, Chapter II, http://www.epa.gov/fueleconomy/420r06017.pdf. 
VIII-10 

its analysis of the fuel savings resulting from alternative CAFE standards for MY 2011-2018 

passenger cars and MY 2012-18 light trucks. 

The number of light vehicles manufactured during each model year that remains in service 

during each subsequent calendar year is estimated by multiplying the estimated proportions of 

vehicles expected to survive to each age up to 26 years for passenger cars (Table VIII-3a) and 36 

years for light trucks (Table VIII-3b) by the number of cars and light trucks forecast to be 

produced during each year. These “survival rates,” which are estimated from experience with 

recent model-year vehicles, are slightly different than the survival rates used in past NHTSA 

analyses since they reflect recent increases in durability and usage of more recent passenger car 

and light truck models.250 Updated estimates of average annual miles driven by vehicle age were 

developed from the Federal Highway Administration’s 2001 National Household Transportation 

Survey, and these also differ from the estimates of annual mileage employed in past NHTSA 

analyses.251 The total number of miles driven by vehicles of a single model year during each 

year of its life span in the fleet in effect is estimated by multiplying these age-specific estimates 

of annual miles driven per vehicle by the number of vehicles projected to remain in service at 

each age. 

Table VIII-3a and VIII-3b provide the new schedules of vehicle miles traveled and survivability 

based on updated analyses performed by NHTSA. These were developed from registration data 

for 1977 through 2003, and from a 2001 survey of household vehicle use. In this analysis, the 

maximum vehicle age was defined as the age when the number remaining in service has declined 

to approximately two percent of the vehicles originally produced. Based on and examination of 

recent registration data for older model years, typical maximum ages appear to be 26 years for 

passenger cars and 36 years for light trucks. Using the 36-year estimate of the maximum 

lifetimes of light trucks results in survival-weighted or “expected” lifetime mileage of 190,066 

miles. Fuel savings and other benefits resulting from higher light truck CAFE standards are 

calculated over this expected 36 year lifetime and total mileage. In contrast, NHTSA’s previous 

estimate of lifetime VMT in the 2006 final rule was 179,954 miles over a 36-year lifetime for 

light trucks. The resulting survival-weighted mileage over the 26-year maximum lifetime of 

passenger cars is 161,847 miles, and fuel savings and other benefits resulting from higher 

passenger car CAFE standards are calculated over this 26-year lifetime and total mileage. It 

should be noted, however, that survival-weighted VMT is extremely low (less than 1,000 miles 

per year) after age 20 for cars and age 25 for light trucks, and thus has little impact on lifetime 

fuel savings or other benefits from higher fuel economy, particularly after discounting those 

benefits to their present values. 

The primary source of data for determining vehicles in operation is the National Vehicle 

Population Profile (NVPP) compiled by R.L. Polk and Company. The NVPP is an annual 

census, as of July 1 of each year, of passenger cars and light trucks registered for on-road 

operation in the United States. NVPP registration data was used from vehicle model years 1977 

 

250 The survival rates were calculated from R.L. Polk, National Vehicle Population Profile, 1977-2003; see NHTSA, 

“Vehicle Survivability and Travel Mileage Schedules,” Office of Regulatory Analysis and Evaluation, NCSA, 

January 2006, pp. 9-11, Docket No. 22223-2218. 251 See also NHTSA, “Vehicle Survivability and Travel Mileage Schedules,” Office of Regulatory Analysis and 

Evaluation, January 2006, pp. 15-17. 
VIII-11 

to 2003. Survival rates were averaged for the five most recent model years for vehicles up to 20 

years old, and regression models were fitted to these data to develop smooth relationships 

between age and the proportion of cars or light trucks surviving to that age. The survival rates 

predicted by these models are used to develop the estimates of annual mileage and fuel 

consumption used to calculate fuel savings and other impacts of higher fuel economy. 

The 2001 National Household Travel Survey (NHTS) sponsored by the Federal Highway 

Administration, Bureau of Transportation Statistics, and the National Highway Traffic Safety 

Administration attempted to develop up-to-date information on household vehicle ownership and 

use. The NHTS is the integration of two previous national travel surveys: the Federal Highway 

Administration-sponsored Nationwide Personal Transportation Survey (NPTS) and the Bureau 

of Transportation Statistics-sponsored American Travel Survey (ATS).252 The 2001 NHTS was 

the source of updated information on annual miles driven by age for passenger cars and light 

trucks. 

Finally, it should be noted that the estimates of average annual miles driven by passenger cars and 

light trucks, while new for NHTSA, are based on data collected during 2001-2002, and reflect the 

historically low gasoline prices that prevailed at the time the survey was conducted. To account for 

the effect on vehicle use of subsequent increases in fuel prices, the estimates of annual vehicle use 

derived from the NHTS are adjusted to reflect projected future gasoline prices using the rebound 

effect, which is discussed in detail later in this chapter. Two factors affect the cost of gasoline per 

mile driven - fuel prices per gallon, and fuel economy in miles-per-gallon. Because the intensity of 

vehicle use depends partly on the cost per mile of driving, the estimates of vehicle use developed from 

NHTS data reflect both fuel prices and fuel economy levels that prevailed during 2001 and 2002, when 

the survey was conducted. In analyzing the final rule, the agency adjusted the annual usage estimates 

derived from the NHTS data to reflect the effect of the higher EIA fuel prices that are forecast over the 

covered vehicles’ expected lifetimes, which exceed those that existed during 2001-2002. 

Specifically, the adjustment accounted for the difference between the average price per gallon of fuel 

forecast over the expected lifetimes of model year 2011 passenger cars and light trucks253 and the 

average price that prevailed during 2000 and 2001. When expressed in percentage terms, this 

difference was assumed to represent the percent increase in fuel cost per mile driven between the time 

the survey was conducted and the time period when model year 2011 passenger cars and light trucks 

would be in service. 

The same elasticity of annual vehicle use with respect to fuel cost per mile that was used to estimate 

the increase in vehicle use resulting from improved fuel economy (see detailed discussion of the 

“rebound effect” earlier in this chapter), assumed to be –0.15, was applied to this percent difference to 

adjust the estimates of vehicle use derived from the survey to reflect the effect of higher future fuel 

prices. In contrast, this adjustment reduces model year 2011 passenger cars’ and light trucks’ average 

annual usage at each age to account for the fact that fuel cost per mile driven is expected to be higher 

throughout their expected lifetimes than at the time the NHTS was conducted. The results of this 

adjustment are shown in Table VIII-2c for passenger cars and in Table VIII-2d for light trucks. The 

unadjusted average lifetime mileage is estimated to be 161,847 for passenger cars and 190,066 for 

 

252 For details on survey coverage and procedures, see http://nhts.ornl.gov/quickStart.shtml. 253 Based on the AEO High price forecast from the AEO 2008 report. 
VIII-12 

light trucks. After adjusting for the rebound effect, the average lifetime mileage is estimated to be 

146,547 for passenger cars and 171,590 for light trucks. 
VIII-13 

Table VIII-3a 

Survival Rates and Unadjusted Annual Vehicle-Miles Traveled (VMT) 

by Age for Passenger Cars 

Vehicle Age 

Estimated 

Survivability

(1977 to 2002 NVPP)

Estimated VMT 

(2001 NHTS) 

Weighted Yearly 

Travel Miles 

1 0.9950 14,231 14,160 

2 0.9900 13,961 13,821 

3 0.9831 13,669 13,438 

4 0.9731 13,357 12,998 

5 0.9593 13,028 12,497 

6 0.9413 12,683 11,938 

7 0.9188 12,325 11,324 

8 0.8918 11,956 10,662 

9 0.8604 11,578 9,961 

10 0.8252 11,193 9,237 

11 0.7866 10,804 8,499 

12 0.7170 10,413 7,466 

13 0.6125 10,022 6,138 

14 0.5094 9,633 4,907 

15 0.4142 9,249 3,831 

16 0.3308 8,871 2,934 

17 0.2604 8,502 2,214 

18 0.2028 8,144 1,652 

19 0.1565 7,799 1,220 

20 0.1200 7,469 896 

21 0.0916 7,157 656 

22 0.0696 6,866 478 

23 0.0527 6,596 348 

24 0.0399 6,350 253 

25 0.0301 6,131 185 

26 0.0227 5,940 135 

 

Estimated Passenger Car Lifetime VMT 161,847 
VIII-14 

Table VIII-3b 

Survival Rates and Unadjusted Annual Vehicle-Miles Traveled (VMT) 

by Age for Light Trucks 

Vehicle Age 

Estimated 

Survivability

(1977 to 2002 NVPP)

Estimated VMT 

(2001 NHTS) 

Weighted Yearly 

Travel Miles 

1 0.9950 16,085 16,004 

2 0.9741 15,782 15,374 

3 0.9603 15,442 14,829 

4 0.9420 15,069 14,195 

5 0.9190 14,667 13,479 

6 0.8913 14,239 12,691 

7 0.8590 13,790 11,845 

8 0.8226 13,323 10,960 

9 0.7827 12,844 10,053 

10 0.7401 12,356 9,145 

11 0.6956 11,863 8,252 

12 0.6501 11,369 7,391 

13 0.6042 10,879 6,573 

14 0.5517 10,396 5,735 

15 0.5009 9,924 4,971 

16 0.4522 9,468 4,281 

17 0.4062 9,032 3,669 

18 0.3633 8,619 3,131 

19 0.3236 8,234 2,665 

20 0.2873 7,881 2,264 

21 0.2542 7,565 1,923 

22 0.2244 7,288 1,635 

23 0.1975 7,055 1,393 

24 0.1735 6,871 1,192 

25 0.1522 6,739 1,026 

26 0.1332 6,663 887 

27 0.1165 6,648 774 

28 0.1017 6,648 676 

29 0.0887 6,648 590 

30 0.0773 6,648 514 

31 0.0673 6,648 447 

32 0.0586 6,648 390 

33 0.0509 6,648 338 

34 0.0443 6,648 294 

35 0.0385 6,648 256 

36 0.0334 6,648 222 

 

Estimated Lifetime Light Truck VMT 190,066 
VIII-15 

Table VIII-3c 

Survival Rates and Annual Vehicle-Miles Traveled (VMT) Adjusted for Rebound Effect 

by Age for Passenger Cars 

Vehicle Age Estimated 

Survivability Adjusted VMT Weighted Yearly Travel Miles 

1 0.9950 12,885 12,821 

2 0.9900 12,641 12,515 

3 0.9831 12,377 12,167 

4 0.9731 12,094 11,769 

5 0.9593 11,796 11,316 

6 0.9413 11,484 10,810 

7 0.9188 11,160 10,253 

8 0.8918 10,825 9,654 

9 0.8604 10,483 9,020 

10 0.8252 10,135 8,363 

11 0.7866 9,783 7,695 

12 0.7170 9,429 6,760 

13 0.6125 9,075 5,558 

14 0.5094 8,722 4,443 

15 0.4142 8,374 3,469 

16 0.3308 8,032 2,657 

17 0.2604 7,698 2,005 

18 0.2028 7,374 1,495 

19 0.1565 7,061 1,105 

20 0.1200 6,763 812 

21 0.0916 6,481 594 

22 0.0696 6,217 433 

23 0.0527 5,972 315 

24 0.0399 5,750 229 

25 0.0301 5,551 167 

26 0.0227 5,379 122 

Adjusted Lifetime Passenger Car VMT 146,547 
VIII-16 

Table VIII-3d 

Survival Rates and Annual Vehicle-Miles Traveled (VMT) Adjusted for rebound Effect 

by Age for Light Trucks 

Vehicle Age Estimated 

Survivability Adjusted VMT Weighted Yearly Travel Miles 

1 0.9950 14,521 14,449 

2 0.9741 14,248 13,879 

3 0.9603 13,941 13,388 

4 0.9420 13,604 12,815 

5 0.9190 13,241 12,168 

6 0.8913 12,855 11,457 

7 0.8590 12,449 10,694 

8 0.8226 12,028 9,895 

9 0.7827 11,596 9,076 

10 0.7401 11,155 8,256 

11 0.6956 10,710 7,450 

12 0.6501 10,264 6,673 

13 0.6042 9,821 5,934 

14 0.5517 9,385 5,178 

15 0.5009 8,960 4,488 

16 0.4522 8,548 3,865 

17 0.4062 8,154 3,312 

18 0.3633 7,781 2,827 

19 0.3236 7,434 2,406 

20 0.2873 7,115 2,044 

21 0.2542 6,829 1,736 

22 0.2244 6,579 1,476 

23 0.1975 6,369 1,258 

24 0.1735 6,203 1,076 

25 0.1522 6,084 926 

26 0.1332 6,015 801 

27 0.1165 6,001 699 

28 0.1017 6,001 610 

29 0.0887 6,001 532 

30 0.0773 6,001 464 

31 0.0673 6,001 404 

32 0.0586 6,001 352 

33 0.0509 6,001 305 

34 0.0443 6,001 266 

35 0.0385 6,001 231 

36 0.0334 6,001 200 

 

Adjusted Lifetime Light Truck VMT 171,590 
VIII-17 

 In interpreting the survivability and annual mileage estimates reported in Tables VIII-2a through 

VIII-2d, it is important to understand that vehicles are considered to be of age 1 during the 

calendar year that coincides with their model year Thus for example, model year 2010 vehicles 

will be considered to be of age 1 during calendar year 2010. This convention is used in order to 

account for the fact that vehicles produced during a model year typical are first offered for sale in 

June through September of the preceding calendar year (for example, sales of a model year 

typically begin in June through September of the previous calendar year, depending on 

manufacturer). Thus virtually all of the vehicles produced during a model year will be in use for 

some or all of the calendar year coinciding with their model year, and they are considered to be 

of age 1 during that year.254 As an illustration, virtually the entire production of model year 

2008 vehicles will have been sold and placed in service by the end of calendar year 2008, so 

model year 2008 vehicles are defined to be of age 1 during calendar year 2008.Model year 2008 

vehicles are subsequently defined to be of age 2 during calendar year 2009, age 3 during 

calendar year 2010, and so on, until they reach their maximum age of 36 years in calendar year 

2043 (2008 + 35 = 2043). 

To determine the impact of improved CAFE standards, fuel consumption is calculated using both 

current and revised CAFE levels. The difference between these estimates represents the net 

savings from increased CAFE standards. With the current CAFE standard assumed to remain in 

effect, total fuel consumption by each model year’s vehicles during each calendar year they 

remain in service is calculated by dividing the total number of miles they are driven during that 

year by the average on-road fuel economy level they would achieve under the higher of either the 

manufacturer-specific standard or their production plans. With the final rule in effect, total fuel 

consumption by each model year’s vehicles during each future calendar year is calculated by 

dividing the total number of miles they are driven by the higher on-road fuel economy level 

associated with that stricter CAFE standard. The total number of miles that vehicles are driven 

each year is different under the final rule than with the current standards remaining in effect as a 

result of the fuel economy “rebound effect,” which is discussed in detail later in this chapter. 

The economic benefits to vehicle owners that result from future fuel savings are valued in this 

analysis over the complete expected lifetimes of the vehicles affected by the final rule. This 

reflects the assumption that while the purchaser and first owner of a new vehicle might not 

realize the full lifetime benefits of improved fuel economy, subsequent owners of that same 

vehicle will continue to experience the resulting fuel savings until the vehicle is retired from 

service. It is important to note, however, that not all vehicles produced during a model year 

remain in service for the complete lifetime (26-year for passenger cars or 36 –year for light 

trucks) of each model year assumed in this analysis. Due to the pattern of vehicle retirement 

over this period, the expected or average lifetime of a representative vehicle is approximately 

half of that figure. 

CAFE’s most immediate impacts are on individual consumers, but regulating fuel economy also 

has a broader societal impact that must be considered. The agency believes that CAFE standards 

should reflect the true economic value of resources that are saved when less fuel is produced and 

 

254 One complication arises because registration data are typically collected for July 1 of each calendar year, so not 

all vehicles produced during a model year will appear in registration data until the calendar year when they have 

reached age 2 (and sometimes age 3) under this convention. 
VIII-18 

consumed, higher vehicle prices, and, to the extent possible, any externalities that impact the 

broader society. Consumers’ perceptions of these values may differ from their actual impacts, 

but they will nonetheless experience the full value of actual fuel savings just as they will pay the 

full increased cost when the vehicle is purchased. 

Moreover, the first and any subsequent owners of a vehicle will together realize these savings 

throughout its entire on-road lifetime. While a vehicle’s buyer may only experience fuel savings 

for the limited time he or she typically owns that vehicle, any subsequent purchasers and owners 

of that used vehicle will continue to experience the fuel savings resulting from its higher fuel 

economy throughout the remainder of its useful life. The agency restricts its analysis of the sales 

impacts of higher new vehicle prices to the length of time the buyers of new vehicles typically 

own the vehicles they purchase, under the assumption that their purchase decisions will be 

influenced only by the benefits they receive during the time they expect to own the vehicles they 

purchase new. The agency estimates the length of this period using the average term of new car 

loans, which has recently averaged almost exactly 5 years.255 However, the agency believes that 

the value of fuel savings resulting from more efficient operation over the entire lifetime of 

vehicles should be reflected in its analysis of the societal impacts that will determine fuel 

economy standards. 

As noted in Chapter 1, the economic value of fuel savings resulting from the final rule is 

estimated by applying the forecast of future fuel prices from the High Price Case from the 

Energy Information Administration’s Annual Energy Outlook 2008 to each future year’s 

estimated fuel savings.256 (The uncertainty analysis reported in Chapter X uses fuel price 

forecasts from the Low and Reference Oil Price Scenarios included in AEO 2008 to examine the 

effects a range of possible fuel price scenarios) The AEO 2008 forecast of future fuel prices, 

which is reported in Table VIII-4, represents retail prices per gallon of fuel, which includes 

Federal, State, and any applicable local taxes. While the retail price of fuel is the proper measure 

for valuing fuel savings from the perspective of vehicle owners, two adjustments to the retail 

price are necessary in order to reflect the economic value of fuel savings to society as a whole. 

First, Federal and State taxes are excluded from the social value of fuel savings because these do 

not reflect costs of resources used in fuel production, and thus do not reflect resource savings 

that would result from reducing fuel consumption. Instead, fuel taxes simply represent resources 

that are transferred from one segment of the population to another. Any reduction in State and 

Federal fuel tax payments by consumers will reduce government revenues by the same amount, 

thus ultimately reducing the value of government-financed services by approximately that same 

amount. The benefit derived from lower taxes to individuals is thus likely to be offset exactly by 

a reduction in the value of services provided to society. 

Second, the economic cost of externalities generated by imports and consumption of petroleum 

products will be reduced in proportion to gasoline savings resulting from the final rule. The 

 

255 This estimate is derived from Federal Reserve Board, Federal Reserve Statistical Release G. 19: Consumer 

Credit, November 7, 2007, http://www.federalreserve.gov/releases/g19/Current/. 256 U.S. Department of Energy, Energy Information Administration, Annual Energy Outlook 2008, High Price Case 

Table 12, http://www.eia.doe.gov/oiaf/aeo/excel/aeohptab_12.xls. 
VIII-19 

estimated economic value of these externalities is converted into its per-gallon equivalent and 

added to the pre-tax price of gasoline in order to measure this additional benefit to society for 

each gallon of fuel saved. This also allows the magnitude of these externalities to be easily 

compared to the value of the resources saved from reduced fuel production and use, which 

represents the most important component of the social benefits from saving gasoline. A 

discussion of these externality values is included in the next section of this chapter 

Table VIII-4 illustrates the adjustment of forecast retail fuel prices to remove the value of fuel 

taxes and add the value of economic externalities from petroleum imports and use. The 

derivation of the estimated value of reduced economic externalities from petroleum use shown in 

the table is explained in detail in the following section. While the High Price Case fuel price 

forecasts reported in AEO 2008 extend through 2030, the agency’s analysis of the value of fuel 

savings over the 26-year maximum lifetimes of MY 2011 passenger cars and 36-year maximum 

lifetimes MY 2011 light trucks requires forecasts extending through calendar year 2050. The 

agency assumes that retail fuel prices will remain at the 2030 forecast values reported in the AEO 

2008 High Price Case forecast over the period from 2030 through 2052 (in constant-dollar 

terms). As Table VIII-4 shows, the projected retail price of gasoline expressed in 2007 dollars 

rises steadily over most of the forecast period, from $2.95 in 2011 to $3.51 in 2024, and then 

decreasing for a few years until it reaches $3.62 in 2030. As mentioned above, it is assumed to 

remain at that level through 2052. 

Since gasoline taxes are a transfer payment and not a societal cost, the value of gasoline taxes is 

subtracted from the estimated gasoline price to estimate the value to society of saving gasoline. 

The agency has updated its estimates of gasoline taxes, using updated State tax rates reported for 

January 1, 2006257 expressed in 2007 dollars, Federal gasoline taxes are currently $0..184, while 

State and local gasoline taxes together average $0.236 per gallon, for a total tax burden of $0.420 

per gallon. 

Following the assumptions used by EIA in its National Energy Modeling System (NEMS), state 

and local gasoline taxes are assumed to keep pace with inflation in nominal terms, and thus to 

remain constant when expressed in constant 2007dollars. In contrast, federal gasoline taxes are 

assumed to remain unchanged in nominal terms, and thus to decline throughout the forecast 

period when expressed in constant 2007 dollars. These differing assumptions about the likely 

future behavior of federal and state/local fuel taxes are consistent with recent historical 

experience, and reflect the fact that Federal motor fuel taxes and most State taxes are specified 

on a cents-per-gallon basis (some State taxes are levied as a percentage of the wholesale price of 

fuel), and typically require legislation to change. 

 

Actual fuel economy levels achieved by light-duty vehicles in on-road driving fall somewhat 

short of their levels measured under the laboratory-like test conditions used by EPA to establish 

its published fuel economy ratings for different models. In analyzing the fuel savings from 

alternative CAFE standards, NHTSA has previously adjusted the actual fuel economy 

performance of each light truck model downward from its rated value to reflect the expected size 

 

257 FHWA, Highway Statistics 2006, Section I: Motor Fuel -- Rates and Revenues, Table MF-121T, 

available at http://www.fhwa.dot.gov/policy/ohim/hs06/pdf/mf121t.pdf. 
VIII-20 

of this on-road fuel economy “gap.” On December 27, 2006, EPA adopted changes to its 

regulations on fuel economy labeling, which were intended to bring vehicles’ rated fuel economy 

levels closer to their actual on-road fuel economy levels.258

In its Final Rule, EPA estimated that actual on-road fuel economy for light-duty vehicles 

averages 20 percent lower than published fuel economy levels. For example, if the overall EPA 

fuel economy rating of a light truck is 20 mpg, the on-road fuel economy actually achieved by a 

typical driver of that vehicle is expected to be 16 mpg (20*.80). NHTSA has employed EPA’s 

revised estimate of this on-road fuel economy gap in this analysis of the fuel savings resulting 

from alternative CAFE standards proposed in this rulemaking. 

 

258 71 FR 77871 (Dec. 27, 2006). 
VIII-21 

Table VIII-4 

Adjustment of Forecast Retail Gasoline Price to Reflect Social Value of Fuel Savings 

Year 

AE0 2008 Forecast of 

Retail Gasoline Price 

(2007 $/gallon) 

Estimated Federal 

and State Taxes 

(2007 $/gallon) 

Forecast Gasoline Price 

Excluding Taxes 

(2007 $/gallon) 

Forecast Gasoline Price 

Including Externalities

(2007 $/gallon) 

2011 $2.949 $0.420 $2.529 $2.911 

2012 $2.974 $0.416 $2.558 $2.939 

2013 $3.023 $0.412 $2.611 $2.993 

2014 $3.077 $0.409 $2.668 $3.049 

2015 $3.093 $0.405 $2.688 $3.069 

2016 $3.138 $0.402 $2.736 $3.117 

2017 $3.200 $0.399 $2.801 $3.182 

2018 $3.241 $0.395 $2.846 $3.228 

2019 $3.301 $0.392 $2.909 $3.291 

2020 $3.363 $0.388 $2.975 $3.357 

2021 $3.451 $0.385 $3.066 $3.447 

2022 $3.491 $0.381 $3.110 $3.491 

2023 $3.492 $0.378 $3.114 $3.496 

2024 $3.510 $0.374 $3.136 $3.518 

2025 $3.485 $0.371 $3.114 $3.496 

2026 $3.494 $0.371 $3.123 $3.504 

2027 $3.518 $0.371 $3.147 $3.529 

2028 $3.545 $0.371 $3.174 $3.555 

2029 $3.576 $0.371 $3.205 $3.586 

2030-2052 $3.618 $0.371 $3.247 $3.628 

Other Economic Benefits from Reducing Petroleum Use 

The agency believes that assessing the economic case for increasing the stringency of fuel 

economy standards requires a comprehensive analysis of the resulting benefits and costs to the 

U.S economy, rather than simply comparing the direct costs associated with petroleum use and 

fuel production to current fuel taxes. The benefits of more stringent fuel economy standards 

include the market value of the savings in resources from producing less fuel, together with the 

resulting reductions in the costs of economic externalities associated with petroleum 

consumption, and of environmental externalities caused by fuel consumption and production. 

Environmental externalities include adverse health impacts associated with criteria pollutants and 

environmental damage associated with greenhouse gases. The costs imposed on the U.S. 

economy by more stringent fuel economy regulation include those costs for manufacturing more 

fuel-efficient vehicles, as well as the increased external costs of congestion, crashes, noise and 

pollution from added driving caused by the rebound effect. 

Vehicle buyers value improved fuel economy using retail fuel prices and miles per gallon, but 

may consider fuel savings only over the time they expect to own a vehicle, while the value to the 

U.S. economy of saving fuel is measured by its pre-tax price, and includes fuel savings over the 
VIII-22 

entire lifetime of vehicles. Thus, it cannot simply be assumed that the interaction of 

manufacturers’ costs and vehicle buyers’ demands in the private marketplace will determine 

optimal fuel economy levels, and that these levels should only be adjusted by Federal regulation 

if the external costs of fuel production and use exceed current fuel taxes. 

The Agency’s analysis estimates the value of each category of benefits and costs separately, and 

it compares the total benefits resulting from each alternative level to its total costs in order to 

assess its desirability. This more complete accounting of benefits and costs to the U.S. economy 

from reducing fuel use is necessary to assess the case for fuel economy regulation generally, and 

for increasing the stringency of the current passenger car and light truck fuel economy standards 

in particular. 

U.S. consumption and imports of petroleum products also impose costs on the domestic 

economy that are not reflected in the market price for crude petroleum, or in the prices paid by 

consumers of petroleum products such as gasoline. These costs include (1) higher prices for 

petroleum products resulting from the effect of U.S. oil import demand on the world oil price; (2) 

the risk of disruptions to the U.S. economy caused by sudden reductions in the supply of 

imported oil to the U.S.; and (3) expenses for maintaining a U.S. military presence to secure 

imported oil supplies from unstable regions, and for maintaining the strategic petroleum reserve 

(SPR) to cushion against resulting price increases. Higher U.S. imports of crude oil or refined 

petroleum products raise the magnitude of these external economic costs, thus increasing the true 

economic cost of supplying transportation fuels above the resource costs of producing them. 

Conversely, reducing U.S. imports of crude petroleum or refined fuels or reducing fuel 

consumption can reduce these external costs. Any reduction in their total value that results from 

improved vehicle fuel economy represents an economic benefit of raising fuel economy 

standards in addition to the value of fuel savings and emissions reductions itself. 

Demand costs 

Increased U.S. oil imports can impose higher costs on all purchasers of petroleum products, 

because the U.S. is a sufficiently large purchaser of foreign oil supplies that changes in U.S. 

demand can affect the world price. The effect of U.S. petroleum imports on world oil prices is 

determined by the degree of OPEC monopoly power over global oil supplies, and the degree of 

monopsony power over world oil demand exerted by the U.S. The combination of these two 

factors means that increases in domestic demand for petroleum products that are met through 

higher oil imports can cause the price of oil in the world market to rise, which imposes economic 

costs on all other purchasers in the global petroleum market in excess of the higher prices paid 

by U.S. consumers.259 Conversely, reducing U.S. oil imports can lower the world petroleum 

price, and thus generate benefits to other oil purchasers by reducing these “monopsony costs.” 

 

259 For example, if the U.S. imports 10 million barrels of petroleum per day at a world oil price of 

$80 per barrel, its total daily import bill is $800 million. If increasing imports to 11 million 

barrels per day causes the world oil price to rise to $81 per barrel, the daily U.S. import bill rises 

to $891 million. The resulting increase of $91 million per day ($891 million minus $800 

million) is attributable to increasing daily imports by only 1 million barrels. This means that the 

incremental cost of importing each additional barrel is $91, or $10 more than the newly-
VIII-23 

Although the degree of current OPEC monopoly power is subject to considerable debate, the 

consensus appears to be that OPEC remains able to exercise some degree of control over the 

response of world oil supplies to variation in world oil prices, so that the world oil market does 

not behave competitively.260 The extent of U.S. monopsony power is determined by a complex 

set of factors including the relative importance of U.S. imports in the world oil market, and the 

sensitivity of petroleum supply and demand to its world price among other participants in the 

international oil market. Most evidence appears to suggest that variation in U.S. demand for 

imported petroleum continues to exert some influence on world oil prices, although this 

influence appears to be limited.261 

In analyzing benefits from its recent actions to increase light truck CAFE standards for model 

years 2005-07 and 2008-11, NHTSA relied on a 1997 study by Oak Ridge National Laboratories 

(ORNL) to estimate the value of reduced economic externalities from petroleum consumption 

and imports.262 More recently, ORNL updated its estimates of the value of these externalities, 

using the analytic framework developed in its original 1997 study in conjunction with recent 

estimates of the variables and parameters that determine their value. 263 These include world oil 

prices, current and anticipated future levels of OPEC petroleum production, U.S. oil import 

levels, the estimated responsiveness of oil supplies and demands to prices in different regions of 

the world, and the likelihood of oil supply disruptions. ORNL’s prepared its updated estimates 

of oil import externalities were for use by EPA in evaluating the benefits of reductions in U.S. oil 

consumption and imports expected to result from its recently-issued Renewable Fuel Standard 

Rule of 2007 (RFS)264. 

The updated ORNL study was subjected to a detailed peer review and its estimates of the value 

of oil import externalities were subsequently revised to reflect their comments and 

recommendations. 265 Specifically, reviewers recommended that ORNL increase its estimates of 

the sensitivity of oil supply by non-OPEC producers and oil demand by nations other than the 

U.S. to changes in the world oil price, as well as reduce its estimate of the sensitivity of U.S. 

gross domestic product (GDP) to potential sudden increases in world oil prices. After making 

 

increased world price of $81 per barrel. This additional $10 per barrel represents a cost imposed 

on all other purchasers in the global petroleum market by U.S. buyers, in excess of the price they 

pay to obtain those additional imports. 

260 For a summary see Leiby, Paul N., Donald W. Jones, T. Randall Curlee, and Russell Lee, Oil Imports: An 

Assessment of Benefits and Costs, ORNL-6851, Oak Ridge National Laboratory, November 1, 1997, at 17. 

Available at http://dmses.dot.gov/docimages/pdf93/343894_web.pdf (last accessed Dec. 2, 2007). 261 Id., at 18-19. 262 Leiby, Paul N., Donald W. Jones, T. Randall Curlee, and Russell Lee, Oil Imports: An Assessment of Benefits 

and Costs, ORNL-6851, Oak Ridge National Laboratory, November 1, 1997. Available at

http://dmses.dot.gov/docimages/pdf93/343894_web.pdf (last accessed Dec. 2, 2007). 

263 Leiby, Paul N. "Estimating the Energy Security Benefits of Reduced U.S. Oil Imports," Oak Ridge National 

Laboratory, ORNL/TM-2007/028, Revised July 23, 2007. Available at http://pzl1.ed.ornl.gov/energysecurity.html 

(click on link below “Oil Imports Costs and Benefits”) (last accessed Sept. 10, 2007). 264 Federal Register Vol.72, #83, May 1, 2007 pp.23,900-24,014 

265 Peer Review Report Summary: Estimating the Energy Security Benefits of Reduced U.S. Oil Imports, 

ICF, Inc., September 2007. 
VIII-24 

the revisions recommended by peer reviewers, ORNL’s updated estimates of the monopsony 

cost associated with U.S. oil imports range from $2.77 to $13.11per barrel, with a most likely 

estimate of $7.41 per barrel (2005$). These estimates imply that each gallon of fuel saved as a 

result of adopting higher CAFE standards will reduce the monopsony costs of U.S. oil imports 

by $0.066 to $0.312 per gallon, with the actual value most likely to be $0.176 per gallon saved 

(2005$). The agency notes, however, that the monopsony cost varies directly with world oil 

prices, and that the forecast of world oil prices used in this analysis differs significantly from that 

assumed in the ORNL study. Thus NHTSA has further adjusted the updated ORNL estimate of 

the monopsony cost to reflect the AEO 2008 High Price case forecast of world oil prices, which 

averages $88 per barrel (in 2007 dollars) over the period from 2011-30. Expressed in 2007 

dollars, NHTSA’s revised estimates of the reductions in monopsony costs are $0.266 per gallon 

of fuel saved. This represents an economic benefit in addition to the value of savings in fuel 

production costs that would result from improving fuel economy. 

Disruption and Adjustment Costs 

The second component of external economic costs imposed by U.S. petroleum imports arises 

partly because an increase in oil prices triggered by a disruption in the supply of imported oil 

reduces the level of output that the U.S. economy can produce. The reduction in potential U.S. 

economic output depends on the extent and duration of the increases in petroleum product prices 

that result from a disruption in the supply of imported oil, as well as on whether and how rapidly 

these prices return to pre-disruption levels. Even if prices for imported oil return completely to 

their original levels, however, economic output will be at least temporarily reduced from the 

level that would have been possible without a disruption in oil supplies. 

Because supply disruptions and resulting price increases tend to occur suddenly rather than 

gradually, they can also impose costs on businesses and households for adjusting their use of 

petroleum products more rapidly than if the same price increase had occurred gradually over 

time. These adjustments impose costs because they temporarily reduce economic output even 

below the level that would ultimately be reached once the U.S. economy completely adapted to 

higher petroleum prices. The additional costs to businesses and households reflect their inability 

to adjust prices, output levels, and their use of energy and other resources quickly and smoothly 

in response to rapid changes in prices for petroleum products. 

Since future disruptions in foreign oil supplies are an uncertain prospect, each of these disruption 

costs must be adjusted by the probability that the supply of imported oil to the U.S. will actually 

be disrupted. The “expected value” of these costs – the product of the probability that an oil 

import disruption will occur and the costs of reduced economic output and abrupt adjustment to 

sharply higher petroleum prices – is the appropriate measure of their magnitude. Any reduction 

in these expected disruption costs resulting from a measure that lowers U.S. oil imports 

represents an additional economic benefit beyond the direct value of savings from reduced 

purchases of petroleum products. 

While the vulnerability of the U.S. economy to oil price shocks is widely thought to depend on 

total petroleum consumption rather than on the level of oil imports, variation in imports is still 

likely to have some effect on the magnitude of price increases resulting from a disruption of 

import supply. In addition, changing the quantity of petroleum imported into the U.S. may also 
VIII-25 

affect the probability that such a disruption will occur. If either the size of the likely price 

increase or the probability that U.S. oil supplies will be disrupted is affected by oil imports, the 

expected value of the costs from a supply disruption will also depend on the level of imports. 

Businesses and households use a variety of market mechanisms, including oil futures markets, 

energy conservation measures, and technologies that permit rapid fuel switching to “insure” 

against higher petroleum prices and reduce their costs for adjusting to sudden price increases. 

While the availability of these market mechanisms has likely reduced the potential costs of 

disruptions to the supply of imported oil, consumers of petroleum products are unlikely to take 

account of costs they impose on others, so these costs are probably not reflected in the price of 

imported oil. Thus changes in oil import levels probably continue to affect the expected cost to 

the U.S. economy from potential oil supply disruptions, although this component of oil import 

costs is likely to be significantly smaller than estimated by studies conducted in the wake of the 

oil supply disruptions during the 1970s. 

ORNL’s updated and revised estimates of the increase in the expected costs associated with oil 

supply disruptions to the U.S. and the resulting rapid increase in prices for petroleum products 

amount to $2.10 to $7.40 per barrel, although its most likely estimate of $4.59 per barrel is very 

close to the lower end of this range. According to these estimates, each gallon of fuel saved will 

reduce the expected costs disruptions to the U.S. economy by $0.050 to $0.176, with the actual 

value most likely to be $0.109 per gallon (2005$). Updated to 2007 dollars, the value of oil 

supply disruptions is estimated to be $.116 per gallon. Like the reduction in monopsony costs, 

the reduction in expected disruption costs represents an economic benefit in addition to the value 

of savings in fuel production costs that would result from improving fuel economy. 

Military Security and Strategic Petroleum Reserve Costs 

The third component of the external economic costs of importing oil into the U.S. includes 

government outlays for maintaining a military presence to secure the supply of oil imports from 

potentially unstable regions of the world and to protect against their interruption. Some analysts 

also include outlays for maintaining the U.S. Strategic Petroleum Reserve (SPR), which is 

intended to cushion the U.S. economy against the consequences of disruption in the supply of 

imported oil, as additional costs of protecting the U.S. economy from oil supply disruptions. 

NHTSA currently believes that while costs for U.S. military security may vary over time in 

response to long-term changes in the actual level of oil imports into the U.S., these costs are 

unlikely to decline in response to any reduction in U.S. oil imports resulting from raising future 

CAFE standards for light-duty vehicles. U.S. military activities in regions that represent vital 

sources of oil imports also serve a broader range of security and foreign policy objectives than 

simply protecting oil supplies, and as a consequence are unlikely to vary significantly in 

response to changes in the level of oil imports prompted by higher standards. 

Neither the Congress nor the Executive Branch has ever attempted to calibrate U.S. military 

expenditures, force levels, or deployments to any oil market variable, or to some calculation of 

the projected economic consequences of hostilities in the Persian Gulf. Instead, changes in U.S. 

force levels, deployments, and thus military spending in that region have been largely governed 
VIII-26 

by political events, emerging threats, and other military and political considerations, rather than 

by shifts in U.S. oil consumption or imports. NHTSA thus concludes that the levels of U.S. 

military activity and expenditures are likely to remain unaffected by even relatively large 

changes in light duty vehicle fuel consumption. 

Nevertheless, the agency conducted a sensitivity analysis of the potential effect of assuming that 

some reduction military spending would result from fuel savings and reduced petroleum imports 

in order to investigate its impacts on the standards and fuel savings. Assuming that the 

preceding estimate of total U.S. military costs for securing Persian Gulf oil supplies is correct, 

and that approximately half of these expenses could be reduced in proportion to a reduction in 

U.S. oil imports from the region, the estimated savings would range from $0.02 to $0.08 (in 2007 

dollars) for each gallon of fuel savings that was reflected in lower U.S. imports of petroleum 

from the Persian Gulf. If the Persian Gulf region is assumed to be the marginal source of supply 

for U.S. imports of crude petroleum and refined products, then each gallon of fuel saved might 

reduce U.S. military outlays by $0.05 per gallon, the midpoint of this range. NHTSA employs 

this estimate in its sensitivity analysis. 

Similarly, while the optimal size of the SPR from the standpoint of its potential influence on 

domestic oil prices during a supply disruption may be related to the level of U.S. oil consumption 

and imports, its actual size has not appeared to vary in response to recent changes in oil imports. 

Thus while the budgetary costs for maintaining the Reserve are similar to other external costs in 

that they are not likely to be reflected in the market price for imported oil, these costs do not 

appear to have varied in response to changes in oil import levels. As a result, the agencies’ 

analysis of benefits from alternative CAFE standards does not include cost savings from either 

reduced outlays for U.S. military operations or maintaining a smaller SPR among the external 

benefits of reducing gasoline consumption and petroleum imports by means of tightening future 

standards. This view concurs with that of the recent ORNL study of economic costs from U.S. 

oil imports, which concludes that savings in government outlays for these purposes are unlikely 

to result form modest reductions in consumption of petroleum products and oil imports. 

Thus, for purposes of setting the MY 2011 standards, NHTSA has included only the likely 

reductions in monopsony and disruption costs from lower U.S. petroleum imports in its estimate 

of the savings in external economic costs from reducing fuel consumption. The updated and 

revised ORNL estimates suggest that the combined reduction in monopsony costs and expected 

costs to the U.S. economy from oil supply disruptions resulting from lower fuel consumption 

total $0.152 to $0.657 per gallon, with a most likely estimate of $0.381 per gallon. This 

represents the additional economic benefit likely to result from each gallon of fuel saved by 

higher CAFE standards, beyond the savings in resource costs for producing and distributing each 

gallon of fuel saved. NHTSA employed this estimate in its analysis of the benefits from fuel 

savings projected to result from alternative CAFE standards for model year 2011. 

The Effect of Fuel Savings on Fuel Supply

Based on a detailed analysis of differences in fuel consumption, petroleum imports, and imports 

of refined petroleum products among the Reference Case, High Economic Growth, and Low 

Economic Growth Scenarios presented in the Energy Information Administration’s Annual 

Energy Outlook 2008, the agency estimates that approximately 50 percent of the reduction in 
VIII-27 

fuel consumption resulting from adopting higher CAFE standards is likely to be reflected in 

reduced U.S. imports of refined fuel, while the remaining 50 percent would be expected to be 

reflected in reduced domestic fuel refining. Of this latter figure, 90 percent is anticipated to 

reduce U.S. imports of crude petroleum for use as a refinery feedstock, while the remaining 10 

percent is expected to reduce U.S. domestic production of crude petroleum. Thus on balance, 

each gallon of fuel saved as a consequence of higher CAFE standards is anticipated to reduce 

total U.S. imports of crude petroleum or refined fuel by 0.95 gallons.266 

Emissions Reductions Resulting from Fuel Savings 

Emissions of carbon dioxide and other greenhouse gases (GHGs) occur throughout the process 

of producing and distributing transportation fuels, as well as from fuel combustion itself. By 

reducing the volume of fuel consumed by passenger cars and light trucks, higher CAFE 

standards will thus reduce GHG emissions generated by fuel use, as well as throughout the fuel 

supply cycle. Lowering these emissions is likely to slow the projected pace and reduce the 

ultimate extent of future changes in the global climate, thus reducing future economic damages 

that changes in the global climate are otherwise expected to cause. Further, by reducing the 

probability that climate changes with potentially catastrophic economic or environmental 

impacts will occur, lowering GHG emissions may also result in economic benefits that exceed 

the resulting reduction in the expected future economic costs caused by gradual changes in the 

earth’s climatic systems. 

Quantifying and monetizing benefits from reducing GHG emissions is thus an important step in 

estimating the total economic benefits likely to result from establishing higher CAFE standards. 

Since direct estimates of the economic benefits from reducing GHG emissions are generally not 

reported in published literature on the impacts of climate change, these benefits are typically 

assumed to be the “mirror image” of the estimated incremental costs resulting from an increase 

in those emissions. That is, the benefits from reducing emissions are usually measured by the 

savings in estimated economic damages that an equivalent increase in emissions would otherwise 

have caused. 

Researchers usually estimate the economic costs of increased GHG emissions in several steps. 

The first is to project future changes in the global climate and the resulting economic damages 

that are expected to result under a baseline projection of net global GHG emissions. These 

projections are usually developed using models that relate concentrations of GHGs in the earth’s 

atmosphere to changes in summary measures of the global climate such as temperature and sea 

levels, and in turn estimate the reductions in global economic output that are expected to result 

from changes in climate. Since the effects of GHG emissions on the global climate occur 

decades or even centuries later, and there is considerable inertia in the earth’s climate systems, 

changes in the global climate and the resulting economic impacts must be estimated over a 

comparably long future period. 

Next, this same process is used to project future climate changes and resulting economic 

damages under the assumption that GHG emissions increase by some increment during a stated 

future year. The increase in projected global economic damages resulting from the assumed 

 

266 This figure is calculated as 0.50 + 0.50*0.9 = 0.50 + 0.45 = 0.95. 
VIII-28 

increase in future GHG emissions, which also occurs over a prolonged period extending into the 

distant future, represents the added economic costs resulting from the assumed increase in 

emissions. Discounted to its current value as of the year when the increase in emissions are 

expected to occur and expressed per unit of GHG emissions (usually per ton of carbon emissions, 

with non-CO2 GHGs converted to their equivalents in terms of carbon emissions), the resulting 

value represents the global economic cost of increasing GHG emissions by one unit – usually a 

metric ton of carbon – in a stated future year. This value is often referred to in published 

research and debates over climate policy as the Social Cost of Carbon (SCC), and applies 

specifically to increased emissions during that year. 

This process involves multiple sources of uncertainty, including those in scientific knowledge 

about the effects of varying levels of GHG emissions on the magnitude and timing of changes in 

the functioning of regional and global climatic and ecological systems. In addition, significant 

uncertainty surrounds the anticipated extent, geographic distribution, and timing of the resulting 

impacts on the economies of nations located in different regions of the globe. Because the 

climatic and economic impacts of GHG emissions are projected to occur over the distant future, 

uncertainty about the correct rate at which to discount these future impacts also significantly 

affects the estimated economic benefits of reducing GHG emissions. 

Researchers have not yet been able to quantify many of the potentially significant effects of 

GHG emissions and their continued accumulation in the earth’s atmosphere on the global 

climate. Nor have they developed complete models to represent the anticipated impacts of 

changes in the global climate on economic resources and the productivity with which they are 

used to generate economic output. As a consequence, the estimates of economic damages 

resulting from increased GHG emissions that are generated using integrated models of climate 

and economic activity exclude some potentially significant sources of costs that are likely to 

result from increased emissions. As a result, estimates of economic benefits derived from these 

models’ estimates of the likely future climate-related economic damages caused by increased 

GHG emissions may underestimate the true economic value of reducing emissions, although the 

extent to which they are likely to do so remains unknown. 

In the NPRM, NHTSA explained how it accounted for the economic benefits of reducing CO2

emissions in this rulemaking, both in developing the proposed CAFE standards and in assessing 

the economic benefits of each alternative that was considered. The agency noted that the Ninth 

Circuit found in CBD v. NHTSA that NHTSA had been arbitrary and capricious in deciding not 

to monetize the benefit of reducing CO2 emissions, stating that the agency had not substantiated 

the conclusion in its April 2006 final rule that the appropriate course was not to monetize (i.e., 

quantify the value of) carbon emissions reduction at all. NHTSA’s discussion in the NPRM of 

how it estimated the economic value of reductions in CO2 emissions received a great deal of 

attention from commenters, so for the reader’s benefit, it is largely reproduced below. 

To that end, NHTSA reviewed published estimates of the “social cost of carbon” (SCC) 

emissions. As noted above, the SCC refers to the marginal cost of additional damages caused by 

the increase in expected climate impacts resulting from the emission of each additional metric 
VIII-29 

ton of carbon, which is emitted in the form of CO2.

267 It is typically estimated as the net present 

value of the impact over some extended time period (100 years or longer) of one additional ton 

of carbon emitted into the atmosphere. Because atmospheric concentrations of greenhouse gases 

are increasing over time, and the potential damages from global climate are believed to increase 

with higher atmospheric GHG concentrations, the economic damages resulting from an 

additional ton of CO2 emissions are expected to increase over time. Thus, estimates of the SCC 

are typically reported for a specific year, and these estimates are generally larger for emissions in 

more distant future years. 

NHTSA found substantial variation among different authors’ estimates of the SCC, much of 

which can be traced to differences in their underlying assumptions about several variables. 

These variables include the sensitivity of global temperatures and other climate attributes to 

increasing atmospheric concentrations of GHGs, discount rates applied to future economic 

damages from climate change, whether damages sustained by developing regions of the world 

should be weighted more heavily than damages to developed nations, how long climate changes 

persist once they occur, and the economic valuation of specific climate impacts.268

NHTSA explained that, taken as a whole, recent estimates of the SCC may underestimate the 

true damage costs of carbon emissions because they often exclude damages caused by extreme 

weather events or climate response scenarios with low probabilities but potentially extreme 

impacts, and may underestimate the climate impacts and damages that could result from multiple 

stresses on the global climatic system. At the same time, however, many studies do not consider 

potentially beneficial impacts of climate change, and do not adequately account for how future 

technological innovations, development patterns, and adaptations could reduce potential impacts 

from climate change or the economic damages they cause. 

Given the uncertainty surrounding estimates of the SCC, NHTSA suggested that the use of any 

single study may not be advisable, since its estimate of the SCC will depend on many 

assumptions made by its authors. NHTSA cited the Working Group II’s contribution to the 

Fourth Assessment Report of the United Nations Intergovernmental Panel on Climate Change 

(IPCC) as noting that: 

The large ranges of SCC are due in large part to differences in assumptions regarding 

climate sensitivity, response lags, the treatment of risk and equity, economic and noneconomic impacts, the inclusion of potentially catastrophic losses, and discount rates.269

 

267 Carbon itself accounts for 12/44, or about 27 percent, of the mass of carbon dioxide (12/44 is the ratio of the 

molecular weight of carbon to that of carbon dioxide). Thus, each ton of carbon emitted is associated with 44/12, or 

3.67, tons of carbon dioxide emissions. Estimates of the SCC are typically reported in dollars per ton of carbon, and 

must be divided by 3.67 to determine their equivalent value per ton of carbon dioxide emissions. 

268 For a discussion of these factors, see Yohe, G.W., R.D. Lasco, Q.K. Ahmad, N.W. Arnell, S.J. Cohen, C. Hope, 

A.C. Janetos, and R.T. Perez, “Perspectives on climate change and sustainability,” 2007, in Climate Change 2007: 

Impacts, Adaptation and Vulnerability, Contribution of Working Group II to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, L.P. Palutikof, P.J. van der Linden and 

C.E. Hanson, eds., Cambridge University Press, 2007, at 821-824. Available at http://www.ipcc.ch/ipccreports/ar4-

wg2.htm (last accessed March 23, 2009). 

269 Climate Change 2007: Impacts, Adaptation and Vulnerability, Contribution of Working Group II to the Fourth 

Assessment Report of the Intergovernmental Panel on Climate Change, at 17. Available at

http://www.ipcc.ch/ipccreports/ar4-wg2.htm (last accessed March 23, 2009). 
VIII-30 

Although the IPCC is considered authoritative on the topic of the SCC, it did not recommend a 

single estimate. However, the IPCC did cite the Tol (2005) study on four separate occasions as 

the only available survey of the peer-reviewed literature that has itself been subjected to peer 

review.270 Tol developed a probability function using the SCC estimates of the peer-reviewed 

literature, which ranged from less than zero to over $200 per metric ton of carbon. In an effort to 

resolve some of the uncertainty in reported estimates of climate damage costs from carbon 

emissions, Tol (2005) reviewed and summarized 103 estimates of the SCC from 28 published 

studies. He concluded that when only peer-reviewed studies published in recognized journals are 

considered, “...climate change impacts may be very uncertain but it is unlikely that the marginal 

damage costs of carbon dioxide emissions exceed $50 per [metric] ton carbon,”271 which is about 

$14 per metric ton of CO2. In the NPRM, NHTSA assumed that the summary SCC estimates 

reported by Tol were denominated in U.S. dollars of the year of his article’s publication, 2005. 

NHTSA stated that because of the number of assumptions required by each study, the wide range 

of uncertainty surrounding these assumptions, and their critical influence on the resulting 

estimates of climate damage costs, some studies have undoubtedly produced estimates of the 

SCC that are unrealistically high, while others are likely to have estimated values that are 

improbably low. Using a value for the SCC that reflects the central tendency of estimates drawn 

from many studies reduces the chances of relying on a single estimate that subsequently proves 

to be biased. 

It is important to note that the published estimates of the SCC almost invariably include the value 

of worldwide damages from potential climate impacts caused by carbon dioxide emissions, and 

are not confined to damages likely to be suffered within the U.S. In contrast, the other estimates 

of costs and benefits of raising fuel economy standards included in this proposal include only the 

economic values of impacts that occur within the U.S. For example, the economic value of 

reducing criteria air pollutant emissions from overseas oil refineries is not counted as a benefit 

resulting from this rule, because any reduction in damages to health and property caused by 

overseas emissions are unlikely to be experienced within the U.S. 

In contrast, the reduced value of transfer payments from U.S. oil purchasers to foreign oil 

suppliers that results when lower U.S. oil demand reduces the world price of petroleum (the 

reduced “monopsony effect”) is counted as a benefit of reducing fuel use.272 The agency state 

that if its analysis were conducted from a worldwide rather than a U.S. perspective, however, the 

benefit from reducing air pollution overseas would be included, while reduced payments from 

U.S. oil consumers to foreign suppliers would not. 

In the NPRM, NHTSA tentatively concluded that in the interest of analytical consistency, i.e., in 

order to be consistent with the agency’s use of exclusively domestic costs and benefits in prior 

CAFE rulemakings, the appropriate value to be placed on climate damages caused by carbon 

emissions should be the one that reflects the change in damages to the U.S. alone. Accordingly, 

 

270 Id., at 17, 65, 813, and 822. 271 Tol, Richard S.J., “The marginal damage costs of carbon dioxide emissions: an assessment of the uncertainties,” 

Energy Policy 33 (2005), 2064-2074, at 2072. 

272 The reduction in payments from U.S. oil purchasers to domestic petroleum producers is not included as a benefit, 

however, since it represents a transfer that occurs entirely within the U.S. economy. 
VIII-31 

NHTSA noted that the value for the benefits of reducing CO2 emissions might be restricted to the 

fraction of those benefits that are likely to be experienced within the U.S. 

Although no estimates are currently available for the benefits to the U.S. itself that are likely to 

result from reducing CO2 emissions, NHTSA explained that it expected that if such values were 

developed, the agency would employ those, rather than global benefit estimates, in its analysis. 

NHTSA also stated that it anticipated that if such values were developed, they would be lower 

than comparable global values, since the U.S. is likely to sustain only a fraction of total global 

damages resulting from climate change. 

In the meantime, NHTSA explained that it elected to use the mean value of peer-reviewed 

estimated global value reported by Tol (2005), which was $43 per metric ton of carbon, as an 

upper bound on the global benefits resulting from reducing each metric ton of U.S. emissions.273 

This value corresponds to approximately $12 per metric ton of CO2 when expressed in 2006 

dollars. The Tol (2005) study is cited repeatedly as an authoritative survey in various IPCC 

reports, which are widely accepted as representing the general consensus in the scientific 

community on climate change science. 

Since Tol’s estimate includes the worldwide costs of potential damages from carbon dioxide 

emissions, NHTSA elected to employ it as an upper bound on the estimate value of the reduction 

in U.S. domestic damage costs that is likely to result from lower CO2 emissions.274 NHTSA 

noted that Tol had a more recent (2007) and inclusive survey published online with peer-review 

comments. NHTSA stated that it had elected not to rely on this study, but that it would consider 

doing so in its analysis for the final rule if the survey had been published, and would also 

consider any other newly-published evidence. 

NHTSA noted that the IPCC Working Group II Fourth Assessment Report (2007, at 822) further 

suggests that the SCC is growing at an annual rate of 2.4 percent, based on estimated increases in 

damages from future emissions reported in published studies. NHTSA also elected to apply this 

growth rate to Tol’s original 2005 estimate. Thus, by 2011, NHTSA estimated that the upper 

bound on the benefits of reducing CO2 emissions will have reached about $14 per metric ton of 

CO2, and will continue to increase by 2.4 percent annually thereafter. 

In setting a lower bound, the agency agreed with the IPCC Working Group II report (2007) that 

“significant warming across the globe and the locations of significant observed changes in many 

systems consistent with warming is very unlikely to be due solely to natural variability of 

temperatures or natural variability of the systems.” (p. 9) Although this finding suggests that the 

global value of economic benefits from reducing carbon dioxide emissions is unlikely to be zero, 

 

273 $43 per ton of carbon emissions was reported by Tol (at 2070) as the mean of the “best” estimates reported in 

peer-reviewed studies (at the time). It thus differs from the mean of all estimates reported in the peer-reviewed 

studies surveyed by Tol. The $43 per ton value was also attributed to Tol by IPCC Working Group II (2007), at 

822. 

274 For purposes of comparison, NHTSA noted that in the rulemaking to establish CAFE standards for MY 2008-11 

light trucks, NRDC recommended a value of $10-$25 per ton of CO2 emissions reduced by fuel savings, and both 

EDF and UCS recommended a value of $50 per ton of carbon, which is equivalent to about $14 per ton of CO2

emissions. 
VIII-32 

NHTSA stated that it does not necessarily rule out low or zero values for the benefit to the U.S. 

itself from reducing emissions. 

In some of the analysis it performed to develop the CAFE standards, NHTSA employed a point 

estimate for the value of reducing CO2 emissions. For this estimate, the agency used the 

midpoint of the range from $0 to $14, or $7.00, per metric ton of CO2 as the initial value for the 

year 2011, and assumed that this value would grow at 2.4 percent annually thereafter. This 

estimate was employed for the analyses conducted using the Volpe model to support 

development of the proposed standards. The agency also conducted sensitivity analyses of the 

benefits from reducing CO2 emissions using both the upper ($14/metric ton) and lower 

($0/metric ton) bounds of this range. 

NHTSA sought comment on its tentative conclusion for the value of the SCC, the use of a 

domestic versus a global value for the economic benefit of reducing CO2 emissions, the rate at 

which the value of the SCC grows over time, the desirability of and procedures for incorporating 

benefits from reducing emissions of GHGs other than CO2, and any other aspects of developing a 

reliable SCC value for purposes of establishing CAFE standards. 

NHTSA received many comments on its assumptions in the NPRM about the SCC. The 

comment summaries are presented below and grouped by topic: 

(1) NHTSA’s proposal of a single value for the SCC; 

(2) NHTSA’s proposal of $7 as the value for the SCC; 

(3) NHTSA’s proposal of $0 as the lower bound estimate for the domestic U.S. value for 

the SCC; 

(4) NHTSA’s proposal of $14 as the upper bound estimate for the domestic U.S. value 

for the SCC; 

(5) other values that NHTSA could have proposed for the SCC; 

(6) NHTSA’s use of a domestic versus a global value for the economic benefit of 

reducing CO2 emissions; 

(7) the rate at which the SCC grows over time; 

(8) the discount rate that should be used for SCC estimates; and 

(9) other issues raised by commenters. 

(1) NHTSA’s proposal of a single value for the SCC

NHTSA received a comment on its proposal of a single value for the SCC from Prof. Gary Yohe, 

an economist who has considered the SCC extensively and whom NHTSA cited in the NPRM. 

Prof. Yohe commented that the NPRM had stated that “Using a value for the SCC that reflects 

the central tendency of estimates drawn from many studies reduces the chances of relying on a 

single estimate that subsequently proves to be biased.”275 Prof. Yohe argued that proposing a 

single value for the SCC inherently creates bias, because “Any value is based on presumptions 

about pure rate of time preference, risk and/or inequity aversion, and climate sensitivity.” 

(2) NHTSA’s proposal of $7 as the value for the SCC

NHTSA received comments from 3 individuals, CARB, the Attorneys General, 10 U.S. Senators, 

10 environmental and consumer groups, and the Alliance. Prof. Tol, whose 2005 paper provided 

 

275 73 FR 24414 (May 2, 2008). 
VIII-33 

the basis for NHTSA’s proposal of an SCC number, commented that contrary to NHTSA’s belief 

that the dollars used in Tol (2005) were 2005 dollars, they were in fact 1995 dollars. Prof. Tol 

also commented that NHTSA should “alert the reader” that although Tol (2007) was only 

“conditionally accepted,” as NHTSA had noted in the NPRM, the newer study “finds larger 

estimates than the 2005 paper.” Sierra Club et al., in its comments, also stated that Prof. Tol had 

commented on the NPRM, arguing that using 1995 instead of 2005 dollars “would make his 

1995 value of $14 closer to a 2005 value of $19.26.” 

Several commenters disputed NHTSA’s proposal of $7 as the midpoint between $0 and $14. 

UCS argued that proposing $7 puts as much weight on $0 as on $14, even though failing to 

assign a value was declared by the Ninth Circuit to be arbitrary and capricious. CBD 

commented that “NHTSA’s methodology for the selection of an estimate of the value of 

reducing greenhouse gas emissions is arbitrary and designed to minimize the estimate.” CBD 

argued that “...simply splitting the difference between two points is not a defensible 

methodology, particularly when the low point of the range is not part of a valid range but simply 

an arbitrary selection of zero as an endpoint.” 

EDF also commented NHTSA’s decision to propose $7 because it is the midpoint between $0 

and $14 also “lacks a reasoned basis,” for which “NHTSA fails to provide any justification.” 

The Sierra Club et al. commented that NHTSA is wrong to place “equal weighting and 

probability” on $0 and $14 and pick the median, and that $7 is “far below current carbon 

estimates,” citing the 2006 Stern Review which found an SCC of “on the order of” $85/tonne 

CO2. The Sierra Club argued that this shows how “misguided and unrealistic NHTSA’s carbon 

pricing really is.” 

The Attorneys General commented that NHTSA’s decision to simply halve Tol’s estimate was 

“not a reasoned judgment.” 

Public Citizen argued that there is no justification for using the midpoint, and that NHTSA 

should instead “weight the credibility of each estimate,” by making “apples to apples” 

comparisons between the studies by “looking at studies based on their assumptions.” Public 

Citizen argued that this will help NHTSA avoid skewing the result of averaging estimates from 

multiple studies. NRDC similarly argued that proposing $7 as “a simple average of its proposed 

upper and lower bounds....assumes a normal distribution of damages, which is decidedly not the 

distribution of social cost of carbon estimates.” NRDC further argued that “...most social cost of 

carbon estimates are biased downwards, for the simple reason that almost all models assume 

perfect substitutability between normal consumption goods and environmental goods.” NRDC 

cited 2007 research by Sterner and Persson disaggregating “goods” into “environmental goods” 

and “consumption goods,” which found that the price of an environmental good like carbon 

reductions increased at a faster rate as damage progressed than consumption goods would 

increase. Accordingly, NRDC argued, “NHTSA’s social cost of carbon is much too low.” 

Prof. Hanemann also commented that NHTSA did not justify its decision to pick the midpoint 

(between $0 and $14) and then project it to 2011, although he focused more particularly on 
VIII-34 

NHTSA’s not having applied “the escalation factor of a 2.4 percent increase in real terms 

beginning in 2005.” 

The Alliance commented that proposing $7 as the midpoint between $0 and $14 is incorrect. 

The Alliance argued that NHTSA must try harder to estimate the purely domestic effects of CO2

emissions reductions, and stated that NERA had found that the U.S. portion of world gross 

product “is a much better means of allocating the United States’ share of any benefits in reduced 

CO2 emissions” than picking the midpoint of a range of global SCC estimates. NERA assumed 

that the U.S. portion is 20 percent, which “reduces NHTSA’s estimate of CO2 benefits with the 

‘optimized standard’ for MY2015 from $869 million to $348 million.” NERA also argued that 

this was conservative, since the U.S., as a developed country, should be better able to adapt to 

negative global warming consequences. 

Several commenters also criticized Tol (2005) as being out of date. Prof. Hanemann made this 

point, and commented that “more recent analyses show higher damage estimates.” The 

Attorneys General similarly commented that “It seems likely that there are better estimates” than 

Tol’s, “Since [that] article is now three years old, and it itself explains in detail the many 

deficiencies in the economic literature at that time.” The Attorneys General stated that “NHTSA 

should consult with EPA on this issue, and conduct a review of the current scientific and 

economics literature.” 

Several commenters simply argued that $7/ton is too low a value for the SCC. CARB argued 

that “NHTSA’s assumed social cost of carbon in the future is also unreasonably low, and if set at 

defensible levels that also properly value cumulative impacts, could affect the stringency of the 

standards.” Carin Skoog, an individual, similarly commented that “The arbitrary decision to use 

$7/ton underestimates the economic, social, and environmental consequences of the impacts of 

global warming.” ACEEE similarly commented that NHTSA’s use of $7/ton is both 

“inconsistent with current estimates” and “fails to take into account the potentially high 

probability of a catastrophic climate change situation.” The 10 U.S. Senators who commented 

stated that NHTSA’s value of $7 per ton is “underestimated,” and “likely to be found arbitrary 

and capricious.” 

(3) NHTSA’s proposal of $0 as the lower bound estimate for the domestic U.S. value for the 

SCC

No commenters supported NHTSA’s use of $0/ton as the lower bound estimate for the U.S. 

domestic SCC. Several commenters, including UCS, EDF, and Prof. Hanemann cited the IPCC 

Fourth Assessment Report as evidence that, as Prof. Hanemann stated, “there is no credible 

evidence of any significant net benefit to the U.S. from the climate change scenarios developed 

for the Fourth IPCC Report.” The U.S. Senators who commented also stated that in citing the 

IPCC as not precluding low or zero values to the U.S., NHTSA had “fail[ed] to recognize that 

IPCC was looking at global estimates which are not disaggregated.” 

Commenters also mentioned other reports as providing evidence that there would be some net 

adverse impact on the U.S. from climate change, and thus a lower bound value of $0 was 

untenable. Prof. Hanemann cited the recent USCCSP report “conclusively eliminates the notion 

that climate change is likely to have no net adverse impact on the United States.” 
VIII-35 

UCS argued that proposing $0 as the lower bound “implies the possibility that climate change 

won’t have any negative consequences,” which “stands in stark contrast to recent government 

study findings on U.S. climate change effects and findings from ... the Academies of Science for 

the G8+5.” 

EDF commented that “A recent review of economic studies on the predicted impacts of climate 

change on different economic sectors in the U.S. by the Center for Integrative Environmental 

Research at the University of Maryland, ‘The US Economic Impacts of Climate Change and the 

Costs of Inaction: A Review and Assessment,’ also demonstrates the range and scope of adverse 

impacts that climate change will have on different sectors and regions of the U.S. economy.” 

EDF stated that “The study concluded that ‘Scientific evidence is mounting that climate change 

will directly or indirectly affect all economic sectors and regions of the country, though not all 

equally. Although there may be temporary benefits from a changing climate, the costs of climate 

change rapidly exceed benefits and place major strains on public sector budgets, personal income 

and job security.’” 

Sierra Club et al. commented that “several government reports [that] have clearly stated that CO2

emissions do have a significant impact on our economy.” NHTSA’s conclusion that “it does not 

necessarily rule out low or zero carbon values for the benefit to the U.S. itself from reducing 

emissions” is arbitrary given agency’s admission that “the global value of economic benefits 

from reducing carbon dioxide emissions is unlikely to be zero.” 

NRDC cited a U.S. government report that “documents that many of the projected impacts have 

already begun,” as well as the Stern Review which “estimated that impacts could result in a loss 

of 5-20 percent of world GDP by 2100,” and its own May 2008 report which “found U.S. 

damages from four impacts alone would cost 1.8 percent of GDP by 2100.” 

Several commenters instead raised objections to studies that may show a positive net benefit to 

the U.S. from climate change, such that a domestic SCC value could be $0. CBD stated that 

NHTSA offered “absolutely no evidence to support” proposing $0 as the lower bound, and 

argued that “only one study surveyed in Tol (2005) included central estimates below $0.00; and 

that was a non-peer-reviewed article, also authored by Tol.” CBD further argued that Tol (2005) 

never found, nor included as a consideration in developing SCC estimates, as NHTSA suggested 

in the NPRM, that any studies failed “to consider potentially beneficial impacts of climate 

change,” or to account adequately “for how future development patterns and adaptations could 

reduce potential impacts from climate change or the economic damages they cause.” 

Prof. Hanemann also argued that studies suggesting any possible positive net benefit to U.S. 

from global warming “have serious flaws and cannot withstand serious scrutiny,” and concluded 

that a value of $0 per ton is “wildly unrealistic” “even [for] a sensitivity analysis.” 

NRDC commented that “NHTSA’s lower bound seems to be based upon the fact that some 

estimates exist that are zero and even negative.” However, NRDC argued that “These lower 

bound estimates are likely based on outdated science.” NRDC “urge[d] NHTSA to do a rigorous 
VIII-36 

re-examination of Tol’s work, eliminating outdated zero estimates and adjusting for fat tailed 

upper distributions.” 

Several commenters also focused on the CBD decision to argue that NHTSA may not use $0 as 

the lower bound estimate, because as UCS stated, “the Ninth Circuit found a value of $0 to be 

arbitrary and capricious.” EDF also commented that NHTSA’s decision to pick $0 as the lower 

bound “lacks a reasoned basis,” given the Ninth Circuit decision. Sierra Club et al. and the U.S. 

Senators similarly commented that $0 as the lower bound is contrary to CBD. The comment by 

the U.S. Senators stated that “...we can only conclude that the purpose of this ‘low bound’ 

estimate is to cut the more accurate value in half in an arbitrary manner. We recommend 

NHTSA remove or justify this low bound estimate in its final CAFE regulation.” 

(4) NHTSA’s proposal of $14 as the upper bound estimate for the domestic U.S. value for the 

SCC 

No commenters supported NHTSA’s proposal of $14/ton, based on Tol (2005), as the upper 

bound estimate for the domestic U.S. value for the SCC. ACEEE argued that “NHTSA’s 

decision to use Tol’s estimate of $14 as the upper bound based on the argument that this value 

includes the worldwide costs CO2 is flawed,” although the commenter did not explain why. 

Some commenters argued that NHTSA should not have picked the median from Tol (2005) as its 

upper bound estimate. 

The U.S. Senators who commented stated that NHTSA is wrong to use $14 as the upper bound 

because Tol’s median is an average of multiple estimates, and averages should be used as 

averages and not as maximums. The Senators stated further that “NHTSA selected the lower of 

Tol’s two estimates without explanation.” The U.S. Senators also commented that Tol (2007) 

updates the previous study and finds a median of over $19/ton. NRDC also cited Tol (2007) as 

reflecting an increase in the median from $14 to $20 dollars per ton of CO2. 

Sierra Club et al. commented that $14 is an incorrect “maximum,” because the maximum that 

Tol “states that the maximum carbon value is in the range of $55-$95 per metric ton CO2.” The 

commenter further argued that if NHTSA could justify $0 as the lower bound, “then it should not 

be able to rule out the high value of $95 per ton CO2 in the study, and the average value would 

be much higher.” 

NRDC commented that NHTSA should not have used Tol’s median value of $14 as its upper 

bound for two reasons. First, a median value is not properly reflective of climate change damage 

estimate distributions, which are “asymmetric” with “fat” upper tails. And second, because of 

the unique aspects of climate change damage estimates, such as “nonlinearities, abrupt change, 

and thresholds,” “a full probability density function should be estimated, using the full range of 

all [SCC] estimates from the studies, not simply a collection of their ‘best-guesses.’” [Emphasis 

in original.] NRDC argued that research has shown that “When the same traditional social cost 

of carbon analyses are rerun incorporating the potential for nonlinear change, the resulting policy 

conclusions are changed considerably to greater mitigation,” and that “Another recent study has 

shown that incorporating the potential for low-probability, high-damage events can increase the 

social cost of carbon by a factor of 20.” 
VIII-37 

NRDC also cited Prof. Weitzman to argue that the complications of climate change damage 

estimates require any analysis to weigh more heavily the “low probability/high catastrophic 

risks,” because these will otherwise be insufficiently accounted for. In discussing the 

uncertainties associated with climate change, NRDC cited Weitzman as stating that 

The result of this immense cascading of huge uncertainties is a “reduced form” of truly 

stupendous uncertainty about the aggregate-utility impacts of catastrophic climate 

change, which mathematically is represented by a very-spread-out very-fat-tailed PDF 

[probability density function] of what might be called (present discounted) “welfare 

sensitivity”...[T]he value of “welfare sensitivity” is effectively bounded only by some 

very big number representing something like the value of statistical civilization as we 

know it or maybe even the value of statistical life on earth as we know it. 

Thus, NRDC argued, using an upper bound of $14 cannot possibly account for the uncertainties 

and risk of climate change. Like Sierra Club et al., NRDC further argued that “...for consistency 

with the rationale used for proposing the lower bound, NHTSA’s upper bound should be based 

upon some function of the highest estimates in the Tol 2005 study (the very highest was 

$1,666).”

Some commenters argued that NHTSA had overlooked particular aspects of the Tol (2005) 

study, and thus arrived at $14 incorrectly. 

CBD argued that NHTSA overlooked key aspects of the Tol (2005) analysis in proposing $14 

per ton, including the fact that Tol included significantly higher estimates in his analysis. EDF 

similarly commented that NHTSA had failed to “discuss the significant gaps in the existing 

research reviewed in [Tol (2005)] and focuse[d] on a specific estimate of the SCC that is biased 

toward lower value estimates.” EDF stated that NHTSA’s decision to use only peer-reviewed 

studies from Tol (2005) introduced particular bias, because those studies “systematically used 

higher discount rates...which may have biased their results downward” compared to averaging 

all the studies together. 

Some commenters argued that Tol (2005) was flawed to the point that it could not provide a 

reliable basis for NHTSA to use its median estimate as the upper bound. 

CBD commented that “the studies cited in the Tol (2005) survey dated back as much as 18 years, 

to 1991, and 25 of the 28 studies cited were published more than five years ago,” so given that 

climate change science is progressing very rapidly, these studies are probably outdated. 

EDF also argued that “Most of the 28 studies surveyed by Tol” are outdated and “consider only a 

limited number of potential impacts from climate change,” as Tol recognizes by cautioning that 

the estimates analyzed “may understate the true cost of climate change.” EDF stated that the 

IPCC’s “most recent compilation of SCC research” agrees. EDF also commented that Tol’s 

meta-analysis “compares studies with widely different methodologies and assumptions,” 

particularly discount rates, which EDF stated NHTSA should have controlled for because it “can 

have a considerable impact on SCC estimates.” 
VIII-38 

NRDC criticized Tol (2005) extensively in its comments. NRDC stated that Tol’s estimate was 

based on studies which exclude (1) “non-market costs, such as damage to and loss of entire 

ecosystems and species;” and (2) “studies of national security costs caused by conflicts over 

stressed resources and increased migration from heavily impacted areas,” which “describe global 

warming as a ‘threat multiplier.’” NRDC recognized that Tol acknowledged that “costs such as 

those described above are poorly accounted for in current social cost of carbon estimates,” but 

insisted that NHTSA must nonetheless account for them. 

NRDC also argued that Tol’s estimate is based on outdated studies, because “there are smaller 

natural sinks for carbon than Tol assumed, higher emissions than he assumed, a higher 

temperature response to emissions than he assumed, and faster changes in observed impacts than 

he assumed.” NRDC commented that recent events like Hurricane Katrina are evidence that the 

U.S. cannot adapt to climate change-related disasters as fast as previously thought. NRDC 

further commented that it was unclear whether Tol’s estimate “included any valuation for lost 

lives,” suggesting that including this valuation could raise SCC considerably, and arguing that 

EPA accounts for it in Clean Air Act rulemakings. 

(5) Other values that NHTSA could have chosen for the SCC 

Many commenters suggested other SCC values that they thought NHTSA should use instead of a 

value based on Tol (2005). 

Several commenters mentioned SCC values produced by EPA. In March 2008, EPA produced 

an analysis for the Senate Committee on Environment and Public Works for S. 2191, “America’s 

Climate Security Act,” also known as the Lieberman-Warner bill.276 Public Citizen commented 

that NHTSA’s upper bound estimate should be at least as high as EPA’s estimates for the 

Lieberman-Warner bill, which Public Citizen said “are more recent than the Tol estimate cited in 

NHTSA’s notice.” Public Citizen commented that EPA “estimated the value of CO2 in 2015 

between $22 and $40 per metric ton of CO2, and cited two other analyses with higher estimates 

of $48 and $50 per metric ton CO2.” Sierra Club et al. also commented that NHTSA must use a 

higher SCC value, and stated that “EPA’s recent analysis of America’s Climate Security Act of 

2007 noted that the value of a ton of CO2 could be as high as $22-$40.28.” An individual, Carin 

Skoog, also commented that “The US EPA recently suggested the value of a ton of CO2 could be 

as high as $22-35.” ACEEE appeared to refer obliquely to the EPA estimates, recommending 

that NHTSA use a higher CO2 estimate. ACEEE argued that “legislative efforts to implement a 

carbon regime in which the projected market cost of CO2 is expected to lie between $20 and $30 

– significantly higher than the average damage cost assumed by NHTSA – serves as evidence 

that the U.S. is now beginning to contemplate the high risk of rising greenhouse gas emissions.” 

NRDC commented that NHTSA cited “compliance cost estimates provided by NRDC and others 

in the 2006 light truck rulemaking” in describing its proposal of the upper bound estimate. 

NRDC argued that NHTSA should instead consider damage costs and not rely on compliance 

cost estimates. NRDC stated that “If NHTSA were to consider compliance costs it must consider 

current analyses, such as EPA’s analysis of S.2191, which finds that CO2 allowances would cost 

 

276 Available at http://www.epa.gov/climatechange/downloads/s2191_EPA_Analysis.pdf (last accessed March 23, 

2009). 
VIII-39 

19 to 67 (2005) dollars per ton of CO2-equivalent in 2012 rising at 5 percent per year real (the 

range for EPA’s Core Scenario is $19 to $35 in 2012, rising at 5 percent per year real).” 

EPA also recently released a “Technical Support Document on the Benefits of Reducing GHG 

Emissions,”277 (TSD) to accompany an Advance Notice of Proposed Rulemaking (ANPRM) on 

regulating GHG emissions under the Clean Air Act.278 EDF commented in its original 

comments that “The higher SCC estimates contained in EPA's draft ANPR, and EPA’s 

accompanying discussion of the remaining omissions and weaknesses in state-of-the-art SCC 

research, further demonstrates that NHTSA's estimates are underestimating the benefits of 

reducing carbon dioxide emissions, and therefore setting CAFE standards below optimal levels.” 

After the TSD was released, EDF submitted it to NHTSA’s NPRM docket, and submitted late 

additional comments arguing that NHTSA must “adjust its final rulemaking action in accordance 

with EPA’s assessment and findings,” because “EPA's assessment is far more rigorous than 

NHTSA's proposal, and EPA's determinations are supported by a considerable and well-reasoned 

volume of information.” EDF stated that EPA did its own meta-analysis “building on” Tol 

(2005) and (2007), but including “only recent peer reviewed studies that met a range of quality 

criteria in its evaluation.” EDF further stated that EPA arrived at an estimate of $40/tCO2 (using 

a 3 percent discount rate), or $60/tCO2 (using a 2 percent discount rate). EDF commented that 

EPA concluded that estimates “likely underestimate costs of carbon dioxide emissions,” because 

they do not account for all the climate change impacts identified by the IPCC, like “non-market 

damages, the effects of climate variability, risks of potential extreme weather, socially contingent 

events [(such as violent conflict)], and potential long-term catastrophic events.” 

The U.S. Senators who commented argued that NHTSA’s use of $14/ton based on Tol (2005) as 

the “high bound” estimate was incorrect because EPA had been working since 2007 “to develop 

more accurate, ‘state-of-the-art’ estimates of the benefits of reducing greenhouse gas pollution.” 

The Senators stated that “Although EPA’s estimates have not been finalized, the Agency used 

$40 per ton as the value of reducing carbon dioxide emissions.” The Senators further stated that 

“NHTSA’s draft rule inexplicably makes no mention of EPA’s extensive research and analysis in 

this area.” 

Other commenters argued that NHTSA should have used or considered the value at which CO2

allowances are currently trading in the EU regulatory system. UCS stated that using $14 as the 

upper end is “unacceptably low,” given that “The European Climate Exchange, which provides a 

futures market value for global warming pollution in Europe’s carbon constrained market, 

indicates 2011 contracts for carbon dioxide at approximately $45 (U.S.) per metric ton—well 

above the figure cited by NHTSA.” UCS argued that “This value represents a predicted 

marginal abatement cost (the cost of avoiding global warming pollution), and is likely a 

conservative estimate of the benefit of reducing global warming since the cost of avoiding 

climate change is lower than the cost of fixing the damage after it occurs.” UCS further argued 

that this number is also “generally consistent with other recent allowance price estimates, such as 

the EPA’s assessment of GHG allowance prices under Lieberman-Warner: $22-$40 in 2015 and 

$28-$51 in 2020 (EPA figures are in 2005 dollars per ton of CO2-equivalent.)” 

 

277 Available at Docket No. NHTSA-2008-0089-0456.2. 278 EPA’s ANPRM was signed July 11, 2008, after NHTSA’s NPRM was published. See 73 FR 44353 (July 30, 

2008). 
VIII-40 

Sierra Club et al., Public Citizen, and CARB all also commented that NHTSA’s value for the 

SCC is too low, and that NHTSA should instead use a CO2 damage value based on the market 

value in the European Trading System, either the current value (which Public Citizen stated was 

“recently... around €30 per allowance (one metric ton CO2 equivalent),” and CARB stated was 

“currently trading around $42 per ton”), or some future value. Sierra Club et al. argued that “the 

futures market value for a metric ton of CO2 in 2011 is already up to $45,” while CARB went on 

to argue that “...Germany Deutsche Bank [is] forecasting EUA prices of $60 for 2008 and EUA 

prices as high as $100 by 2020 [citation removed].” 

Other commenters suggested other SCC values different from any discussed so far. For 

example, Prof. Hanemann argued that, based on his own research, NHTSA use a value of “about 

$25 per metric ton [of CO2] in 2005$,” and should apply a real growth rate of 2.4 percent per 

year to determine the value of reducing emissions in future years. CARB, in contrast, 

commented that “NHTSA should also consider using substantially higher estimates.” CARB 

stated that “the International Energy Agency (IEA) recently estimated that to limit global CO2

emissions by the 50 percent GHG reduction that the IPCC concluded is needed to keep global 

temperatures from rising more than two degrees Celsius by 2050, CO2 offset prices will need to 

rise to up to $200 per ton....” CARB further argued that “...even this higher market price for 

carbon may not incorporate the true cost of all natural resources damages, an externality.” 

Mr. Montgomery commented that NHTSA should use an SCC value of $0, because he argued 

that “If a comprehensive cap on [CO2] emissions is put in place, as many commentators and 

policymakers predict, then the choice of policy instrument will have no effect on the overall level 

of emissions,” such that “Tightening a CAFE standard will only result in greater mitigation in 

emissions from [motor vehicles] and less mitigation in parts of the economy where decisions are 

made in response to carbon prices without specific regulatory mandates.” Thus, Mr. 

Montgomery concluded that “the damages from global warming will be the same no matter what 

the level of the CAFE standard, so that the SCC used should be zero.” 

Mr. Montgomery also commented that an SCC based on Tol’s estimates will be too high if the 

“global policy objective toward greenhouse gas emissions...is a lower concentration than that on 

which the Tol estimates are based.” Mr. Montgomery argued that “Marginal damages depend on 

the level of GHG concentrations at which they are measured,” so that “If the goal for global 

concentrations is set at a high level (e.g., 750 ppm) then damages from an additional ton of CO2

(due to higher concentrations during the period of its residence in the atmosphere) will be higher 

than if the goal is set at a low level (350 ppm) at which point most of the damaging 

consequences have been eliminated.” 

Ford redacted much of its discussion of the SCC based on confidentiality concerns, but seemed 

to argue generally that reducing CO2 emissions from motor vehicles is expensive compared to 

reducing emissions in other sectors, and commented that “All sectors must contribute” to 

reducing emissions. Ford “recommended that NHTSA consider using CO2 mitigation cost in 

their analysis in lieu of emission damage cost.” 
VIII-41 

NADA commented that “NHTSA should consider incorporating into its analysis the $2.97 per 

metric ton recently paid by the U.S. House of Representatives for carbon offsets.”279

The Alliance was the only commenter to suggest that NHTSA not quantify the SCC at all. The 

Alliance argued that “...given the fact that no published studies of which we are aware address 

the SCC apportionment issue, NHTSA would be well within its rights to decide that SCC will be 

considered purely in a qualitative balancing fashion and not quantified.” The Alliance cited 

Transmission Access Policy Study Group v. FERC, 225 F.3d 667, 736 (D.C. Cir. 2000) (“Given 

that FERC’s comparison of the frozen efficiency case to its base case yielded little difference, the 

agency had no reason to conduct further analysis. By rigorously examining the frozen efficiency 

case, even though it believed the case to be unreasonable, FERC ensured that its decision was 

‘fully informed’ and ‘well-considered.’”). 

(6) NHTSA’s use of a domestic versus a global value for the economic benefit of reducing CO2

emissions 

NHTSA received a number of comments on its tentative decision to employ a domestic value for 

the SCC instead of a global value. Several commenters supported a domestic value, while other 

commenters supported a global value. 

The Alliance argued that NHTSA must consider only domestic impacts both because of EPCA, 

which refers to “the need of the United States to conserve energy,” and because of the 

“extraterritoriality” or “Aramco canon,” see EEOC v. Arabian American Oil Co., 499 U.S. 244, 

260 (1991) (“It is a longstanding principle of American law ‘that legislation of Congress, unless 

a contrary intent appears, is meant to apply only within the territorial jurisdiction of the United 

States.’) (quoting Foley Bros. v. Filardo, 336 U.S. 281, 285 (1949)). The Alliance further 

argued that because NHTSA must consider only domestic impacts, it must “develop some 

mechanism for scaling down the global SCC estimates produced in the published literature,” 

besides NHTSA’s proposal which just took the midpoint between $0 and $14 as the domestic 

SCC value. The Alliance argued that it would be inappropriate to use land mass to determine the 

domestic portion, since so much of the land mass on the planet is uninhabited; and also argued 

that it would be inappropriate to use population, since “not all human beings live in areas that are 

expected to be equally impacted by climate change.” As discussed above, the Alliance cited to 

the NERA Report that it included with its comments as having found that an SCC value based on 

the U.S. share of world gross product was more appropriate. 

NADA similarly commented that “NHTSA should account only for any domestic impacts of 

reducing the social costs of motor vehicle CO2, given that EPCA focuses on U.S. energy security 

and all other costs and benefits evaluated with respect to the proposed CAFE standards are 

domestic only.” 

Mr. Delucchi agreed with NHTSA’s discussion that “consistency requires” that only U.S. 

domestic “global warming damages” be considered if NHTSA also accounts for the monopsony 

effect in the reduced value of transfer payments from U.S. oil purchasers to foreign oil suppliers. 

 

279 NADA cited the “Statement of Daniel P. Beard, Chief Administrative Officer, U.S. House of Representatives, 

Concerning the Purchase of Carbon Offsets,” which does not list the specific price paid for the offsets described. 

Available at http://cao.house.gov/press/cao-20080205.shtml (last accessed March 23, 2009). 
VIII-42 

Mr. Delucchi suggested that NHTSA use a procedure described in his previous research to 

estimate the fraction of global damages from climate change that would be borne within the U.S., 

and apply this fraction to the estimated global SCC to determine the value of U.S. domestic 

benefits from reducing emissions. This procedure adjusts the fraction of global GDP accounted 

for by the U.S. by the relative sensitivity of the U.S. to climate damages compared to the 

remainder of the world, which Delucchi measures by the ratio of U.S. dollar damages from 

climate change per dollar of U.S. GDP to global economic damages from climate change per 

dollar of global GDP. Using this method, he estimates that U.S. damages from climate change 

are likely to represent 0-14 percent of total global damages, and thus that the value to the U.S. of 

reducing carbon emissions is equal to that same percentage of the estimated global value of the 

SCC.280

 Mr. Montgomery argued that a domestic SCC value was appropriate, commenting that “U.S. 

policy should be based on marginal damages to the U.S. from CO2 emissions in the U.S., as 

stated in relevant OMB circulars on cost-benefit analysis and suggested in the draft.” Mr. 

Montgomery further stated that “The consensus appears to be that richer countries are less 

vulnerable than poorer, and that temperature increases will be least in temperate regions like the 

U.S.” Thus, Mr. Montgomery argued that a conservative estimate of U.S. damages would be a 

calculation “based on the ration of U.S. GDP to world GDP.” 

Other commenters argued that NHTSA should use a global SCC value. NRDC commented that 

because “Carbon dioxide is a global pollutant, and much of the damages other countries will 

experience are a result of U.S. emissions,” and because “emissions in other countries will cause 

damages in the U.S.,” that “It is fundamentally inconsistent with the global circulation of these 

pollutants to arbitrarily limit assessment of the benefits of reducing U.S. emissions to those 

accruing in our own territory.” NRDC also commented that national security studies show that 

the global social costs of carbon will “spill over” to the U.S. and other wealthy countries. EDF 

also commented that NHTSA should use a global SCC number rather than a domestic one, 

because “Climate change is clearly a global issue,” so EDF “recommend[s] that benefits of 

reducing CO2 concentrations should reflect benefits to society as a whole.” 

EDF and the U.S. Senators commented that use of a global SCC value would be consistent with 

OMB guidance that international impacts of regulations may be considered if appropriate. The 

Senators also commented that the U.S. must consider the global climate change effects of its 

regulations because it ratified the United Nations Framework Convention on Climate Change in 

1992. If every nation considers only domestic effects of climate change, the Senators argued, 

emissions reduction policies will fall “far short of the socially optimized level.” 

CBD similarly commented that NHTSA should use a global value for CO2, arguing that using $7 

“fails to incorporate the full economic costs of global climate change, values that are difficult to 

monetize, and costs to the world outside the boundaries of the United States.” CBD stated that 

“In general, the estimate of the social costs of climate change fails to incorporate the loss of 

 

280 Mark A. Delucchi, Summary of the Non-Monetary Externalities of Motor Vehicle Use, UCD-ITS-RR-96-3 (9) 

rev.1, Institute of Transportation Studies, University of California, Davis, originally published September 1998, 

revised October 2004. Available at http://www.its.ucdavis.edu/publications/2004/UCD-ITS-RR-96-03(09)_rev1.pdf 

(last accessed March 23, 2009). 
VIII-43 

biodiversity, complex and large-scale ecosystem services, and the disproportionate impacts of 

global climate change on the developing world.” CBD also stated that NHTSA’s use of $0 as the 

lower bound estimate is “[p]resumably ... meant to imply that the United States might benefit 

economically by letting other countries bear the costs of unabated American greenhouse gas 

emissions. Setting aside the tremendous ethical implications of such a position, NHTSA 

provides absolutely no evidence to support the claim.” 

In its late comments accompanying its submission of EPA’s TSD, EDF argued that EPA’s TSD 

concluded that a global number is correct, for several reasons. Because GHGs are global 

pollutants and affect everyone, using “domestic only” estimates would “omit potential impacts 

on the United States (e.g., economic or national security impacts) resulting from climate change 

impacts in other countries.” Consequently, a global number must be used to avoid missing any 

benefits and to maximize global net benefits (i.e., “countries would need to mitigate up to the 

point where their domestic marginal cost equals the global marginal benefit.” EDF stated that 

EPA’s TSD cites Nordhaus (2006), and says that “Net present value estimates of global marginal 

benefits internalize the global and intergenerational externalities of reducing a unit of emissions 

and can therefore help guide policies towards an efficient level of provision of the public good.” 

(7) The rate at which the SCC grows over time 

Several commenters cited the IPCC Fourth Assessment Report with regard to the rate at which 

the SCC should increase over time. CBD commented that as part of the Fourth Assessment 

Report, the IPCC “...states that ‘It is virtually certain that the real social cost of carbon and other 

greenhouse gases will increase over time; it is very likely that the rate of increase will be 2% to 

4% per year.’” The U.S. Senators commented that the 2.4 percent per year increase that NHTSA 

used in the NPRM is incorrect, because “the IPCC report states that ‘it is very likely that the rate 

of increase will be 2% to 4% per year.’” 

EDF stated that IPCC’s recommendation of a 2.4 percent growth rate was meant to be used in 

combination with a low, intergenerational discount rate. EDF further argued that after the Fourth 

Assessment Report was released, one of the lead authors recommended using a growth rate of 3 

percent, but that “The OMB equivalent guidance for the UK ... recommend using a 2 percent 

yearly increase.” EDF thus concluded that the 2.4 percent growth rate could be used, but only 

with a maximum 3 percent discount rate, and argued that a range of growth rates should be run in 

the sensitivity analysis “because of considerable uncertainty.” 

(8) The discount rate that should be used for SCC estimates

Commenters urged NHTSA to consider a low or even negative discount rate in choosing an 

estimate for the SCC. CBD, for example, stated that Stern found that “‘If consumption falls 

along a path, the discount rate can be negative. If inequality rises over time, this would work to 

reduce the discount rate, for the social welfare functions typically used. If uncertainty rises as 

outcomes further into the future are contemplated, this would work to reduce the discount rate, 

with the welfare functions typically used.’” CBD then argued that “A negative discount rate 

would dramatically increase the cost of climate change in the cost-benefit analyses in the 

proposed rule.” 
VIII-44 

NRDC commented that NHTSA should use a discount rate of no more than 3 percent for the 

entire rulemaking, and returned to this argument in its SCC discussion, criticizing Tol’s estimate 

for relying “primarily upon estimates that did not use current accepted climate change 

discounting procedures of a declining discount rate over time.” 

In its initial comments, EDF stated that NHTSA should only consider recent studies that use a 3 

percent discount rate for estimating SCC. In its late comments, EDF stated that EPA’s TSD 

concluded that “a low discount rate is most appropriate for SCC estimation,” for several reasons. 

First, because OMB Circular A-4 allows agencies to use a lower discount rate when there are 

inter-generational benefits associated with a rulemaking. Second, because “In this intergenerational context, a three percent discount rate is consistent with observed interest rates from 

long-term intra-generational investments (net of risk premiums) as well as interest rates relevant 

for monetary estimates of the impacts of climate change that are primarily consumption effects.” 

Third, because EPA had found that the scientific literature supports the use of a discount rate of 3 

percent or lower, as being “...more consistent with conditions associated with long-run 

uncertainty in economic growth and interest rates, intergenerational considerations, and the risk 

of high impact climate damages (which could reduce or reverse economic growth).” 

(9) Other issues raised by commenters

The remaining issues raised by commenters with regard to NHTSA’s proposal regarding the 

value for the SCC were as follows: 

 

Public Citizen commented that NHTSA should also have considered “the costs of inaction on 

reducing greenhouse gas emissions and the resultant consequences of global warming,” 

including other environmental and health consequences such as those analyzed in NHTSA’s 

DEIS. Public Citizen cited EPA’s denial of California’s waiver request and “a recent report from 

the University of Maryland” as evidence of some of these costs, and argued that NHTSA needed 

to estimate “the costs of inaction” in making its final decision. 

NRDC commented that emissions reductions may be “greater than what CAFE accomplishes,” 

such that the U.S. would “get...a larger social cost of carbon benefits stream,” if the U.S. actions 

in “taking a lead in reducing emissions... [helps to] induce other countries, especially China and 

India, to also reduce.” NRDC also argued that “Carbon dioxide has a very slow decay rate in the 

atmosphere, lasting hundreds of years into the future,” which means that “the social costs of 

carbon extend well past the life time of the vehicle.” Thus, “Any sensible benefits stream would 

extend them at least several decades past the lifetime of a vehicle.” 

In its original comments, EDF argued that NHTSA should have considered using a riskmanagement framework in developing an SCC estimate, because cost-benefit analysis “cannot 

capture the range of uncertainty and risk that characterizes climate change.” EDF cited Prof. 

Weitzman’s work as highlighting “that the expected damages of climate change may be 

dominated by the existence of consequences which have very low probability but very high 

damages (such as double-digit increases in mean global temperature), or a ‘fat tail’ in the 

distribution of possible outcomes.” In its late comments, EDF added that EPA’s TSD also 

suggested that a risk assessment framework may be more appropriate than cost-benefit analysis 

“in light of the ethical implications of climate change and the difficulty in valuing catastrophic 
VIII-45 

risks to future generations.” The TSD went on to say that “Economics alone cannot answer the 

questions, policy, legal, ethical considerations are relevant too, and many cannot be quantified. 

When there is much uncertainty, economics recommends a risk management framework for 

guiding policy.” 

Agency response: 

In determining its responses to the public comments on the value of reducing CO2 emissions, the 

agency was mindful that the 9th Circuit remanded rulemaking to NHTSA “for it to include a 

monetized value for this benefit [the reduced risk of global warming as a result of reducing CO2

emissions] in its analysis of the proper CAFE standards.”281 (Emphasis added.) NHTSA 

understands this directive to require the agency to include within its modeling, with at least some 

level of specificity, actual values for the SCC. Further, as in the case of other public comments, 

the agency is required by the Administrative Procedure Act to respond to the relevant and 

significant public comments, including those central to the agency’s decision on standards under 

EPCA, in a manner reflecting consideration of the relevant factors. 

As noted above, in the NPRM, we tentatively selected the mean value ($14) in Tol (2005) as a 

global value, and announced plans to attempt to develop and possibly use a domestic value for 

the final rule. For most of the analysis it performed to develop the proposed standards using the 

Volpe CAFE model, NHTSA used a single estimate for a domestic value of reducing CO2

emissions. The agency thus elected to use the midpoint of the range from $0 to $14 (or $7.00) 

per metric ton of CO2 as the initial value for the year 2011, and assumed that this value would 

grow at 2.4 percent annually thereafter. This estimate was employed for the analyses conducted 

using the Volpe CAFE model to support development of the proposed standards. The agency 

also conducted sensitivity analyses of the benefits from reducing CO2 emissions using both the 

upper ($14 per metric ton, since the domestic value could not exceed the global one) and lower 

($0 per metric ton) bounds of this range. 

After considering comments on the approach it employed in the NPRM and more recent 

estimates of the SCC, NHTSA has decided to employ a range of estimates for the value of 

reducing GHG emissions in the analysis it performed to support this Final Rule for MY 2011 as 

discussed in further detail below. To do so, the agency identified a range of estimates from 

current peer-reviewed estimates of the value of the SCC, and then tested the sensitivity of 

alternative CAFE standards to this range of uncertainty while holding the other economic 

parameters used in its analysis fixed at their estimated values. The range of estimates, which the 

agency believes fairly represents the uncertainty surrounding the value of the SCC, consists of a 

domestic value ($2) at the lower end, a global value ($33) equal to the mean value in Tol (2008) 

and a global value ($80) one standard deviation above the mean value. NHTSA believes that, 

based on currently available information and analysis, $2 is a reasonable domestic value and $33 

is a reasonable global value, but notes the uncertainty regarding both values. The agency tested 

the sensitivity of alternative CAFE standards to this range of uncertainty while holding the other 

economic parameters used in its analysis fixed at their estimated values. 

On the basis of this analysis, the agency has concluded that its adopted standards for MY 2011 

are not sensitive to the alternative estimates of the value of reducing CO2 emissions, so although 

 

281 CBD, 508 F.3d 508, 535. 
VIII-46 

it has selected global and domestic values for the SCC for use in analyzing the effects of 

different SCC values on the standards in this one-year rulemaking, NHTSA believes that is not 

necessary for purposes of this rulemaking to make definitive, long term choices about the most 

appropriate global or domestic value or to choose between using a global versus domestic value. 

This approach is sufficient for this rulemaking and will allow efforts to make more specific 

choices to be deferred until additional scientific and economic evidence can be accumulated, and 

the participation of other federal agencies in those efforts can enable the development of a 

consistent estimate for use in those agencies’ respective regulatory and policy-making activities, 

including the next CAFE rulemaking. 

The agency is well aware that scientific and economic knowledge about the contribution of GHG 

emissions to changes in the future global climate and the potential resulting damages to the 

world economy continues to evolve rapidly. Thus, any value placed in this rulemaking on 

reducing CO2 emissions is subject to likely change. NHTSA recognizes the importance of 

continuing to monitor current research on the potential economic damages resulting from climate 

change, and of periodically updating estimates of the value of reducing CO2 emissions to reflect 

continuing advances in scientific and economic knowledge about the nature and extent of climate 

change and the threat it poses to world economic development. NHTSA recognizes the interest 

and expertise of other federal agencies, particularly EPA and DOE, in the issue of valuing the 

reductions in climate damages that are likely to result from those agencies’ own efforts to reduce 

GHG emissions. NHTSA will continue to work closely with those and other federal agencies in 

the development and review of the economic values of reducing GHG emissions that it plans to 

employ in its next CAFE rulemaking. 

Global value of reducing CO2 emissions 

To develop a range of estimates that accurately reflects the uncertainty surrounding the value of 

reducing emissions, NHTSA relied on Tol’s (2008) expanded and updated survey of 211 

estimates of the global SCC, which was published after the agency completed the analysis it 

conducted to develop its proposed CAFE standards.282 Tol’s 2008 survey encompasses a larger 

number of estimates for the global value of reducing carbon emissions than its previouslypublished counterpart, Tol (2005), and continues to represent the only recent, publicly-available 

compendium of peer-reviewed estimates of the SCC that has itself been peer-reviewed and 

published. The wide range of estimates it includes reflects their authors’ varying assumptions 

about critical parameters that affect the SCC, including the sensitivity of the global climate 

system to increasing atmospheric concentrations of CO2 and other GHGs, the extent of economic 

damages likely to result from climate change, the rate at which to discount future damages, the 

relative valuation of climate damages likely to be sustained by nations with different income 

levels, and the degree of collective aversion to the risk of extreme climate change and the 

resulting potential for equally extreme economic damages. NHTSA believes that Tol’s updated 

survey provides a reliable and consistent current basis for establishing a range of plausible values 

for reducing CO2 emissions from fuel production and use. 

Tol’s updated survey includes 125 estimates of the SCC published in peer-reviewed journals 

through the year 2006. Each of these represents an independent estimate of the world-wide value 

 

282 Richard S.J. Tol (2008), The social cost of carbon: trends, outliers, and catastrophes, Economics -- the OpenAccess, Open-Assessment E-Journal, 2 (25), 1-24. 
VIII-47 

of increased economic damages from global climate change that would be likely to result from a 

small increase in carbon emissions, and by implication, the global value of the reduction in 

future economic damages from climate change that would result from an incremental decline in 

GHG emissions. Tol reports that the mean value of these estimates is $71 per ton of carbon 

emissions, and that the standard deviation of this estimate – a measure of how much a typical 

estimate differs from their average value – is $98 per ton; the fact that this latter measure is 

significantly larger than the mean value indicates the broad range spanned by the estimates. 

NHTSA staff confirmed in conversations with the author that these values apply to carbon 

emissions occurring during the mid-1990s time frame, and are expressed in approximately 1995 

dollars.283 The $71 mean value of the social cost of increased carbon emissions reported by Tol 

corresponds to a global value of $19 per metric ton of CO2 emissions reduced or avoided when 

expressed in 1995 dollars, while the $98 standard deviation for carbon emissions corresponds to 

$27 per ton of CO2.

284 Adjusted to reflect increases since the mid-1990s in the marginal damage 

costs of emissions at now-higher atmospheric concentrations of GHGs, and expressed in 2007 

dollars, Tol’s mean value corresponds to a global damage cost of $33 per ton of CO2 emitted 

during the year 2007, with a standard deviation of nearly $47 per ton. Thus, the value that is one 

standard deviation above the $33 figure is $80 per ton of CO2. 

Many commenters noted that some recent estimates of the SCC are significantly higher that 

those reported by Tol (2005), and suggested that NHTSA employ these higher estimates of the 

SCC to determine the value of reducing CO2 emissions. Specifically, commenters highlighted 

the widely-cited Stern Review’s estimate that the current SCC is likely to be in excess of $300 

per metric ton of carbon, or approximately $80 per ton of CO2.

285 Some commenters argued that 

Stern’s estimate should be given substantial weight in determining the value of reducing CO2

emissions used to develop the agency’s final CAFE standards. Although Stern’s estimate is 

reported in Tol’s 2008 survey, it is not included in the estimates that form the basis for NHTSA’s 

revised range of values, because Stern’s study has not yet been subjected to formal peer review. 

NHTSA notes that the Stern Report’s estimate of the SCC employs a low value for the discount 

rate it applies to future economic damages from climate change, and that this assumption is 

largely responsible for its high estimate of the SCC. Hope and Newbury demonstrate that 

substituting a more conventional discount rate would reduce Stern’s estimate of the benefits from 

reducing emissions to the range of $20-25 per ton of CO2, which is well within the range of other 

 

283 Tol (2008), Table 1, p. 16. 284 As noted in an earlier footnote, carbon itself accounts for 12/44, or about 27 percent, of the mass of carbon 

dioxide (12/44 is the ratio of the molecular weight of carbon to that of carbon dioxide). Thus, each ton of carbon 

emitted is associated with 44/12, or 3.67, tons of carbon dioxide emissions. Estimates of the SCC are typically 

reported in dollars per ton of carbon, and must be divided by 3.67 to determine their equivalent value per ton of 

carbon dioxide emissions. 

285 Stern, N.H., S.Peters, V.Bakhshi, A.Bowen, C.Cameron, S.Catovsky, D.Crane, S.Cruickshank, S.Dietz, 

N.Edmonson, S.-L.Garbett, L.Hamid, G.Hoffman, D.Ingram, B.Jones, N.Patmore, H.Radcliffe, R.Sathiyarajah, 

M.Stock, C.Taylor, T.Vernon, H.Wanjie, and D.Zenghelis (2006), Stern Review: The Economics of Climate Change 

Cambridge University Press, Cambridge, England. 
VIII-48 

estimates summarized in Tol’s 2008 survey, and significantly below the $33 equivalent of the 

mean of peer-reviewed estimates Tol reports.286

Other commenters noted that EPA has recently developed preliminary estimates of the value of 

reducing CO2 emissions, and recommended that NHTSA employ these values in its analysis of 

alternative CAFE standards. EPA’s estimates are reported in that agency’s Technical Support 

Document on Benefits of Reducing GHG Emissions (GHG Benefits TSD) accompanying its 

Advance Notice of Proposed Rulemaking on motor vehicle CO2 emissions.287 In that document, 

EPA derives estimates of the SCC using the subset of estimates included in Tol’s 2008 survey 

drawn from peer-reviewed studies published after 1995 that do not employ so-called equity 

weighting.288 Updated from their original mid-1990s values to reflect increases in the marginal 

damage costs of emissions at growing atmospheric concentrations of CO2 and expressed in 2006 

dollars, EPA reports average values of $40 per ton of CO2 for studies using a 3 percent discount 

rate, and $68 per ton for studies using a 2 percent discount rate. 289 (The discount rates employed 

in developing the 125 peer-reviewed estimates surveyed by Tol ranged from 1 to 10 percent.290) 

NHTSA recognizes that in a recent rulemaking, DOE used a range of values from $0 to $20 (in 

2007 dollars) per ton to estimate the benefits of reductions in CO2 emissions resulting from new 

energy conservation standards for commercial air conditioning equipment.291 DOE derived the 

upper bound of this range from the mean of published estimates of the SCC reported in the same 

earlier survey by Tol (2005) that NHTSA relied upon for the value it used to analyze the CAFE 

standards proposed in the NPRM, and the lower bound from the assumption that reducing CO2

emissions would produce no economic benefit. However, NHTSA believes that the estimates of 

the mean and standard deviation derived from Tol’s more recent (2008) and comprehensive 

survey of published estimates of the SCC provides a more up-to-date range of values for 

reductions in CO2 emissions resulting from higher CAFE standards, primarily because Tol’s 

2008 survey includes a larger number of estimates of the SCC, as well as more recentlypublished estimates. 

The agency is aware that rapid advances in modeling climate change and its potential economic 

damages have occurred over the past decade, and that the choice of discount rates has an 

 

286 See Hope, Chris, and David Newbery, “Calculating the Social Cost of Carbon,” unpublished paper, Cambridge 

University, May 2006, p. 15. 

287 U.S. EPA, Technical Support Document on Benefits of Reducing GHG Emissions, EPA-HQ-OAR-2008-318-

0078.pdf, June 12, 2008.

288 Equity weighting assigns higher weights per dollar of economic damage from climate change that are expected to 

be borne by lower-income regions of the globe, in an attempt to make the welfare changes corresponding to those 

damages more comparable to the damages expected to be sustained by higher-income world regions. 

289 These values are reported in EPA, Table 1. p. 12. Using the original estimates included in Tol’s 2008 survey, 

which were supplied to NHTSA by the author, the agency calculates these values at $38 per ton and $62 per ton for 

3% and 2% discount rates, slightly below the estimates reported by EPA. These differences may be attributable to 

the two agencies’ use of different measures of inflation to update the original estimates from mid-1990s to 2007 

price levels (NHTSA employs the Implicit Price Deflator for U.S. GDP, generally considered to be an accurate 

index of economy-wide price inflation). 

290 Tol (2008), Table A1. 291 Department of Energy, 10 CFR Part 431, Energy Conservation Program for Commercial and Industrial 

Equipment: Packaged Terminal Air Conditioner and Packaged Terminal Heat Pump Energy Conservation 

Standards: Final Rule, Federal Register, October 7, 2008, pp. 58813-58814. 
VIII-49 

important influence on estimates of the SCC. In its next CAFE rulemaking, NHTSA will be 

working closely with EPA and other federal agencies to review the arguments for more selective 

use of published estimates of the SCC advocated by the EPA. However, based on the 

information gathered and analysis performed by the agency through last fall, and in view of the 

fact that this is a one model year rulemaking and the agency will review matters in considerable 

detail for the post MY 2011 proposal to be issued later this year, NHTSA is not now taking that 

step. Thus, for the purposes of this final rule, NHTSA has elected to use all 125 SCC estimates 

from peer-reviewed studies reported by Tol, instead of the more limited subset of these estimates 

relied upon by EPA. Including the full array of studies provides a reasonable basis for valuing 

reductions in CO2 emissions. Specifically, NHTSA believes that there is still value at this time 

in considering pre-1995 studies and those that employ equity weighting (which account for 58 of 

the 125 peer-reviewed estimates included in Tol’s survey), particularly recognizing that those 

studies have been published in peer-reviewed journals.292 

For the purpose of this rulemaking, NHTSA has also elected not to base its estimates of the value 

of reducing CO2 emissions solely on estimates that utilize a single discount rate. NHTSA 

acknowledges that the varying discount rates employed by different researchers are an important 

source of the significant differences in their resulting estimates of the SCC. However, the 

agency believes that the appropriate rate at which to discount economic damages occurring in the 

distant future is an economic parameter whose correct value for the purpose of analyzing future 

climate change and the resulting economic damages is subject to significant uncertainty,

analogous to that surrounding other critical scientific and economic parameters in climate 

analysis. In the agency’s view, it is reasonable to consider estimates based on different discount 

rates at the present time instead of attempting to resolve this uncertainty in the time left to 

complete this one-year rulemaking by limiting the sample of estimates to those that employ the 

single discount rate it regards as most appropriate. In its next CAFE rulemaking, NHTSA will 

work with EPA, DOE and other federal agencies to consider anew the issue of whether to rely 

exclusively on values of the SCC that are developed using discount rates that are consistent with 

the rate the agency uses to discount the value of reductions in future GHG emissions reductions 

to their present values.293 

 

292 Again using the original estimates from Tol’s 2008 survey supplied by the author, NHTSA estimates that 

excluding the 18 pre-1995 estimates from the 125 used to develop the $33 per ton mean estimate would increase it 

to $36 per ton, while excluding the 40 estimates that employ equity weighting would reduce the mean estimate to 

$23 per ton. Excluding both pre-1995 estimates and those that employ equity weighting would eliminate a total of 

58 of the 125 peer-reviewed estimates, and reduce their mean value to $20 per ton. 

293 Climate economic studies report estimates of the SCC for specific future years, often in the form of a value for 

some stated base year and an estimate of the annual rate at which it will grow, as total atmospheric concentrations of 

GHGs are assumed to increase. These studies use some assumed rate to discount economic damages that are 

projected to occur over a very long span of future years to their present values as of the future year when emissions 

increases are assumed to occur. These estimates of the SCC during specific future years are used to value the 

reductions in GHG emissions that would result each year over the lifetimes of vehicles affected by CAFE standards; 

for example, higher CAFE standards for model year 2011 cars and light trucks would reduce GHG emissions each 

year from 2011 through approximately 2047, and the value of reducing those emissions by one ton will rise each 

year over that span. The estimated economic values of the reductions in GHG emissions during each of those future 

years must in turn be discounted to their present values as of today, so that they can be compared with the present 

values of other benefits and with vehicle manufacturers’ costs for meeting higher CAFE standards. The rate used to 

perform this latter discounting must be selected by NHTSA, and the choice of its value is discussed in detail in 

Section V.B.14 
VIII-50 

As some commenters pointed out, another approach NHTSA could rely on to estimate the value 

of reducing GHG emissions would be to use actual or projected prices for CO2 emission permits 

in nations that have adopted or proposed GHG emission cap and trade systems. In theory, permit 

prices would reflect the incremental costs for achieving the last emissions reductions necessary 

to comply with the overall emissions cap. If this cap were based on an estimate of the level of 

global emissions required to prevent an unacceptable degree of climate change, permit prices 

could provide an estimate of the benefits of reducing GHG emissions to a level that forestalls 

unacceptable climate change. A related approach would be to use estimates of the cost of 

reducing emissions from specific sources other than passenger cars or light trucks to estimate the 

value of reducing CO2 emissions via higher CAFE standards, under the reasoning that requiring 

higher fuel economy for cars and light trucks would allow these costs to be avoided or saved. 

NHTSA considered the use of CO2 permit prices to measure the benefits from reducing 

emissions via higher CAFE standards, but did not select this approach primarily because of the 

current difficulty in deciding what is considered an “acceptable” degree of climate change. The 

answer to that question cannot be provided by environmental, technological or economic 

analyses alone or even in combination; answering that question also involves policy judgment. 

The agency also notes that there would also be considerable scientific uncertainty in determining 

the level of emissions reduction that would be necessary to limit climate change to any degree 

that was deemed acceptable, even if agreement on the latter could be achieved. Since permit 

prices would depend on the level of emission reduction that is required, they are likely to reflect 

this uncertainty. Additionally, as a general matter, permit prices reflect avoided costs of 

emission reductions and there is no direct or necessary relationship between avoided costs and 

benefits. 

Finally, still other commenters urged the agency to take into account the economic value of any 

reduction in the risk of catastrophic climate events resulting from lower GHG emissions when 

estimating the benefits from reducing emissions. Most of the estimates of the SCC that are 

included in Tol’s updated review treat the risks and potential damages from catastrophic events 

using conventional probabilistic methods to compute the “expected” value of a wide range of 

potential changes in climate and associated economic damages. However, few studies of the 

SCC attempt to include explicit premiums that measure the population’s aversion to accepting 

the risks of catastrophic climate damages.294 Further, most published studies of climate damages 

report insufficiently detailed results to allow the calculation of appropriate risk premiums. 

 

294 Under the conventional assumption that successive increases in consumption produce progressively smaller 

improvements in economic welfare, the welfare level associated with the mean of a range of possible consumption 

levels is higher than the mean of the welfare levels associated with each possible level of consumption. Moreover, 

the difference between these welfare levels increases as the span of possible consumption levels is broadened, as 

would occur if increased GHG emissions have the potential to cause drastic climate changes and result in similarly 

drastic economic damages. In this situation, the true economic costs of increased emissions include not only the 

resulting increase in the probabilistic expected value of climate-related economic damages, but also the 

compensation that those suffering these damages would require in order to willingly accept the increased risk of 

catastrophic damages, even if that risk is extremely small. Conversely, the value of reducing GHG emissions should 

include not only the resulting reduction in the expected value of future climate-related economic damages, but also 

the added amount people would be willing to pay for the associated reduction in the risk that such catastrophic 

damage might occur. 
VIII-51 

NHTSA acknowledges that including an appropriate premium to reflect the value of reducing the 

risks of catastrophic climate events could significantly increase its estimate of the value of 

reducing CO2 emissions, but it has not attempted to do so at this time.295 (For discussion of 

NHTSA’s consideration of abrupt climate change, see § 3.4.3.2.4 of the FEIS.) However, the 

agency is aware of recent research suggesting that including an appropriate risk premium can 

significantly increase estimates of the SCC, and by implication increase the estimated value of 

reducing CO2 emissions.296 In working with EPA, DOE and other federal agencies in the 

development of revised estimates of the benefits from reducing CO2 emissions that could be used 

in the next CAFE rulemaking, NHTSA will carefully consider any new research that explicitly 

estimates risk premiums, and evaluate their applicability to the issue of estimating economic 

benefits from reductions in CO2 emissions resulting from future CAFE standards. The agency 

will also work with those agencies and departments in exploring the possibility of calculating an 

appropriate risk premium using results reported in published studies of the SCC together with 

any necessary assumptions about the underlying economic behavior, such as the response of 

welfare to successive increases in consumption levels. 

Domestic value of reducing CO2 emissions 

The agency was able to develop a domestic value by using the mean estimate of the global value 

of reduced economic damages from climate change resulting from reducing CO2 emissions as a 

starting point; estimating the fraction of the reduction in global damages that is likely to be 

experienced within the U.S.; and applying this fraction to the mean estimate of global benefits 

from reducing emissions to obtain an estimate of the U.S. domestic benefits from lower GHG 

emissions. 

The agency constructed an estimate of the U.S. domestic benefits from reducing CO2 emissions 

using estimates of U.S. domestic and global benefits from reducing greenhouse gas emissions 

developed by EPA and reported in that agency’s Technical Support Document accompanying its 

advance notice of proposed rulemaking on motor vehicle CO2 emissions.297 Specifically, 

NHTSA calculated the ratio of domestic to global values of reducing CO2 emissions estimated 

by EPA using the Climate Framework for Uncertainty, Negotiation, and Distribution (FUND) 

integrated assessment model. 

EPA’s central estimates of domestic and global values for reducing GHG emissions during 2007 

using the FUND model using a 3 percent discount rate were $1 and $17 per metric ton (in 

2006$), which suggests that benefits to the U.S. from reducing CO2 emissions are likely to 

represent about 6 percent of their global total. The comparable figures derived using a 2 percent 

discount rate are $4 and $88 for 2007, suggesting that U.S. domestic benefits from reductions in 

CO2 emissions would amount to less than 5 percent of their global total. EPA’s results also 

suggest that these fractions are likely to remain roughly constant over future decades.298 

 

295 Tol estimates that including an appropriate risk premium would increase the mean estimate of the SCC included 

in his more recent survey by 15-27%; see Tol (2008), Table 2. 

296 Hope, Chris, and David Newbery (2006), Calculating the social cost of carbon, University of Cambridge, May 2, 

2006. 

297 U.S. EPA, Technical Support Document on Benefits of Reducing GHG Emissions, June 12, 2008. 298 These values are reported in EPA, Table 1. p. 12. 
VIII-52 

Applying the 5-6 percent figure to the $33 per metric ton mean estimate of the global value of 

reducing CO2 emissions derived previously yields an estimate of approximately $2 per metric 

ton for the domestic benefit from reducing U.S. CO2 emissions in 2007. 

NHTSA also constructed a second estimate of the fraction of global economic damages from 

climate change likely to be borne by the U.S., using the procedure described by Delucchi in his 

comments on the NPRM.299 Delucchi noted that the fraction of global damages from climate 

change borne within the U.S. can be estimated by adjusting the U.S. share of world economic 

output, measured by the ratio of U.S. GDP to gross world product, by the relative sensitivity of 

U.S. and world economic output to damages resulting from climate change. Using data on the 

U.S. share of world economic output (which ranges from 20-28 percent) and published estimates 

of the relative sensitivity of the U.S. economy to climate damages compared to the world 

economy as a whole, Delucchi estimated that the U.S. fraction of global economic damages from 

climate change is likely to range from 0-14 percent. Applying the midpoint of this range (7 

percent) to the $33 per ton mean estimate of the global value of reducing CO2 emissions also 

yields an estimate of approximately $2 per metric ton for the domestic benefit from reducing 

U.S. CO2 emissions in 2007. 

Choosing between a global value and a domestic value, and estimating the global values 

As the IPCC has noted, CO2 and other GHGs are chemically stable, and thus remain in the 

atmosphere for periods of a decade to centuries or even longer, becoming well-mixed throughout 

the earth’s atmosphere. As a consequence, emissions of these gases have extremely long-term 

effects on the global climate. Further, emissions from any particular geographic area (for 

example, the U.S.), are expected to contribute to changes in the global climate that will affect 

many other countries around the world. Similarly, emissions occurring in other countries will 

contribute to changes in the earth’s future climate that are expected to affect the well-being of the 

U.S. The long-lived nature of atmospheric GHGs means that emissions of these gases from any 

location or source can affect the global climate over a prolonged period, and can thus result in 

economic damages to many other nations as well as over subsequent generations. 

In view of the global effects of GHG emissions, reducing those emissions to an economically 

efficient level, i.e., one that maximizes the difference between the total benefits from limiting the 

extent of climate change and the total costs of achieving the reduction in emissions necessary to 

do so, would require each individual nation to limit its own domestic emissions to the point 

where its domestic costs for further reducing emissions within its borders equal the global value 

of reduced economic damages that result from limiting climate change. NHTSA believes that 

this argument has considerable merit from the standpoint of economic theory. 

If individual nations were instead to consider only the domestic benefits they receive from 

limiting the pace or extent of climate change, each nation would reduce emissions only to the 

point where its costs for achieving further reductions equal the benefits to its domestic economy 

from limiting the impacts of climate change. As a result, the combined global reduction in 

 

299 Mark A. Delucchi, Summary of the Non-Monetary Externalities of Motor Vehicle Use, UCD-ITS-RR-96-3 (9) 

rev.1, Institute of Transportation Studies, University of California, Davis, originally published September 1998, 

revised October 2004, pp. 49-51. Available at http://www.its.ucdavis.edu/publications/2004/UCD-ITS-RR-96-

03(09)_rev1.pdf (last accessed March 23, 2009). 
VIII-53 

emissions resulting from individual nations’ comparisons of their domestic benefits from 

limiting climate change to their domestic costs for reducing emissions might be inadequate to 

slow or limit climate change. 

At the same time, however, the agency must also consider the economic, environmental and 

other effects on the U.S. that a choice of a global value in this rulemaking might have, given the 

current stage of ongoing domestic legislative activity and negotiations regarding effective 

international cooperation and coordination. NHTSA notes that there might be risks to nations 

that unilaterally attempt to reduce their emissions by adopting policies or regulations whose 

domestic marginal costs equal the global marginal benefits from reducing the threat of climate 

change. Such actions could induce economic activity within their borders – particularly 

production by emissions-intensive industries – to shift to nations that adopt less stringent 

regulations or lower economic penalties on emissions within their respective borders. Such a 

shift would cause emissions abroad to increase, offsetting at least some of the benefits of 

domestic emissions reductions. 

The agency recognizes that the arguments for using global versus domestic values of reducing 

GHG emissions are complex, and cannot be resolved satisfactorily by the unilateral actions of 

any single federal agency. Instead, resolution of whether to use a domestic or global value for 

reducing emissions, and developing reliable estimates of those values, as relevant, will require 

active participation by all federal agencies whose regulatory and policy-making activities will be 

affected by this decision, as well as leadership from the Administration. In reaching such a 

consensus, participants will need to assess not only the economic arguments favoring global 

versus domestic values of reducing emissions, but also the prospects for effective international 

cooperation to reduce global GHG emissions, the likelihood that leadership by the U.S. in 

seeking emissions reductions would spur international efforts to reduce emissions, and the 

precedents established by federal agencies that have previously evaluated benefits from 

regulations that lower GHG emissions. They will also need to consider arguments that U.S. 

citizens may attach some value to reductions in the threat of climate impacts occurring in other 

regions of the globe, and that reducing the impacts of climate change on other nations may have 

important “spillover” benefits to the U.S. itself. A position has not been adopted by the relevant 

entities. 

 In these circumstances, NHTSA decided to take a pragmatic approach to estimating the value of 

reducing GHG emissions for the immediate and limited purpose of this rulemaking. As noted 

above, we used the mean value in Tol (2008). To develop a reasonable upper-bound estimate of 

that value for purposes of this rule, the agency used a value one standard deviation above the $33 

mean value.300 As also noted above, the standard deviation of peer-reviewed estimates from 

Tol’s 2008 survey is $47 per ton when expressed in comparable terms, which yields an upperbound estimate of $80 per ton (equal to $33 plus $47) of CO2 emissions avoided.301 Because the 

 

300 A two-standard deviation range around the agency’s $33 per ton central estimate would extend from minus $59 

to $126 per ton of CO2 emissions. The agency notes that the lower end of this range implies economic benefits of 

$59 for each additional ton of CO2 emissions during 2007, while its upper end significantly exceeds all but two of 

the 125 peer-reviewed estimates included in Tol’s 2008 survey. 301 A value one standard deviation below the $33 mean would be -$14 per ton, which implies economic benefits of 

$14 for each additional ton of emissions. Because of this implication, NHTSA regards the $2 per ton estimate of the 
VIII-54 

$80 per ton value is higher than those corresponding to nearly 90% of the 125 peer-reviewed 

estimates of the SCC included in the survey, the agency views it as a reasonable upper bound on 

the likely global value of reducing CO2 emissions.302 For the purposes of this rulemaking, 

NHTSA believes that the range extending from the $2 per ton estimate of the domestic value of 

reducing CO2 emissions to the $80 per ton estimate of the global value is sufficiently broad to 

illustrate the sensitivity of alternative MY 2011 CAFE standards and the resulting fuel savings 

and emissions reductions to plausible differences in the SCC. 

Rate of growth of SCC 

The marginal cost per ton of additional CO2 emissions is generally expected to rise over time, 

because the increased pace and degree of climate change – and thus the resulting economic 

damages – caused by additional emissions are both expected to rise in proportion to the existing

concentration of CO2 in the earth’s atmosphere. The IPCC Fourth Assessment Report variously 

reported that the climate-related economic damages resulting from an additional ton of carbon 

emissions are likely to grow at a rate of 2.4 percent annually, and at a rate of 2-4 percent 

annually.303 Virtually all commenters who addressed this issue indicated that the IPCC intended 

the 2.4 percent growth rate it reported for the SCC in one passage to instead read “2-4 percent,” 

and many urged NHTSA to apply a 3 percent or higher growth rate to determine the future value 

of the SCC. 

NHTSA staff reviewed the underlying references from which the disputed figure was derived, 

and those sources clearly report the growth rate implied by their estimates of the future value of 

the SCC for different future years as 2.4 percent, instead of the 2-4 percent asserted by 

commenters.304 Although most studies that estimate economic damages caused by increased 

GHG emissions in future years produce an implied growth rate in the SCC, neither the rate itself 

nor the information necessary to derive its implied value is commonly reported. NHTSA has 

been unable to locate other published research that reports the likely future rate of growth in 

damage costs from CO2 emissions or the information required to derive it. NHTSA understands 

that other researchers may be using alternative growth rates. The agency may revise the 

estimated rate of growth it uses in its future analyses based on emerging estimates in the 

literature and on interagency coordination with the EPA, DOE and other federal agencies. 

For the purposes of this rulemaking, NHTSA used the 2.4 percent annual growth rate to calculate 

the future increases in its estimates of both the domestic ($2/metric ton in 2007) and global 

($33/metric ton and $80/metric ton in 2007) values of reducing CO2 emissions. Over the 

lifetimes of cars and light trucks subject to the CAFE standards it is establishing for model year 

2011, these values average nearly $4, $61, and $157 per ton of CO2 emissions, approximately 

 domestic value of reducing emissions as a more plausible lower bound on the value of reducing emissions than the 

$-14 per ton figure. 

302 Tol reports that the 90% confidence limit of the distribution of peer-reviewed values is $170 per ton, while 

adding one standard deviation to his reported mean yields a value of $169; see Tol (2008), Table 1. 

303 Yohe et al. (2007), p. 13 reports that “...it is very likely that the rate of increase [in the social cost of carbon] will 

be 2% to 4% per year.” However, p. 822 states that “...the SCC will increase over time; current knowledge suggests 

a 2.4% per year rate of growth.” 

304 Hope, C.W. (2006), The Marginal Impact of CO2 from PAGE2002: An Integrated Assessment Model 

Incorporating the IPCC's Five Reasons for Concern, Integrated Assessment Journal, 6, (1), 19-56; and Hope, Chris, 

and David Newbery (2006), Calculating the social cost of carbon, University of Cambridge, May 2, 2006. 
VIII-55 

twice their estimated values during 2007. The agency is unaware of the basis for EDF’s 

assertion that the 2.4 percent growth rate is to be used only in conjunction with an 

intergenerational discount rate with a maximum of 3 percent. Although the agency’s analysis 

did follow EDF’s suggestion in any case, NHTSA selected the growth rate in the future value of 

reducing CO2 emissions and the discount rate applied to these benefits for separate reasons, as 

discussed in detail previously. 

Insensitivity of MY 2011 standards to different values of SCC 

NHTSA examined the sensitivity of alternative CAFE standards for MY 2011 to the choice 

among three different estimates of the value of reducing CO2 emissions from fuel production and 

use: (1) the mean estimate of the global value of reducing emissions derived as discussed 

previously from Tol’s 2008 survey--$33 per ton; (2) a value one standard deviation above this 

mean estimate--$80 per ton; and (3) the estimate of the value of U.S. domestic benefits from 

lower emissions derived as discussed above--$2 per ton.305 

The agency tested the sensitivity of its “optimized” CAFE standards for MY 2011 passenger cars 

and light trucks to the choice among those three alternative values for reducing CO2 emissions. 

The agency’s analysis revealed that the optimized CAFE standards for MY 2011 cars and light 

trucks were unaffected by the choice among those values for reducing CO2 emissions from fuel 

production and use. The detailed results of this analysis are reported in the agency’s previouslyreleased Final Environmental Impact Statement for MY 2011-15 CAFE standards. 

There are several reasons for the insensitivity of the MY 2011 standards to the different values of 

the SCC. First, not more than 15 percent of all models are being redesigned for MY 2011, thus 

limiting the changes that can be made. Second, in any year, the value of gasoline has a far 

greater effect on the potential level of the CAFE standards than the SCC. Third, in the analyses 

that employ the $33 or $80 per ton global values of the benefits from reducing CO2 emissions, 

NHTSA reduces the savings in monopsony costs from lower U.S. petroleum consumption and 

imports to zero.306 This is done in order to be consistent with the fact that monopsony payments 

are a transfer rather than a real economic benefit when viewed from the same global perspective. 

This reduction partly offsets the effect of the higher CO2 value on the optimized CAFE standards 

and resulting benefits. It does not do so completely, however, because the value of reducing CO2

emissions continues to grow at the assumed 2.4 percent rate over the period spanned by the 

analysis, nearly doubling over the lifetimes of MY 2011 vehicles. 

Decision regarding the value of SCC 

Given the insensitivity of the potential standards to the various values of SCC used in the above 

analysis, NHTSA concludes that it is unnecessary for the agency to select a single estimate of the 

 

305 In all analyses that employ its estimated value of the global benefits from reducing CO2 emissions, NHTSA 

reduces the value of the savings in monopsony costs from lower U.S. petroleum consumption and imports to zero. 

This is consistent with the fact that when viewed from the same global perspective that justifies the use of a global 

value for reducing emissions, these monopsony payments represent a transfer of economic resources from 

consumers of petroleum products to petroleum producers, rather than an actual savings in economic resources, and 

thus do not constitute a real economic benefit. 

306 As noted above earlier in the discussion of SCC, NHTSA plans to review this practice in the next CAFE 

rulemaking. 
VIII-56 

value of reducing CO2 emissions for inclusion in its analysis as part of this rulemaking. For that 

reason and in view of the significance that announcing the selection of either a domestic or 

global value in this rulemaking might have in the context of ongoing legislative activities and 

international negotiations, we are deferring the choice between a domestic SCC and a global 

SCC and, for the appropriate choice, the monetized value for the benefit of reduction, until the 

next CAFE rulemaking. This will provide the time necessary for more refined analysis and for 

the various affected federal agencies to work together and identify a consistent value for use in 

their respective regulatory and policy-making activities. NHTSA expects to participate actively 

in the process of developing an appropriate range of estimates for that value. By the time we 

issue a proposal this summer for MY 2012 and beyond, we anticipate those activities and efforts 

will have progressed sufficiently to enable the federal agencies to make an informed choice that 

we can use as a basis for that rulemaking. NHTSA expects that the economic value of reducing 

CO2 emissions will play an important role in developing and analyzing standards in the next 

CAFE rulemaking which, unlike this rulemaking, we expect to be a five-year rulemaking. 

Consumer Benefits from Additional Driving 

The increase in travel associated with the rebound effect produces additional benefits to vehicle 

owners, which reflect the value to drivers and other vehicle occupants of the added (or more 

desirable) social and economic opportunities that become accessible with additional travel. As 

evidenced by the fact that they elect to make more frequent or longer trips when the cost of 

driving declines, the benefits from this added travel are at least as large as drivers’ added costs 

for the fuel it consumes (measured at the improved level of fuel economy resulting from stricter 

CAFE standards).307 The benefits from additional rebound effect travel also include the 

consumer surplus received by vehicle buyers who value the opportunities that increased travel 

makes available to them at more than the fuel cost of the additional driving. Because it depends 

on the improvement in fuel economy, the value of benefits from increased vehicle use changes 

by model year and alternative CAFE standard, and is shown in Tables VIII-6 through VIII-10. 

Added Costs from Congestion, Crashes, and Noise

While it provides some benefits to drivers, increased vehicle use associated with the fuel 

economy rebound effect can also contribute to increased traffic congestion, motor vehicle 

crashes, and highway noise. Additional vehicle use can contribute to traffic congestion and 

delays by increasing recurring congestion on heavily-traveled roadways during peak travel 

periods, depending on how the additional travel is distributed over the day and on where it 

occurs. By increasing the number of crashes and disabled vehicles, added driving can also 

increase the delays that often result from these incidents, although the extent to which it actually 

does so again depends on when and where the added travel occurs. In either case, any added 

delays impose higher costs on drivers and other vehicle occupants in the form of increased travel 

time and operating expenses, and these should be considered as an additional economic cost 

associated with the rebound effect. Because drivers do not take these added costs into account in 

deciding when to make trips or where they travel, they must be accounted for separately as a cost 

of the added driving associated with the rebound effect. 

 

307 These benefits are included in the value of fuel savings reported in Tables VIII-5 through VIII-9. 
VIII-57 

Increased passenger car and light truck use due to the rebound effect may also increase the costs 

associated with traffic crashes. Drivers presumably take account of the potential costs they (and 

the other occupants of their vehicles) face from the possibility of being involved in a crash when 

they decide to make additional trips. However, they probably do not consider all of the potential 

costs they impose on occupants of other vehicles and on pedestrians when crashes occur, so any 

increase in these “external” crash costs must be considered as another cost of additional reboundeffect driving. Like increased delay costs, any increase in these external crash costs caused by 

added driving is likely to depend on the traffic conditions under which it takes place, since 

crashes are more frequent in heavier traffic, but their severity may be reduced by the slower 

speeds at which heavier traffic typically moves. Thus estimates of the increase in external crash 

costs from the rebound effect also need to account for when and where the added driving occurs. 

Finally, added vehicle use from the rebound effect may also increase traffic noise. Noise 

generated by vehicles causes inconvenience, irritation, and potentially even discomfort to 

occupants of other vehicles, to pedestrians and other bystanders, and to residents or occupants of 

surrounding property. Because none of these effects are likely to be taken into account by the 

drivers whose vehicles contribute to traffic noise, they represent additional externalities 

associated with motor vehicle use. Although there is considerable uncertainty in estimating its 

value, the added inconvenience and irritation caused by increased traffic noise imposes economic 

costs on those it affects, and these added costs are unlikely to be taken into account by drivers of 

the vehicles that cause it. Thus any increase in noise costs resulting from added vehicle use must 

be included together with other increased external costs from the rebound effect. 

Our analysis uses estimates of the congestion costs, crash costs, and noise costs for pickup trucks 

and vans developed by the Federal Highway Administration to estimate the increased external 

costs caused by added light truck use from the rebound effect.308 These estimates are intended to 

measure the increases in external costs – that is, the marginal external costs – from added 

congestion, property damages and injuries in traffic crashes, and noise levels caused by 

additional usage of light trucks that are borne by persons other than their drivers. FHWA’s 

“Middle” estimates for congestion, crash, and noise costs imposed by passenger cars are 5.22 

cents, 2.26 cents and 0.07 cents per vehicle mile when expressed in 2006 dollars.309 For pickup 

trucks and vans these costs are 4.66 cents, 2.51 cents, and 0.07 cents per vehicle-mile. These 

costs are multiplied by the estimated increases in passenger car and light truck use from the 

rebound effect during each year of the affected model years’ lifetimes in the fleet to yield the 

estimated increases in congestion, crash, and noise externality costs during that year. The 

resulting estimates are discounted to their present values as of the date each model year is sold 

and summed to obtain their total values. 

The Federal Highway Administration’s estimates of these costs agree closely with some other 

recent estimates. For example, recent published research conducted by Resources for the Future 

(RFF) estimates marginal congestion and external crash costs for increased light-duty vehicle use 

 

308 These estimates were developed by FHWA for use in its 1997 Federal Highway Cost Allocation Study. 

 

309 Federal Highway Administration, 1997 Federal Highway Cost Allocation Study, Tables V-22, V-23, and V-24, 

http://www.fhwa.dot.gov/policy/hcas/final/index.htm. The higher congestion cost for automobiles than for light 

trucks reflects the larger fraction of auto than of light truck use that occurs within congested urban areas. 
VIII-58 

in the U.S. to be 3.9 and 3.4 cents per vehicle-mile when converted to 2006 dollars.310 These 

estimates incorporate careful adjustments of congestion and crash costs that are intended to 

reflect the traffic conditions under which additional driving is likely to take place, as well as its 

likely effects on both the frequency and severity of motor vehicle crashes. 

Costs from Increased Air Pollutant Emissions 

Finally, as noted previously under Emissions Reductions Resulting from Fuel Savings, additional 

passenger car and light truck use associated with the rebound effect will increase emissions of air 

pollutants that occur as motor vehicles are driven. Predominant air pollutants emitted by motor 

vehicles include hydrocarbon compounds (usually referred to as “volatile organic compounds,” 

or VOC), nitrogen oxides (NOx), fine particulate matter (PM), and sulfur dioxide (SO2). The 

increased use of passenger cars and light trucks that occurs through the rebound effect causes 

higher emissions of these “criteria” pollutants, since Federal standards limit their permissible 

emissions by motor vehicles on a per-mile basis. The increase in emissions of these pollutants 

from additional vehicle use is estimated by multiplying the increase in total miles driven by 

vehicles of each model year and age during a calendar year by age-specific emission rates per 

vehicle-mile developed using the U.S. Environmental Protection Agency’s MOBILE6.2 motor 

vehicle emissions factor model311. The monetized value of changes in criteria pollutant 

emissions (fine PM, NOx, SO2, VOCs andCO) are derived from EPA estimates of the value of 

health and welfare-related damages (incurred or avoided). These estimates, expressed as dollars 

per ton, are based on the benefits associated with recently-adopted regulations that limit 

emissions of air pollutants from mobile sources, a category that includes passenger cars, light 

trucks, and other highway vehicles.312 

The Value of Increased Driving Range 

 Improving the fuel economy of passenger cars and light-duty trucks may also increase their 

driving range before they require refueling. By reducing the frequency with which drivers 

typically refuel their vehicles, and by extending the upper limit of the range they can travel 

before requiring refueling, improving fuel economy thus provides some additional benefits to 

their owners. (Alternatively, if manufacturers respond to improved fuel economy by reducing 

the size of fuel tanks to maintain a constant driving range, the resulting cost saving will 

presumably be reflected in lower vehicle sales prices.) 

No direct estimates of the value of extended vehicle range are readily available, so the agency’s 

analysis calculates the reduction in the annual number of required refueling cycles that results 

from improved fuel economy, and applies DOT-recommended values of travel time savings to 

convert the resulting time savings to their economic value.313 As an illustration of how the value 

 

310 Ian W.H. Parry and Kenneth A. Small, “Does Britain or the U.S. Have the Right Gasoline Tax?” Discussion 

Paper 02-12, Resources for the Future, March 2002, pp. 19 and Table 1, http://www.rff.org/rff/Documents/RFF-DP02-12.pdf. 

311 U.S. Environmental Protection Agency, MOBILE6 Vehicle Emission Modeling Software, 

http://www.epa.gov/otaq/m6.htm#m60 

312 EPA, “Mobile Source $ per Ton Estimates,” document provided to NHTSA by EPA Office of Transportation and 

Air Quality staff, June 26, 2007. 

313 See http://ostpxweb.dot.gov/policy/Data/VOT97guid.pdf and 

http://ostpxweb.dot.gov/policy/Data/VOTrevision1_2-11-03.pdf
VIII-59 

of extended refueling range is estimated, a typical small light truck model has an average fuel 

tank size of approximately 20 gallons. Assuming that drivers typically refuel when their tanks 

are 20 percent full (i.e., 4 gallons in reserve), increasing this model’s actual on-road fuel 

economy from 24 to 25 mpg would extend its driving range from 384 miles (= 16 gallons x 24 

mpg) to 400 miles (= 16 gallons x 25 mpg). Assuming that it is driven 12,000 miles/year, this 

reduces the number of times it needs to be refueled each year from 31.3 (= 12,000 miles per year 

/ 384 miles per refueling) to 30.0 (= 12,000 miles per year / 400 miles per refueling), or by 1.3 

refuelings per year. 

Weighted by the nationwide mix of urban (about 2/3) and rural (about 1/3) driving and average 

vehicle occupancy for all driving trips (1.6 persons), the DOT-recommended value of travel time 

per vehicle-hour is $24.00 (in 2006 dollars).314 Assuming that locating a station and filling up 

requires ten minutes, the annual value of time saved as a result of less frequent refueling amounts 

to $5.20 (calculated as 10/60 x 1.3 x $24.00). This calculation is repeated for each future 

calendar year that light trucks of each model year affected by the alternative CAFE standards 

considered in this rule would remain in service. Like fuel savings and other benefits, however, 

the value of this benefit declines over a model year’s lifetime, because a smaller number of 

vehicles originally produced during that model year remain in service each year, and those 

remaining in service are driven fewer miles. 

Table VIII-5 summarizes the values used to calculate the impacts of each scenario. 

 

314 The hourly wage rate during 2006 is estimated to be $24.00. Personal travel (94.4% of urban travel) is valued at 

50 percent of the hourly wage rate. Business travel (5.6% or urban travel) is valued at 100 percent of the hourly 

wage rate. For intercity travel, personal travel (87%) is valued at 70 percent of the wage rate, while business travel 

(13%) is valued at 100 percent of the wage rate. The resulting values of travel time are $12.67 for urban travel and 

$17.66 for intercity travel, and must be multiplied by vehicle occupancy (1.6) to obtain the estimate value of time 

per vehicle hour. 
VIII-60 

Table VIII-5 

Economic Values for Benefits Computations (2007$) 

 

Fuel Prices (average retail gasoline price per gallon, 

2011-30) $3.33 

Rebound Effect (VMT Elasticity) -0.15 

Discount Rates Applied to Future Benefits 

 Reductions in CO2 Emissions 

 Other Benefits 

3% 

7% 

Payback Period (years) 5.0 

"Gap" between Test and On-Road MPG 20% 

Value of Travel Time per Vehicle ($/hour) $24.64 

Economic Costs of Oil Imports ($/gallon) 

"Monopsony" Component $0.266 

Price Shock Component $0.116 

Military Security Component - 

Total Economic Costs ($/gallon) $0.381 

External Costs from Additional Automobile Use Due to 

"Rebound" Effect ($/vehicle-mile) 

Congestion $0.054 

Accidents $0.023 

Noise $0.001 

Total External Costs $0.078 

External Costs from Additional Light Truck Use Due to 

"Rebound" Effect ($/vehicle-mile) 

Congestion $0.048 

Accidents $0.026 

Noise $0.001 

Total External Costs $0.075 

Emission Damage Costs 

Carbon Monoxide ($/ton) $ - 

Volatile Organic Compounds ($/ton) $1,700 

Nitrogen Oxides ($/ton) $4,000 

Particulate Matter ($/ton) $168,000 

Sulfur Dioxide ($/ton) $16,000 

Carbon Dioxide ($/metric ton) $ 2.00 

 Carbon Dioxide ($/metric ton) 

 (U.S. domestic value) 

 (Mean global value from Tol (2008) 

 (One standard deviation above mean global value 

$2.00 

$33.00 

$80.00 

Annual Increase in CO2 Damage Cost 2.4% 
VIII-61 

Summary of Benefits 

Benefits were calculated separately for passenger cars and light trucks under each alternative 

CAFE requirement for each model year covered by this proposal. In Tables VIII-6 through VIII7, the societal impacts for passenger car and light truck CAFE standards under the proposed 

Optimized Net Benefits alternative is shown for model year 2011. These tables include 

undiscounted values as well as present value calculations at 7 percent. They also show changes 

in the physical units of measure that produced these values. Negative values in these tables 

reflect net reductions in fuel consumption or emissions and their resulting economic impacts, 

which represent benefits from the proposal, while positive values represent increasing emissions, 

congestion, noise or crash severity and their added costs. The net social benefit from these 

societal impacts is shown on the Total line in each table. 

The proposed standards for passenger cars would save approximately 463 million gallons of fuel 

and prevent 4 million metric tons of tailpipe CO2 emissions over the lifetime of the passenger 

cars sold during those model years, compared to the fuel savings and emissions reductions that 

would occur if the standards remained at the adjusted baseline (i.e., the higher of manufacturer’s 

plans or the manufacturer’s required level of average fuel economy for MY 2010). 

The total value of societal benefits of the proposed passenger car standards would be $1billion315

over the lifetime of the MY 2011fleet. This estimate of societal benefits includes direct impacts 

from lower fuel consumption as well as externalities, and also reflects offsetting societal costs 

resulting from the rebound effect. Direct benefits to consumers, including fuel savings, 

consumer surplus from additional driving, and reduced refueling time, account for 87.7 percent 

of the gross consumer benefits316 resulting from increased passenger car CAFE. Petroleum 

market externalities account for 10 percent. Environmental externalities, i.e., reduction of air 

pollutants accounts for 2.3 percent. 

The proposed standards for light trucks would save approximately 424 million gallons of fuel 

and prevent 4 million metric tons of tailpipe CO2 emissions over the lifetime of the light trucks 

sold during those model years, compared to the fuel savings and emissions reductions that would 

occur if the standards remained at the adjusted baseline (i.e., the higher of manufacturer’s plans 

or the manufacturer’s required level of average fuel economy for MY 2010). 

The total value of societal benefits of the proposed light truck standards would be $920 

million317. This estimate of societal benefits includes direct impacts from lower fuel 

consumption as well as externalities, and also reflects offsetting societal costs resulting from the 

rebound effect. Direct benefits to consumers, including fuel savings, consumer surplus from 

additional driving, and reduced refueling time, account for 87.6 percent of the gross consumer 

 

315 The $1 billion estimate is based on a 7% discount rate for valuing future impacts. Undiscounted, these benefits 

are valued at almost $1.6 billion. 

316 Gross consumer benefits are benefits measured prior to accounting for the negative impacts of the rebound effect. 

They include fuel savings, consumer surplus from additional driving, reduced refueling time, petroleum market 

externalities, reduced criteria pollutants, and reduced greenhouse gas production. Negative impacts from the 

rebound effect include added congestion, noise, and crash costs due to additional driving. 

317 The $920 million estimate is based on a 7% discount rate for valuing future impacts. Undiscounted, these 

benefits are valued at about $1.5 billion 
VIII-62 

benefits resulting from increased light truck CAFE. Petroleum market externalities account for 

10 percent. Environmental externalities, i.e., reduction of air pollutants accounts for 2.4 percent. 

Table VIII-8 summarizes the fuel savings from all alternatives for passenger cars and light 

trucks. As would be expected, benefit levels parallel the increasing stringency of the various 

alternatives that were examined. The two Optimized scenarios pushes technology up to the point 

where is ceases to be cost effective, but the 3% based scenario produces more benefits than the 

7% based scenario because it places a higher value on benefits experienced in the future. The 

TC=TB scenario produces benefits that exceed the Optimized scenarios because it allows 

benefits that accrue from cost-beneficial technologies to offset costs that accrue from 

technologies that are not cost-beneficial. As might be expected, the High Technology scenario, 

which assumes the maximum use of all available technologies in all vehicles regardless of cost, 

produces higher savings than any of the 6 other scenarios. The 25% Below Optimized, 25% 

Above Optimized, and 50% Above Optimized scenarios were designed to produce results 

relative to the Optimized scenario, and their benefits accordingly reflect this. 

Tables VIII-9 summarizes the total social benefits from all alternatives for passenger cars and 

light trucks. These tables summarize the value of net consumer benefits over the lifetime of the 

vehicles manufactured. The value of societal benefits mirrors the trends in stringency across 

alternative scenarios. 
VIII-63 

Table VIII-6 

 Lifetime Monetized Societal Impacts, Optimized 7%, MY 2011, 

 Passenger Cars 

 

Societal Effect Physical Units Undiscounted 

Value (2007$ 

millions) 

Present Discounted 

Value @ 7% 

Lifetime Fuel Expenditures -462,739(kgal) 1,296 842

Consumer Surplus from 

Additional Driving 1,827,193(kmiles) 158 103

Refueling Time Value 2,291,110(hours) 56 38

Petroleum Market 

Externalities -462,739(kgal) 168 112

Congestion Costs 1,827,193(kmiles) -98 -65

Noise Costs 1,827,193(kmiles) -1 -1

Crash Costs 1,827,193(kmiles) -42 -28

CO2 -4(mmT) 14 8

CO -44,493(tons) 0 0

VOC -2,171(tons) 4 2

NOX -1,547(tons) 6 4

PM -56(tons) 9 6

SOX -616(tons) 10 7

Total 1,580 1,027

 
VIII-64 

Table VIII-7 

Lifetime Monetized Societal Impacts, 

Optimized 7%, MY 2011, Light Trucks 

 

Societal Effect Physical Units Undiscounted 

Value (2007$ 

millions) 

Present Discounted 

Value @ 7% 

Lifetime Fuel Expenditures -424,238(kgal) 1,206 747

Consumer Surplus from 

Additional Driving 1,370,561(kmiles) 147 92

Refueling Time Value 1,613,123(hours) 40 25

Petroleum Market 

Externalities -424,238(kgal) 154 98

Congestion Costs 1,370,561(kmiles) -66 -42

Noise Costs 1,370,561(kmiles) -1 -1

Crash Costs 1,370,561(kmiles) -35 -22

CO2 -4(mmT) 15 8

CO 5,409(tons) 0 0

VOC -1,047(tons) 2 1

NOX -737(tons) 3 2

PM -69(tons) 12 7

SOX -554(tons) 9 6

Total 1,484 921
VIII-65 

Table VIII-8 

Savings in Millions of Gallons of Fuel 

Undiscounted, over the Lifetime of the Model Year 2011 Fleet 

 Passenger Cars Light Trucks Passenger Cars and 

Light Trucks 

Combined 

25% Below Optimized (7%) 352 424 776 

Optimized (7%) 463 424 887 

25% Above Optimized (7%) 598 456 1,054 

50% Above Optimized (7%) 794 456 1,250 

Optimized (3%) 946 424 1,371 

TC = TB (7%) 1,121 567 1,687 

Technology Exhaustion (7%) 2,982 1,420 4,402 

Table VIII-9 

Present Value of Lifetime Social Benefits 

(Millions of 2007 Dollars) 

 Passenger Cars Light Trucks Passenger Cars and 

Light Trucks 

Combined 

25% Below Optimized (7%) 786 921 1,707 

Optimized (7%) 1,027 921 1,948 

25% Above Optimized (7%) 1,332 989 2,321 

50% Above Optimized (7%) 1,773 989 2,763 

Optimized (3%) 2,647 1,176 3,824 

TC = TB (7%) 2,487 1,189 3,676 

Technology Exhaustion (7%) 6,406 2,950 9,356 
VIII-66 

References 

Argonne National Laboratories, The Greenhouse Gas and Regulated Emissions from 

Transportation (GREET) Model, Version 1.6, February 2002. 

Greene, David L., “Vehicle Use and Fuel Economy: How Big is the Rebound Effect?” The 

Energy Journal, 13:1 (1992), 117-143. 

Greene, David L., Donald W. Jones, and Paul N. Leiby, The Outlook for U.S. Oil Dependence, 

ORNL-6873, Oak Ridge National Laboratory, May 11, 1995. 

Greene, David L., James R. Kahn, and Robert C. Gibson, “Fuel Economy Rebound Effect for 

Household Vehicles,” The Energy Journal, 20:3 (1999), 1-31. 

Greene, David L., and Nataliya I. Tishchishyna, Costs of Oil Dependence: A 2000 Update, 

ORNL/TM-2000/152, Oak Ridge National Laboratory, May 2000. 

Haughton, Jonathan, and Soumodip Sarkar, “Gasoline Tax as a Corrective Tax: Estimates for the 

United States,” The Energy Journal, 17:2, 103-126. 

Jones, Clifton T., “Another Look at U.S. Passenger Vehicle Use and the ‘Rebound’ Effect from 

Improved Fuel Efficiency, The Energy Journal, 14:4 (1993), 99-110. 

Leiby, Paul N., Donald W. Jones, T. Randall Curlee, and Russell Lee, Oil Imports: An 

Assessment of Benefits and Costs, ORNL-6851, Oak Ridge National Laboratory, November 1, 

1997. 

Pickrell, Don H., “Description of VMT Forecasting Procedure for ‘Car Talk’ Base Line 

Forecasts,” manuscript, Volpe National Transportation Systems Center, U.S. Department of 

Transportation, 1994. 

Puller, S.L., and L.A. Greening, “Household Adjustment to Gasoline Price Changes: An 

Analysis Using Nine Years of U.S. Survey Data,” Energy Economics, 21:1, pp. 37-52. 

Small, K.A. and VanDender, K. (2005) “A Study to Evaluate the Effect of Reduced Greenhouse 

Gas Emissions on Vehicle Miles Traveled”, State of California Air Resources Board, California 

Environmental Protection Agency, and the California Energy Commission. 

U.S. Department of Energy, Program Analysis Methodology Office of Transportation 

Technology: Quality Metrics 2002, Final Report, Office of Transportation Technologies, May 9, 

2001. 
VIII-67 

U.S. Environmental Protection Agency, MOBILE Motor Vehicle Emission Factor Model, 

version 6.2, November 2002. 
IX-1 

IX. NET BENEFITS AND SENSITIVITY ANALYSES 

This chapter compares the costs of technologies needed to make improvements in fuel economy 

with the potential benefits, expressed in total costs (millions of dollars) from a societal 

perspective for each model year. The costs do not include fines, since these are transfer 

payments. Thus, the total costs shown in this section do not match the total costs shown in 

Chapter VII. These are incremental costs and benefits compared to the adjusted baseline of 

manufacturers’ plans. Sensitivity analyses are also performed on some of the assumptions made 

in this analysis. Finally, a payback period is calculated, from the consumer’s perspective. 

Table IX-1 provides the total incremental costs (in millions of dollars) from a societal 

perspective. Table IX-2 provides the total benefits from a societal perspective for all vehicles 

produced. Table IX-3 shows the total net benefits in millions of dollars for the projected fleet 

of sales for model year 2011. 

Total costs follow a predictable pattern with costs rising to reflect the more expensive 

technologies that manufacturers must apply in order to achieve the CAFE levels that are required 

under the more aggressive alternatives, with the exception of the Optimized (3%) alternative for 

light trucks. For the combined fleet, total compliance costs for the Total Cost = Total Benefit 

alternative is roughly 3.5 times those for the Optimized (7%) alternative. Relative to the 

proposed Optimized (7%) alternative, Technology Exhaustion produces costs that are 15.8 times 

the Optimized cost levels. 

From Table IX-2, lifetime societal benefits follow a similar predictable pattern, with higher 

benefits associated with the more expensive technologies that are enabled under the more 

aggressive alternatives. For the combined fleet, the TC=TB alternative produces gross benefits 

roughly 1.9 times as high as the Optimized (7%) alternative, and the Technology Exhaustion 

alternative produces gross benefits that are 4.8 times the Optimized (7%) alternative. 

While the pattern for benefits is directionally similar to the pattern for costs, the more aggressive 

technology scenarios do not increase benefits by as high a ratio as they do for costs. For 

example, the TC=TB alternative increases total benefits, but it also increases total costs, resulting 

in a net loss to society of $334 million. This is a function of the more aggressive alternatives 

relatively unrestrained functions. While the Optimized (7%) alternative adds technology until 

the marginal cost to society begins to exceed the marginal benefit, the TC=TB scenario and the 

Technology exhaustion scenario allow for continued investment in technology despite its 

negative net return. Thus, while both costs and benefits continue to rise with more aggressive 

technologies, the costs rapidly begin to exceed the benefits that society derives from the added 

investment. 

The impact of the relatively unrestricted technology application that is enabled by the more 

aggressive scenarios is apparent from Table IX-3, which shows net total lifetime societal benefits 

under each alternative. The Optimized (7%) or the Optimized (3%) alternative produces the 

highest net total benefits to society, as would be expected. The TC=TB and Technology 

Exhaustion alternatives produce a net loss to society. 
IX-2 

Table IX-1 

Incremental Total Cost – Societal Perspective 

(Millions of 2007 Dollars) 

 Passenger Cars Light Trucks Passenger Cars and 

Light Trucks 

Combined 

25% Below Optimized (7%) 291 649 940 

Optimized (7%) 496 649 1,145 

25% Above Optimized (7%) 1,003 915 1,918 

50% Above Optimized (7%) 1,630 915 2,545 

Optimized (3%) 1,820 649 2,469 

TC = TB (7%) 2,619 1,391 4,009 

Technology Exhaustion (7%) 11,907 6,214 18,120 

Table IX-2 

Present Value of Lifetime Societal Benefits by Alternative 

(Millions of 2007 Dollars) 

 Passenger Cars Light Trucks Passenger Cars and 

Light Trucks 

Combined 

25% Below Optimized (7%) 786 921 1,707 

Optimized (7%) 1,027 921 1,948 

25% Above Optimized (7%) 1,332 989 2,321 

50% Above Optimized (7%) 1,773 989 2,763 

Optimized (3%) 2,647 1,176 3,824 

TC = TB (7%) 2,487 1,189 3,676 

Technology Exhaustion (7%) 6,406 2,950 9,356 
IX-3 

Table IX-3 

Net Total Benefits 

Over the Vehicle’s Lifetime – Present Value 

(Millions of 2007 Dollars) 

 Passenger Cars Light Trucks Passenger Cars and 

Light Trucks 

Combined 

25% Below Optimized (7%) 496 272 767 

Optimized (7%) 531 272 802 

25% Above Optimized (7%) 329 75 403 

50% Above Optimized (7%) 143 75 218 

Optimized (3%) 828 527 1,355 

TC = TB (7%) (132) (202) (334) 

Technology Exhaustion (7%) (5,501) (3,264) (8,765) 

Sensitivity Analyses 

The agency has performed several sensitivity analyses to examine important assumptions. The 

analyses include: 

1) The value of CO2. We examined $2 per metric ton as a domestic value, $33 per metric 

ton as a global value and $80 per metric ton as a global value. These values can be 

translated into cents per gallon by multiplying by 0.0089318, as shown below: 

$2 per ton CO2 = $2*0.0089 = $0.0178 per gallon 

$33.00 per ton CO2 = $33*0.0089 = $0.2937 per gallon 

$80.00 per ton CO2 = $80*0.0089 = $0.712 per gallon 

2) The value of monopsony costs. For domestic values of CO2, the main analysis uses $0.27 

per gallon for monopsony costs. At the low end of the range for domestic values, the 

sensitivity analysis examines $0.21. For global values of CO2, a $0 value of monopsony 

cost is appropriate. 

3) The price of gasoline. The main analysis uses the AEO 2008 high cost case estimate for 

the price of gasoline (see Table VIII-3). In this sensitivity analysis we also examine the 

reference case estimate of the price of gasoline from AEO 2008 estimate. 

 

318 The molecular weight of Carbon (C) is 12, the molecular weight of Oxygen (O) is 16, thus the molecular weight of 

CO2 is 44. One ton of C = 44/12 tons CO2 = 3.67 tons CO2. 1 gallon of gas weighs 2,819 grams, of that 2,433 grams 

are carbon. $1.00 CO2 = $3.67 C and 

$3.67/ton * ton/1000kg * kg/1000g * 2433g/gallon = (3.67 * 2433) / 1000 * 1000 = $0.0089/gallon 
IX-4 

4) Military security. For one of the scenarios, we added a $0.05 per gallon military security 

cost. 

Sensitivity analyses were performed on just the optimized (7%) alternative. Presented are 

information on the average mpg expected to be achieved by the manufacturers, the price per 

vehicle increase, total benefits, the total cost increase, the total lifetime fuel saved and the total 

CO2 emissions reduction. 

 

Table IX-4 

Sensitivity Analyses 

 Fuel Prices CO2 Value Monopsony Military Security 

Final Rule High $2 $0.27 0 

Low Global 

Carbon 

High $33 0 0 

High Global 

Carbon 

High $80 0 0 

Low Fuel Low $2 $0.21 0 

Low Fuel 

High Military 

Low $2 $0.21 $.05 

In the PRIA, we examined the sensitivity of the price of gasoline (low, reference, and high case), 

values of CO2 ($0 to $14 per ton), combined externalities ($0.120 and $0.504 per gallon), and 

the rebound effect (10 to 20 percent). Only the price of gasoline had a significant impact on the 

results. We repeated the rebound effect sensitivity analysis for the Final Environmental Impact 

Statement (FEIS). The results of these sensitivity analyses are shown in the FEIS at Section 

3.4.4.2. Reducing the rebound effect from the 15 percent to 10 percent would have only a slight 

effect on fuel savings and reductions in CO2 emissions. In contrast, increasing the rebound 

effect from the 15 percent value to 20 percent would lower the combined passenger car and light 

truck fuel savings by 0.5 to 1.5 mpg for the scenarios examined in Tables 3.4-3 and 3.4-4 of the 

FEIS. 

The results of the sensitivity analyses indicate that the much wider values of CO2 examined have 

almost no impact on the achieved mpg levels for passenger cars and a small impact on the light 

truck levels. The low fuel price has an impact on the light truck levels of 0.3 mpg. The high 

military cost (only $0.05 per gallon) has no impact on the level of the standards. 

Note that there are some slight inconsistencies in the relationships one would expect when 

comparing the required mpg levels for corresponding model years in the various sensitivity 

analyses to those under the final rule CAFE standards. For example, the level of the standard 

should increase when CO2 is assigned a higher value, because this increases the benefit of each 

gallon of fuel saved, but the optimized standards are actually lower with the high CO2 value than 

under the final rule. Problems such as this arise when making slight changes in parameter values 
IX-5 

used by the CAFE model, since the model derives a relationship between net benefits and the 

stringency level of standards, and minor changes in parameter values can affect the exact shapes 

and positions of those curves. In any case, the seemingly anomalous results are mostly small 

(0.1 mpg or less). When larger variations are made to the model’s parameters or other inputs, 

such as substituting the Reference Case gasoline price forecast, the sensitivity analysis invariable 

produces the anticipated result. 
IX-6 

Table IX-5 

Passenger Car Sensitivity Analyses 

(mpg) 

 

 MY 2011 

Final Rule 30.7 

Low Global Carbon 30.7 

High Global Carbon 30.7 

Low Fuel 30.7 

Low Fuel, High Military 30.7 

 MY 2011 

Per Vehicle 

Cost 

($) 

MY 2011 

Total Benefits 

($Mill.) 

MY 2011 

Total Cost 

$(Mill.) 

Total Fuel 

Saved 

(Bill. Gal.) 

Total CO2

Emissions 

(mmt) 

Final Rule 64 1,027 496 463 4.3 

Low Global 

Carbon 

48 935 354 392 3.6 

High Global 

Carbon 

48 1,121 354 392 3.6 

Low Fuel 45 662 317 404 3.7 

Low Fuel 

High Military 

45 662 317 404 3.7 
IX-7 

Table IX-6 

Light Truck Sensitivity Analyses 

(mpg) 

 MY 2011 

Final Rule 23.2 

Low Global Carbon 23.1 

High Global Carbon 23.1 

Low Fuel 22.9 

Low Fuel, High Military 22.9 

 MY 2011 

Per Vehicle 

Cost 

($) 

MY 2011 

Total Benefits 

($Mill.) 

MY 2011 

Total Cost 

$(Mill.) 

Total Fuel 

Saved 

(Bill. Gal.) 

Total CO2

Emissions 

(mmt) 

Final Rule 126 921 649 424 3.9 

Low Global 

Carbon 

121 944 613 408 3.8 

High Global 

Carbon 

316 3,774 1,794 1,372 12.6 

Low Fuel 95 297 560 220 2.0 

Low Fuel 

High Military 

95 297 560 220 2.0 
IX-8 

Payback Period 

The “payback period” represents the length of time required for a vehicle buyer to recoup, 

through savings in fuel use, the higher cost of purchasing a more fuel-efficient vehicle. Thus, 

only these two factors are considered (purchase price and fuel savings). When a higher CAFE 

standard requires a manufacturer to improve the fuel economy of some of its vehicle models, the 

manufacturer’s added costs for doing so are reflected in higher prices for these models. While 

buyers of these models pay higher prices to purchase these vehicles, their improved fuel 

economy lowers the consumer’s costs for purchasing fuel to operate them. Over time, buyers 

may recoup the higher purchase prices they pay for these vehicles in the form of savings in 

outlays for fuel. The length of time required to repay the higher cost of buying a more fuelefficient vehicle is referred to as the buyer’s payback period. 

The length of this payback period depends on the initial increase in a vehicle’s purchase price, 

the improvement in its fuel economy, the number of miles it is driven each year, and the retail 

price of fuel. We calculated payback periods using the fuel economy improvement and average 

price increase estimated to result from the standard, the future retail gasoline prices, and 

estimates of the number of miles vehicles are driven each year as they age. These calculations 

are taken from a consumer’s perspective, not a societal perspective. Thus, only gasoline savings 

are included on the benefits side of the equation. The price of gasoline includes fuel taxes and 

future savings are not discounted to present value, since consumers generally only consider and 

respond to what they pay at the pump. The payback periods are estimated as an average for all 

manufacturers for the different alternatives. The payback periods for MY 2011 are shown in 

Table IX-7. 

Table IX-7 

Payback Period for MY 2011 Average Vehicles 

(in years) 

Passenger 

Cars 

Light 

Trucks 

25% Below 

Optimized 3.7 7.7

Optimized 

(7%) 4.4 7.7

25% Above 

Optimized 5.2 10.0

50% Above 

Optimized 8.2 10.0

Optimized 

(3%) 7.7 7.7

TC = TB 9.2 Never

Technology 

Exhaustion Never Never
X-1

X. PROBABILISTIC UNCERTAINTY ANALYSIS 

OMB Circular A-4 requires formal probabilistic uncertainty analysis of complex rules where 

there are large, multiple uncertainties whose analysis raises technical challenges or where effects 

cascade and where the impacts of the rule exceed $1 billion. CAFE meets all of these criteria. 

This chapter identifies and quantifies the major uncertainties in the preliminary regulatory impact 

analysis and estimates the probability distribution of the benefits, costs, and net benefits of the 

compliance options selected for the proposed rule for MY 2011 passenger car and light truck 

CAFE standards. Throughout the course of the main analysis, input values were selected from a 

variety of often conflicting sources. Best estimates were selected based on the preponderance of 

data and analyses available, but there is inevitably a level of uncertainty in these selections. 

Some of these inputs contributed less to the overall variations of the outcomes, and, thus, are less 

significant. Some inputs depend on others or are closely related (e.g. oil import externalities), 

and thus can be combined. With the vast number of uncertainties imbedded in this regulatory 

analysis, this uncertainty analysis identifies only the major independent uncertainty factors 

having appreciable variability and impact on the end results and quantifies them by their 

probability distributions. These newly defined values are then randomly selected and fed back 

into the model to determine the net benefits using the Monte Carlo statistical simulation 

technique.319 The simulation technique induces the probabilistic outcomes accompanied with 

degrees of probability or plausibility. This facilitates a more informed decision-making process. 

The analysis is based on the actual processes used to derive net benefits as described in the 

previous chapters. Each variable (e.g., cost of technology) in the mathematical model represents 

an uncertainty factor that would potentially alter the modeling outcomes if its value was 

changed. We assume that these variables are independent of each other. The confidence 

intervals around the costs and benefits of technologies reflect independent levels of uncertainty 

regarding costs and benefits, rather than linked probabilities dependent on higher or lower 

quality versions of a specific technology. By contrast, there is reason to believe that monopsony 

costs may be dependent on fuel prices. However, monopsony costs are only one of several oil 

import externalities, and the range of monopsony costs is quite narrow. The potential for 

significant error due to an assumption of independence for monopsony costs is thus quite low. 

Given this, the agency has elected to treat monopsony costs as an independent variable. 

 The uncertainties of these variables are described by appropriate probability distribution 

functions based on available data. If data are not sufficient or not available, professional 

judgments are used to estimate the probability distributions of these uncertainty factors. A 

complete description of the formulas and methods used in the CAFE model is available in the 

public docket.320 

 

319 See, for example, Morgan, MG, Henrion, M, and Small M, “Uncertainty: A Guide to Dealing with Uncertainty in 

Quantitative Risk and Policy Analysis”, Cambridge University Press, 1990. 320 CAFE Compliance and Effects Modeling System Documentation, Volpe Center, U.S. Dept. of Transportation, 

July 2005, pp. 27-46 and C-22 to C-35. Docket No. NHTSA 21974-2.
X-2

After defining and quantifying the major uncertainty factors, the next step is to simulate the 

model to obtain probabilistic results rather than single-value estimates. In the uncertainty 

analysis, CAFE levels were kept constant; in other words, we did not change the CAFE 

standards for each run based on net benefits. The simulation process was run repeatedly for 

20,000 trials under each discount rate scenario. Each complete run is a trial. For each trial, the 

simulation first randomly selects a value for each of the uncertainty factors based on their 

probability distributions. The selected values are then fit into the models to forecast results. In 

addition to the simulation results, the program also estimates the degree of certainty (or 

confidence, credibility). The degree of certainty provides the decision-maker with an additional 

piece of important information with which to evaluate the forecast results. 

A. Simulation Models and Uncertainty Factors 

A Monte Carlo simulation was conducted using the CAFE modeling system that was developed 

to estimate the impacts of higher CAFE requirements described in previous chapters. The focus 

of the simulation model was variation around the chosen uncertainty parameters and their 

resulting impact on the key output parameters, fuel savings, and net benefits. Net benefits 

measure the difference between (1) the total dollar value that would be saved in fuel and other 

benefits and (2) the total costs of the rule. 

The agency reviewed the inputs and relationships that drive the CAFE model to determine the 

factors that are the major sources of uncertainty. Five factors were identified as contributing the 

most uncertainty to the estimated impacts of higher CAFE standards: 

(1) Technology costs; 

(2) Technology effectiveness; 

(3) Fuel prices; 

(4) The value of oil consumption externalities; and 

(5) The rebound effect. 

(6) Greenhouse gas values 

Technology Costs 

The costs incurred by manufacturers to modify their vehicles to meet new CAFE levels are 

assumed to be passed on to consumers in the form of higher new car prices. These technology 

costs are the primary determinant of the overall cost of improving fuel economy. 

Forty different technologies were examined as possible methods to comply with higher CAFE 

standards. These technologies were summarized in Chapter V earlier in this analysis. Chapter V 

also summarizes the estimated range of costs for these technologies. The expected values (midrange values) were used in the main analysis. For the uncertainty analysis, the full range of NAS 

cost estimates is used. The uncertainty model assumes a normal distribution for these costs, with 

each end of the range being three standard deviations from the mean (or expected) value. Since 

only 9 of the 40 technologies had range estimates for costs, the range across the remaining 31 

technologies was estimated based on the average range found in the 9 technologies with range 
X-3

estimates (+-29%) Figure X-1 graphically demonstrates the distributions of a hypothetical 

sample of three of the technologies. 

Figure X-1 

Normal Distributions for 3 Different Technologies 

-

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0 50 100 150 200 250 300

Retail Price Equivalent Increase ($)

Probability Density

Aero. Drag Reduction ($0-146)

Cylinder Deactivation ($116-262)

Engine Acc. Improvement ($87-116)

Technology Effectiveness 

The modifications adopted by manufacturers to enable their vehicles to meet new CAFE levels 

will improve fuel efficiency and reduce the cost of operating the more efficient vehicles. The 

effectiveness of each technology determines how large an impact it will have towards enabling 

manufacturers to meet the higher CAFE standards, and will thus determine how much additional 

improvement is needed and which additional technologies will be required to achieve full 

compliance. In selecting the likely path that manufacturers will choose to meet CAFE, the 

CAFE model tests the interaction of technology costs and effectiveness to achieve an optimal 

(cost-minimizing) technological solution. Technology effectiveness is thus a primary 

determinant of the overall cost and benefit of improving fuel economy. 

As noted above, forty different technologies were examined as possible methods to comply with 

higher CAFE standards. These technologies were summarized in Chapter V earlier in this 

analysis. Chapter V also summarizes the estimated range of effectiveness for these technologies. 

The expected values (mid-range values) were used in the main analysis. For the uncertainty 

analysis, the full range of effectiveness estimates is used. The uncertainties model assumes a 
X-4

normal distribution for these values, with each end of the range being three standard deviations 

from the mean (or expected) value. Since only 30 of the 40 technologies had range estimates for 

effectiveness, the range across the remaining 10 technologies was estimated based on the average 

range found in the 30 technologies with range estimates (+-31%) 

Fuel Prices 

Higher CAFE standards will result in reduced gasoline consumption, which will translate into 

lower vehicle operating costs for consumers. The value of this reduced fuel consumption is a 

direct function of fuel prices. Fuel prices are thus a primary determinant of the overall social 

benefit that will result from improving fuel economy. 

The analysis attempts to measure impacts that occur as much as 40 years in the future and 

estimating gasoline prices this far in advance is an uncertain process. In the main analysis, the 

agency utilized predicted fuel prices from the Energy Information Administration’s (EIA) 

publication Annual Energy Outlook 2008 (AEO). For reasons discussed previously, the main 

analysis is based on the AEO High Case scenario, which represents the Agency’s best estimate 

of future fuel prices. For the uncertainty analysis, the Agency examined two other AEO 

scenarios, the Low Oil Price scenario (LOP) and the Reference Oil Price scenario (ROP). Both 

scenarios were also derived from the AEO 2008. These 2 alternate scenarios were chosen to 

allow for the possibility that the EIA’s High Case predictions could overestimate the price of 

gasoline in the future. Oil prices have been extremely volatile over the past year, climbing to 

record highs and then most recently dropping to levels consistent with a year ago. 

 

Each of these scenarios was applied as a discrete input (i.e., draws were not made from among 

the three scenarios separately for each future year). Rather, for each draw, one of the three 

scenarios was chosen and applied across the full vehicle life for each model year. The 

probability of selection for each of the three scenarios was modeled using discrete weights of 60 

percent for the High Case, and 35 percent for the Reference Case and 5 percent for the LOP 

Case. Table X-1 lists the AEO gasoline price forecasts under each scenario. These same prices 

are demonstrated graphically (in 2007 economics) in Figure X-2. Note that these prices include 

Federal, State, and local fuel taxes. For the uncertainty analysis, taxes were removed because 

they are viewed as transfer payments (see discussion in Chapter VIII). Estimated retail prices are 

shown here because they are a better reference point for most readers. 

 

 
X-5

Table X-1 

AEO 2008 Gasoline Price Scenarios 

(2007 dollars) 

Year Low Reference High 

2011 $2.397 $2.551 $2.949 

2012 $2.263 $2.475 $2.974 

2013 $2.141 $2.404 $3.023 

2014 $2.032 $2.388 $3.077 

2015 $1.906 $2.315 $3.093 

2016 $1.791 $2.254 $3.138 

2017 $1.791 $2.266 $3.200 

2018 $1.791 $2.292 $3.241 

2019 $1.815 $2.360 $3.301 

2020 $1.890 $2.419 $3.363 

2021 $1.866 $2.384 $3.451 

2022 $1.883 $2.404 $3.491 

2023 $1.879 $2.412 $3.492 

2024 $1.862 $2.407 $3.510 

2025 $1.858 $2.423 $3.485 

2026 $1.851 $2.436 $3.494 

2027 $1.853 $2.449 $3.518 

2028 $1.858 $2.472 $3.545 

2029 $1.877 $2.496 $3.576 

2030 $1.892 $2.512 $3.618 

2031 $1.892 $2.512 $3.618 

2032 $1.892 $2.512 $3.618 

2033 $1.892 $2.512 $3.618 

2034 $1.892 $2.512 $3.618 

2035 $1.892 $2.512 $3.618 

2036 $1.892 $2.512 $3.618 

2037 $1.892 $2.512 $3.618 

2038 $1.892 $2.512 $3.618 

2039 $1.892 $2.512 $3.618 

2040 $1.892 $2.512 $3.618 

2041 $1.892 $2.512 $3.618 

2042 $1.892 $2.512 $3.618 

2043 $1.892 $2.512 $3.618 

2044 $1.892 $2.512 $3.618 

2045 $1.892 $2.512 $3.618 

2046 $1.892 $2.512 $3.618 

2047 $1.892 $2.512 $3.618 

 
X-6

Figure X-2 

AEO 2008 Retail Fuel Price Scenarios

$0.00

$0.50

$1.00

$1.50

$2.00

$2.50

$3.00

$3.50

$4.00

2011201420172020202320262029203220352038204120442047

Year

Retail Price

Low

Reference

High

 

Oil Consumption Externalities 

Reduced fuel consumption can benefit society by lowering the world market price for oil, 

reducing the threat of petroleum supply disruptions, and reducing the cost of maintaining 

military security in oil producing regions and operating the strategic petroleum reserve. These 

benefits are called “externalities” because they are not reflected directly in the market price of 

fuel. A full description of these externalities is included in Chapter VIII under “Other Economic 

Benefits from Reducing Petroleum Use.” These factors increase the net social benefits from 

reduced fuel consumption. Although they represent a relatively small portion of overall social 

benefits, there is a significant level of uncertainty as to their values. For this reason, they were 

examined in the uncertainty analysis. 

Table X-3 lists the range of values that were examined for oil consumption externalities. The 

expected values were used in the main analysis. Both the value of reducing U.S. demand on the 

world market price for oil and the value of reduced threat of supply disruptions were derived 

from a study by Leiby (2008) (see Chapter VIII). For reasons noted in Chapter VIII, military 

security is not specifically valued in this analysis. A normal distribution was assumed for the 

range of values for oil consumption externalities with the low and high values assumed to be two 

standard deviations from the mean, based on the Leiby estimates. 
X-7

Table X-2 

Uncertainty Ranges for Oil Consumption Externalities ($/gallon) 

 

Low Expected High 

For reducing U.S. demand on world 

market price 

$0.008 $0.266 $0.524 

For reducing the threat of supply 

disruptions 

$0.034 $0.116 $0.198 

The Rebound Effect 

By reducing the amount of gasoline used and, thus, the cost of operating a vehicle, higher CAFE 

standards are expected to result in a slight increase in annual miles driven per vehicle. This 

“rebound effect” impacts net societal benefits because the increase in miles driven offsets a 

portion of the gasoline savings that results from more fuel-efficient vehicles. Although 

consumers derive some value from this extra driving, it also leads to increases in crash, 

congestion, noise, and pollution costs associated with driving. Most recent estimates of the 

magnitude of the rebound effect for light duty vehicles fall in the range of 10-20 percent (i.e., 

increasing vehicle use will offset 10-20 percent of the fuel savings resulting from an 

improvement in fuel economy). A more complete discussion of the rebound effect is included in 

Chapter VIII. The agency employed a rebound effect of 15 percent in the main analysis. For 

the uncertainty analysis, a range of 10 to 20 percent is used and employed in a skewed Beta 

distribution which produced a mean of approximately 14 percent. The skewed distribution 

reflects the agency’s belief that the more credible studies that differ from the 15 percent value 

chosen for the main analysis fall below this value and differ by more substantial margins than the 

upper range of credible values. 

Greenhouse Gas Emissions 

Emissions of carbon dioxide (CO2) and other greenhouse gases (GHG) occur throughout the 

process of producing and distributing transportation fuels, as well as from fuel combustion itself. 

By reducing the volume of fuel consumed by passenger cars and light trucks, higher CAFE 

standards will thus reduce GHG emissions generated by fuel use, as well as throughout the fuel 

supply cycle. Lowering these emissions is likely to slow the projected pace and reduce the 

ultimate extent of future changes in the global climate, thus reducing future economic damages 

that changes in the global climate would otherwise cause. By reducing the probability that 

climate changes with potentially catastrophic economic or environmental impacts will occur, 

lowering GHG emissions may also result in economic benefits that exceed the resulting 

reduction in the expected future economic costs caused by gradual changes in the earth’s climatic 

systems. In Chapter VIII a full discussion of this issue, including alternate estimates of values 

for Greenhouse gases is presented. We had to pick a number for the uncertainty analysis. We 

could have chosen any of the numbers discussed in Chapter VIII. We chose $2 per metric ton of 

CO2 emissions with a standard deviation of $1.00 per metric ton. 

 Table X-3 Summarizes the economic parameters used in the uncertainty analysis. 
X-8

 

Table X-3 

Monte-Carlo Specific Parameters 

 

Rebound Randomization Parameters 

Rebound Alpha Shape 15.0 

Rebound Beta Shape 6.6 

Rebound Scale -0.20 

Rebound Base -0.05 

Monopsony Randomization Parameters 

Monopsony Mean $0.266 

Monopsony Standard Deviation $0.129 

Price Shock Randomization Parameters 

Price Shock Mean $0.116 

Price Shock Standard Deviation $0.041 

Military Security Randomization Parameters 

Military Security Mean $0.000 

Military Security Standard Deviation $0.000 

Carbon Dioxide Randomization Parameters 

CO-2 Mean $2.00 

CO-2 Standard Deviation $1.00 

Default Cost and Effectiveness Variations 

Cost Variation % 29% 

Effectiveness Variation % 31% 

Fuel Path Randomization Parameters 

Low 5% 

Reference 35% 

High 60% 

Modeling Results – Trial Draws 

Because of the complexity of the CAFE model, the computer time required to perform the 

uncertainty analysis was significant. The uncertainty analysis conducted a total of 40,000 trials 

(20,000 for each discount rate) Figures X- 3 through X-14 graphically illustrate the draw results 

for a sample of the 84 variables (40 technology effectiveness rates, 40 technology costs, the fuel 

price scenario, oil import externalities, the rebound effect, and CO2.) that were examined. 

Tables X-4 through X-8 list the draw results for each economic input, technology cost, and 

technology effectiveness. 
X-9

Figure X-3 

Monte Carlo Draw Profile, Passenger Car Costs 

Turbocharging and Downsizing

0

200

400

600

800

1000

1200

1400

1600

$668 $848 $1,028 $1,208 $1,388

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %

 

 
X-10

Figure X-4 

Monte Carlo Draw Profile, Passenger Car Effectiveness 

Turbocharging and Downsizing

0

200

400

600

800

1000

1200

1400

1600

0.038 0.040 0.041 0.042 0.044

Fuel Consumption Reduction (gpm)

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %

Figure X-5 

Monte Carlo Draw Profile, Passenger Cars, Costs 

Conversion to Diesel following TRBDS

0

200

400

600

800

1000

1200

1400

1600

1800

2000

$1,910 $2,010 $2,110 $2,210 $2,310

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %
X-11

Figure X-6 

Monte Carlo Draw Profile, Passenger Cars, Effectiveness 

Conversion to Diesel following TRBDS

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0.051 0.056 0.061 0.066 0.071

Fuel Consumption Reduction (gpm)

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %

Figure X-7 

Monte Carlo Draw Profile, Passenger Cars, Costs 

Dual Clutch or Automated Manual Transmission

0

200

400

600

800

1000

1200

1400

$5 $57 $109 $161 $213

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %
X-12

Figure X-8 

Monte Carlo Draw Profile, Passenger Cars, Effectiveness

Dual Clutch or Automated Manual Transmission

0

200

400

600

800

1000

1200

1400

0.034 0.039 0.044 0.049 0.054

Fuel Consumption Reduction (gpm)

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %

Figure X-9 

Monte Carlo Draw Profile

Pretax Fuel Price Path 

Fuel Price Estimates

Low, 4.8%

Average, 

35.5%

High, 59.7%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

 
X-13

Figure X-10 

Monte Carlo Draw Profile

CO2 Cost ($/metric ton)

0

500

1000

1500

2000

2500

$0.07 $1.41 $2.75 $4.09 $5.43

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %

Figure X-11

Monte Carlo Draw Profile

Monopsony Cost ($/gal.)

0

500

1000

1500

2000

2500

$0.01 $0.18 $0.34 $0.51 $0.68

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %
X-14

Figure X-12 

Monte Carlo Draw Profile 

Rebound Effect

0

500

1000

1500

2000

2500

3000

3500

-0.052 -0.092 -0.132 -0.172 -0.212

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %

Figure X-13 

Monte Carlo Draw Profile

Price Shock Cost ($/gal.)

0

500

1000

1500

2000

2500

3000

$0.00 $0.06 $0.12 $0.18 $0.24

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %
X-15

Figure X-14 

Monte Carlo Draw Profile

Total Economic Cost of Petroleum ($/gal.)

0

500

1000

1500

2000

2500

$0.03 $0.21 $0.39 $0.57 $0.75

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %

 Table X-4 

 Monte Carlo Draw Results, Economic Inputs 

Economic Inputs Minimum Maximum Mean StdDev 

 

Rebound Effect -0.247363 -0.058833 -0.186533 0.024108 

Monopsony Cost 2.112E-05 0.8328859 0.270747 0.1210186 

Price Cost Shock 1.944E-05 0.2958011 0.1160486 0.0402068 

Total Economic Costs 0.0262398 0.9144824 0.3867956 0.1273687 

CO2 Costs 0.000961 6.6922461 2.0517406 0.9371776 
X-16

Table X-5 

Monte Carlo Draw Results, Passenger Car Technology Costs 

Passenger Car Technology Costs Minimum Maximum Mean StdDev 

Low Friction Lubricants $3.19 $7.28 $5.00 $0.48 

Engine Friction Reduction $6.31 $58.79 $31.01 $6.03 

VVT - Coupled Cam Phasing (CCP) on SOHC $37.89 $87.04 $60.99 $5.87 

Discrete Variable Valve Lift (DVVL) on SOHC $118.51 $275.63 $188.81 $18.18 

Cylinder Deactivation on SOHC $43.49 $101.67 $70.80 $6.82 

VVT - Intake Cam Phasing (ICP) $36.84 $88.25 $60.99 $5.89 

VVT - Dual Cam Phasing (DCP) $36.97 $89.25 $61.03 $5.84 

Discrete Variable Valve Lift (DVVL) on DOHC $115.55 $257.50 $188.57 $18.29 

Continuously Variable Valve Lift (CVVL) $172.36 $407.52 $283.34 $27.43 

Cylinder Deactivation on DOHC $46.30 $97.20 $70.80 $6.83 

Cylinder Deactivation on OHV $31.61 $71.54 $50.94 $4.93 

VVT - Coupled Cam Phasing (CCP) on OHV $37.65 $88.45 $60.95 $5.90 

Discrete Variable Valve Lift (DVVL) on OHV $97.77 $224.79 $157.90 $15.45 

Conversion to DOHC with DCP $222.89 $478.16 $353.58 $34.17 

Stoichiometric Gasoline Direct Injection (GDI) $65.53 $111.74 $88.14 $5.64 

Combustion Restart $84.90 $199.86 $141.17 $13.54 

Turbocharging and Downsizing $681.50 $1,597.47 $1,122.99 $108.04 

Exhaust Gas Recirculation (EGR) Boost $111.02 $237.59 $172.83 $16.67 

Conversion to Diesel following TRBDS $1,950.09 $2,351.85 $2,143.92 $47.08 

Conversion to Diesel following CBRST $3,238.68 $3,675.06 $3,440.37 $52.49 

6-Speed Manual/Improved Internals $208.46 $457.04 $337.99 $32.85 

Improved Auto. Trans. Controls/Externals $36.11 $85.05 $58.99 $5.70 

Continuously Variable Transmission $186.55 $438.16 $300.16 $28.97 

6/7/8-Speed Auto. Trans with Improved 

Internals $251.70 $474.10 $360.39 $26.52 

Dual Clutch or Automated Manual 

Transmission $0.08 $259.88 $120.22 $35.88 

Electric Power Steering $102.88 $122.11 $112.49 $2.49 

Improved Accessories $166.76 $214.06 $192.02 $6.31 

12V Micro-Hybrid $268.05 $587.90 $436.94 $41.89 

Higher Voltage/Improved Alternator $51.12 $119.34 $84.00 $8.12 

Belt mounted Integrated Starter Generator $1,263.54 $2,822.47 $2,091.42 $200.61 

Power Split Hybrid $2,195.51 $2,253.54 $2,225.28 $7.33 

2-Mode Hybrid $7,451.27 $7,830.93 $7,645.98 $48.93 

Plug-in Hybrid $15,563.84 $32,715.96 $24,095.03 $2,313.54 

Material Substitution (1%) $0.84 $2.13 $1.50 $0.17 

Material Substitution (2%) $0.86 $2.10 $1.50 $0.17 
X-17

Passenger Car Technology Costs Minimum Maximum Mean StdDev 

Material Substitution (5%) $1.63 $4.45 $3.00 $0.33 

Low Rolling Resistance Tires $5.55 $9.65 $7.50 $0.50 

Low Drag Brakes $53.60 $121.49 $88.91 $8.62 

Secondary Axle Disconnect - Ladder Frame $72.53 $162.54 $116.93 $11.40 

Aero Drag Reduction $51.17 $130.84 $87.99 $9.38 

Table X-6 

Monte Carlo Draw Results, Passenger Car Fuel Economy Improvement Rates 

Passenger Car Fuel Economy Improvement 

Rates Minimum Maximum Mean StdDev 

Low Friction Lubricants 0.003081 0.006944 0.005004 0.000520

Engine Friction Reduction 0.008423 0.021196 0.015017 0.001680

VVT - Coupled Cam Phasing (CCP) on SOHC 0.006509 0.031585 0.019517 0.003163

Discrete Variable Valve Lift (DVVL) on 

SOHC 0.006988 0.032878 0.019508 0.003169

Cylinder Deactivation on SOHC 0.024094 0.031399 0.027480 0.000833

VVT - Intake Cam Phasing (ICP) 0.008318 0.021437 0.014987 0.001672

VVT - Dual Cam Phasing (DCP) 0.019176 0.032757 0.025008 0.001668

Discrete Variable Valve Lift (DVVL) on 

DOHC 0.007146 0.031442 0.019499 0.003197

Continuously Variable Valve Lift (CVVL) 0.011316 0.040263 0.025042 0.003351

Cylinder Deactivation on DOHC 0.000001 0.006360 0.002498 0.000833

Cylinder Deactivation on OHV 0.037523 0.059210 0.047002 0.002660

VVT - Coupled Cam Phasing (CCP) on OHV 0.009449 0.015728 0.012492 0.000833

Discrete Variable Valve Lift (DVVL) on OHV 0.001237 0.029994 0.015507 0.003511

Conversion to DOHC with DCP 0.008036 0.030776 0.018013 0.002669

Stoichiometric Gasoline Direct Injection (GDI) 0.017140 0.032116 0.023978 0.001675

Combustion Restart 0.016894 0.025485 0.020999 0.001014

Turbocharging and Downsizing 0.038320 0.044068 0.041346 0.000737

Exhaust Gas Recirculation (EGR) Boost 0.038821 0.040267 0.039498 0.000167

Conversion to Diesel following TRBDS 0.055095 0.072376 0.063902 0.002208

Conversion to Diesel following CBRST 0.132909 0.144731 0.138004 0.001357

6-Speed Manual/Improved Internals 0.002921 0.006953 0.004999 0.000519

Improved Auto. Trans. Controls/Externals 0.013493 0.027226 0.020011 0.001676

Continuously Variable Transmission 0.005850 0.024451 0.013511 0.002154

6/7/8-Speed Auto. Trans with Improved 0.011587 0.036830 0.024001 0.003343
X-18

Passenger Car Fuel Economy Improvement 

Rates Minimum Maximum Mean StdDev 

Internals 

Dual Clutch or Automated Manual 

Transmission 0.034972 0.057801 0.046578 0.002969

Electric Power Steering 0.008506 0.022496 0.015024 0.001663

Improved Accessories 0.008457 0.021425 0.014979 0.001674

12V Micro-Hybrid 0.021328 0.035888 0.028333 0.001894

Higher Voltage/Improved Alternator 0.001109 0.008370 0.004740 0.000908

Belt mounted Integrated Starter Generator 0.051607 0.063482 0.057622 0.001520

Power Split Hybrid 0.129323 0.137372 0.133660 0.001073

2-Mode Hybrid 0.005196 0.022135 0.013360 0.001993

Plug-in Hybrid 0.599984 0.640456 0.619019 0.004634

Material Substitution (1%) 0.002063 0.005055 0.003499 0.000364

Material Substitution (2%) 0.002151 0.004818 0.003501 0.000362

Material Substitution (5%) 0.005825 0.014986 0.009997 0.001028

Low Rolling Resistance Tires 0.008153 0.021865 0.014995 0.001663

Low Drag Brakes 0.004202 0.010680 0.007507 0.000834

Secondary Axle Disconnect - Ladder Frame 0.009563 0.015715 0.012492 0.000834

Aero Drag Reduction 0.018163 0.031236 0.024991 0.001671

 

Table X-7 

Monte Carlo Draw Results, Light Truck Technology Costs 

Light Truck Technology Costs Minimum Maximum Mean StdDev 

Low Friction Lubricants $3.19 $7.28 $5.00 $0.48 

Engine Friction Reduction $6.31 $58.79 $31.01 $6.03 

VVT - Coupled Cam Phasing (CCP) on 

SOHC $37.89 $87.04 $60.99 $5.87 

Discrete Variable Valve Lift (DVVL) on 

SOHC $109.97 $255.76 $175.20 $16.87 

Cylinder Deactivation on SOHC $46.07 $107.70 $75.00 $7.22 

VVT - Intake Cam Phasing (ICP) $36.84 $88.25 $60.99 $5.89 

VVT - Dual Cam Phasing (DCP) $36.97 $89.25 $61.03 $5.84 

Discrete Variable Valve Lift (DVVL) on 

DOHC $107.22 $238.93 $174.97 $16.97 

Continuously Variable Valve Lift (CVVL) $154.68 $365.73 $254.28 $24.61 

Cylinder Deactivation on DOHC $49.04 $102.97 $74.99 $7.24 

Cylinder Deactivation on OHV $31.38 $71.02 $50.56 $4.89 
X-19

Light Truck Technology Costs Minimum Maximum Mean StdDev 

VVT - Coupled Cam Phasing (CCP) on 

OHV $37.65 $88.45 $60.95 $5.90 

Discrete Variable Valve Lift (DVVL) on 

OHV $33.53 $77.09 $54.15 $5.30 

Conversion to DOHC with DCP $210.08 $450.69 $333.27 $32.21 

Stoichiometric Gasoline Direct Injection 

(GDI) $59.34 $101.19 $79.82 $5.11 

Combustion Restart $84.90 $199.86 $141.17 $13.54 

Turbocharging and Downsizing $619.49 $1,452.12 $1,020.81 $98.21 

Exhaust Gas Recirculation (EGR) Boost $111.02 $237.59 $172.83 $16.67 

Conversion to Diesel following TRBDS $3,095.29 $3,732.99 $3,402.95 $74.73 

Conversion to Diesel following CBRST $4,327.81 $4,910.94 $4,597.32 $70.14 

6-Speed Manual/Improved Internals $208.46 $457.04 $337.99 $32.85 

Improved Auto. Trans. Controls/Externals $36.11 $85.05 $58.99 $5.70 

Continuously Variable Transmission $186.55 $438.16 $300.16 $28.97 

6/7/8-Speed Auto. Trans with Improved 

Internals $322.56 $607.58 $461.85 $33.98 

Dual Clutch or Automated Manual 

Transmission $0.05 $172.00 $79.57 $23.75 

Electric Power Steering $102.88 $122.11 $112.49 $2.49 

Improved Accessories $166.76 $214.06 $192.02 $6.31 

12V Micro-Hybrid $299.01 $655.81 $487.41 $46.73 

Higher Voltage/Improved Alternator $51.12 $119.34 $84.00 $8.12 

Belt mounted Integrated Starter Generator $1,432.05 $3,198.90 $2,370.36 $227.37 

Power Split Hybrid $2,819.76 $2,894.29 $2,858.00 $9.42 

2-Mode Hybrid $10,623.90 $11,165.22 $10,901.52 $69.77 

Plug-in Hybrid $15,697.59 $32,997.09 $24,302.08 $2,333.42 

Material Substitution (1%) $0.84 $2.13 $1.50 $0.17 

Material Substitution (2%) $0.86 $2.10 $1.50 $0.17 

Material Substitution (5%) $1.63 $4.45 $3.00 $0.33 

Low Rolling Resistance Tires $5.55 $9.65 $7.50 $0.50 

Low Drag Brakes $53.60 $121.49 $88.91 $8.62 

Secondary Axle Disconnect - Ladder Frame $72.53 $162.54 $116.93 $11.40 

Aero Drag Reduction $51.17 $130.84 $87.99 $9.38 

 
X-20

Table X-8 

Monte Carlo Draw Results, Light Truck Fuel Economy Improvement Rates 

Light Truck Fuel Economy Improvement 

Rates Minimum Maximum Mean StdDev 

Low Friction Lubricants 0.003081 0.006944 0.005004 0.000520

Engine Friction Reduction 0.008423 0.021196 0.015017 0.001680

VVT - Coupled Cam Phasing (CCP) on SOHC 0.006509 0.031585 0.019517 0.003163

Discrete Variable Valve Lift (DVVL) on 

SOHC 0.006988 0.032878 0.019508 0.003169

Cylinder Deactivation on SOHC 0.024094 0.031399 0.027480 0.000833

VVT - Intake Cam Phasing (ICP) 0.008318 0.021437 0.014987 0.001672

VVT - Dual Cam Phasing (DCP) 0.019176 0.032757 0.025008 0.001668

Discrete Variable Valve Lift (DVVL) on 

DOHC 0.007146 0.031442 0.019499 0.003197

Continuously Variable Valve Lift (CVVL) 0.011316 0.040263 0.025042 0.003351

Cylinder Deactivation on DOHC 0.000001 0.006360 0.002498 0.000833

Cylinder Deactivation on OHV 0.037523 0.059210 0.047002 0.002660

VVT - Coupled Cam Phasing (CCP) on OHV 0.009449 0.015728 0.012492 0.000833

Discrete Variable Valve Lift (DVVL) on OHV 0.001237 0.029994 0.015507 0.003511

Conversion to DOHC with DCP 0.008036 0.030776 0.018013 0.002669

Stoichiometric Gasoline Direct Injection (GDI) 0.017140 0.032116 0.023978 0.001675

Combustion Restart 0.016894 0.025485 0.020999 0.001014

Turbocharging and Downsizing 0.022433 0.025799 0.024205 0.000432

Exhaust Gas Recirculation (EGR) Boost 0.038821 0.040267 0.039498 0.000167

Conversion to Diesel following TRBDS 0.044485 0.058439 0.051596 0.001783

Conversion to Diesel following CBRST 0.107210 0.116746 0.111320 0.001094

6-Speed Manual/Improved Internals 0.002921 0.006953 0.004999 0.000519

Improved Auto. Trans. Controls/Externals 0.013493 0.027226 0.020011 0.001676

Continuously Variable Transmission 0.005850 0.024451 0.013511 0.002154

6/7/8-Speed Auto. Trans with Improved 

Internals 0.011587 0.036830 0.024001 0.003343

Dual Clutch or Automated Manual 

Transmission 0.025527 0.042190 0.033998 0.002167

Electric Power Steering 0.008506 0.022496 0.015024 0.001663

Improved Accessories 0.008457 0.021425 0.014979 0.001674

12V Micro-Hybrid 0.025690 0.043228 0.034128 0.002282

Higher Voltage/Improved Alternator 0.000993 0.007492 0.004242 0.000813

Belt mounted Integrated Starter Generator 0.054636 0.067207 0.061003 0.001610

Power Split Hybrid 0.136395 0.144884 0.140969 0.001132

2-Mode Hybrid 0.017174 0.073159 0.044157 0.006589

Plug-in Hybrid 0.600961 0.641500 0.620027 0.004641
X-21

Light Truck Fuel Economy Improvement 

Rates Minimum Maximum Mean StdDev 

Material Substitution (1%) 0.002063 0.005055 0.003499 0.000364

Material Substitution (2%) 0.002151 0.004818 0.003501 0.000362

Material Substitution (5%) 0.005825 0.014986 0.009997 0.001028

Low Rolling Resistance Tires 0.008153 0.021865 0.014995 0.001663

Low Drag Brakes 0.004202 0.010680 0.007507 0.000834

Secondary Axle Disconnect - Ladder Frame 0.009563 0.015715 0.012492 0.000834

Aero Drag Reduction 0.018163 0.031236 0.024991 0.001671

 

Modeling Results – Output 

Tables X-9 and X-10 summarize the modeling results for fuel saved, total costs, societal benefits, 

and net benefits for passenger cars and trucks respectively under a 7% discount rate. They also 

indicate the probability that net benefits exceed zero. These results are also illustrated in Figures 

X-15 through X-18 for passenger cars under Optimized CAFE at 7 percent. Although not shown 

here, the general shape of the resulting output distributions are similar for the light trucks. The 

humped shape that occurs for both social benefits and net benefits reflects the three different 

gasoline price scenarios. About half of all draws were selected from the AEO Reference Case, 

while about one quarter were drawn from the Low Oil Price scenario and one quarter were drawn 

from the High Oil Price scenario. This produces three separate humps which reflect the 

increasing impact on benefits from the three progressively higher oil price scenarios. The Low 

Oil scenario is close enough to the Forecast scenario that the 2 humps visually begin to merge. 

However, the difference between the High Oil Price scenario and the Forecast is typically more 

than double the difference between the Forecast and the Low Oil price scenario, which results in 

a separate distribution further up the x axis. The following discussions summarize the range of 

results presented in these tables for the combined passenger car and light truck across both the 7 

percent (typically the lower range) and 3 percent (typically upper range) discount rates321. 

Fuel Savings: The analysis indicates that MY 2011 vehicles (both passenger cars and light 

trucks) will experience between 732 million and 1,114 million gallons of fuel savings over their 

useful lifespan. 

Total Costs: The analysis indicates that owners of MY 2011 passenger cars and light trucks will 

pay between $760 million and $2,235 million in higher vehicle prices to purchase vehicles with 

improved fuel efficiency 

 

321 In a few cases the upper range results were obtained from the 7% rate and the lower range results were obtained 

from the 3% rate. While this may seem counterintuitive, it results from the random selection process that is inherent 

in the Monte Carlo technique. 
X-22

Societal Benefits: The analysis indicates that changes to MY 2011 passenger cars and light 

trucks to meet the proposed CAFE standards will produce overall societal benefits valued 

between $1,003 million and $2,229 million. 

Net Benefits: The uncertainty analysis indicates that the net impact of the higher CAFE 

requirements for MY 2011 passenger cars and light trucks will range from a net loss of $913 

million to a net benefit of $1,224 million. There is at least an 80 percent certainty (the lower of 

the passenger car and light truck certainty levels) that changes made to MY 2011 vehicles to 

achieve the higher CAFE standards will produce a net benefit. 
X-23

Table X-9 

Uncertainty Analysis Results, Passenger Cars 

(7% Discount Rate) 

MY 2011 Mean Low High 

Fuel Saved (mill. gall.) 445 383 566 

Total Cost ($mill.) 496 332 776 

Societal Benefits ($mill.) 868 512 1,183 

Net Benefits ($mill.) 372 (121) 734 

% Certainty Net Ben. > 0 100% 

Table X-10 

Uncertainty Analysis Results, Light Trucks 

(7% Discount Rate) 

MY 2011 Mean Low High 

Fuel Saved (mill. gall.) 407 349 548 

Total Cost ($mill.) 673 428 1,459 

Societal Benefits ($mill.) 788 491 1,046 

Net Benefits ($mill.) 115 (792) 490 

% Certainty Net Ben. > 0 80% 

Table X-11 

Uncertainty Analysis Results, Passenger Cars and Light Trucks 

(7% Discount Rate) 

MY 2011 Mean Low High 

Fuel Saved (mill. gall.) 852 732 1114 

Total Cost ($mill.) 1169 760 2235 

Societal Benefits ($mill.) 1656 1003 2229 

Net Benefits ($mill.) 487 -913 1224 
X-24

Figure X-15 

Model Output Profile 

Cars: Fuel Savings for "Optimized Reformed 

Standards" (2015) at 7% Discount Rate

0

200

400

600

800

1000

1200

1400

3,951,180

4,097,080

4,242,980

4,388,880

4,534,780

4,680,680

4,826,580

4,972,480

5,118,380

5,264,280

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %

Figure X-16 

Model Output Profile 

Cars: Societal Benefits for "Optimized Reformed 

Standards" (2015) at 7% Discount Rate

0

200

400

600

800

1000

1200

1400

1600

1800

4,552 5,312 6,072 6,832 7,592 8,352 9,112 9,872 10,632 11,392

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %
X-25

Figure X-17 

Model Output Profile 

Cars: Total Cost for "Optimized Reformed Standards" 

(2015) at 7% Discount Rate

0

200

400

600

800

1000

1200

1400

1600

1800

6,763 7,078 7,393 7,708 8,023 8,338 8,653 8,968 9,283 9,598

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %

Figure X-18 

Model Output Profile 

Cars: Net Benefits for "Optimized Reformed 

Standards" (2015) at 7% Discount Rate

0

200

400

600

800

1000

1200

1400

-3,733 -2,898 -2,063 -1,228 -393 442 1,277 2,112 2,947 3,782

0%

20%

40%

60%

80%

100%

120%

Frequency Cumulative %
XI-1

XI. REGULATORY FLEXIBILITY ACT AND UNFUNDED MANDATES

REFORM ACT ANALYSIS 

Regulatory Flexibility Act 

The Regulatory Flexibility Act of 1980 (5 U.S.C §601 et seq.) requires agencies to evaluate the 

potential effects of their proposed and final rules on small business, small organizations and 

small Government jurisdictions. 

5 U.S.C §603 requires agencies to prepare and make available for public comments initial and 

final regulatory flexibility analysis (RFA) describing the impact of proposed and final rules on 

small entities. Section 603(b) of the Act specifies the content of a RFA. Each RFA must 

contain: 

1. A description of the reasons why action by the agency is being considered; 

2. A succinct statement of the objectives of, and legal basis for a final rule; 

3. A description of and, where feasible, an estimate of the number of small entities to which 

the final rule will apply; 

4. A description of the projected reporting, recording keeping and other compliance 

requirements of a final rule including an estimate of the classes of small entities which 

will be subject to the requirement and the type of professional skills necessary for 

preparation of the report or record; 

5. An identification, to the extent practicable, of all relevant Federal rules which may 

duplicate, overlap or conflict with the final rule; 

6. Each final regulatory flexibility analysis shall also contain a description of any significant 

alternatives to the final rule which accomplish the stated objectives of applicable statutes 

and which minimize any significant economic impact of the final rule on small entities. 

1. Description of the reason why action by the agency is being considered

NHTSA is proposing this action to improve vehicle fuel economy. 

2. Objectives of, and legal basis for, the final rule

The Energy Policy and Conservation Act requires the agency to set light truck fuel economy 

standards every year and allows the agency to update passenger car fuel economy standards. The 

Energy Independence and Security Act (EISA) mandates the setting of separate standards for 

passenger cars and for light trucks at levels sufficient to ensure that the average fuel economy of 

the combined fleet of all passenger cars and light trucks sold by all manufacturers in the U.S. in 

model year 2020 equals or exceeds 35 miles per gallon. 

 

3. Description and estimate of the number of small entities to which the final rule will apply

The final rule will affect motor vehicle manufacturers. There are no light truck manufacturers 

that are small businesses. However, there are four domestically owned small passenger car 

manufacturers. 

 

Business entities are defined as small business using the North American Industry Classification 

System (NAICS) code, for the purpose of receiving Small Business Administration assistance. 
XI-2

One of the criteria for determining size, as stated in 13 CFR 121.201, is the number of employees 

in the firm. For establishments primarily engaged in manufacturing or assembling automobiles, 

light and heavy duty trucks, buses, motor homes, or motor vehicle body manufacturing, the firm 

must have less than 1,000 employees to be classified as a small business. 

We believe that the rulemaking would not have a significant economic impact on the small 

vehicle manufacturers because under Part 525, passenger car manufacturer making less than 

10,000 vehicles per year can petition NHTSA to have alternative standards set for those 

manufacturers. Those manufacturers that currently don’t meet the 27.5 mpg standard can 

petition the agency for relief. If the standard is raised, it has no meaningful impact on these 

manufacturers, they still must go through the same process and petition for relief. Other small 

manufacturers (Tesla and Fisker) make electric vehicles or hybrid vehicles that will pass the final 

rule. 

Currently, there are six small passenger car motor vehicle manufacturers in the United States. 

Table X1-1 provides information about the 6 small domestic manufacturers in MY 2007. All are 

small manufacturers, having much less than 1,000 employees. 
XI-3

Table XI-1 

Small Vehicle Manufacturers 

Manufacturer Employees Estimated Sales Sale Price Range Est. Revenues* 

Fisker 

Automotive** N/A 

15,000 

projected $80,000 N/A 

Mosler 

Automotive 25 20 $189,000 $2,000,000 

Panoz Auto 

Development 

Company 50 150 

$90,000 to 

$125,000 $16,125,000 

Saleen Inc. 170 1,000#

$39,000 to 

$59,000 $49,000,000 

Saleen Inc. 170 16## $585,000 $9,000,000 

Standard 

Taxi*** 35 N/A $25,000 $2,000,000 

Tesla Motors, 

Inc. 250 2,000 

$65,000 to 

$100,000 N/A 

* Assuming an average sales price from the sales price range. 

** Fisker Automotive is a joint venture of Quantum Fuel Systems Technologies Worldwide, 

Inc. and Fisker Coachbuild, LLC. 

*** Standard Taxi is a subsidiary of the Vehicle Production Group LLC. 35 employees is the 

total for VPG LLC. 

#

 Ford Mustang Conversions 

The agency has not analyzed the impact of the final rule on these small manufacturers 

individually. However, assuming those that do not meet the final rule would petition the agency, 

rather than meet the final rule, the cost is not expected to be substantial. 

4. A description of the projected reporting, record keeping and other compliance requirements of 

a final rule including an estimate of the classes of small entities which will be subject to the 

requirement and the type of professional skills necessary for preparation of the report or record. 

This final rule includes no new requirements for reporting, record keeping of other compliance 

requirements. 

5. An identification, to the extent practicable, of all relevant Federal rules which may duplicate, 

overlap, or conflict with the final rule 

We know of no Federal rules which duplicate, overlap, or conflict with the final rule. 
XI-4

6. A description of any significant alternatives to the final rule which accomplish the stated 

objectives of applicable statutes and which minimize any significant economic impact of the 

final rule on small entities. 

There are no other alternatives that can achieve the stated objectives without installing fuel 

economy technologies into the vehicle. 

A. Unfunded Mandates Reform Act 

The Unfunded Mandates Reform Act of 1995 (Public Law 104-4) requires agencies to prepare a 

written assessment of the costs, benefits, and other effects of proposed or final rules that include 

a Federal mandate likely to result in the expenditures by States, local or tribal governments, in 

the aggregate, or by the private sector, of more than $100 million annually (adjusted annually for 

inflation with base year of 1995). Adjusting this amount by the implicit gross domestic product 

price deflator for 2007 results in $130 million (119.816/92.106 = 1.30). The assessment may be 

included in conjunction with other assessments, as it is here.