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EO12866_GHG+Fuel Eff Stds for Med-Heavy-Duty Engines+Vehicles 2060-AP61 FRM 

RIA_20110722_Ch 02 Technology and Cost Effectiveness.docx

Chapter 2: Technologies, Cost, and Effectiveness

2.1 Overview of Technologies 

In discussing the potential for CO2 emission and fuel consumption reductions, it can be 

helpful to think of the work flow through the system. The initial work input is fuel. Each 

gallon of fuel has the potential to produce some amount of work and will produce a set 

amount of CO2 (about 22 pounds (10 kg) of CO2 per gallon of diesel fuel). The engine 

converts the chemical energy in the fuel to useable work to move the truck. Any reductions in 

work demanded of the engine by the vehicle or improvements in engine fuel conversion 

efficiency will lead directly to CO2 emission and fuel consumption reductions. 

Current diesel engines are 35-38 percent efficient over a range of operating conditions 

with peak efficiency levels between 40 and 45 percent depending on engine sizes and 

applications, while gasoline engines are approximately 30 percent efficient overall. This 

means that approximately one-third of the fuel’s chemical energy is converted to useful work 

and two-thirds is lost to friction, gas exchange, and waste heat in the coolant and exhaust. In

turn, the truck uses this work delivered by the engine to overcome overall vehicle-related 

losses such as aerodynamic drag, tire rolling resistance, friction in the vehicle driveline, and to 

provide auxiliary power for components such as air conditioning and lights. Lastly, the 

vehicle’s operation, such as vehicle speed and idle time, affects the amount of total energy

required to complete its activity. While it may be intuitive to look first to the engine for CO2

reductions given that only about one-third of the fuel is converted to useable work, it is 

important to realize that any improvement in vehicle efficiency reduces both the work 

demanded and also the waste energy in proportion. 

Technology is one pathway to improve heavy-duty truck GHG emissions and fuel 

consumption. Near-term solutions exist, such as those being deployed by SmartWay partners 

in heavy-duty truck long haul applications. Other solutions are currently underway in the 

Light-Duty vehicle segment, especially in the Large Pickup sector where many of the 

technologies can apply to the heavy-duty pickup trucks covered under this rulemaking. Longterm solutions are currently under development to improve efficiencies and cost-effectiveness. 

While there is not a “silver bullet” that will significantly eliminate GHG emissions from 

heavy-duty trucks like the catalytic converter has for criteria pollutant emissions, significant 

GHG and fuel consumption reductions can be achieved through a combination of engine, 

vehicle system, and operational technologies. 

The following sections will discuss technologies in relation to each of the regulatory

categories – Heavy-Duty Pickup Trucks and Vans, Heavy-Duty Engines, Class 7/8 Sleeper 
Regulatory Impact Analysis 

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and Day Cabs, and Class 2b-8 Vocational Vehicles. In each of these sections information on 

technological approaches, costs, and percent improvements is provided. Not all of the 

technologies discussed in these sections are assumed to be used for compliance with the 

engine and vehicle standards, for reasons that are also discussed in each section. A summary

of technologies, costs, fuel consumption and GHG emissions improvement percentages is 

provided in Tables 2-36 and 2-37 at the end of this chapter for each of the engine/vehicle 

types listed above.

EPA and NHTSA collected information on the cost and effectiveness of fuel 

consumption and CO2 emission reducing technologies from several sources. The primary 

sources of information were the 2010 National Academy of Sciences report on Technologies 

and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles 

(NAS)1, TIAX’s assessment of technologies to support the NAS panel report (TIAX)2, EPA’s 

Heavy-Duty Lumped Parameter Model3, the analysis conducted by NESCCAF, ICCT, 

Southwest Research Institute and TIAX for reducing fuel consumption of heavy-duty long 

haul combination tractors (NESCCAF/ICCT)4, and the technology cost analysis conducted by 

ICF for EPA (ICF).5 In addition, the agencies used the vehicle simulation model (the 

Greenhouse Gas Emissions Model or GEM) to quantify the effectiveness of various 

technologies on CO2 emission and fuel consumption reductions in terms of vehicle 

performance as they are evaluated in determining compliance with the HD program. The 

simulation tool is described in RIA Chapter 4 in more detail. 

2.1.1 Baseline Engine and Vehicle Configuration

The agencies have derived the baseline engine and vehicle configuration for each 

regulatory category by examining engines and vehicles in the existing fleet to represent the 

typical 2010 model year vehicle and engine, as described later in this RIA chapter. The 

technology paths that the agencies considered available for each category for purposes of 

determining what regulatory standards would be cost-effective, and technologically feasible 

and otherwise appropriate in the leadtime afforded by the rule are, in turn, built from the 

baseline.

Table 2-1: Baseline Engine and Vehicle Configurations

Regulatory Category Baseline Configuration

Heavy-Duty Gasoline Pickup Truck 

and Van

 V8 engine

 Electronic control

 Naturally aspirated

 Coupled cam phasing

 6 speed automatic transmission

Heavy-Duty Diesel Pickup Truck and 

Van

 2010 emission compliant diesel engine

 Electronic control

 6 speed automatic transmission

Heavy-Duty Gasoline Engine  V8 engine

 Electronic control

 Naturally aspirated
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 Fixed valve timing

Heavy-Duty Diesel Engine  Electronic control

 SCR/EGR/DPF exhaust aftertreatment system which 

achieves 2010MY criteria emissions standards

 Turbocharged with variable geometry turbocharger

 2200 bar injection pressure

 Single fixed overhead valve

 Belt driven accessories

Combination Tractor  Aerodynamics: tractor fleet consists of 25% Bin I, 

70% Bin II, and 5% Bin III

 Tires: Dual tires with steel wheels, RRc=7.8 (steer) 

and 8.2 (drive)

 Body and Chassis: steel components

 Idle Reduction: Currently 30% of sleeper cabs 

contain an idle reduction technology, but not 

necessarily an automatic engine shutoff

 Vehicle Speed Limiter: 0% of tractors contain a 

non-override VSL set at below 65 mph

Vocational Vehicle  Tires: average tire with a RRc=9.0

2.2 Overview of Technology Cost Methodology

Section 2.2.1 presents the methods used to address indirect costs in this analysis. Section 

2.2.2 presents the learning effects applied throughout this analysis. Section 2.9 presents a 

summary in tabular form of all the technology costs expected to be implemented in response 

to the standards.

2.2.1 Markups to Address Indirect Costs

To produce a unit of output, engine and truck manufacturers incur direct and indirect 

costs. Direct costs include cost of materials and labor costs. Indirect costs are all the costs 

associated with producing the unit of output that are not direct costs – for example, they may

be related to production (such as research and development [R&D]), corporate operations 

(such as salaries, pensions, and health care costs for corporate staff), or selling (such as 

transportation, dealer support, and marketing). Indirect costs are generally recovered by 

allocating a share of the costs to each unit of good sold. Although it is possible to account for 

direct costs allocated to each unit of good sold, it is more challenging to account for indirect 

costs allocated to a unit of goods sold. To make a cost analysis process more feasible, markup 

factors, which relate total indirect costs to total direct costs, have been developed. These 

factors are often referred to as retail price equivalent (RPE) multipliers.
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Cost analysts and regulatory agencies (including both EPA and NHTSA) have 

frequently used these multipliers to predict the resultant impact on costs associated with 

manufacturers’ responses to regulatory requirements. The best approach, if it were possible, to 

determining the impact of changes in direct manufacturing costs on a manufacturer’s indirect 

costs would be to actually estimate the cost impact on each indirect cost element. However, 

doing this within the constraints of an agency’s time or budget is not always feasible, or the 

technical, financial, and accounting information to carry out such an analysis may simply be 

unavailable. 

RPE multipliers provide, at an aggregate level, the relative shares of revenues 

(Revenue = Direct Costs + Indirect Costs + Net Income) to direct manufacturing costs. Using 

RPE multipliers implicitly assumes that incremental changes in direct manufacturing costs 

produce common incremental changes in all indirect cost contributors as well as net income.

However, a concern in using the RPE multiplier in cost analysis for new technologies added 

in response to regulatory requirements is that the indirect costs of vehicle modifications are 

not likely to be the same for different technologies. For example, less complex technologies 

could require fewer R&D efforts or less warranty coverage than more complex technologies. 

In addition, some simple technological adjustments may, for example, have no effect on the 

number of corporate personnel and the indirect costs attributable to those personnel. The use 

of RPEs, with their assumption that all technologies have the same proportion of indirect 

costs, is likely to overestimate the costs of less complex technologies and underestimate the 

costs of more complex technologies.

To address this concern, modified multipliers have been developed by EPA, working 

with a contractor, for use in rulemakings. These multipliers are referred to as indirect cost 

multipliers (or ICMs). In contrast to RPE multipliers, ICMs assign unique incremental 

changes to each indirect cost contributor as well as net income.

ICM = (direct cost + adjusted indirect cost)/(direct cost)

Developing the ICMs from the RPE multipliers requires developing adjustment factors 

based on the complexity of the technology and the time frame under consideration: the less 

complex a technology, the lower its ICM, and the longer the time frame for applying the 

technology, the lower the ICM. This methodology was used in the cost estimation for the 

recent light-duty fuel economy and GHG rule. The ICMs for the light-duty context were 

developed in a peer-reviewed report from RTI International and were subsequently discussed 

in a peer-reviewed journal article.6 

For the heavy-duty pickup truck and van cost projections in the proposal, the agencies 

used ICM adjustment factors developed for light-duty vehicles, inclusive of a return on 

capital, primarily because the manufacturers involved in this segment of the heavy-duty

market are the same manufacturers which build light-duty trucks. The cost of capital 

(reflected in profit) is included because of the assumption implicit in ICMs (and RPEs) that 

capital costs are proportional to direct costs, and businesses need to be able to earn returns on 

their investments. The capital costs are those associated with the incremental costs of the new 

technologies.
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For the combination tractors, vocational vehicles, and heavy-duty engine cost 

projections in the proposal, EPA contracted with RTI International to update EPA’s 

methodology for accounting for indirect costs associated with changes in direct manufacturing 

costs for heavy-duty engine and truck manufacturers.7In addition to the indirect cost 

contributors varying by complexity and time frame, there is no reason to expect that the 

contributors would be the same for engine manufacturers as for truck manufacturers. The 

resulting report from RTI provides a description of the methodology, as well as calculations 

of the indirect cost multipliers used in the proposal. These indirect cost multipliers were used, 

along with calculations of direct manufacturing costs, to provide estimates of the full 

additional costs associated with new technologies. 

For the analysis supporting this final rulemaking, the agencies have made some 

changes to both the ICMs factors and to the method of applying those factors to arrive at a 

final cost estimate. The first of these changes was done in response to continued thinking 

among the EPA-NHTSA team about how past ICMs have been developed and what are the 

most appropriate data sources to rely upon in determining the appropriate ICMs. The second 

change has been done in response to both staff concerns and public feedback suggesting that 

the agencies were inappropriately applying learning effects to indirect costs via the 

multiplicative approach to applying the ICMs.

Regarding the first change – to the ICM factors themselves – a little background must 

first be provided. In the original work done under contract to EPA by RTI International,8

EPA experts had undergone a consensus approach to determining the impact of specific 

technology changes on the indirect costs of a company. Subsequent to that effort, EPA 

experts underwent a blind survey to make this determination on a different set of technology

changes. This subsequent effort, referred to by EPA as a modified-Delphi approach, resulted 

in different ICM determinations. This effort is detailed in a memorandum contained in the 

docket for this rule.9 Upon completing this effort, EPA determined that the original RTI 

values should be averaged with the modified-Delphi values to arrive at the final ICMs for low 

and medium complexity technologies and that the original RTI values would be used for high 

complexity level 1 while the modified-Delphi values would be used for high complexity level 

2. These final ICMs were used in the 2012-2016 light-duty GHG/CAFE rulemaking. 

Subsequent to that, EPA contracted RTI to update their light-duty report with an eye to the 

heavy-duty industry. In that effort, RTI determined the RPE of both the heavy-duty engine 

and heavy truck industries, then applied the light-duty indirect cost factors—those resulting 

from the averaging of the values from their original report with the modified-Delphi values—

to the heavy-duty RPEs to arrive at heavy-duty specific ICMs. That effort is described in 

their final heavy-duty ICM report mentioned above.10

More recently, the EPA and NHTSA team has decided that the original light-duty RTI 

values, given the technologies considered for low and medium complexity, should no longer 

be used and that we should rely solely on the modified-Delphi values for these complexity

levels. The original light-duty RTI study used low rolling resistance tires as a low complexity

technology example and a dual clutch transmission as a medium complexity technology. 

Upon further thought, the technologies considered for the modified Delphi values (passive 
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aerodynamic improvements for low complexity and turbocharging with downsizing for 

medium complexity_were considered to better represent the example technologies). As a 

result, the modified-Delphi values were to become the working ICMs for low and medium 

complexity rather than averaging those values with the original RTI report values. NHTSA 

and EPA staff also re-examined the technology complexity categories that were assigned to 

each light-duty technology and modified these assignments to better reflect the technologies 

that are now used as proxies for each category. This decision impacts the low and medium 

complexity heavy-duty ICMs too because the modified-Delphi values alone were now to be 

applied to the heavy-duty RPEs to arrive at heavy-duty ICMs rather than using the averaged 

values developed for the 2012-2016 rule. 

A secondary-level change was also made as part of this ICM recalculation to the lightduty ICMs and, therefore, to the ICMs used in this analysis for HD pickups and vans. That 

change was to revise upward the RPE level reported in the original RTI report from an 

original value of 1.46 to 1.5 to reflect the long term average RPE. The original RTI study was 

based on 2008 data. However, an analysis of historical RPE data indicates that, although 

there is year to year variation, the average RPE has remained roughly 1.5. ICMs will be 

applied to future year’s data and therefore NHTSA and EPA staff believe that it would be 

appropriate to base ICMs on the historical average rather than a single year’s result. 

Therefore, ICMs were adjusted to reflect this average level.. As a result, the High 1 and High 

2 ICMs used for HD pickups and vans have also changed.

Table 2-2 shows both the ICM values used in the proposal and the new ICM values 

used for the analysis supporting this final rule. Near term values (2014 through 2021 in this 

analysis) account for differences in the levels of R&D, tooling, and other indirect costs that 

will be incurred. Once the program has been fully implemented, some of the indirect costs 

will no longer be attributable to the standards and, as such, a lower ICM factor is applied to 

direct costs in 2022 and later. 
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Table 2-2 Indirect Cost Multipliers Used in this Analysisa

PROPOSAL FINAL

CLASS COMPLEXITY NEAR 

TERM

LONG 

TERM

NEAR 

TERM

LONG 

TERM

HD Pickup Trucks and 

Vans

Low 1.17 1.13 1.24 1.19

Medium 1.31 1.19 1.39 1.29

High1 1.51 1.32 1.56 1.35

High2 1.70 1.45 1.77 1.50

Loose diesel engines Low 1.11 1.09 1.15 1.12

Medium 1.18 1.13 1.24 1.18

High1 1.28 1.19 1.28 1.19

High2 1.43 1.29 1.43 1.29

Loose gasoline engines Low 1.17 1.13 1.24 1.19

Medium 1.31 1.19 1.39 1.29

High1 1.51 1.32 1.56 1.35

High2 1.70 1.45 1.77 1.50

Vocational Vehicles and 

Combination Tractors

Low 1.14 1.10 1.18 1.14

Medium 1.26 1.16 1.30 1.23

High1 1.42 1.27 1.42 1.27

High2 1.57 1.36 1.57 1.36

a Rogozhin, A., et. al., “Using indirect cost multipliers to estimate the total cost of 

adding new technology in the automobile industry,” International Journal of 

Production Economics (2009); “Documentation of the Development of Indirect Cost 

Multipliers for Three Automotive Technologies,” Helfand, G., and Sherwood, T., 

Memorandum dated August 2009; “Heavy Duty Truck Retail Price Equivalent and 

Indirect Cost Multipliers,” Draft Report prepared by RTI International and 

Transportation Research Institute, University of Michigan, July 2010

The second change made to the ICMs has to do with the way in which the ICMs are 

applied. To date, we have applied the ICMs, as done in any analysis that relied on RPEs, as a 

pure multiplicative factor. This way, a direct manufacturing cost of, say, $100 would be 

multiplied by an ICM of 1.24 to arrive at a marked up technology cost of $124. However, as 

learning effects (discussed below) are applied to the direct manufacturing cost, the indirect 

costs are also reduced accordingly. Therefore, in year 2 the $100 direct manufacturing cost 

might reduce to $97 and the marked up cost would become $120 ($97 x 1.24). As a result, 

indirect costs have been reduced from $24 to $20. Given that indirect costs cover many 

things such as facility-related costs, electricity, etc., it is perhaps not appropriate to apply the 

ICM to the learned direct costs, at least not for those indirect cost elements unlikely to change 

with learning. The EPA-NHTSA team believes that it is appropriate only to allow warranty 

costs to decrease with learning since warranty costs are tied to direct manufacturing costs 

(since warranty typically involves replacement of actual parts which should be less costly

with learning). However, the remaining elements of the indirect costs should remain constant 

year-over-year, at least until some of those indirect costs are no longer attributable to the 

rulemaking effort that imposed them (such as R&D).
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As a result, the ICM calculation has become more complex with the analysis 

supporting this final action. We must first establish the year in which the direct 

manufacturing costs are considered “valid.” For example, a cost estimate might be considered 

valid today, or perhaps not until high volume production is reached which will not occur until 

MY 2015. That year is known as the base year for the estimated cost. That cost is the cost 

used to determine the “non-warranty” portion of the indirect costs. For example, the nonwarranty portion of the loose diesel engine low complexity ICM in the short-term is 0.149

(the warranty versus non-warranty portions of the ICMs are shown in Table 2-3). For the 

improved water pump technology we have estimated a direct manufacturing cost of $79 in 

MY 2014. So the non-warranty portion of the indirect costs would be $11.77 ($79 x 0.149). 

This value would be added to the learned direct manufacturing cost for each year through 

2021. Beginning in 2022, when long-term indirect costs begin, the additive factor would 

become $9.64 ($79 x 0.122). Additionally, the $79 cost in 2014 would become $76.63 in MY 

2015 due to learning ($79 x (1-3%)). So, while the warranty portion of the indirect costs 

would be $0.47 ($79 x 0.006) in 2014, they would decrease to $0.46 ($76 x 0.006) in 2015 as 

warranty costs decrease with learning. The resultant indirect costs for the water pump would 

be $12.24 ($11.77+$0.47) in MY 2014 and $12.23 ($11.77+$0.46) in MY2015, and so on for 

subsequent years.

Table 2-3 Warranty and Non-Warranty Portions of ICMs

SHORT-TERM LONG-TERM

CLASS COMPLEXITY WARRANTY NONWARRANTYWARRANTY NONWARRANTY

HD Pickup

Trucks and 

Vans

Low 0.012 0.230 0.005 0.187

Medium 0.045 0.343 0.031 0.259

High1 0.065 0.499 0.032 0.314

High2 0.074 0.696 0.049 0.448

Loose diesel 

engines

Low 0.006 0.149 0.003 0.122

Medium 0.022 0.213 0.016 0.165

High1 0.032 0.249 0.016 0.176

High2 0.037 0.398 0.025 0.265

Loose 

gasoline 

engines

Low 0.012 0.230 0.005 0.187

Medium 0.045 0.343 0.031 0.259

High1 0.065 0.499 0.032 0.314

High2 0.074 0.696 0.049 0.448

Vocational

Vehicles and 

Combination 

Tractors

Low 0.013 0.165 0.006 0.134

Medium 0.051 0.252 0.035 0.190

High1 0.073 0.352 0.037 0.233

High2 0.084 0.486 0.056 0.312
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There is some level of uncertainty surrounding both the ICM and RPE markup 

factors. The ICM estimates used in this final rulemaking group all technologies into three 

broad categories and treat them as if individual technologies within each of the three 

categories (low, medium, and high complexity) will have the same ratio of indirect costs to 

direct costs. This simplification means it is likely that the direct cost for some technologies 

within a category will be higher and some lower than the estimate for the category in general. 

More importantly, the ICM estimates have not been validated through a direct accounting of 

actual indirect costs for individual technologies. Rather, the ICM estimates were developed 

using adjustment factors developed in two separate occasions: the first, a consensus process, 

was reported in the RTI report; the second, a modified Delphi method, was conducted 

separately and reported in an EPA memo. Both these panels were composed of EPA staff 

members with previous background in the automobile industry; the memberships of the two 

panels overlapped but were not the same. The panels evaluated each element of the industry’s 

RPE estimates and estimated the degree to which those elements would be expected to change 

in proportion to changes in direct manufacturing costs. The method and estimates in the RTI

report were peer reviewed by three industry experts and subsequently by reviewers for the 

International Journal of Production Economics.11 RPEs themselves are inherently difficult to

estimate because the accounting statements of manufacturers do not neatly categorize all cost 

elements as either direct or indirect costs. Hence, each researcher developing an RPE 

estimate must apply a certain amount of judgment to the allocation of the costs. Moreover, 

RPEs for heavy- and medium-duty trucks and for engine manufacturers are not as well 

studied as they are for the light-duty automobile industry. Since empirical estimates of ICMs 

are ultimately derived from the same data used to measure RPEs, this affects both measures. 

However, the value of RPE has not been measured for specific technologies, or for groups of 

specific technologies. Thus, even if we assume that the examined technology accurately 

represents the average impact on all technologies in its representative category, applying a 

single average RPE to any given technology by definition overstates costs for very simple 

technologies, or understates them for more advanced technologies in that group. 

2.2.2 Learning Effects on Technology Costs

For some of the technologies considered in this analysis, manufacturer learning effects 

would be expected to play a role in the actual end costs. The “learning curve” or “experience 

curve” describes the reduction in unit production costs as a function of accumulated 

production volume. In theory, the cost behavior it describes applies to cumulative production 

volume measured at the level of an individual manufacturer, although it is often assumed—as 

both agencies have done in past regulatory analyses—to apply at the industry-wide level, 

particularly in industries that utilize many common technologies and component supply

sources. Both agencies believe there are indeed many factors that cause costs to decrease 

over time. Research in the costs of manufacturing has consistently shown that, as 

manufacturers gain experience in production, they are able to apply innovations to simplify

machining and assembly operations, use lower cost materials, and reduce the number or 

complexity of component parts. All of these factors allow manufacturers to lower the per-unit 

cost of production (i.e., the manufacturing learning curve).12
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NHTSA and EPA have a detailed description of the learning effect in the 2012-2016 

light-duty rule. Most studies of the effect of experience or learning on production costs 

appear to assume that cost reductions begin only after some initial volume threshold has been 

reached, but not all of these studies specify this threshold volume. The rate at which costs 

decline beyond the initial threshold is usually expressed as the percent reduction in average 

unit cost that results from each successive doubling of cumulative production volume, 

sometimes referred to as the learning rate. Many estimates of experience curves do not 

specify a cumulative production volume beyond which cost reductions would no longer occur, 

instead depending on the asymptotic behavior of the effect for learning rates below 100 

percent to establish a floor on costs. 

In past rulemaking analyses, as noted above, both agencies have used a learning curve 

algorithm that applied a learning factor of 20 percent for each doubling of production volume. 

NHTSA has used this approach in analyses supporting recent CAFE rules. In its analysis, 

EPA has simplified the approach by using an “every two years” based learning progression 

rather than a pure production volume progression (i.e., after two years of production it was 

assumed that production volumes would have doubled and, therefore, costs would be reduced 

by 20 percent). 

In the 2012-2016 light-duty rule, the agencies employed an additional learning 

algorithm to reflect the volume-based learning cost reductions that occur further along on the 

learning curve. This additional learning algorithm was termed “time-based” learning simply

as a means of distinguishing this algorithm from the volume-based algorithm mentioned 

above, although both of the algorithms reflect the volume-based learning curve supported in 

the literature.13 To avoid confusion, we are now referring to this learning algorithm as the 

“flat-portion” of the learning curve. This way, we maintain the clarity that all learning is, in 

fact, volume-based learning, the level of cost reductions depend only on where on the learning 

curve a technology’s learning progression is. We distinguish the flat-portion of the curve 

from the steep-portion of the curve to indicate the level of learning taking place in the years 

following implementation of the technology. The agencies have applied the steep-portion 

learning algorithm for those technologies considered to be newer technologies likely to 

experience rapid cost reductions through manufacturer learning and the flat-portion learning

algorithm for those technologies considered to be mature technologies likely to experience 

minor cost reductions through manufacturer learning. As noted above, the steep-portion

learning algorithm results in 20 percent lower costs after two full years of implementation 

(i.e., the 2016 MY costs are 20 percent lower than the 2014 and 2015 model year costs). 

Once two steep-portion learning steps have occurred (for technologies having the steepportion learning algorithm applied while flat-portion learning would begin in year 2 for 

technologies having the flat-portion learning algorithm applied), flat-portion learning at 3 

percent per year becomes effective for 5 years. Beyond 5 years of learning at 3 percent per 

year, 5 years of learning at 2 percent per year, then 5 at 1 percent per year become effective. 

Learning effects are applied to most but not all technologies because some of the 

expected technologies are already used rather widely in the industry and, presumably, 

learning impacts have already occurred. The steep-portion learning algorithm was applied for 

only a handful of technologies that are considered to be new or emerging technologies. Most 

technologies have been considered to be more established given their current use in the fleet 
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and, hence, the lower flat-portion learning algorithm has been applied. The learning 

algorithms applied to each technology are summarized in Table 2-4.
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Table 2-4 Learning Effect Algorithms Applied to Technologies Used in this Analysis

TECHNOLOGY APPLIED TO LEARNING 

ALGORITHM

Cylinder head improvements Engines Flat

Turbo efficiency improvements Engines Flat

EGR cooler efficiency improvements Engines Flat

Water pump improvements Engines Flat

Oil pump improvements Engines Flat

Fuel pump improvements Engines Flat

Fuel rail improvements Engines Flat

Fuel injector improvements Engines Flat

Piston improvements Engines Flat

Valve train friction reductions Engines Flat

Turbo compounding Engines Flat

Engine friction reduction Engines Flat

Coupled cam phasing Engines Flat

Stoichiometric gasoline direct injection Engines Flat

Low rolling resistance tires Vocational vehicles Flat

Low rolling resistance tires Trucks Flat

Aero (except Aero SmartWay Advanced) Trucks Flat

Aero SmartWay Advanced Trucks Steep

Weight reduction (via single wide tires and/or 

aluminum wheels)

Trucks Flat

Auxiliary power unit Trucks Flat

Air conditioning leakage Trucks Flat

The learning effects discussed here impact the technology costs considered here in that 

those technology costs for which learning effects are considered applicable are changing 

throughout the period of implementation and the period following implementation. For 

example, some of the technology costs considered in this analysis are taken from the 2012-

2016 light-duty rule and scaled appropriately giving consideration to the heavier weights and 

loads in the heavy-duty segment. Many of the costs in the 2012-2016 light-duty rule were 

consider “applicable” for the 2012 model year. If flat-portion learning were applied to those 

technologies, the 2013 cost would be 3 percent lower than the 2012 cost, and the 2014 model 

year cost 3 percent lower than the 2013 cost, etc. As a result, the 2014 model year cost 

presented in, for example, Section 2.3 would reflect those two years of flat learning and 

would not be identical to the 2012 model year cost presented in the 2012-2016 light-duty rule.

2.3 Heavy-Duty Pickup Truck and Van (Class 2b and 3) Technologies and 

Costs 

2.3.1 Gasoline Engines 

Spark ignited (gasoline) engines used in Class 2b and 3 vehicles include engines 

offered in a manufacturer’s light-duty truck counterparts, as well as engines specific to the 
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Class 2b and 3 segment. Based on 2010 MY specifications, these engines typically range in 

displacement between 5 and 7 liters, though smaller and larger engines have also been used in 

this market. The majority of these engines are a V8 configuration, although the V10 

configuration is also marketed. 

The engine technologies are based on the technologies described in the Light-Duty

Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy 

Standards Joint Technical Support Document.14 Some of the references come from the 2010 

NAS Report, Technologies and Approaches to Reducing the Fuel Consumption of Medium 

and Heavy-Duty Vehicles. These technologies include engine friction reduction, cam 

phasing, cylinder deactivation and stoichiometric gas direct injection. Included with each 

technology description is an estimate of the improvement in fuel consumption and GHGs that 

is achievable through the use of the technology in heavy-duty pickup trucks and vans. Table 

2-37 at the end of this chapter shows the total potential improvement in heavy-duty pickup 

and van fuel consumption and GHG emissions that can be achieved with the use of 

technologies described in this section.

2.3.1.1 Low Friction Lubricants

One of the most basic methods of reducing fuel consumption in both gasoline and 

diesel 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. This can be accomplished by changes to the oil base stock 

(e.g., switching engine lubricants from a Group I base oils to lower-friction, lower viscosity

Group III synthetic) and through changes to lubricant additive packages (e.g., friction 

modifiers and viscosity improvers). The use of 5W-30 motor oil is now widespread and auto 

manufacturers are introducing the use of even lower viscosity oils, such as 5W-20 and 0W-20, 

to improve cold-flow properties and reduce cold start friction. However, in some cases, 

changes to the crankshaft, rod and main bearings and changes to the mechanical tolerances of 

engine components may be required. In all cases, durability testing would be required to 

ensure that durability is not compromised. The shift to lower viscosity and lower friction 

lubricants will also improve the effectiveness of valvetrain technologies such as cylinder 

deactivation, which rely on a minimum oil temperature (viscosity) for operation.

Based on 2012-2016 Light-duty final rule, and previously-received confidential 

manufacturer data, NHTSA and EPA estimated the effectiveness of low friction lubricants to 

be between 0 to 1 percent.

In the 2012-2016 light-duty FRM, the agencies estimated the cost of moving to low 

friction lubricants at $3 per vehicle (2007$). That estimate included a markup of 1.11 for a 

low complexity technology. For Class 2b and 3, we are using the same base estimate but have 

marked it up to 2009 dollars using the GDP price deflator and have used a markup of 1.24 for 

a low complexity technology to arrive at a value of $4 per vehicle. As in the light-duty rule, 

learning effects are not applied to costs for this technology and, as such, this estimate applies 

to all model years.15,16
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2.3.1.2 Engine Friction Reduction 

Manufacturers can reduce friction and improve fuel consumption by improving the 

design of engine components and subsystems. Approximately 10 percent of the energy

consumed by a vehicle is lost to friction, and just over half is due to frictional losses within 

the engine. Examples include improvements in low-tension piston rings, piston skirt design, 

roller cam followers, improved crankshaft design and bearings, material coatings, material 

substitution, more optimal thermal management, and piston and cylinder surface treatments. 

Additionally, as computer-aided modeling software continues to improve, more opportunities 

for evolutionary friction reductions may become available.

All reciprocating and rotating components in the engine are potential candidates for 

friction reduction, and minute improvements in several components can add up to a 

measurable fuel economy improvement. The 2012-2016 LD rule, 2010 NAS, NESCCAF and 

EEA reports as well as confidential manufacturer data suggested a range of effectiveness for 

engine friction reduction to be between 1 to 3 percent. NHTSA and EPA continue to believe 

that this range is accurate.

Consistent with the 2012-2016 light-duty FRM, the agencies estimate the cost of this 

technology at $15 per cylinder compliance cost (2009$), including the low complexity ICM 

markup value of 1.24. Learning impacts are not applied to the costs of this technology and, as 

such, this estimate applies to all model years. This cost is multiplied by the number of engine 

cylinders.

2.3.1.3 Variable Valve Timing

Variable valve timing (VVT) classifies a family 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 controlling valve timing closer to the 

optimum needed to sustain horsepower and torque. VVT can also improve volumetric 

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 (e.g., in the Atkinson Cycle).

VVT has now become a widely adopted technology in the light duty fleet: in MY 

2007, over half of all new cars and light trucks had engines with some method of variable 

valve timing.17 Manufacturers are currently using many different types of variable valve 

timing, which have a variety of different names and methods. Therefore, the degree of further 

improvement across the fleet is limited by the level of valvetrain technology already

implemented on the vehicles. The three major types of VVT are listed below.

Each of the implementations of VVT uses a cam phaser to adjust the camshaft angular 

position relative to the crankshaft position, referred to as “camshaft phasing.” The 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-
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actuated units, powered by engine oil pressure and managed by a solenoid that controls the oil 

pressure supplied to the phaser.

Based on a survey of the current powertrains being applied to the Class 2b and 3 

segment and the level of powertrain sharing with the light duty vehicle market for these 

vehicles, the majority of light heavy duty gasoline engines in the 2010 Class 2b and 3 vehicle 

models are utilizing some form of cam phasing to achieve power and emission goals, and so 

this technology is considered to be in the baseline.

2.3.1.3.1 Coupled Cam Phasing for Overhead Valve (OHV) and Single Overhead 

Camshaft (SOHC) Engines

Valvetrains with coupled (or coordinated) cam phasing (CCP) can modify the timing 

of both the inlet valves and the exhaust valves an equal amount by varying the phasing of the 

camshaft across an engine’s range of operating speeds; also known as variable valve timing 

(VVT). For engines configured as an overhead valve (OHV) or as a single overhead camshaft 

(SOHC) only one cam phaser is required per camshaft to achieve CCP 

Consistent with the 2012-2016 light-duty rule, the agencies continue to agree with the 

effectiveness values of 1 to 4 percent reduction in fuel consumption for this technology.

2.3.1.3.2 Intake Cam Phasing (ICP) for Dual Overhead Camshaft Engines (DOHC)

Valvetrains with ICP, which is the simplest of the cam phasing technologies, 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 Vconfigured engines have two banks of intake valves.

Some newer Class 2b and 3 market entries are offering dual overhead camshaft 

(DOHC) engine designs where two camshafts are used to operated the intake and exhaust 

valves independently. Currently, for Class 2b and 3 segment, only intake camshaft phasing 

(ICP) technology is applied. Consistent with the 2012-2016 light-duty rule, the agencies 

continue to agree with the effectiveness values of 1 to 2 percent reduction in fuel consumption 

for this technology.

2.3.1.3.3 Dual Cam Phasing (DCP) for Dual Overhead Camshaft Engines (DOHC)

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. Increased internal EGR also results in lower engine-out NOX emissions. The 

amount by which fuel consumption is improved depends on the residual tolerance of the 

combustion system. Additional improvements are observed at idle, where low valve overlap 
Regulatory Impact Analysis 

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could result in improved combustion stability, potentially reducing idle fuel consumption.

DCP requires two cam phasers on each bank of the engine. 

Using 2010MY as the baseline, the agencies are not aware of DCP being applied to 

the Class 2b and 3 segment. However, the agencies note that multiple DCP equipped engines 

are currently available in the light duty counterparts to these vehicles implying this 

technology may crossover to the light heavy duty segment in the near future.

2.3.1.4 Cylinder Deactivation

In conventional spark-ignited engines throttling the airflow controls engine torque 

output. At partial loads, efficiency can be improved by using cylinder deactivation instead of 

throttling. Cylinder deactivation can improve engine efficiency by disabling or deactivating 

(usually) half of the cylinders when the load is less than half of the engine’s total torque 

capability – the valves are kept closed, and no fuel is injected – as a result, the trapped air 

within the deactivated cylinders is simply compressed and expanded as an air spring, with 

reduced friction and heat losses. The active cylinders combust at almost double the load 

required if all of the cylinders were operating. Pumping losses are significantly reduced as 

long as the engine is operated in this “part-cylinder” mode.

Cylinder deactivation control strategy relies on setting maximum manifold absolute 

pressures or predicted torque within which it can deactivate the cylinders. Noise and 

vibration issues reduce the operating range to which cylinder deactivation is allowed, 

although manufacturers are exploring vehicle changes that enable increasing the amount of 

time that cylinder deactivation might be suitable. Some manufacturers may choose to adopt 

active engine mounts and/or active noise cancellations systems to address NVH concerns and 

to allow a greater operating range of activation. 

2.3.1.5 Effectiveness improvements scale roughly with engine displacement-to-vehicle 

weight ratio: the higher displacement-to-weight vehicles, operating at lower 

relative loads for normal driving, have the potential to operate in part-cylinder 

mode more frequently. While several manufacturers have adopted cylinder 

deactivation in their light-duty vehicles equipped with 8 cylinder engines, the 

same or similar engines for heavy-duty application do not utilize this 

technology. Manufacturers discovered that in most heavy-duty applications, 

the opportunity for benefits from this technology are greatly reduced, due to the 

regularly required high load operation for these work-oriented vehicles. 

Cylinder deactivation is thus not part of the technology package on which the 

standards this analysis for the HD pickup and van segment are 

predicated.Stoichiometric Gasoline Direct Injection 

Stoichiometric gasoline direct injection (SGDI) engines inject fuel at high pressure 

directly into the combustion chamber (rather than the intake port in port fuel injection). SGDI

requires changes to the injector design, an additional high pressure fuel pump, new fuel rails 

to handle the higher fuel pressures, and changes to the cylinder head and piston crown design. 

Direct injection of the fuel into the cylinder improves cooling of the air/fuel charge within the 

cylinder, which allows for higher compression ratios and increased thermodynamic efficiency
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2-17

without the onset of combustion knock. Recent injector design advances, improved electronic 

engine management systems and the introduction of multiple injection events per cylinder 

firing cycle promote better mixing of the air and fuel, enhance combustion rates, increase 

residual exhaust gas tolerance and improve cold start emissions. SGDI engines achieve 

higher power density and match well with other technologies, such as boosting and variable 

valvetrain designs.

Several manufacturers have recently introduced vehicles with SGDI engines, 

including GM and Ford, who have announced their plans to increase dramatically the number 

of SGDI engines in their light-duty portfolios.

The 2012-2016 light-duty rule estimated the range of effectiveness to be from 1 to 2 

percent for SGDI. NHTSA and EPA reviewed this estimate for purposes of this HD vehicle 

rulemaking, and continue to find it accurate. 

The NHTSA and EPA cost estimates for SGDI take into account the changes required 

to the engine hardware, engine electronic controls, ancillary and Noise Vibration and 

Harshness (NVH) mitigation systems. Consistent with the 2012-2016 light-duty rule, the 

agencies estimate the cost of conversion to SGDI on a V8 engine at $481 (2009$) for the 

2014MY. This estimate includes a medium complexity ICM of 1.39 and flat-portion of the 

curve learning. Note that this technology was considered low complexity in the proposal but 

has been upgraded to medium complexity for the final analysis as a result of a more detailed 

review of what it involves. 

2.3.2 Diesel Engines 

Diesel engines in this class of vehicle have emissions characteristics that present 

challenges to meeting federal Tier 2 NOx emissions standards. It is a significant systemsengineering challenge to maintain the fuel consumption advantage of the diesel engine while 

meeting U.S. emissions regulations. Fuel consumption can be negatively impacted by

emissions reduction strategies depending on the combination of strategies employed. 

Emission compliance strategies for diesel vehicles sold in the U.S. are expected to include a 

combination of improvements of combustion, air handling system, aftertreatment, and 

advanced system control optimization. These emission control strategies are being introduced 

on Tier 2 light-duty diesel vehicles today

Some of the engine technologies are described in the Light-Duty Vehicle Greenhouse 

Gas Emission Standards and Corporate Average Fuel Economy Standards Joint Technical 

Support Document.18 Others are from the 2010 NAS Report, Technologies and Approaches 

to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles. Several key

advances in diesel technology have made it possible to reduce missions coming from the 

engine prior to aftertreatment. These technologies include engine friction and parasitic loss 

reduction, improved fuel systems (higher injection pressure and multiple-injection capability), 

advanced controls and sensors to optimize combustion and emissions performance, higher 

EGR levels and EGR cooling to reduce NOx, and advanced turbocharging systems.
Regulatory Impact Analysis 

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2.3.2.1 Low Friction Lubricants

Consistent with the discussion above for gasoline engines (see Section 2.3.1.1), the 

agencies are expecting some engine changes to accommodate low friction lubricants. Based 

on the 2012-2016 MY light-duty final rule, and previously-received confidential manufacturer 

data, NHTSA and EPA estimated the effectiveness of low friction lubricants to be between 0 

to 1 percent.

In the 2012-2016 MY light-duty FRM, the agencies estimated the cost of moving to 

low friction lubricants at $3 per vehicle (2007$). That estimate included a markup of 1.11 for 

a low complexity technology. For Class 2b and 3, we are using the same base estimate but 

have marked it up to 2009 dollars using the GDP price deflator and have used a markup of 

1.24 for a low complexity technology to arrive at a value of $4 per vehicle. As in the lightduty rule, learning effects are not applied to costs for this technology and, as such, this 

estimate applies to all model years.19,20

2.3.2.2 Engine Friction Reduction

Reduced friction in bearings, valve trains, and the piston-to-liner interface will 

improve efficiency. Friction reduction opportunities in the engine valve train and at its 

roller/tappet interfaces exist for several production engines. In virtually all production 

engines, the piston at its skirt/cylinder wall interface, wrist pin and oil ring/cylinder wall 

interface offer opportunities for friction reduction. Use of more advanced oil lubricant that 

could be available for production in the future may also eventually play a key role in reducing 

friction. Any friction reduction must be carefully developed to avoid issues with durability or 

performance capability. Estimations of fuel consumption improvements due to reduced 

friction range from 0 percent to 2 percent.21

Consistent with the cost estimated for gasoline engines, the agencies estimate the cost 

of engine friction reduction at $15 per cylinder compliance cost (2009$), including the low 

complexity ICM of 1.24, for a MY 2014 vehicle (learning effects are not applied to engine 

friction reduction). This cost is multiplied by the number of engine cylinders.

2.3.2.3 Combustion and Fuel Injection System Optimization

More flexible fuel injection capability with higher injection pressure provides more 

opportunities to improve engine fuel efficiency, while maintaining the same emission level. 

Combustion system optimization features system level integration and match, which includes 

piston bowl, injector tip and the number of holes, and intake swirl ratio. Cummins reports a 

9.1 percent improvement in fuel consumption compared to a 2007 baseline, while meeting 

Tier 2 Bin 5 emissions when the combustion and fuel injection system are integrated with 

other technologies, such as advanced and integrated aftertreatment technology, and advanced 

air handling system.

22

 Translating this improvement to the 2010 baseline HD pickup and van 

engine, this could result in 4-6 percent improvement assuming that 2010 baseline engine has 

3-5 percent advantage in fuel economy over a 2007 engine baseline.

The cost for this technology includes costs associated with low temperature exhaust 

gas recirculation (see Section 2.3.2.4), improved turbochargers (see Section 2.3.2.5) and 
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2-19

improvements to other systems and components. These costs are considered collectively in 

our costing analysis and termed “diesel engine improvements.” The agencies have estimated 

the cost of diesel engine improvements at $148 based on the cost estimates for several 

individual technologies presented in Table 2-10 for light HD engines. Specifically, the direct 

manufacturing costs we have estimated are: improved cylinder head, $9; turbo efficiency

improvements, $16; EGR cooler improvements, $3; higher pressure fuel rail, $10; improved 

fuel injectors, $13; improved pistons, $2; and reduced valve train friction, $95. All values 

are in 2009 dollars and are applicable in the 2014MY. Applying a low complexity ICM of 

1.24 results in a cost of $184 (2009$) applicable in the 2014MY. We consider the flat portion 

of the learning curve to be appropriate for these technologies.

2.3.2.4 Low Temperature Exhaust Gas Recirculation 

Low temperature exhaust gas recirculation could be one of the options to improve 

engine performance. Most medium-duty vehicle diesel engines sold in the U.S. market today

use cooled EGR, in which part of the exhaust gas is routed through a cooler (rejecting energy

to the engine coolant) before being returned to the engine intake manifold. EGR is a 

technology employed to reduce peak combustion temperatures and thus NOx. Lowtemperature EGR uses a larger or secondary EGR cooler to achieve lower intake charge 

temperatures, which tend to further reduce NOx formation. Low-temperature EGR can allow 

changes such as more advanced injection timing that will increase engine efficiency slightly

more than 1 percent (NESCCAF/ICCT, 2009, p. 62). Because low-temperature EGR reduces 

the engine’s exhaust temperature, it may not be compatible with exhaust energy recovery

systems such as turbocompound or a bottoming cycle.

The agencies’ cost estimate for this technology is discussed in Section 2.3.2.3.

2.3.2.5 Turbocharger Technology 

Compact two stage turbochargers can increase the boost level with wider operation 

range, thus improving engine thermal efficiency. Ford’s new developed 6.7L Scorpion engine 

features a twin-compressor turbocharger23. Cummins is also developing its own two stage 

turbochargers.24 It is expected that this type of technology will continue to be improved by 

better system matching and development of higher compressor and turbine efficiency.

The agencies’ cost estimate for this technology is discussed in Section 2.3.2.3.

2.3.2.6 Reduction of Parasitic Loads

Accessories that are traditionally gear- or belt-driven by a vehicle’s engine can be 

optimized and/or converted to electric power. Examples include the engine water pump, oil 

pump, fuel injection pump, air compressor, power-steering pump, cooling fans, and the 

vehicle’s air-conditioning system. Optimization and improved pressure regulation may

significantly reduce the parasitic load of the water, air and fuel pumps. Electrification may

result in a reduction in power demand, because electrically-powered accessories (such as the 

air compressor or power steering) operate only when needed if they are electrically powered, 
Regulatory Impact Analysis 

2-20

but they impose a parasitic demand all the time if they are engine-driven. In other cases, such 

as cooling fans or an engine’s water pump, electric power allows the accessory to run at 

speeds independent of engine speed, which can reduce power consumption. Electrification of 

accessories can individually improve fuel consumption, but as a package on a hybrid vehicle 

it is estimated that 3 to 5 percent fuel consumption reduction is possible. The TIAX [2009, 

pg. 3-5] study used 2 to 4 percent fuel consumption improvement for accessory electrification, 

with the understanding that electrification of accessories will have more effect in shorthaul/urban applications and less benefit in line-haul applications.

Consistent with the 2012-2016 MY light-duty rule (where this technology was referred 

to as “improved accessories”), the agencies estimate the cost for this technology at $93 

(2009$) for a 2014MY vehicle. This estimate includes a low complexity ICM of 1.24 and 

flat-portion of the curve learning.

2.3.2.7 Improved Aftertreatment Efficiency and Effectiveness

Selective Catalytic Reduction (SCR) systems are used by several manufacturers to 

control NOx emissions. 2010 fuel consumption was reduced 3 to 4 percent when compared to 

2009, depending upon the manufacturer [2009, TIAX]. In the proposal we estimated that 

additional improvements of 3 to 5 percent relative to 2010 may be reasonably expected as 

system effectiveness increases and accumulated knowledge is applied in calibration. We 

received no comments disagreeing with this assessment. Additionally, as SCR system 

effectiveness is improved, diesel particulate filters (DPFs) may be better optimized to reduced 

particulate loading (ability to run at higher engine out NOx), reducing the associated pressure 

drop associated with their presence in the exhaust system. Such DPF changes may result in a 

1.0 – 1.5 percent fuel consumption reduction25

The agencies have estimated the cost of this technology at $25 for each percentage 

improvement in fuel consumption from that of the baseline systems. This cost would cover 

the engineering and test cell related costs necessary to develop and implement the improved 

control strategies that would allow for the improvements in fuel consumption. Importantly, 

the engineering work involved would be expected to result in cost savings to the 

aftertreatment and control hardware (lower platinum group metal (PGM) loadings, lower 

reductant dosing rates, etc.). Those savings are considered to be included in the $25 per 

percent estimate described here. Given the average 4 percent expected improvement in fuel 

consumption results in an estimated cost of $119 (2009$) for a 2014MY vehicle. This 

estimate includes a low complexity ICM of 1.24 and flat-portion of the curve learning from 

2012 forward. We did not receive negative comments on this cost estimate.

2.3.3 Drive Train

NHTSA and EPA have also reviewed the transmission technology estimates used in 

the 2012-2016 light-duty final rule. In doing so, NHTSA and EPA considered or 

reconsidered all available sources and updated the estimates as appropriate. The section 

below describes each of the transmission technologies considered for this rulemaking.
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2.3.3.1 Improved Automatic Transmission Control (IATC) (Aggressive Shift Logic and 

Early Torque Converter Lockup)

Calibrating the transmission shift schedule to upshift earlier and quicker, and to lock

up or partially lock up the torque converter under a broader range of operating conditions can 

reduce fuel consumption and CO2 emissions. However, this operation can result in a 

perceptible degradation in noise, vibration, and harshness (NVH). The degree to which NVH 

can be degraded 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. Given that 

the Aggressive Shift Logic and Early Torque Converter Lockup are best optimized 

simultaneously due to the fact that adding both of them primarily requires only minor 

modifications to the transmission or calibration software, these two technologies are 

combined in the modeling.

2.3.3.2 Aggressive Shift Logic

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. The application of this 

technology does require a manufacturer to confirm that drivability, durability, and NVH are 

not significantly degraded.

We consider this technology to be present in the baseline 6-speed automatic 

transmissions in the majority of Class 2b and 3 trucks in the 2010 model year timeframe, and 

thus do not include it in the package of technologies on whose use the stringency of the 

standard is predicated.

2.3.3.3 Early Torque Converter Lockup

A torque converter is a fluid coupling located between the engine and transmission in 

vehicles with automatic transmissions and continuously-variable transmissions (CVT). This 

fluid coupling allows for slip so the engine can run while the vehicle is idling in gear (as at a 

stop light), provides for smoothness of the powertrain, and also provides for torque 

multiplication during acceleration, and especially launch. During light acceleration and 

cruising, the inherent slip in a torque converter causes increased fuel consumption, so modern 

automatic transmissions utilize a clutch in the torque converter to lock it and prevent this 

slippage. Fuel consumption can be further reduced by locking up the torque converter at 

lower vehicle speeds, provided there is sufficient power to propel the vehicle, and noise and 

vibration are not excessive. If the torque converter cannot be fully locked up for maximum 

efficiency, a partial lockup strategy can be employed to reduce slippage. Early torque 
Regulatory Impact Analysis 

2-22

converter lockup is applicable to all vehicle types with automatic transmissions. Some torque 

converters will require upgraded clutch materials to withstand additional loading and the 

slipping conditions during partial lock-up. As with aggressive shift logic, confirmation of 

acceptable drivability, performance, durability and NVH characteristics is required to 

successfully implement this technology.

We consider this technology to be present in the baseline, 6-speed automatic 

transmissions in the majority of Class 2b and 3 trucks in the 2010 model year timeframe, and 

thus do not include it in the package of technologies on whose use the stringency of the 

standard is predicated.

2.3.3.4 Automatic 6- and 8-Speed Transmissions

Manufacturers can also choose to replace 4- and 5-speed transmission with 6- or 8-

speed automatic transmissions. Additional ratios allow for further optimization of engine 

operation over a wider range of conditions, but this is subject to diminishing returns as the 

number of speeds increases. As additional planetary gear sets are added (which may be 

necessary in some cases to achieve the higher number of ratios), additional weight and friction 

are introduced. Also, the additional shifting of such a transmission can be perceived as 

bothersome to some consumers, so manufacturers need to develop strategies for smooth 

shifts. Some manufacturers are replacing 4- and 5-speed automatics with 6-speed automatics, 

and 7- and 8-speed automatics have also entered production, albeit in lower-volume 

applications in luxury and performance oriented cars.

As discussed in the 2012-2016 light-duty final rule, 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. GM has publicly claimed a fuel economy improvement of up to 4 percent for 

its new 6-speed automatic transmissions26. 

NHTSA and EPA reviewed and revised these effectiveness estimates based on usage 

and testing methods for Class 2b and 3 vehicles along with confidential business information. 

When combined with IATC, the agencies estimate the effectiveness for a conversion from a 4 

to a 6-speed transmission to be 5.3 percent and a conversion from a 6 to 8-speed transmission 

to be 1.7 percent.

As for costs, the agencies have considered the recent study conducted by NAS (NAS 

2010) which showed an incremental cost of $210 for an 8 speed automatic transmission 

relative to a 6 speed automatic transmission (the baseline technology for 2010MY Class 2b & 

3 pickups and vans). Considering this to be a valid cost for 2012MY and applying a low 

complexity ICM of 1.24 results in a cost of $294 in 2012. Considering flat-portion of the 

curve learning to be appropriate for automatic transmissions and applying two years of 

learning results in a 2014MY cost of $281 (2009$). This technology is considered applicable 

to both gasoline and diesel trucks and vans.
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2.3.3.5 Electric Power Steering/Electro-hydraulic Power Steering (EPS/EHPS)

Electric power steering (EPS) or Electrohydraulic power steering (EHPS) provides a 

potential reduction in CO2 emissions and fuel consumption over hydraulic power steering 

because of reduced overall accessory loads. This eliminates the parasitic losses associated 

with belt-driven power steering pumps which consistently draw load from the engine to pump 

hydraulic fluid through the steering actuation systems even when the wheels are not being 

turned. EPS is an enabler for all vehicle hybridization technologies since it provides power 

steering when the engine is off. EPS may be implemented on most vehicles with a standard 

12V system. Some heavier vehicles may require a higher voltage system which may add cost 

and complexity.

The 2010 light-duty final rule estimated a 1 to 2 percent effectiveness based on the 

2002 NAS report, a Sierra Research report, and confidential manufacturer data. NHTSA and 

EPA reviewed these effectiveness estimates and found them to be accurate, thus they have 

been retained for this final rule.

NHTSA and EPA adjusted the EPS cost for the current rulemaking based on a review 

of the specification of the system. Adjustments were made to include potentially higher 

voltage or heavier duty system operation for Class 2b and 3. Accordingly, higher costs were 

estimated for systems with higher capability. After accounting for the differences in system 

capability and applying the ICM markup of low complexity technology of 1.24, the estimated 

costs for this rulemaking are $115 for a MY 2014 truck or van (2009$). As EPS systems are 

in widespread usage today, flat-portion of the curve learning is deemed applicable. EHPS 

systems are considered to be of equal cost and both are considered applicable to gasoline and 

diesel engines. 

2.3.3.6 Hybrids

Commenters arguing for more stringent standards cited the 2010 NAS study (and an 

associated TIAX report) finding that technologies such as hybridization are feasible. 

However, in the ambitious timeframe we are focusing on for these rules, targeting as it does 

technologies implementable in the HD pickup and van fleet starting in 2014 and phasing in 

with normal product redesign cycles through 2018, our assessment shows that the standards 

we are establishing, which are not based on significant hybridization, are appropriate. More 

advanced technologies considered in the NAS report would be appropriate for consideration 

in future rulemaking activity.

2.3.4 Aerodynamics

Aerodynamic drag is an important aspect of the power requirements for Class 2b and 3 

trucks. Because aerodynamic drag is a function of the cube of vehicle speed, small changes in 

the aerodynamics of a Class 2b and 3 can reduce drag, fuel consumption, and GHG emissions. 

Some of the opportunities to reduce aerodynamic drag in Class 2b and 3 vehicles are similar 
Regulatory Impact Analysis 

2-24

to those in Class 1 and 2 (i.e., light-duty) vehicles. In general, these transferable features make 

the cab shape more aerodynamic by streamlining the airflow over the bumper, grill, 

windshield, sides, and roof. Class 2b and 3 vehicles may also borrow from light-duty vehicles 

certain drag reducing accessories (e.g., streamlined mirrors, operator steps, and sun visors). 

The great variety of applications for Class 2b and 3 trucks result in a wide range of 

operational speed profiles (i.e., in-use drive cycles) and functional requirements (e.g., shuttle 

buses that must be tall enough for standing passengers, trucks that must have racks for 

ladders). This variety makes it challenging to develop aerodynamic solutions that consider 

the entire vehicle.

Consistent with the 2012-2016 light-duty rule, the agencies have estimated the cost for 

this technology at $58 (2009$) including a low complexity ICM of 1.24. This cost is 

applicable in the 2014 model year to both gasoline and diesel trucks and vans and is 

considered to be on the flat-portion of the learning curve.

2.3.5 Tires

Typically, tires used on Class 2b/3 vehicles are not designed specifically for the 

vehicle. These tires are designed for broader use and no single parameter is optimized. 

Similar to vocational vehicles, the market has not demanded tires with improved rolling 

resistance thus far; therefore, manufacturers have not traditionally designed tires with low 

rolling resistance for Class 2b/3 vehicles. EPA and NHTSA believe that a regulatory program 

that incentivizes the optimization of tire rolling resistance, traction and durability can bring 

about GHG emission and fuel consumption reductions from this segment.

Based on the 2012-2016 Light-duty final rule and the 2010 NAS report, the agencies 

have estimated the cost for low rolling resistance tires to be $7 (2009$) per Class 2b truck or 

van, and $10 (2009$) per Class 3 truck or van.27 The higher cost for the Class 3 trucks and 

vans is due to the predominant use of dual rear tires and, thus, 6 tires per truck. Due to the 

commodity-based nature of this technology, cost reductions due to learning are not applied. 

This technology is considered applicable to both gasoline and diesel. 

2.3.6 Mass Reduction

Reducing a vehicle’s mass, or down-weighting the vehicle, decreases fuel 

consumption by reducing the energy demand needed to overcome forces resisting motion, and 

rolling resistance. Manufacturers employ a systematic approach to mass reduction, where the 

net mass reduction is the addition of a direct component or system mass reduction plus the 

additional mass reduction that can be taken from indirect ancillary systems and components, 

as a result of full vehicle optimization, effectively compounding or obtaining a secondary

mass reduction from a primary mass reduction. For example, use of a smaller, lighter engine 

with lower torque-output subsequently allows the use of a smaller, lighter-weight 

transmission and drive line components. Likewise, the compounded weight reductions of the 

body, engine and drivetrain reduce stresses on the suspension components, steering 

components, wheels, tires and brakes, allowing further reductions in the mass of these 

subsystems. The reductions in unsprung masses such as brakes, control arms, wheels and 
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tires further reduce stresses in the suspension mounting points. This produces a compounding 

effect of mass reductions.

Estimates of the synergistic effects of mass reduction and the compounding effect that 

occurs along with it can vary significantly from one report to another. For example, in 

discussing its estimate, an Auto-Steel Partnership report states that “These secondary mass 

changes can be considerable—estimated at an additional 0.7 to 1.8 times the initial mass 

change.”28 This means for each one pound reduction in a primary component, up to 1.8 

pounds can be reduced from other structures in the vehicle (i.e., a 180 percent factor). The 

report also discusses that a primary variable in the realized secondary weight reduction is 

whether or not the powertrain components can be included in the mass reduction effort, with 

the lower end estimates being applicable when powertrain elements are unavailable for mass 

reduction. However, another report by the Aluminum Association, which primarily focuses 

on the use of aluminum as an alternative material for steel, estimated a factor of 64 percent for 

secondary mass reduction even though some powertrain elements were considered in the 

analysis.29 That report also notes that typical values for this factor vary from 50 to 100 

percent. Although there is a wide variation in stated estimates, synergistic mass reductions do 

exist, and the effects result in tangible mass reductions. Mass reductions in a single vehicle 

component, for example a door side impact/intrusion system, may actually result in a 

significantly higher weight savings in the total vehicle, depending on how well the 

manufacturer integrates the modification into the overall vehicle design. Accordingly, care 

must be taken when reviewing reports on weight reduction methods and practices to ascertain 

if compounding effects have been considered or not.

Mass reduction is broadly applicable across all vehicle subsystems including the engine, 

exhaust system, transmission, chassis, suspension, brakes, body, closure panels, glazing, seats 

and other interior components, engine cooling systems and HVAC systems. It is estimated 

that up to 1.25 kilograms of secondary weight savings can be achieved for every kilogram of 

weight saved on a vehicle when all subsystems are redesigned to take into account the initial 

primary weight savings.30,31

Mass reduction can be accomplished by proven methods such as:

 Smart Design: Computer aided engineering (CAE) tools can be used to better 

optimize load paths within structures by reducing stresses and bending moments 

applied to structures. This allows better optimization of the sectional thicknesses of 

structural components to reduce mass while maintaining or improving the function of 

the component. Smart designs also integrate separate parts in a manner that reduces 

mass by combining functions or the reduced use of separate fasteners. In addition, 

some “body on frame” vehicles are redesigned with a lighter “unibody” construction. 

 Material Substitution: Substitution of lower density and/or higher strength materials 

into a design in a manner that preserves or improves the function of the component. 

This includes substitution of high-strength steels, aluminum, magnesium or composite 

materials for components currently fabricated from mild steel. 
Regulatory Impact Analysis 

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 Reduced Powertrain Requirements: Reducing vehicle weight sufficiently allows for 

the use of a smaller, lighter and more efficient engine while maintaining or increasing 

performance. Approximately half of the reduction is due to these reduced powertrain 

output requirements from reduced engine power output and/or displacement, changes 

to transmission and final drive gear ratios. The subsequent reduced rotating mass (e.g., 

transmission, driveshafts/halfshafts, wheels and tires) via weight and/or size reduction 

of components are made possible by reduced torque output requirements.

 Automotive companies have largely used weight savings in some vehicle subsystems 

to offset or mitigate weight gains in other subsystems from increased feature content 

(sound insulation, entertainment systems, improved climate control, panoramic roof, 

etc.). 

 Lightweight designs have also been used to improve vehicle performance parameters 

by increased acceleration performance or superior vehicle handling and braking.

Many manufacturers have already announced final future product plans reducing the 

weight of a vehicle body through the use of high strength steel body-in-white, composite body

panels, magnesium alloy front and rear energy absorbing structures reducing vehicle weight 

sufficiently to allow a smaller, lighter and more efficient engine. Nissan has stated that it will 

be reducing average vehicle curb weight by 15% by 2015.32 Ford has identified weight 

reductions of 250 to 750 lb per vehicle as part of its implementation of known technology

within its sustainability strategy between 2011 and 2020.33 Mazda has stated that it plans to 

reduce vehicle weight by 220 pounds per vehicle or more as models are redesigned.34,35

Ducker International estimates that the average curb weight of light-duty vehicle fleet will 

decrease approximately 2.8% from 2009 to 2015 and approximately 6.5% from 2009 to 2020 

via changes in automotive materials and increased change-over from previously used bodyon-frame automobile and light-truck designs to newer unibody designs.32 While the 

opportunity for mass reductions available to the light-duty fleet may not in all cases be 

applied directly to the heavy-duty fleet due to the different designs for the expected duty

cycles of a “work” vehicle, mass reductions are still available, particularly to areas unrelated 

to the components and systems necessary for the work vehicle aspects. 

Due to the payload and towing requirements of these heavy-duty vehicles, engine 

downsizing was not considered in the estimates for CO2 reduction in the area of mass 

reduction and material substitution. NHTSA and EPA estimate that a 3 percent mass 

reduction with no engine downsizing results in a 1 percent reduction in fuel consumption. In

addition, a 5 and 10 percent mass reduction with no engine downsizing result in an estimated 

CO2 reduction of 1.6 and 3.2 percent respectively. These effectiveness values are 50% of the 

2012-2016 light-duty final rule values due to the elimination of engine downsizing for this 

class of vehicle.

The agencies have recently completed work on an Interim Joint Technical Assessment 

Report (TAR) that considers light-duty GHG and fuel economy standards for the years 2017 

through 2025 and have continued this work for the proposed light-duty vehicle rule. Based on 

new information from various industry and literature sources, the TAR report modified the 

mass reduction/cost relationship used in the 2012-2016 light-duty final rule to begin at the 
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origin (0% weight reduction) and to have increasing cost with increasing mass reduction.B 

The resulting analysis showed costs for 5% mass reduction on light-duty vehicles to be near 

zero or cost parity. 

At proposal for heavy-duty vehicles, we estimated mass reduction costs based on the 

2012-2016 light-duty analysis without accounting for the new work completed in the Interim 

Joint Technical Assessment. Since the proposal, we have been able to consider our cost 

estimates here in the context of both light-duty and heavy-duty vehicle bodies of work. For 

this final action, in aggregate, we estimate a 5 percent mass reduction at a cost of $80-100 per 

vehicle. We are estimating the following direct manufacturer costs for a 5% mass reduction; 

Class 2b gasoline $85, 2b diesel $95, 3 gasoline $90, 3 diesel trucks $100. Including a low 

complexity ICM of 1.24 and using learning on the flat portion of the curve, these values 

become $103, $115, $109 and $121, respectively, applicable in the 2016 MY and expressed in 

2009 dollars. This estimate is higher than our most recent estimate of mass reduction 

contained in the light-duty vehicle Interim Joint Technical Assessment Report because we do 

not believe that all of the weight reduction opportunities for light-duty vehicles can be applied 

to heavy-duty trucks. However, we do believe reductions in the following components and 

systems can be found that do not affect the payload and towing requirements of these heavyduty vehicles; body, closure panels, glazing, seats and other interior components, engine 

cooling systems and HVAC systems. 

2.4 Heavy-Duty Engines 

The regulatory structure for heavy-duty engines separates the compression ignition (or 

“diesel”) engines into three regulatory subcategories and from spark ignition (or “gasoline”) 

engines into a single regulatory subcategory. Therefore, the subsequent discussion will assess 

each type of engine separately.

The light-heavy-duty diesel engines typically range between 4.7 and 6.7 liters 

displacement, the medium-heavy-duty diesel engines typically have some overlap in 

displacement with the light-heavy-duty diesel engines and range between 6.7 and 9.3 liters. 

The heavy-heavy-duty diesel engines typically are represented by engines between 10.8 and 

16 liters. The heavy-duty gasoline engines have ranged in the past between 4.8 and 8.1 liters.

2.4.1 Spark Ignition Engines 

Spark ignition engines are certified for the heavy-duty market. These engines have 

historically ranged in displacement between five and eight liters and are either V8 or V10 

configurations. As found in the 2010 NAS study, most are either V8 or V10 engines with 

port fuel injection, naturally aspirated with fixed valve timings. Most recently, the primary

 

B

“Interim Joint Technical Assessment Report: Light-Duty Vehicle Greenhouse Gas Emission Standards and 

Corporate Average Fuel Economy Standards for Model Years 2017-2025;” September 2010; available at 

http://epa.gov/otaq/climate/regulations/ldv-ghg-tar.pdf and in the docket for this rule.
Regulatory Impact Analysis 

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producers of the gasoline engines were limited to Ford and General Motors. The engines sold 

separately, which require an engine certificate in lieu of a chassis certificate, are the same as 

or very similar to the engines used in the pickup truck and vans. Therefore, NHTSA and EPA 

developed the baseline list of engine technologies and standards to reflect this commonality.

2.4.1.1 Baseline SI Engine CO2 and Fuel Consumption

Similar to the gasoline engine used as the baseline in the Light-Duty GHG rule (an 

assumption not questioned in the comments to that rulemaking), the agencies assumed the 

baseline engine in this segment to be a naturally aspirated, single overhead valve V8 engine. 

The following discussion of effectiveness is generally in comparison to 2010 baseline engine 

performance.

NHTSA and EPA developed the baseline fuel consumption and CO2 emissions for the 

gasoline engines from manufacturer-reported CO2 values used in the certification of nonGHG pollutants. The baseline engine for the analysis was developed to represent a 2011 

model year engine, because this is the most current information available. The average CO2

performance of the heavy-duty gasoline engines was 660 g/bhp-hour, which will be used as a 

baseline. 

2.4.1.2 Gasoline Engine Technologies

The engine technologies projected for the gasoline heavy-duty engines are based on 

the technologies used in the Light-Duty Vehicle Greenhouse Gas Emission Standards and 

Corporate Average Fuel Economy Standards Joint Technical Support Document.37 The 

effectiveness of the technology packages were evaluated using the EPA Lumped Parameter 

model HD Version 1.0.0.1.38 The HD version of the Lumped Parameter model includes a 

subset of the technologies included in the Large Pickup Truck version of the Light-Duty

rulemaking to recognize that some technologies will have limited effectiveness due to the 

higher operating weights of these trucks. The HD Lumped Parameter model also has reduced 

the effectiveness of several of the remaining individual technologies, again to recognize the 

higher test weights used in regulatory programs.

2.4.1.2.1 Engine Friction Reduction 

In addition to low friction lubricants, manufacturers can also reduce friction and 

improve fuel consumption by improving the design of engine components and subsystems. 

Examples include improvements in low-tension piston rings, piston skirt design, roller cam 

followers, improved crankshaft design and bearings, material coatings, material substitution, 

more optimal thermal management, and piston and cylinder surface treatments. Additionally, 

as computer-aided modeling software continues to improve, more opportunities for 

evolutionary friction reductions may become available. All reciprocating and rotating 

components in the engine are potential candidates for friction reduction, and minute 

improvements in several components can add up to a measurable fuel economy improvement. 

The 2012-2016 MY light-duty rule, 2010 NAS Report, and the NESCCAF and EEA reports,

as well as confidential manufacturer data suggested a range of effectiveness for engine 
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friction reduction to be between 1 to 3 percent. NHTSA and EPA continue to believe that this 

range is accurate.

NHTSA and EPA believe that the cost estimate is closer to the lower end of the model 

year (MY) 2011 CAFE final rule range and thus for this rulemaking are projecting $10 per 

cylinder compliance cost (2009$), plus a low complexity Indirect Cost Multiplier (ICM) 

markup value of 1.24, for a MY 2016 engine (learning effects are not applied to engine 

friction reduction). This cost is multiplied by the eight cylinders resulting in a cost of $95

(2009$) per engine for this technology.

2.4.1.2.2 Coupled Cam Phasing

Valvetrains with coupled (or coordinated) cam phasing (CCP) 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. For overhead cam 

engines, this requires the addition of a cam phaser on each bank of the engine so SOHC Vengines 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 variable valve timing 

(VVT) implementation option available and requires only one cam phaser. Current overhead 

cam engines in the heavy duty sector contain a single camshaft per head which typically

requires a phaser per cam or two per engine. Based on 2010 Light-Duty final rule, previouslyreceived confidential manufacturer data, and the NESCCAF report, NHTSA and EPA 

estimated the effectiveness of CCP to be between 1 to 4 percent. NHTSA and EPA reviewed 

this estimate for purposes of this rulemaking, and continue to find it accurate.

Consistent with the 2010 2012-2016 Light-Duty final rule, NHTSA and EPA estimate 

the cost of a cam phaser at $49 (2009$) in the 2014MY. This estimate includes a low 

complexity ICM of 1.24. With two years of flat-portion of the curve learning this cost 

becomes $46 (2009$) in the 2016MY. The majority of heavy-duty gasoline loose engines are

over-head valve engines (OHV) and, as such, would require only one cam phaser for coupled 

cam phasing. The most recently designed engines, both overhead valve and overhead cam 

installed in heavy-duty pickup trucks and vans contain coupled cam phasing and are expected 

in the future to replace any legacy loose engines.

2.4.1.2.3 Cylinder Deactivation 

In conventional spark-ignited engines throttling the airflow controls engine torque 

output. At partial loads, efficiency can be improved by using cylinder deactivation instead of 

throttling. Cylinder deactivation (DEAC) can improve engine efficiency by disabling or 

deactivating (usually) half of the cylinders when the load is less than half of the engine’s total 

torque capability – the valves are kept closed, and no fuel is injected – as a result, the trapped 

air within the deactivated cylinders is simply compressed and expanded as an air spring, with 

reduced friction and heat losses. The active cylinders combust at almost double the load 
Regulatory Impact Analysis 

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required if all of the cylinders were operating. Pumping losses are significantly reduced as 

long as the engine is operated in this “part cylinder” mode.

Cylinder deactivation control strategy relies on setting maximum manifold absolute 

pressures or predicted torque within which it can deactivate the cylinders. Noise vibration and 

harshness (NVH) issues reduce the operating range to which cylinder deactivation is allowed, 

although manufacturers are exploring vehicle changes that enable increasing the amount of 

time that cylinder deactivation might be suitable. Some manufacturers may choose to adopt 

active engine mounts and/or active noise cancellations systems to address NVH concerns and 

to allow a greater operating range of activation. Cylinder deactivation has seen a recent 

resurgence thanks to better valvetrain designs and engine controls. General Motors and 

Chrysler Group have incorporated cylinder deactivation across a substantial portion of their 

V8-powered lineups in the light-duty market. 

Effectiveness improvements scale roughly with engine displacement-to-vehicle weight 

ratio: the higher displacement-to-weight vehicles, operating at lower relative loads for normal 

driving, have the potential to operate in part-cylinder mode more frequently. Cylinder 

deactivation is less effective on heavily-loaded vehicles because they require more power and 

spend less time in areas of operation where only partial power is required. The technology

also requires proper integration into the vehicles which is difficult in the vocational vehicle 

segment where often the engine is sold to a chassis manufacturer or body builder without 

knowing the type of transmission or axle used in the vehicle or the precise duty cycle of the 

vehicle. The cylinder deactivation requires fine tuning of the calibration as the engine moves 

into and out of deactivation mode to achieve acceptable NVH. Additionally, cylinder 

deactivation would be difficult to apply to vehicles with a manual transmission because it 

requires careful gear change control. NHTSA and EPA adjusted the 2010 light-duty final rule 

estimates using updated power to weight ratings of heavy-duty trucks and confidential 

business information and downwardly adjusted the effectiveness to 0 to 3 percent for these 

vehicles to reflect the differences in drive cycle and operational opportunities compared to 

light-duty vehicles Unlike light-duty, cylinder deactivation is not expected to penetrate the 

heavy-duty sector due to the unique duty cycle resulting in lower effectiveness. 

2.4.1.2.4 Stoichiometric gasoline direct injection (SGDI)

SGDI engines inject fuel at high pressure directly into the combustion chamber 

(rather than the intake port in port fuel injection). SGDI requires changes to the injector 

design, an additional high-pressure fuel pump, new fuel rails to handle the higher fuel 

pressures and changes to the cylinder head and piston crown design. Direct injection of the 

fuel into the cylinder improves cooling of the air/fuel charge within the cylinder, which allows 

for higher compression ratios and increased thermodynamic efficiency without the onset of 

combustion knock. Recent injector design advances, improved electronic engine management 

systems and the introduction of multiple injection events per cylinder firing cycle promote 

better mixing of the air and fuel, enhance combustion rates, increase residual exhaust gas 

tolerance and improve cold start emissions. SGDI engines achieve higher power density and 

match well with other technologies, such as boosting and variable valvetrain designs. NHTSA 
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and EPA continue to agree with estimated effectiveness of SGDI in the range of 1 to 2 percent 

improvement for SGDI.

The NHTSA and EPA cost estimates for SGDI take into account the changes required 

to the engine hardware, engine electronic controls, ancillary and NVH mitigation systems.

The NHTSA and EPA cost estimates for SGDI take into account the changes required 

to the engine hardware, engine electronic controls, ancillary and Noise Vibration and 

Harshness (NVH) mitigation systems In the proposal, consistent with the 2012-2016 lightduty rule, the agencies estimated the cost of conversion to SGDI on a V8 engine at $395 

(2008$) for the 2014MY including a low complexity ICM of 1.17. For this final analysis, 

based on further review, we have changed the complexity level of this technology to medium 

and, with the markup of 1.39 the cost becomes $474 (2009$) in the 2014MY. We consider 

flat-portion of the curve learning to be appropriate for this technology so the cost becomes 

$452 (2009$) for the 2016MY. SI Engine Technology Package

The average CO2 performance of the two heavy-duty gasoline engines certified for 

2010 and 2011 model years was 660 g CO2/bhp-hour. The HD Lumped Parameter model 

analysis projects that the package of the three technologies (friction reduction, closed couple 

cam phasing, and stoichiometric direct injection) could reduce CO2 emissions and fuel 

consumption by 5 percent. Therefore, the agencies are finalizing the standard in 2016 model 

year at 627 g CO2/bhp-hr.

2.4.1.3 SI Engine Technology Cost

As shown in Table 2-5, the overall projected engine package cost for a 2016 model 

year engine is $594(2009$).

Table 2-5 Estimated 2016MY Costs for a Spark-Ignition HD Engine (2009 dollars)

DIRECT MFG 

COST

ICM MARKED UP 

COSTS

Engine Friction Reduction $76 1.24 $95

Coupled Cam Phasing (OHV)a$37 1.24 $46

Stoichiometric Gas Direct Injection $321 1.39 $452

Total $435 $594

a Note: the direct manufacturing cost of cam phasing would be $74for engines with dual cams.

2.4.2 Diesel Engines 

2.4.2.1 Baseline Engines

The agencies developed the baseline diesel engine as a 2010 model year engine with 

an aftertreatment system which meets EPA’s 0.20 grams of NOx/bhp-hr standard with a 

selective catalytic reduction (SCR) system along with EGR and meets the PM emissions 

standard with a diesel particulate filter (DPF) with active regeneration. The engine is 
Regulatory Impact Analysis 

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turbocharged with a variable geometry turbocharger, based on the agencies’ assessment of 

today’s engines. The following discussion of technologies describes improvements over the 

2010 model year baseline engine performance, unless otherwise noted. 

The CO2 performance over the FTP for the baseline engines were developed through 

manufacturer reporting of CO2 in their non-GHG certification applications for 2010 model 

year. This data was carefully considered to ensure that the baseline represented an engine 

meeting the 0.20 g/bhp-hr NOx standard. For those engines that were not at this NOx level or 

higher, then the agencies derived a CO2 correction factor to bring them to a 0.20 g/bhp-hr 

NOx emissions. The CO2 correction factor is derived based on available experimental data 

obtained from manufacturers and public literature. The agencies then sales-weighted the CO2

performance to derive a baseline CO2 performance for each engine subcategory.

In order to establish baseline SET performance for the Heavy Heavy-Duty and 

Medium Heavy-Duty Diesel Engines, several sources were considered. Some engine 

manufacturers provided the agencies with SET modal results or fuel consumption maps to 

represent their 2009 model year engine fuel consumption performance. As a supplement to 

this, complete engine map CO2 data (including SET modes) acquired in EPA test cells were 

also considered. The pre-2010 maps are subsequently adjusted to represent 2010 model year 

engine maps by using predefined technologies, including SCR and other advanced systems 

that are being used in current 2010 production.

In summary, the baseline CO2 performance for each diesel engine category is included 

in Table 2-6.

Table 2-6: Baseline CO2 Performance (g/bhp-hr)

LHDD - FTP MHDD - FTP HHDD - FTP HHDD - SET

630 630 584 490

The agencies used the baseline engine to assess the potential of each of the following 

technologies.

2.4.2.2 Combustion System Optimization

Continuous improvements on the fuel injection system allows more flexible fuel 

injection capability with higher injection pressure, which can provide more opportunities to 

improve engine fuel efficiency, while maintaining the same emission level. Combustion 

system optimization, featuring piston bowl, injector tip and the number of holes, in 

conjunction with the advanced fuel injection system, is able to further improve engine 

performance and fuel efficiency. At this point, all engine manufacturers are spearheading

substantial efforts into this direction in the hope that their development efforts would be 

translated into production in the near futures. Some examples include the combustion 

development programs conducted by Cummins39 and Detroit Diesel40 funded by Department 

of Energy. Cummins and Detroit Diesel both claim that 10 percent thermal efficiency

improvement at 2010 emission level is achievable. While their findings are still more towards 

research environment, their results do enhance the possibility that some of technologies they

are developing could be applied to production in the time frame of 2017. The agencies have 
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determined that up to a 2.5 percent reduction in fuel consumption and CO2 emissions is 

feasible in the 2017 model year through the use of these technologies.

The cost for this technology includes costs associated with several individual 

technologies, specifically, improved cylinder head, turbo efficiency improvements, EGR 

cooler improvements, higher pressure fuel rail, improved fuel injectors and improved pistons. 

The cost estimates for each of these technologies are presented in Table 2-8 through Table 

2-10 for heavy HD, medium HD and light HD engines, respectively. The agencies consider a 

low complexity ICM of 1.15 and flat-portion of the curve learning from 2014 forward to be 

appropriate for these technologies.

Significant progress on advanced engine control has been made in the past few years, 

including model based calibration. Detroit Diesel introduced the next generation model based 

control concept, achieving 4 percent thermal efficiency improvement while simultaneously

reducing emissions in transient operations.41 Their model based concept features a series of 

real time optimizers with multiple inputs and multiple outputs. This controller contains many

physical based models for engine and aftertreatment. It produces fully transient engine 

performance and emissions predictions in a real-time manner. Although this control concept 

may still not be mature in 2014 production, it would be a realistic estimate that this type of 

real time model control could be in production before 2017, thus significantly improving 

engine fuel economy. The agencies have included the costs of control development in the 

research and development costs applied separately to each engine manufacturer.

2.4.2.3 Turbocharging and Air Handling System

Many advanced turbocharger technologies can be potentially added into production in 

the time frame between 2014 and 2017, and some of them are already in production, such as 

mechanical or electric turbocompound, two-stage turbochargers with intercooler, and high 

efficient low speed compressor. 

A turbocompound system extracts energy from the exhaust to provide additional 

power. Mechanical turbocompounding includes a power turbine located downstream of the 

turbine which in turn is connected to the crankshaft to supply additional power. As noted in 

the 2010 NAS report, it typically includes a fluid coupling (to allow for speed variation and to 

protect the power turbine from engine torsional vibration) and a gear set to match power 

turbine speed to crankshaft speed. Turbocompound has been used in production by Detroit 

Diesel for their DD15 and DD16 engines and they claim a 3 to 5 percent fuel consumption 

reduction due to the system.42 The 2010 NAS report43 includes published information from 

four sources on the fuel consumption reduction from mechanical turbocompounding ranging 

from 2.5 to 5 percent. Some of these differences may depend on the operating condition or 

duty cycle that was considered by the different researchers. The performance of a 

turbocompound system tends to be best at full load, and it can be much less effective, or even 

act as an energy sink, to suck the energy at light loads. Because of that, a clutch that can 

separate the engine crankshaft from turbocompound gear train could be put into production in 

order to overcome the drawbacks of turbocompound at light loads, thus improving fuel 

efficiency over the entire speed and load ranges. The agencies have assessed mechanical 
Regulatory Impact Analysis 

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turbocompound technology effectiveness at up to 5 percent, as shown in Table 2-12. 

Incremental cost increases associated with the addition of mechanical turbocompounding are 

significant, due to the complexity of the mechanical power transmission system required to 

connect the power turbine to the drivetrain. Such costs are estimated to be $1,049 inclusive of 

an RPE factor of 1.28 (i.e., $820 in direct manufacturing costs) in 2014 MY.

44

 

Electric turbocompound is another potential device, although it is still not as mature in 

terms of production compared to mechanical turbocompound. An electric turbocompound 

system uses a power turbine to drive an electrical generator which is used to power electric 

accessories or provide extra power to the engine. As noted in the 2010 NAS report,45 electric 

turbocompound is a technology that fits particularly well with a hybrid electric powertrain for 

long-haul applications where regenerative braking opportunities are limited. The benefits of 

electric turbocompound and an electric hybrid powertrain can be additive. TIAX used a range 

of 4 to 5 percent for its estimates, which included the benefits of electric accessories.46 The 

2010 NAS report includes the benefit projections from three studies, as listed below. 

However, none of these systems have been demonstrated commercially.

47

 

 The NESCCAF/ICCT study modeled an electric turbocompound system and 

estimated benefits at 4.2 percent, including electrification of accessories. 

 Caterpillar, Inc., as part of Department of Energy (DOE) funded work, 

modeled a system that showed 3 to 5 percent improvement48

 John Deere investigated a system (off-highway) that offered 10 percent 

improvement.

Two-stage turbocharger technology has been used in production by Navistar and other 

manufacturers. Ford’s new developed 6.7L diesel engine features a twin-compressor 

turbocharger. Higher boost with wider range of operations and higher efficiency can further 

enhance engine performance, thus fuel economy. It is expected that this type of technology 

will continue to be improved by better matching with system and developing higher 

compressor and turbine efficiency.

For this analysis, we have estimated the cost of turbocompounding at $875 (2009$)

based on the cost estimate noted above developed by ICF. This estimate includes a low 

complexity ICM of 1.15. This cost is applicable in the 2017MY when engines placed in day

cab and sleeper cab tractors are expected to add this technology. Flat-portion of the curve

learning is considered applicable to this technology. For the more basic technology of 

improving the turbo efficiency, the agencies have estimated a cost of $18 (2009$) including a 

low complexity ICM of 1.15. That estimate would be considered valid in the 2014MY and 

flat-portion of the learning curve would be applied going forward.

Higher efficiency air handling (air and exhaust transport) processes may also be 

produced in the 2014 and 2017 time frame. To maximize the efficiency of such processes, 

induction systems may be improved by manufacturing more efficiently designed flow paths 

(including those associated with air cleaners, chambers, conduit, mass air flow sensors and 

intake manifolds) and by designing such systems for improved thermal control. Improved 
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turbocharging and air handling systems must include higher efficiency EGR systems and 

intercoolers that reduce frictional pressure loss while maximizing the ability to thermally 

control induction air and EGR. EGR systems that often rely upon an adverse pressure 

gradient (exhaust manifold pressures greater than intake manifold pressures) must be 

reconsidered and their adverse pressure gradients minimized. “Hybrid” EGR strategies which 

rely upon pressure gradients and EGR pumps may provide pathways for improvement. Other 

components that offer opportunities for improved flow efficiency include cylinder heads, 

ports and exhaust manifolds to further reduce pumping losses. Variable air breathing systems 

such as variable Valve Actuation may provide additional gains at different loads and speeds. 

The NESCCAF/ICCT study indicated up to 1.2% reduction could be achieved solely through 

improved EGR systems. 

2.4.2.4 Engine Parasitic and Friction Reduction

Engine parasitic and friction reduction is another key technical area that can be further 

improved in production moving to 2014 and 2017 time frame. Reduced friction in bearings, 

valve trains, and the piston-to-liner interface will improve efficiency. Friction reduction 

opportunities in the engine valve train and at its roller/tappet interfaces exist for several 

production engines. The piston at its skirt/cylinder wall interface, wrist pin and oil 

ring/cylinder wall interface offers opportunities for friction reduction. Use of more advanced 

oil lubricant that could be available for production in the future can also play a key role in 

reducing friction. Any friction reduction must be carefully developed to avoid issues with 

durability or performance capability. Estimations of fuel consumption improvements due to 

reduced friction range from 0 percent to 2 percent.49 The agencies determined the 

effectiveness of reduced friction and parasitic at 0 to 1.5 percent for 2014 model year and 

beyond. All fuel injection system manufacturers are working hard to reduce parasitic loss due 

to high pressure pumps and common rail flow loss in the hope that those development would 

add up further fuel efficiency improvement.

Incremental manufacturing costs increases associated with the reduction of parasitics 

and friction may include those associated with an optimized, electric water pump, replacing a 

mechanically driven water pump ($100). Additionally, an improved mechanical oil pump 

with more efficient relief mechanism and optimized hydrodynamic design may incur costs 

($5). A fuel pump capable of delivering higher pressures and with efficient regulation may

require improved materials and more elaborate regulating hardware ($5). Improved pistons 

with less friction generated at the skirt may require incrementally more precision in finish 

machine operations ($3). Finally, a more efficient, reduced friction valve train will require 

more precise machining processes and an increased parts count ($90). All costs were 

developed based on EPA’s engineering judgment and are the same as proposal. The costs 

presented here are considered to include a retail price equivalent factor of 1.28.

Removing the 1.28 RPE factor from the above cost estimates and instead applying a 

low complexity ICM of 1.15 results in the following costs: electric water pump, $91; 

improved mechanical oil pump, $5, improved fuel pump, $5; improved pistons, $3; reduced 

friction valve train, $109 for LHDD engines and $82 for HHDD engines. All costs are in 
Regulatory Impact Analysis 

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2009 dollars and are applicable to the 2014MY. Flat-portion of the curve learning is 

considered applicable to all of these costs.

2.4.2.5 Integrated Aftertreatment System

All manufacturers use diesel particulate filter (DPF) to reduce particulate matter (PM). 

All except Navistar rely on SCR to reduce NOx emissions. Periodic regeneration to remove 

loaded soot is required for all DPF. One way is to directly inject the fuel into exhaust stream, 

called active regeneration, and a diesel oxidation catalyst (DOC) or other device then oxidizes 

the fuel in the exhaust stream, providing the heat required for DPF regeneration and 

increasing the fuel consumption of the vehicle. The other method is to use NO2, called 

passive regeneration, to directly react with soot at much lower exhaust temperature than 

active regeneration. Use of advanced thermal management could be made in production to 

eliminate active regeneration, thus significantly improving fuel efficiency. Volvo has 

announced in 2009 that their 2010 DPF+SCR system has eliminated active regeneration for 

on-highway vehicles.50 All other manufacturers using SCR are working in the same direction, 

minimizing or eliminating active regeneration, thus improving fuel economy, providing 

efficiency improvements in the real world, although they are not reflected in the HD engine 

test procedure.

Higher SCR NOx conversion efficiency will allow higher engine-out NOx emissions

(while still meeting the tailpipe NOx standard due to the aftertreatment), and therefore, will 

give more room for engine system optimization, while maintaining the same or even less 

diesel engine fluid (DEF) consumption. Advanced model based control on DEF usage and 

slip can further improve DEF consumption, and thus fuel efficiency. For those manufacturers 

that use SCR as their NOx reduction devices, properly integrated DPF and SCR system is 

essential, which is not only able to improve emissions reductions, but also to improve fuel 

efficiency through more advancing canning design, thus minimizing pressure drop across the

system. Improvements in aftertreatment system efficiency should be technology cost neutral, 

requiring no increases in precious metal loading or manufacturing expense, and only require 

additional development costs. 

The agencies have estimated the cost of additional improvements to the 

aftertreatement system at $25 for each percentage improvement in fuel consumption. This 

estimate is based on the agencies’ belief that this technology is, in fact, a very cost effective 

approach to improving fuel consumption. As such, $25 per percent improvement is 

considered a reasonable cost. This cost would cover the engineering and test cell related costs 

necessary to develop and implement the improved control strategies that would allow for the 

improvements in fuel consumption. Importantly, the engineering work involved would be 

expected to result in cost savings to the aftertreatment and control hardware (lower platinum 

group metal (PGM) loadings, lower reductant dosing rates, etc.). Those savings are

considered to be included in the $25 per percent estimate described here. Given the 4 percent 

expected improvement in fuel consumption results in an estimated cost of $117 (2009$) for a 

2014MY vehicle. This estimate includes a low complexity ICM of 1.15 and flat-portion of 

the curve learning from 2014 forward. Note that this cost is applied only to LHD diesel 

engines. The cost for this technology is considered separately for MHD and HHD diesel 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-37

engines since the cost is considered largely one of research and development which probably 

results in lower actual part cost.

2.4.2.6 Electrification

Many accessories that are traditionally gear or belt driven by a vehicle’s engine can be 

decoupled with the engine speed, so that those accessories can be tailored to a specific engine 

speed reducing parasitic loads, thus producing better efficiency. Examples include the engine 

water pump, oil pump, fuel injection pump, air compressor, power-steering pump, cooling 

fans, and the vehicle’s air-conditioning system. TIAX’s assessment of electrified accessories 

found that they could provide 0 to 3 percent improvement in fuel consumption.51 The most 

tangible development toward production in 2017 time frame would be electric water and oil 

pumps. The agencies expect that about 0.5 to 1.0 percent thermal efficiency improvement 

could be achieved with electrification of these two pumps.

Costs for electrification are considered as part of the costs for improved water and oil 

pumps discussed in Section 2.4.2.4.

2.4.2.7 Waste Heat Recovery

Waste heat recovery uses exhaust gas or other heat sources (such as EGR or coolant) 

from the primary engine to develop additional power. Waste heat recovery systems have other 

names such as bottoming cycle or Rankine cycle. As described in the 2010 NAS report, a 

typical system consists of the following components: a feed pump to drive the working fluid 

from the condenser to the evaporator (or boiler); the evaporator, which transfers waste heat 

energy from the primary engine to the working fluid; an expander, which takes energy from 

the working fluid to make mechanical power; and a condenser that rejects unused heat energy

from the bottoming cycle working fluid before starting a new cycle. TIAX estimated a 12 

kWh waste heat recovery system would cost of $8,400 per truck.52 Such costs include 

necessary power extraction unit and gearbox, heat exchangers and compressor. Alternatively, 

the waste heat recovery system could produce electrical power. This type of system would 

need to be combined with hybridization so that the electrical energy could be stored and used 

directly when needed to supplement engine power. The 2010 NAS report cited two studies 

related to waste heat recovery, as listed below.53

 Cummins has shown a projected increase of thermal efficiency from 49.1 to 

52.9 percent (7.2 percent decrease in fuel consumption) using an organic 

Rankine cycle.54 Cummins reports recovering 2.5 thermal efficiency points 

from the exhaust and 1.3 thermal efficiency points from the coolant and EGR 

stream.

 The NESCCAF/ICCT report showed the effect of a steam bottoming cycle to 

reduce fuel consumption by up to 10 percent. 

The agencies’ assessment of this technology indicates that it currently exists only in 

the research phase and concluded that there is insufficient lead-time between now and 2017 
Regulatory Impact Analysis 

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for this promising technology to be developed and applied generally to all heavy-duty 

engines. TIAX noted in their report to the NAS committee that the engine improvements 

beyond 2015 model year included in their report are highly uncertain, though they include 

Rankine cycle type waste heat recovery as applicable sometime between 2016 and 2020.C 

The Department of Energy, along with industry are both working to develop waste heat 

recovery systems for heavy-duty engines. At the Diesel Engine-Efficiency and Emissions 

Research (DEER) conference in 2010, Caterpillar presented details regarding their waste heat 

recovery systems development effort. In their presentation, Caterpillar clearly noted that the 

work is a research project and therefore does not imply commercial viability.

D

 At the same 

conference, Concepts NREC presented a status of exhaust energy recovery in heavy-duty 

engines. The scope of Concepts NREC included the design and development of prototype 

parts.E Cummins, also in coordination with DOE, is also active in developing exhaust energy

recovery systems. Cummins made a presentation to the DEER conference in 2009 providing 

an update on their progress which highlighted opportunities to achieve a 10 percent engine 

efficiency improvement during their research, but indicated the need to focus their future 

development on areas with the highest recovery opportunities (such as EGR, exhaust, and 

charge air).F Cummins also indicated that future development would focus on reducing the 

high additional costs and system complexity. Based upon the assessment of this information, 

the agencies did not include these technologies in determining the stringency of the final 

standards. However, we do believe the bottoming cycle approach represents a significant 

opportunity to reduce fuel consumption and GHG emissions in the future. 

2.4.2.8 2014 Model Year HHD Diesel Engine Package

The agencies assessed the impact of technologies over each of the SET modes to 

project an overall improvement in the 2014 model year. The agencies considered 

improvements in parasitic and friction losses through piston designs to reduce friction, 

improved lubrication, and improved water pump and oil pump designs to reduce parasitic 

losses. The aftertreatment improvements are available through additional improvements to 

lower backpressure of the systems and further optimization of the engine-out NOx levels. 

Improvements to the EGR system and air flow through the intake and exhaust systems, along 

with turbochargers, can also produce engine efficiency improvements. Lastly, an increase in 

combustion pressures and controls can reduce fuel consumption of the engine. The projected 

impact of each set of these technologies is included in Table 2-7. Based on the 

improvements listed in the table, the overall weighted reduction based on the SET mode 

weightings is projected at 3 percent. It should be pointed out that the improvements listed in 

 

C TIAX Report (2009). Page 4-29.

D Kruiswyk, R. “An Engine System Approach to Exhaust Waste Heat Recovery.” Presented at DOE DEER 

Conference on September 29, 2010. Last viewed on May 11, 2011 at 

http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2010/wednesday/presentations/deer10_kruiswyk.pdf

E Cooper, D,, N. Baines, N. Sharp. “Organic Rankine Cycle Turbine for Exhaust Energy Recovery in a Heavy 

Truck Engine.” Presented at the 2010 DEER Conference. Last viewed on May 11, 2011 at 

http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2010/wednesday/presentations/deer10_baines.pdf

F Nelson, C. “Exhaust Energy Recovery.” Presented at the DOE DEER Conference on August 5, 2009. Last 

viewed on May 11, 2011 at 

http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2009/session5/deer09_nelson_1.pdf
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-39

Table 2-5 are not all additive, meaning that total benefits of individual technologies would not 

be equal to the benefits that are added up by each technology numerically.

Table 2-7: Projected Percent CO2 Impact for SET Modes in 2014 Model Year

SET 

Mode

Speed/% 

Load

Parasitics, 

Friction 

Aftertreatment 

Improvement

Turbocharger, 

Air Handling 

System

Advanced 

Controls, 

Combustion,

&Fuel 

injection

Improvements

1 Idle -0.4 -0.4 -0.8 -0.8

2 A, 100 -0.8 -1.0 -0.8 -0.4

3 B, 50 -1.3 -1.3 -1.5 -2.1

4 B, 75 -0.8 -0.8 -0.8 -0.8

5 A, 50 -1.3 -1.0 -1.5 -2.1

6 A, 75 -0.6 -1.0 -1.3 -1.0

7 A, 25 -0.6 -0.4 -1.3 -1.3

8 B, 100 -0.8 -1.0 -0.8 -0.4

9 B, 25 -0.8 -0.8 -1.3 -1.3

10 C, 100 -0.8 -1.0 -0.8 -0.4

11 C, 25 -0.8 -1.0 -1.3 -0.8

12 C, 75 -1.0 -1.0 -1.0 -0.4

13 C, 50 -1.3 -1.3 -1.3 -0.8

The agencies derived the HHD diesel engine FTP technology effectiveness for the 

2014 model year based on a similar approach. Using the same technologies as discussed for 

the HHD diesel engine SET above, the agencies project the reductions at 3 percent. It should 

be pointed out that individual technology improvement is not additive to each other due to the 

interaction of technology to technology.

The cost estimates for the complete HHD diesel engine packages are shown in Table 

2-8. 

Table 2-8 Technology and Package Costs for HHD Diesel Engines (2009$)

Technology 2014 2015 2016 2017

Cylinder Head $6 $6 $6 $6

Turbo efficiency $18 $18 $17 $17

EGR cooler $4 $4 $3 $3

Water pump $91 $89 $86 $84

Oil pump $5 $4 $4 $4

Fuel pump $5 $4 $4 $4
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Fuel rail $10 $10 $10 $9

Fuel injector $11 $11 $10 $10

Piston $3 $3 $3 $3

Engine Friction Reduction of Valvetrain $82 $80 $78 $76

Turbo-compounding (engines placed in combination tractors only) $0 $0 $0 $875

HHDD Total (vocational truck engines) $234 $228 $222 $216

HHDD Total (combination tractors) $234 $228 $222 $1,091

2.4.2.9 2014 Model Year LHD/MHD Diesel Engine Package

The agencies considered the same 2014 model year technology package developed for 

the HHD diesel engines for the LHD diesel and MHD diesel engines. The package includes 

parasitic and friction reduction, improved lubrication, aftertreatment improvements, EGR 

system and air flow improvements, and combustion pressure increase and controls to reduce 

fuel consumption of the engine. The agencies project that these improvements will produce a 

5 percent reduction in fuel consumption and CO2. 

The cost estimates for the complete MHD diesel engines are shown in 

Table 2-9. The cost estimates for the complete LHD diesel engines are shown in Table 

2-10. 

Table 2-9 Technology and Package Costs for MHD Diesel Engines (2009$)

Technology 2014 2015 2016 2017

Cylinder Head $6 $6 $6 $6

Turbo efficiency $18 $18 $17 $17

EGR cooler $4 $4 $3 $3

Water pump $91 $89 $86 $84

Oil pump $5 $4 $4 $4

Fuel pump $5 $4 $4 $4

Fuel rail $10 $10 $10 $9

Fuel injector $11 $11 $10 $10

Piston $3 $3 $3 $3

Valve train friction reduction $82 $80 $78 $76

Turbo-compounding (engines placed in combination tractors only) $0 $0 $0 $875

MHDD Total (vocational truck engines) $234 $228 $222 $216

MHDD Total (combination tractors) $234 $228 $222 $1,091

Table 2-10 Technology and Package Costs for LHD Diesel Engines (2009$)

Technology 2014 2015 2016 2017

Aftertreatment improvements $117 $114 $111 $108

Cylinder Head $11 $11 $10 $10

Turbo efficiency $18 $18 $17 $17

EGR cooler $4 $4 $3 $3
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Water pump $91 $89 $86 $84

Oil pump $5 $4 $4 $4

Fuel pump $5 $4 $4 $4

Fuel rail $12 $12 $11 $11

Fuel injector $15 $14 $14 $13

Piston $3 $3 $3 $3

Valve train friction reduction $109 $106 $104 $101

LHDD Total $388 $378 $368 $358

2.4.2.10 2014 Model Year Diesel Engine Standards

The agencies applied the 5 percent reduction for the LHDD/MHDD engines and the 3 

percent reduction for the HHD diesel engines based on the projected technology package 

improvements in 2014 model year to the 2010 model year baseline performance included in 

Table 2-6. The results are the final 2014 model year standards (and the equivalent voluntary

fuel consumption standards), as shown in Table 2-11.

Table 2-11: 2014 Model Year Final Standards

LHDD -

FTP

MHDD -

FTP

HHDD -

FTP

MHDDSETHHDD -

SET

CO2 Emissions (g CO2/bhp-hr) 600 600 567 502 475

Fuel Consumption (gal/100 bhphr)5.89 5.89 5.57 4.93 4.67

2.4.2.11 2017 Model Year HHDD Engine Package

The agencies assessed the impact of technologies over each of the SET modes to 

project an overall improvement in the 2017 model year. The agencies considered additional 

improvements in the technologies included in the 2014 model year package in addition to 

turbocompounding. The projected impact of each set of these technologies is included in

Table 2-12. Based on the improvements listed in the table, the overall weighted reduction 

based on the SET mode weightings is projected at 6 percent.

Costs for 2017 are shown in 12.

Table 2-12: Projected CO2 Improvements for SET Modes in 2017 Model Year

SET 

Mode

Speed/% 

Load

Turbocompounding 

with clutch

Parasitics, 

Friction 

Aftertreatment 

Improvement

Turbocharger, 

Air Handling 

System

Advanced Controls, 

Combustion, &Fuel 

injection

Improvements

1 Idle 0.00 -0.5 -0.5 -1.0 -1.0

2 A, 100 -4.50 -1.0 -1.3 -1.0 -0.5
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3 B, 50 -2.50 -1.5 -1.5 -1.8 -2.5

4 B, 75 -4.00 -1.0 -1.0 -1.0 -1.0

5 A, 50 -2.00 -1.5 -1.3 -1.8 -2.5

6 A, 75 -4.00 -0.8 -1.3 -1.5 -1.3

7 A, 25 0.00 -0.8 -0.5 -1.5 -1.5

8 B, 100 -5.00 -1.0 -1.3 -1.0 -0.5

9 B, 25 0.00 -1.0 -1.0 -1.5 -1.5

10 C, 100 -5.00 -1.0 -1.3 -1.0 -0.5

11 C, 25 0.00 -1.0 -1.3 -1.5 -1.0

12 C, 75 -3.00 -1.3 -1.3 -1.3 -0.5

13 C, 50 -2.00 -1.5 -1.5 -1.5 -1.0

The agencies derived the HHDD FTP technology package effectiveness for the 2017 

model year based on a similar approach. However, the addition of turbocompounding shows 

a greater effectiveness on the SET cycle than the FTP cycle because of the steady state nature 

and amount of time spent at higher speeds and loads during the SET. Using the same 

technologies as discussed for the HHDD SET above, the agencies project the reductions at 5 

percent for the FTP. Similar to Table 2-5, individual technology in Table 2-10 is not additive 

to each other due to the interaction of technology to technology.

2.4.2.12 2017 Model Year LHD/MHD Diesel Engine Package

The agencies developed the 2017 model year LHD/MHD diesel engine package based 

on additional improvements in the technologies included in the 2014 model year package. 

The projected impact of these technologies provides an overall reduction of 9 percent over the 

2010 model year baseline.

Costs for the 2017 model year are shown in 

Table 2-9 (MHD) and Table 2-10 (LHD).

2.4.2.13 2017 Model Year Diesel Engine Standards

The agencies applied the 8.6 percent reduction for the LHD/MHD diesel engines and 

the 5 percent reduction for the HHD diesel engines using the FTP and a 6.1 percent reduction 

for HHD diesel engines using the SET based on the projected technology package 

improvements in 2017 model year to the 2010 model year baseline performance included in 

Table 2-6. The results are the final 2014 model year standards (and the equivalent fuel 

consumption standards), as shown in Table 2-13.

Table 2-13 2017 Model Year Final Standards 

LHDD -

FTP

MHDD -

FTP

HHDD -

FTP

MHDDSETHHDD -

SET

CO2 Emissions (g CO2/bhp-hr) 576 576 555 487 460
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Fuel Consumption (gal/100 bhphr)5.66 5.66 5.45 4.78 4.52

2.4.2.14 Optional HD Diesel Engine Phase-in Schedule

The agencies are finalizing an optional phase-in schedule for HD diesel engines which 

aligns with the timing of OBD requirements in 2013 and 2016 model years. The optional 

phase-in schedule requires that engines built in 2013 and 2016 model years achieve greater 

reductions than the engines built in those model years under the primary program, but less 

reduction 2014 and 2015 model year engines. Overall, this phase-in schedule produces an 

equivalent CO2 emissions and fuel consumption reduction as the primary program for the 

engines built in the 2013 through 2017 model year timeframe as shown in Table 2-14 and 

Table 2-15.

Table 2-14: Lifetime CO2 Emissions of Each Model Year Engine Installed in Tractors

HHD SET Engines MHD SET Engines

Primary 

Phase-in 

Standard 

(g/bhp-hr)

Optional 

Phase-in 

Standard 

(g/bhp-hr)

Difference in 

Lifetime CO2

Engine 

Emissions 

(MMT)

Primary 

Phase-in 

Standard 

(g/bhp-hr)

Optional 

Phase-in 

Standard 

(g/bhp-hr)

Difference in 

Lifetime CO2 Engine 

Emissions (MMT)

Baseline 490 490 -- 518 518 --

2013 MY 

Engine 490 485 14 518 512 17

2014 MY 

Engine 475 485 -28 502 512 -28

2015 MY 

Engine 475 485 -28 502 512 -28

2016 MY 

Engine 475 460 42 502 487 42

2017 MY 

Engine 460 460 0 487 487 0

Net Reductions 

(MMT) 0 3

Table 2-15: Lifetime CO2 Emissions Reduction of Each Model Year Engine Installed in Vocational 

Vehicles

HHD FTP LHD/MHD FTP

Primary 

Phase-in 

Standard 

(g/bhp-hr)

Optional 

Phase-in 

Standard 

(g/bhp-hr)

Difference in 

Lifetime CO2

Engine 

Emissions 

(MMT)

Primary 

Phase-in 

Standard 

(g/bhp-hr)

Optional 

Phase-in 

Standard 

(g/bhp-hr)

Difference in 

Lifetime CO2

Engine Emissions 

(MMT)

Baseline 584 584 -- 630 630 --
Regulatory Impact Analysis 

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2013 MY 

Engine 584 577 20 630 618 14

2014 MY 

Engine 567 577 -28 600 618 -22

2015 MY 

Engine 567 577 -28 600 618 -22

2016 MY 

Engine 567 555 34 600 576 29

2017 MY 

Engine 555 555 0 576 576 0

Net 

Reductions 

(MMT)

-3 0

 

2.5 Class 7 and 8 Day Cabs and Sleeper Cabs

The regulatory category for Class 7 and 8 day and sleeper cabs involves nine 

regulatory subcategories. 

Class 7 Day Cab with Low Roof

Class 7 Day Cab with Mid Roof

Class 7 Day Cab with High Roof

Class 8 Day Cab with Low Roof

Class 8 Day Cab with Mid Roof

Class 8 Day Cab with High Roof

Class 8 Sleeper Cab with Low Roof

Class 8 Sleeper Cab with Mid Roof

Class 8 Sleeper Cab with High Roof

The regulatory subcategories differentiate between tractor usages through using 

characteristics of the truck. The technologies considered to reduce fuel consumption and CO2

emissions from tractors can be developed for all of the subcategories. However, the typical 

usage pattern may limit the penetration rate of the technology. For example, aerodynamic 

improvements can reduce the fuel consumption and CO2 emissions of a tractor at high speeds. 

However, this technology could be a detriment to fuel consumption if applied to a tractor 

travelling at low speeds. The agencies discuss technologies, penetration rates, and costs for 

each regulatory subcategory in the sections below.
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2.5.1 Aerodynamics

Up to 25 percent of the fuel consumed by a line-haul truck traveling at highway speeds 

is used to overcome aerodynamic drag forces, making aerodynamic drag a significant 

contributor to a Class 7 or 8 tractor’s GHG emissions and fuel consumption.55 Because 

aerodynamic drag varies by the square of the vehicle speed, small changes in the tractor 

aerodynamics can have significant impacts on GHG emissions and fuel efficiency of that 

vehicle. With much of their driving at highway speed, the benefits of reduced aerodynamic 

drag for Class 7 or 8 tractors can be significant.56

The common measure of aerodynamic efficiency is the coefficient of drag (Cd). The 

aerodynamic drag force (i.e., the force the vehicle must overcome due to air) is a function the 

Cd, the area presented to the wind (i.e., the projected area perpendicular to the direction of 

travel or frontal area), and the cube of the vehicle speed. Cd values for today’s fleet typically 

range from greater than 0.80 for a classic body tractor to approximately 0.58 for tractors that 

incorporate a full package of widely, commercially available aerodynamic features.

2.5.1.1 Challenges of Tractor Aerodynamics

The aerodynamic efficiency of heavy-duty vehicles has gained increasing interest in 

recent years as fuel prices, competitive freight markets, and overall environmental awareness 

has focused owners and operators on getting as much useful work out of every gallon of 

diesel fuel as possible. While designers of heavy-duty vehicles and aftermarket products try

to aerodynamically streamline heavy-duty vehicles, there are some challenges. Foremost is 

balancing the need to maximize the amount of freight that can be transported. For a tractor, 

this often means pulling a trailer that is as tall and as wide as motor safety laws permit, 

thereby presenting a large, drag-inducing area perpendicular to the wind (i.e., projected 

frontal area). As a result, the tractor must also present a relatively large projected frontal area 

to smoothly manage the flow of air along the cab and transition it to trailer. In instances 

where the height of the cab is not properly matched with that of trailer, aerodynamic drag can 

be significantly increased by creating large wakes (when the trailer is much shorter than the 

cab) or presenting a large non-aerodynamic surface (when the trailer is taller than the cab). 

Aerodynamic design must also meet practical and safety needs such as providing for physical 

access and visual inspections of vehicle equipment. Because weight added to the vehicle 

impacts its overall fuel efficiency and GHG emissions and, in some circumstances the amount 

of freight the vehicle can carry, aerodynamic design and devices will sacrifice some benefit to 

overcoming their contribution to the vehicle weight. Aerodynamic designs and devices also 

must balance being as light and streamlined as possible with being durable enough to 

withstand the rigors a working, freight vehicle encounters while traveling or loading and 

unloading. Durability can be a significant concern for cabs designed for specialty 

applications, such as “severe duty” cabs that may operate on unimproved roads. In addition, 

absent mandatory requirements, aerodynamic features for heavy-duty vehicles must appeal to 

the owners and operators. Finally, because the behavior of airflow across the cab (and cab 

and trailer combination) is dependent upon the entire system, it is not possible to make 

inferences about the vehicle’s aerodynamic performance based upon the performance of 
Regulatory Impact Analysis 

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individual components. This can make it difficult to assess the benefit of adding (or 

subtracting) individual aerodynamic features, and can discourage owners and operators from 

adopting aerodynamic technologies. 

2.5.1.2 Technology to Reduce Aerodynamic Drag

Addressing aerodynamic drag in Class 7 and 8 tractors requires considering the entire 

vehicle as a system to include the tractor and trailer. The overall shape can be optimized to 

minimize aerodynamic drag and, in fact, the tractor body must have at least a moderately 

aerodynamic shape (and its relatively smooth flow) to benefit from add-on aerodynamic 

components. Whether integrated into the shape of the tractor body or as an add-on 

component to a generally aerodynamic tractor, there is a wide range of technologies available 

for Class 7 and 8 tractors. Table 2-16 describes several of these potential aerodynamic 

features and components. 

Table 2-16: Technologies to Address Aerodynamic Drag

LOCATION 

ON CAB

TECHNOLOGY 

TYPE

DESIGNED EFFECT

Front Bumper, grill, hood, 

windshield

Minimize pressure created by front of vehicle moving 

ambient air to make way for truck 

Side Fuel tank fairings Reduce surface area perpendicular to wind, minimize 

opportunity to trap airflow, and smooth surface

Top Roof fairings 

(integrated) and wind 

visors (attached)

Transition air to flow smoothly over trailer and 

minimize surface area perpendicular to the wind (for 

tractor and trailer)

Rear Side extending gap 

reducers

Transition air to flow smoothly over trailer and reduce 

entrapment of air in gap between tractor and trailer

Undercarriage Underbelly treatment Manage flow of air underneath tractor to reduce 

eddies and smoothly transition flow to trailer

Accessories Mirrors, signal horns, 

exhaust

Reducing surface area perpendicular to travel and 

minimizing complex shapes that may induce drag

General Active air management Manage airflow by actively directing or blowing air 

into reduce pressure drag

General Advanced, passive air 

management

Manage airflow through passive aerodynamic shapes 

or devices that keep flow attached to the vehicle 

(tractor and trailer)

2.5.1.3 Aerodynamics in the Current Fleet

Aerodynamics in the Class 7 and 8 tractors fleet currently on the road ranges from 

trucks with few modern aerodynamic features, to those that address the major areas of 

aerodynamic drag, to tractors applying more advanced techniques. Because they operate at 

highway speeds less of the time, Class 7 and 8 tractors configured as day cabs (i.e., dedicated 

to regional routes) tend to have fewer aerodynamic features than cabs designed for line-haul 

applications. For tractors, it is useful to consider aerodynamics in the current fleet in terms of 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

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three packages: the “classic” truck body; the “conventional” truck body; and the “SmartWay” 

truck body. 

“Classic” truck body: At the lower end of aerodynamic performance are tractors that 

have a “classic” truck body. These truck bodies prioritize looks or special duty capabilities 

(e.g., clearance, durability on unimproved roads, and visual access to key vehicle

components) and have remained relatively unchanged since the 1970’s. Typical applications 

are logging, waste hauling, and some agricultural related uses. These trucks incorporate few, 

if any, aerodynamic features and several that detract from aerodynamics including equipment 

such as bug deflectors, custom sunshades, air cleaners, b-pillar exhaust stacks, additional 

horns, lights and mirrors. 

“Conventional” truck body: The conventional, modern truck capitalizes on a 

generally aerodynamic shape and avoids classic features that increase drag. The conventional, 

modern truck body has removed extra equipment (e.g., bug deflectors, custom sunshades, 

additional signal horns, decorative lights), moved essential equipment out of the airflow (e.g., 

b-pillar exhaust stacks and air cleaners), and streamlined fixed-position, essential equipment 

(e.g., mirrors, steps, and safety lights).

“SmartWay” truck body: The SmartWay aerodynamic package builds off of the 

aerodynamic package required for a Class 8 sleeper cab high roof tractor to meet the 

SmartWay design specifications and represents the top aerodynamic package that is widely, 

commercially available. The SmartWay package is a fully aerodynamic truck package which 

has an overall streamlined shape, removes drag-inducing features (i.e., those removed or 

moved in conventional, modern truck body), and adds components to reduce drag in the most 

significant areas on the tractor. This includes aerodynamic features at the front to the tractor 

(e.g., streamlined bumper, grill, and hood), sides (i.e., fuel tank fairings and streamlined 

mirrors), top (i.e., roof fairings), and rear (i.e., side extending gap reducers). Regional and 

line-haul applications often employ different approaches, such as removable, rooftop wind 

visors and fully integrated, enclosed roof fairings, respectively, based upon their intended 

operation. 

More advanced aerodynamic features are possible and are the focus of product 

development, pilot and testing projects, and, in some cases, product lines that have seen 

limited fleet adoption. Advanced aerodynamic designs can further optimize the overall shape 

of the tractor and may add other advanced aerodynamic features (e.g., underbody airflow 

treatment, down exhaust, and lowered ride height). Some advanced aerodynamic features, 

including those listed above, show promise but will likely need ongoing refinement as these 

technologies are tailored to specific applications and payback periods are reduced. Fleets 

whose line-haul operations permit are currently testing and using some advanced aerodynamic 

technologies today.

2.5.1.4 Aerodynamic Bins

The agencies have characterized the typical aerodynamic performance (expressed as 

CdA) and cost for select applications. To do so, it was necessary to represent the wide variety 
Regulatory Impact Analysis 

2-48

of tractor aerodynamic shapes – which are a collection of the shapes of the multitude of 

component parts – by developing aerodynamic packages. These are called Bins I, II, III, IV, 

and V. 

Bin I aerodynamic package: As described as a classic truck in section 2.4.1.3, these 

trucks incorporate few, if any, aerodynamic features and several that detract from 

aerodynamics including equipment such as bug deflectors, custom sunshades, air cleaners, bpillar exhaust stacks, additional horns, lights and mirrors may constitute a conventional 

vehicle. No cost for aerodynamics is assumed for this classic package.

Bin II package: As described in section 2.4.1.3 as a conventional tractor this tractor 

capitalizes on a generally aerodynamic shape and avoids classic features that increase drag. 

No cost for aerodynamics is assumed for the conventional package since there has been no 

addition of additional body work and these moderate modifications to the tractor shape would 

not likely require the redesign of other components.

Bin III package: Based upon the design requirements of EPA’s SmartWay Designated 

Tractors, this package has an overall streamlined shape, removes drag inducing features, and 

adds components (i.e., aerodynamic mirrors, side fairings, aerodynamic bumpers, and side 

extending gap reducers) to reduce drag in the most significant areas on the tractor. The Bin 

III aerodynamics package does add some incremental cost above the classic and conventional 

packages.

 Bin IV and Bin V packages: These packages include components similar to that 

found in the SmartWay package but with additional aerodynamic refinement. This can be a 

combination of more sophisticated shape and increased coverage of drag inducing elements. 

Where the Bin IV package represents a tractor using the most advanced aerodynamics 

available today, the Bin V package is designed to represent aerodynamics expected to be 

available in the near future. With more attention paid to aerodynamic performance than the 

conventional package, the Bin IV package is estimated to be slightly more expensive than the 

Bin III package. As a representation of the future aerodynamics, the Bin V package is 

estimated as being 50 percent more expensive than the Bin IV package.

The agencies developed the aerodynamic drag area, CdA, bin values for the tractor 

categories based on coastdown testing conducted by EPA using the enhanced coastdown test 

procedures adopted for the final rule, as described in RIA Chapter 3.2.2.1.3. The agencies 

supplemented these results with the CdA information described in the proposal, which was 

based on a previous EPA coastdown program using slightly different test procedures 

conducted for the proposal and literature surveys. In addition to the absolute CdA values, the 

agencies used the results of a wind tunnel evaluation of aerodynamic components to help 

identify the appropriate width of bins. SAE 2006-01-3456 evaluated aerodynamic 

components on a Class 8 high roof tractor and found that side extenders provide a CdA

reduction of 0.4 and tank and cab skirts provide a CdA reduction of 0.3.57 The agencies 

considered that the results from the earlier test program and literature are based on test 

procedures that are not identical to those adopted for this program, and therefore placed more 

weight on the results from the latest EPA coastdown test program.
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-49

Table 2-17: Tractor CdA Values 

Truck Expected Bin Source CdA (m2)

Class 8 High Roof Sleeper Cab

B-3JM2-2H-TXCR Bin III EPA Test Program 6.4

B-3JM2-4N-TXCR Bin III-IV EPA Test Program 5.7

B-3JM2-2K-TXCR Bin III EPA Test Program 6.3

C-3JM2-1B-TXCR Bin III EPA Test Program 6.2

C-3JE2-1F-TXCR Bin II-III EPA Test Program 6.7

International ProStar Bin III-IV ATDS58 5.3-5.5

Best Aero Truck Bin III DDC Spec Manager 6.0

Full Aero Bin III EPA PERE & 

MOVES Model

5.8

Roof Deflector Bin II EPA PERE & 

MOVES Model

6.4

International 9200i #1 Bin II TRC 7.0

International 9200i #2 Bin II NVFEL 6.9

CE-CERT Bin II EPA PERE & 

MOVES Model

7.3

No Aero Feature Bin I DDC Spec Manager 7.5

Baseline Truck Bin I McCallen, 1999 7.5

Class 8 Day Cab High Roof

B-3XM2-4M-TBCR Bin III EPA Test Program 6.7

International ProStar Bin III ATDS 5.7

Aero Features Bin III SAE 2005-01-3512 6.0

Roof Fairing Only Bin II SAE 2005-01-3512 6.5

Class 8 Sleeper Cab Low Roof

C-4XM7-1C-TGTW Bin II EPA Test Program 4.2

Class 8 Day Cab Low Roof

International ProStar Bin II ATDS 4.7

Class 8 Sleeper Cab Mid Roof

C-3JM3-2K-TGTW Bin II EPA Test Program 5.0

For high roof combination tractor compliance determination, a manufacturer would 

use the aerodynamic results (CdA) determined through testing to establish the appropriate bin, 

as defined in Table 2-18. The manufacturer would then input into GEM the Cd value 

specified for each bin. For example, if a manufacturer tests a Class 8 sleeper cab high roof 

tractor and the test produces a CdA value of 6.2, then the manufacturer would assign this 

tractor to the Class 8 Sleeper Cab High Roof Bin III. The manufacturer would then use the 

Cd value of 0.60 as the input to GEM.

Table 2-18: Aerodynamic Input Definitions to GEM for High Roof Tractors

CLASS 7 CLASS 8

Day Cab Day Cab Sleeper Cab
Regulatory Impact Analysis 

2-50

High Roof High Roof High Roof

Aerodynamic Test Results (CdA in m2)

Bin I ≥ 8.0 ≥ 8.0 ≥ 7.6

Bin II 7.1-7.9 7.1-7.9 6.7-7.5

Bin III 6.2-7.0 6.2-7.0 5.8-6.6

Bin IV 5.6-6.1 5.6-6.1 5.2-5.7

Bin V ≤ 5.5 ≤ 5.5 ≤ 5.1

Aerodynamic Input to GEM (Cd)

Bin I 0.79 0.79 0.75

Bin II 0.72 0.72 0.68

Bin III 0.63 0.63 0.60

Bin IV 0.56 0.56 0.52

Bin V 0.51 0.51 0.47

The CdA values in Table 2-19Error! Reference source not found.Error! Reference 

source not found. are based on testing using the enhanced coastdown test procedures adopted 

for the final rulemaking, which includes aerodynamic assessment of the low and mid roof 

tractors without a trailer. The removal of the trailer significantly reduces the CdA value of 

mid roof tractors with tanker trailers because of the poor aerodynamic performance of the 

tanker trailer. The agencies developed the Cd input for each of the low and mid roof tractor 

bins to represent the Cd of the tractor, its frontal area, and the impact of the Cd value due to 

the trailer such that the GEM value is representative of a tractor-trailer combination, as it is 

for the high roof tractors.

Table 2-19: Aerodynamic Input Definitions to GEM for Low and Mid Roof Tractors

CLASS 7 CLASS 8

Day Cab Day Cab Sleeper Cab

Low Roof Mid Roof Low Roof Mid Roof Low Roof Mid Roof

Aerodynamic Test Results (CdA in m2)

Bin I ≥ 5.1 ≥ 5.6 ≥ 5.1 ≥ 5.6 ≥ 5.1 ≥ 5.6

Bin II ≤ 5.0 ≤ 5.5 ≤ 5.0 ≤ 5.5 ≤ 5.0 ≤ 5.5

Aerodynamic Input to GEM (Cd)

Bin I 0.77 0.87 0.77 0.87 0.77 0.87

Bin II 0.71 0.82 0.71 0.82 0.71 0.82

The agencies have conducted sensitivity analysis of Cd values within GEM to 

determine the effectiveness of aerodynamic technologies, as shown in Figure 2-1. For a Class 

8 sleeper cab with a high roof, the impact of moving from Bin II to Bin III is a 6.5 percent 

reduction in CO2 emissions and fuel consumption.
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-51

Figure 2-1: CO2 Emissions Impact of Coefficient of Drag for a Class 8 Sleeper Cab, High Roof

The agencies estimated the cost of the aerodynamic packages based on ICF’s price 

estimates.59 The agencies applied a 15 percent reduction to the prices to reflect savings due to 

a higher volume production which would be applicable to the tractor manufacturers. 

Although technologies such as roof fairings may already be in widespread use today, the ICF 

study researched retail prices that a consumer would pay for the purchase of a single item in 

addition to researching possible savings based on a large volume manufacturing. In addition, 

the agencies removed an RPE of 1.36 to obtain the direct manufacturer cost and then applied a 

low complexity ICM of 1.18 or a medium complexity ICM of 1.30 (for Bin V) to obtain the 

overall technology costs included in Table 2-20 and Table 2-21. In Table 2-22 and Table 

2-23 the costs are shown including the expected penetration rates which range between 20 

percent and 50 percent for most technologies shown.

Table 2-20 Estimated Aerodynamic Technology Costs for Class 7 & 8 Day Cabs for the 2014MY (2009$)

CLASS 7 DAYCAB CLASS 8 DAYCAB

Low Roof High Roof Low Roof High Roof

Bin I $0 $0 $0 $0

Bin II $0 $0 $0 $0

Bin III $1,126 $1,155 $1,126 $1,155

Bin IV $2,273 $2,303 $2,273 $2,303

Bin V $3,203 $3,245 $3,203 $3,245

-25%

-20%

-15%

-10%

-5%

0%

5%

10%

15%

60

70

80

90

100

110

120

0.4 0.6 0.8 1 1.2

C

O

2

R

ecutio

n (%)

W

eig

hte

d

C

O

2 (g

/to

n -mile)

Cd

Class 8 with high roof sleeper 

CO2 Sensitivity to Cd

Weighted CO2 CO2 Reduction
Regulatory Impact Analysis 

2-52

Table 2-21 Estimated Aerodynamic Technology Costs for Class 8 Sleeper Cabs for the 2014MY (2009$)

LOW ROOF MID ROOF HIGH ROOF

Bin I $0 $0 $0

Bin II $0 $0 $0

Bin III $1,374 $1,404 $1,560

Bin IV $2,601 $2,601 $2,675

Bin V $3,664 $3,664 $3,769

Table 2-22 Estimated Aerodynamic Technology Costs for Class 7 & 8 Day Cabs for the 2014MY Inclusive 

of Penetration Rates (2009$)

CLASS 7 DAYCAB CLASS 8 DAYCAB

Low Roof High Roof Low Roof High Roof

Bin III $675 $693 $675 $693

Bin IV N/A $230 N/A $230

Table 2-23 Estimated Aerodynamic Technology Costs for Class 8 Sleeper Cabs for the 2014MY Inclusive 

of Penetration Rates (2009$)

LOW ROOF MID ROOF HIGH ROOF

Bin II $962 $983 $1,092

Bin IV N/A N/A $535

2.5.2 Tires 

Tire rolling resistance is defined as the energy consumed by the tire per unit of 

distance traveled. Energy is consumed mainly by the deformation of the tires, known as 

hysteresis, but smaller losses are due to aerodynamic drag and other friction forces between 

the tire and road surface and the tire and wheel rim. About 90 percent of a tire’s rolling 

resistance comes from hysteresis. Collectively the forces that result in energy loss from the 

tires are referred to as rolling resistance. The share of truck energy required to overcome 

rolling resistance is estimated at nearly 13 percent for Class 8 trucks.

60

 Reducing a tire’s 

rolling resistance will reduce fuel consumption and lower emissions of CO2 and other 

greenhouse gases. Low rolling resistance tires are commercially available from most tire 

manufacturers. The EPA SmartWay program identified test methods and established criteria 

to designate certain tires as “low rolling resistance” for use in the program’s emissions 

tracking system, verification program, and SmartWay vehicle specifications. Below is a 

discussion of EPA’s approach to quantifying tire rolling resistance and the emission 

reductions associated with reduced rolling resistance, and a discussion of single wide tires, 

retread tires, and replacement tires. 

To measure a tire’s efficiency the vertical load supported by the tire must be factored 

because rolling resistance is a function of the load on a tire. EPA uses a tire’s rolling 

resistance coefficient (RRc), which is measured as the rolling resistance force over vertical 

load (kg/metric ton). The RRc baseline for today’s fleet is 7.8 kg/metric ton for the steer tire 

and 8.2 kg/metric ton for the drive tire, based on sales weighting of the top three 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-53

manufacturers by market share. These values are based on new tires, since rolling resistance 

decreases as the tread wears. 

Beginning in 2007, EPA began designating certain Class 8 sleeper-cab configurations 

as Certified SmartWay Tractors. In order for a tractor to be designated as Certified 

SmartWay, the tractor must be equipped with verified low rolling resistance tires (either dual 

or single wide), among other criteria. In order to be verified as a low rolling resistance tire, a 

steer tire must have a RRc less than 6.6 kg/metric ton and a drive tire must have a RRc less 

than 7.0 kg/metric ton. SmartWay-verified low rolling resistance tires are the best performing 

tires available based on fuel efficiency. The SmartWay program expects to decrease the 

maximum allowable rolling resistance coefficient by 10 percent between 2010 and 2014. As 

more low rolling resistance tires are sold, the baseline rolling resistance coefficient value will 

improve. 

Research indicates the contribution to overall vehicle fuel efficiency by tires is 

approximately equal to the proportion of the vehicle weight on them.

61

 On a fully loaded 

typical Class 8 long-haul truck (tractor and trailer), about 12.5 percent of the total tire energy

loss attributed to rolling resistance is from the steer tires and about 42.5 percent is from the 

drive tires. When evaluating just the tractor, the proportionate amount of energy loss would 

be about 24 percent from the steer tires and 76 percent from the drive tires. 

A tire’s rolling resistance is a factor considered in the design of the tire, and is affected 

by the tread compound material, the architecture of the casing, tread design and the tire 

manufacturing process. Differences in rolling resistance of up to 50 percent have been 

identified for tires designed to equip the same vehicle.

62

 It is estimated that 35 to 50 percent 

of a tire’s rolling resistance is from the tread and the other 50 to 65 percent is from the 

casing.

61

 Tires with increased RRc values are likely designed for treadwear and not fuel 

efficiency.

Research and testing have shown a 5 percent reduction of rolling resistance provides a 

fuel consumption reduction of 1 percent while maintaining similar traction and handling 

characteristics. Bridgestone found a 5 percent improvement in rolling resistance will produce 

a 1.3 to 1.7 percent improvement in fuel economy.

61

 Assuming a truck achieves 6 miles per 

gallon and is driven 100,000 miles annually, a 1.5 percent improvement in fuel economy 

results in a fuel consumption reduction of 1.48 percent, which is in line with EPA’s study. 

According to Bridgestone,

61 use of a fuel-efficient tire, compared to a non-fuel-efficient tire,

will result in approximately a 12 percent improvement in fuel economy at 55 mph, and 9 

percent improvement in fuel economy at 65 mph. 

To further demonstrate the correlation between rolling resistance and fuel economy, 

Michelin modeled vehicle fuel consumption using two drive cycles and various rolling 

resistance values. One drive cycle incorporated several instances of stop and start that 

replicated driving a vehicle on a secondary road; the other drive cycle replicated driving on a 

highway at nearly uniform speed but with several elevation changes. Simulations were 

performed using a base case and for rolling resistance reductions of 10 percent and 20 percent 

for both the secondary roadway and highway drive cycles. Michelin’s simulation modeling 
Regulatory Impact Analysis 

2-54

for the secondary road drive cycle predicts a 1.8 percent and a 3.6 percent improvement in 

fuel economy as a result of the 10 percent and 20 percent reduction in rolling resistance, 

respectively.

6364 The simulation modeling for the highway drive cycle predicts a 2.6 percent 

and a 4.9 percent improvement in fuel economy as a result of the 10 percent and 20 percent 

reduction in rolling resistance, respectively.

63

 The modeling demonstrates less of a benefit 

from reduced rolling resistance when a vehicle is operated on secondary roadways. 

Michelin’s modeling predicts an improvement in fuel economy from a reduction in rolling 

resistance comparable to what Bridgestone demonstrated. A 5 percent reduction in rolling 

resistance results in a 1 percent improvement in fuel economy. 

Proper tire inflation is critical to maintaining proper stress distribution in the tire, 

which reduces heat loss and rolling resistance. Tires with reduced inflation pressure exhibit 

more sidewall flexing and tread shearing, therefore, have greater rolling resistance than a tire 

operating at its optimal inflation pressure. Bridgestone tested the effect of inflation pressure 

and found a 2 percent variation in fuel consumption over a 40 psi range.61 Generally, a 10 psi 

reduction in overall tire inflation results in about a 1 percent reduction in fuel economy.

65

 To 

achieve the intended fuel efficiency benefits of low rolling resistance tires, it is critical that 

tires are maintained at the proper inflation pressure. 

Tire rolling resistance is only one of several performance criteria that affect tire 

selection. The characteristics of a tire also influence durability, traction control, vehicle 

handling and comfort. A single performance parameter can easily be enhanced, but an 

optimal balance of all the criteria must be maintained. Tire design requires balancing 

performance, since changes in design may change different performance characteristics in 

opposing direction.

66

 Truck tires are most often axle-specific in relation to these different 

performance criteria.

67

 The same tire on different axles or used in different applications can 

have a different rolling resistance value. Any changes to a tire would generally be

accompanied with additional changes to suspension tuning and/or suspension design. 

The Center for Transportation Research at Argonne National Laboratory analyzed 

technology options to support energy use projections. The Center estimated the incremental 

cost of low rolling resistance tires of $15 - $20 per tire.

84

 The ICF report estimated the cost of 

low rolling resistance steer and drive tires to be $20 and $43 per tire, respectively. The NAS 

panel estimated $30 per tire. EPA and NHTSA project a cost of $34 per tire or $68 per tractor 

(2009$) for low rolling resistance steer tires (2 per truck) for both Class 7 and 8 tractors 

including a low complexity ICM of 1.18, based on the cost estimates provided by ICF for low 

rolling resistance tires. For low rolling resistance drive tires, the agencies estimate truck-based 

costs of $63 (2009$) and $126 (2009$) for Class 7 and 8 tractors, respectively, including a 

low complexity ICM of 1.18. The higher Class 8 reflects the assumption of one drive axle for 

Class 7 tractors and two drive axles for Class 8 tractors. All costs are considered valid for the 

2014MY and flat-portion of the curve learning would be considered appropriate for this 

technology.

2.5.2.1 Single Wide Tires 

Low rolling resistance tires are offered for dual assembly and as single wide tires. 

They are typically only used on the drive axle of a tractor. A single wide tire is a larger tire 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-55

with a lower profile. The common single wide sizes include 385/65R22.5, 425/65R22.5, 

445/65R22.5, 435/50R22.5 and 445/50R22.5. Generally, a single wide tire has less sidewall 

flexing compared to a dual assembly and therefore less hysteresis occurs. Compared to a dual 

tire assembly, single wide tires also produce less aerodynamic resistance or drag. Single wide 

tires can contribute to improving a vehicle’s fuel efficiency through design as a low rolling 

resistance tire and/or through vehicle weight reduction. 

According to one study, the use of fuel efficient single wide tires can reduce rolling 

resistance by 3.7 to 4.9 percent compared to the most equivalent dual tire.

68

 An EPA study

demonstrated an improvement in fuel economy of 6 percent at 55 mph on the highway, 13 

percent at 65 mph on the highway and 10 percent on a suburban loop69 using single wide tires 

on the drive and trailer axles. EPA attributed the fuel economy improvement to the reduction 

in rolling resistance and vehicle weight reduction from using single wide tires. In 2008 the 

Department of Energy (DOE) compared the effect of different combinations of tires on the 

fuel efficiency of Class 8 trucks. The data collected based on field testing indicates that 

trucks with tractors equipped with single wide tires on the drive axle experience better fuel 

economy than trucks with tractors equipped with dual tires, independent of the type of tire on 

the trailer.

70

 This study in particular indicated a 6.2 percent improvement in fuel economy 

from single wide tires. 

There is also a weight savings associated with single wide tires compared to dual tires. 

Single wide tires can reduce a tractor and trailer’s weight by as much as 1,000 lbs. when 

combined with aluminum wheels. Bulk haulers of gasoline and other liquids recognize the 

immediate advantage in carrying capacity provided by the reduction in the weight of tires and 

have led the transportation industry in retrofitting their tractors and trailers71.

New generation single wide tires, which were first introduced in 2000, are designed to 

replace a set of dual tires on the drive and/or trailer positions. They are designed to be 

interchangeable with the dual tires without any change to the vehicle72. If the vehicle does not 

have hub-piloted wheels, there may be a need to retrofit axle components71. In addition to 

consideration of hub / bearing / axle, other axle-end components may be affected by use of 

single wide tires. To assure successful operation, suitable components should be fitted as 

recommended by the vehicle manufacturer73. 

Current single wide tires are wider than earlier models and legal in all 50 states for a 

5-axle, 80,000 GVW truck68. Single wide tires meet the “inch-width” requirements 

nationwide, but are restricted in certain states up to 17,500 lbs. on a single axle at 500 lbs/inch 

width limit, and are not allowed on single axle positions on certain double and triple 

combination vehicles72. An inch-width law regulates the maximum load that a tire can carry

as a function of the tire width. Typically single wide tires are optimized for highway 

operation and not for city or on/off highway operation. However, newer single wide tires are 

being designed for better scrub resistance, which will allow an expansion of their use. The 

current market share of single wide tires in combination tractor applications is 5 percent and 

the potential market is all combination tractors.68 New generation single wide tires represent 

an estimated 0.5 percent of the 17.5 million tires sold each year in the U.S.72. 
Regulatory Impact Analysis 

2-56

The Center for Transportation Research at Argonne National Laboratory estimated 

incremental capital cost of single wide tires is $30 - $40 per tire.

84

 ICF estimates the 

incremental price of low rolling resistance tires at $20 for drive tires and $43 for steer tires.74 

Based on the ICF estimates, the agencies project the incremental cost would be between $120 

and $160 for four single wide tires replacing eight dual tires on a drive axle of a tractor.

2.5.2.2 Tire Rolling Resistance 

Based on the rolling resistance of today’s tires and the rate of improvement that has 

been made in the recent past, the agencies are projecting the following tire rolling resistance 

performance for setting the final tractor standards, as shown in Table 2-24. 

Table 2-24 Tire Rolling Resistance

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low/

Mid 

Roof

High 

Roof

Low/Mid 

Roof

High 

Roof

Low 

Roof

Mid 

Roof

High 

Roof

Steer Tires (Crr kg/metric ton)

Baseline 7.8 7.8 7.8 7.8 7.8 7.8 7.8

6.6 6.6 6.6 6.6 6.6 6.6 6.6

5.7 5.7 5.7 5.7 5.7 5.7 5.7

Drive Tires (Crr kg/metric ton)

Baseline 8.2 8.2 8.2 8.2 8.2 8.2 8.2

7.0 7.0 7.0 7.0 7.0 7.0 7.0

6.0 6.0 6.0 6.0 6.0 6.0 6.0

Reducing the coefficient of rolling resistance from the baseline scenario of 7.2 kg/metric ton 

to 6.5 kg/metric ton reduces the CO2 emissions and fuel consumption by 3.7 percent, as 

shown in Figure 2-2 below.
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-57

Figure 2-2: Tire Rolling Resistance Impact on CO2 Emissions of a Class 8 Sleeper Cab, High Roof

2.5.3 Weight Reduction 

Mass reduction encompasses a variety of techniques ranging from improved design 

and better component integration to application of lighter and higher-strength materials. Mass 

reduction can be further compounded by reductions in engine power and ancillary systems 

(transmission, steering, brakes, suspension, etc.). Although common on light-duty passenger 

vehicles for fuel economy and performance increases, mass reduction on heavy-duty vehicles 

is more complex due to the size and duty cycle of the vehicles.

Reducing a vehicle’s mass decreases fuel consumption and GHG output by reducing 

the energy demand needed to overcome forces resisting motion, and rolling resistance. 

Passenger vehicle manufacturers employ a systematic approach to mass reduction, where the 

net mass reduction is the addition of a direct component or system mass reduction plus the 

additional mass reduction taken from indirect ancillary systems and components, effectively 

compounding or obtaining a secondary mass reduction from a primary mass reduction. For 

example, use of a smaller, lighter engine with lower torque-output subsequently allows the 

use of a smaller, lighter-weight transmission and drive line components. Likewise, the 

compounded weight reductions of the body, engine and drivetrain reduce stresses on the 

suspension components, steering components, wheels, tires and brakes, allowing further 

reductions in the mass of these subsystems. The reductions in unsprung masses such as 

-20%

-15%

-10%

-5%

0%

5%

10%

15%

60

70

80

90

100

110

3 5 7 9 11

C

O

2

R

e

d

uctio

n (%)

W

eig

hte

d

C

O

2 (g

/to

n -mile)

Weighted Crr (kg/metric ton)

Class 8 with high roof sleeper

CO2 Sensitivity to Crr

Weighted CO2 CO2 Reduction
Regulatory Impact Analysis 

2-58

brakes, control arms, wheels and tires further reduce stresses in the suspension mounting 

points. This produces a compounding ripple effect of possible mass reductions.

A fully loaded tractor-trailer combination can weigh up to 80,000 pounds or more. 

Reduction in overall vehicle weight could enable an increase in freight delivered on a tonmile basis. Practically, this enables more freight to be delivered per truck and improves 

freight transportation efficiency. In certain applications, heavy trucks are weight-limited (i.e. 

bulk cargo carriers), and reduced tractor and trailer weight allows direct increases in the 

quantity of material that can be carried. 

Mass reduction can be accomplished by proven methods such as:

 Smart Design: Computer aided engineering (CAE) tools can be used to better 

optimize load paths within structures by reducing stresses and bending moments 

applied to structures. This allows better optimization of the sectional thicknesses of 

structural components to reduce mass while maintaining or improving the function of 

the component. Smart designs also integrate separate parts in a manner that reduces 

mass by combining functions or the reduced use of separate fasteners. 

 Material Substitution: Substitution of lower density and/or higher strength materials 

into a design in a manner that preserves or improves the function of the component. 

This includes substitution of high-strength steels, aluminum, magnesium or composite 

materials for components currently fabricated from mild steel. Mass reduction 

through material substitution is currently broadly applied across both light- and heavyduty applications in all vehicle subsystems such as aluminum engine block, aluminum 

transmission housing, high-strength steel body structure, etc. 

 Reduced Powertrain Requirements: Reducing vehicle weight sufficiently can allow for 

the use of a smaller, lighter and more efficient engine while maintaining or increasing 

work or cargo requirements. The subsequent reduced rotating mass (e.g., transmission, 

driveshafts/halfshafts, wheels and tires) via weight and/or size reduction of 

components are made possible by reduced torque output requirements.

Reduced mass in heavy-duty vehicles can benefit fuel efficiency and CO2 emissions in 

two ways. If a truck is running at its gross vehicle weight limit with high density freight, more 

freight can be carried on each trip, increasing the truck’s ton-miles per gallon. If the truck is 

carrying lower density freight and is below the GVW (or GCW) limit, the total vehicle mass 

is decreased, reducing rolling resistance and the power required to accelerate or climb grades.

Mass reduction can be achieved by making components with lighter materials (high 

strength steel, aluminum, composites) or by eliminating components from the truck. A 

common component-elimination example is to use single wide tires and aluminum rims to 

replace traditional dual tires and rims, eliminating eight steel rims and eight tires. Although 

many gains have been made to reduce truck mass, many of the features being added to 

modern trucks to benefit fuel economy, such as additional aerodynamic features or idle 

reduction systems, have the effect of increasing truck weight, causing mass to stay relatively 

constant. Material and manufacturing technologies can also play a significant role in vehicle 
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safety by reducing vehicle weight, and in the improved performance of vehicle passive and 

active safety systems. Although new vehicle systems, such as hybrid power trains, fuel cells 

and auxiliary power will present complex packaging and weight issues, this will further 

increase the need for reductions in the weight of the body, chassis, and power train 

components in order to maintain vehicle functionality.

EPA’s SmartWay transport web page discusses how the truck fuel consumption 

increases with the weight of the combination tractor. Many truck components are typically 

made of heavier material, such as steel. Heavier trucks require more fuel to accelerate and to 

climb hills, and may reduce the amount of cargo that can be carried.78 Every 10 percent drop 

in truck weight reduces fuel use about 5 percent.79 Generally, an empty truck makes up about 

one-third of the total weight of the truck. Using aluminum, metal alloys, metal matrix 

composites, and other lightweight components where appropriate can reduce empty truck 

weight (known as “tare weight”), improve fuel efficiency, and reduce greenhouse gas 

emissions. As an example, trimming 3,000 pounds from a heavy truck (about 4 percent of its 

loaded weight) with lighter-weight components could improve fuel economy by up to 3

percent and trucks that employ more weight saving options would save more. In addition, in 

weight-sensitive applications, lightweight components can allow more cargo and increased 

productivity. Another report by the National Commission on Energy Policy estimates that a 

fuel economy gain of 5.0 percent on certain applications could be achieved by vehicle mass 

reduction further illustrating the fuel economy gains possible on heavy-duty applications80. A 

third report, estimated potential reductions in modal GHG emissions are 4.6 percent, however 

also states current light-weight materials are costly and are application and vehicle specific 

with further research and development for advanced materials are needed. 81

In support of the overall goal to cost-effectively enable trucks and other heavy

vehicles to be more energy efficient and to use alternative fuels while reducing emissions, the 

21st Century Truck Partnership seeks to reduce parasitic energy losses due to the weight of 

heavy vehicles without reducing vehicle functionality, durability, reliability, or safety, and to 

do so cost-effectively. Aggressive weight reduction goals vary according to the weight class 

of the vehicle with targets between 10 and 33 percent.82 The weight targets for each vehicle 

class depend on the performance requirements and duty cycle. It is important to note that 

materials or technologies developed for a particular vehicle class are not necessarily limited to 

that class. For example, materials developed for lightweight frames for pickup trucks, vans, or 

SUVs will eventually be used in Class 3-5 vehicles, and materials developed to meet the 

demanding performance requirements for Class 7 and 8 trucks will find application in smaller 

vehicles. Weight reduction must not in any way sacrifice the durability, reliability, and 

performance of the vehicle. Attaining these goals by reducing inertial loading will yield 

substantial benefits such as increased fuel efficiency with concomitant reductions in 

emissions, increased available payload capacity for some vehicles, reduced rolling resistance, 

and optimized safety structures and aerodynamic drag reduction systems. 

A 2009 NESCCAF report evaluated the potential to reduce fuel consumption and CO2 

emissions by reducing weight from the baseline weight of 80,000 pounds. For the purpose of 

this calculation, the weight reduction could come either from carrying lighter freight or from a 
Regulatory Impact Analysis 

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reduction in the empty weight of the truck. If the vehicle mass is reduced to 65,000 pounds, 

the fuel economy improves to 5.9 MPG from 5.4 MPG. The fuel savings and CO2 reduction on 

the baseline vehicle amount to about 0.5 percent per 1,000 pounds of mass reduction.83 This 

result suggests that efforts to reduce the empty vehicle mass will have only a modest benefit 

on fuel economy, for long haul routes. 

Argonne has also simulated the effect of mass reduction on the fuel economy of heavy 

trucks through the National Renewable Energy Laboratory’s Advanced Vehicle Simulator 

Model, ADVISOR. The Argonne simulations relied on a few driving schedules developed by 

the West Virginia University (WVU) because there are no established driving schedules for 

heavy trucks. While simulating a Class 8 truck on the WVU Intercity Driving Schedule, a fuel 

economy gain of 0.6 percent was observed for each 1 percent mass reduction from 65,000 lb 

to 58,000 lb84. The maximum speed during the simulation was 61 mph, and the average 

running speed (excluding stops) was 37.5 mph although most intercity Class 8 trucks average 

a much higher speed than 37.5 mph. Argonne assumed a 0.66 percent increase in fuel 

economy for each 1 percent weight reduction and total possible estimated fuel economy 

increases of 5–10 percent. While simulating a Class 6 truck on a WVU Suburban Driving 

Schedule, a fuel economy gain of 0.48 percent was observed for each 1 percent mass 

reduction from 22,600 lb to 21,800 lb. The maximum speed during the simulation was 44.8 

mph, and the average running speed was 21.5 mph. The potential fuel economy gains for 

medium trucks, both heavy- and light-, were capped at 5 percent since they are less likely to 

be weight or volume limited, and so the use of expensive lightweight material would not be 

cost-effective.

The principal barriers to overcome in reducing the weight of heavy vehicles are 

associated with the cost of lightweight materials, the difficulties in forming and 

manufacturing lightweight materials and structures, the cost of tooling for use in the 

manufacture of relatively low-volume vehicles (when compared to automotive production 

volumes), and ultimately, the extreme durability requirements of heavy vehicles. While lightduty vehicles may have a life span requirement of several hundred thousand miles, typical 

heavy-duty commercial vehicles must last over 1 million miles with minimum maintenance, 

and often are used in secondary applications for many more years. This requires high strength, 

lightweight materials that provide resistance to fatigue, corrosion, and can be economically

repaired. Additionally, because of the limited production volumes and the high levels of 

customization in the heavy-duty market, tooling and manufacturing technologies that are used 

by the light-duty automotive industry are often uneconomical for heavy vehicle 

manufacturers. Lightweight materials such as aluminum, titanium and carbon fiber 

composites provide the opportunity for significant weight reductions, but their material cost 

and difficult forming and manufacturing requirements make it difficult for them to compete 

with low-cost steels. In addition, although mass reduction is currently occurring on both 

vocational and line haul trucks, the addition of other systems for fuel economy, performance 

or comfort increases the truck mass offsetting the mass reduction that has already occurred, 

thus is not captured in the overall truck mass measurement.

Most truck manufacturers offer lightweight tractor models that are 1,000 or more pounds 

lighter than comparable models. Lighter-weight models combine different weight-saving options that 

may include: 85
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 Cast aluminum alloy wheels can save up to 40 pounds each for total savings of 400 pounds

 Aluminum axle hubs can save over 120 pounds compared to ductile iron or steel

 Centrifuse brake drums can save nearly 100 pounds compared to standard brake drums

 Aluminum clutch housing can save 50 pounds compared to iron clutch housing

 Composite front axle leaf springs can save 70 pounds compared to steel springs

 Aluminum cab frames can save hundreds of pounds compared to standard steel frames

2.5.3.1 Derivation of Weight Technology Packages

The agencies see many opportunities for weight reduction in tractors. However, the 

empty curb weight of tractors varies significantly today. Items as common as fuel tanks can 

vary between 50 and 300 gallons each for a given truck model. Information provided by truck 

manufacturers indicates that there may be as much as a 5,000 to 17,000 pound difference in 

curb weight between the lightest and heaviest tractors within a regulatory subcategory (such 

as Class 8 sleeper cab with a high roof). Because there is such a large variation in the 

baseline weight among trucks that perform roughly similar functions with roughly similar 

configurations, there is not an effective way to quantify the exact CO2 and fuel consumption 

benefit of mass reduction using GEM because of the difficulty in establishing a baseline. 

However, if the weight reduction is limited to specific components on the tractor, then both 

the baseline and weight differentials for these are readily quantifiable and well-understood. 

In the NPRM, the agencies proposed basing the standard stringency on a 400 pound 

weight reduction in Class 7 and 8 tractors through the substitution of single wide tires and 

light-weight wheels for dual tires and steel wheels. This approach was taken since there is a 

large variation in the baseline weight among trucks that perform roughly similar functions 

with roughly similar configurations. Because of this, the only effective way to quantify the 

exact CO2 and fuel consumption benefit of mass reduction using GEM is to estimate baseline 

weights for specific components that can be replaced with light weight components. Lightweight wheels are commercially available as are single wide tires and thus data on the weight 

reductions attributable to these two approaches is readily available. 

The agencies received comments on this approach from Volvo, ATA, MEMA, 

Navistar, American Chemistry Council, the Auto Policy Center, Iron and Steel Institute, 

Arvin Meritor, Aluminum Association, and environmental groups and NGOs. Volvo and 

ATA stated that not all fleets can use single wide tires and if this is the case the 400 pound 

weight reduction cannot be met. A number of additional commenters – including American 

Chemistry Council, The Auto Policy Center, Iron and Steel Institute, Aluminum Association, 

Arvin Meritor, MEMA, Navistar, Volvo, and environmental and nonprofit groups – stated 

that manufacturers should be allowed to use additional light weight components in order to 

meet the tractor fuel consumption and CO2 emissions standards. These groups stated that 

weight reductions should not be limited to wheels and tires. Some of the groups asked that 

cab doors, cab sides and backs, cab underbodies, frame rails, cross members, clutch housings, 

transmission cases, axle differential carrier cases, brake drums, and other components be 

allowed to be replaced with light-weight versions. Materials suggested for substitution 

included aluminum, light-weight aluminum, high strength steel, and plastic composites. The 
Regulatory Impact Analysis 

2-62

American Iron and Steel Institute stated there are opportunities to reduce mass by replacing 

mild steel – which currently dominates the heavy-duty industry – with high strength steel. 

In addition, The American Auto Policy Center asked that manufacturers be allowed to 

use materials other than aluminum and high strength steel to comply with the regulations. 

DTNA asked that weight reduction due to engine downsizing be allowed to receive credit. 

Volvo requested that weight reductions due to changes in axle configuration be credited. 

They used the example of a customer selecting a 4 X 2 over a 6 X 4 axle tractor. In this case, 

they assert there would be a 1,000 pound weight savings from removing an axle.

As proposed, many of the material substitutions could have been considered as 

innovative technologies. In response to the above summarized comments, the agencies 

evaluated whether additional materials and components could be used for compliance with the 

tractor weight reduction through the primary program. The agencies reviewed comments and 

data received in response to the NPRM and additional studies cited by commenters. A 

summary of this review is provided in the following paragraphs.

TIAX, in their report to the NAS, cited information from Alcoa identifying several 

mass reduction opportunities from material substitution in the tractor cab components which 

were similar to the ones identified by the Aluminum Association in their comments to this 

rulemaking.G TIAX included studies submitted by Alcoa showing the potential to reduce the 

weight of a tractor-trailer combination by 3,500 to 4,500 pounds.86 In addition, the 

Department of Energy has several projects underway to improve the freight efficiency of 

Class 8 trucks which provide relevant data:87 DOE reviewed prospective lightweighting 

alternative materials and found that aluminum has a potential to reduce mass by 40 to 60 

percent, which is in line with the estimates of mass reductions of various components 

provided by Alcoa, and by the Aluminum Association in their comments and as cited in the 

TIAX report. These combined studies, comments, and additional data provided information 

on specific components that could be replaced with aluminum components.

With regard to high strength steel, the Iron and Steel Institute found that the use of 

high strength steel can reduce the weight of light duty trucks by 25 percent.88 Approximately

10 percent of this reduction results from material substitution and 15 percent from vehicle redesign. While this study evaluated light-duty trucks, the agencies believe that a similar 

reduction could be achieved in heavy-duty trucks since the reductions from material 

substitution would likely be similar in heavy-trucks as in light-trucks. U.S. DOE, in the 

report noted above, identified opportunities to reduce mass by 10 percent through high 

strength steel.89 This study was also for light-duty vehicles.

The agencies considered other materials such as plastic composites and magnesium 

substitutes but were not able to obtain weights for specific components made from these 

materials. We have therefore not included components made from these materials as possible 

 

G TIAX. 2009. Pages 4-62 through 4-64. 
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substitutes in the primary program, but they may be considered through the innovative 

technology provisions. We may consider including these materials as part of the technology

package on which standard stringency is predicated in a subsequent regulation if data 

becomes available. 

The agencies also evaluated the potential of plastic composites and magnesium 

components to reduce heavy-duty vehicle weight. The agencies were not able to obtain 

weights for specific components made from these materials. 

Based on this analysis, the agencies developed an expanded list of weight reduction 

opportunities for the final rulemaking, as listed inTable 2-25. The list includes additional 

components, but not materials, from those proposed in the NPRM. For high strength steel, 

the weight reduction value is equal to 10 percent of the presumed baseline component weight, 

as the agencies used a conservative value based on the DOE report. We recognize that there 

may be additional potential for weight reduction in new high strength steel components which 

combine the reduction due to the material substitution along with improvements in redesign, 

as evidenced by the studies done for light duty vehicles. In the development of the high 

strength steel component weights, we are only assuming a reduction from material 

substitution and no weight reduction from redesign, since we do not have any data specific to 

redesign of heavy-duty components nor do we have a regulatory mechanism to differentiate 

between material substation and improved design. We are finalizing for wheels that both 

aluminum and light weight aluminum are eligible to be used as light-weight materials. Only

aluminum can be used as a light-weight material for other components. The reason for this is 

data was available for light weight aluminum for wheels but was not available for other 

components.

The agencies received comments on the proposal from the American Chemistry

Council highlighting the role of plastics and composites in heavy-duty vehicles. As they

stated, composites can be low density while having high strength and are currently used in 

applications such as oil pans and buses. The DOE mass reduction program demonstrated for 

heavy vehicles proof of concept designs for hybrid composite doors with an overall mass 

savings of 40 percent; 30 percent mass reduction of a hood system with carbon fiber sheet 

molding compound; 50 percent mass reduction from composite tie rods, trailing arms, and 

axles; and superplastically formed aluminum body panels.90 While the agencies recognize 

these opportunities, we do not believe the technologies have advanced far enough to quantify

the benefits of these materials because they are very dependent on the actual composite 

material. The agencies may consider such lightweighting opportunities in future actions, but 

are not including them as part of the technology package underlying the tractor standard. 

Manufacturers which opt to pursue composite and plastic material substitutions may pursue 

credits through the innovative technology provisions.

With regard to Volvo’s request that manufacturers be allowed to receive credit for 

trucks with fewer axles, the agencies recognize that truck options exist today which have less 

mass than other options. However, we believe the decisions to add or subtract such 

components will be made based on the intended use of the vehicle and not based on a 
Regulatory Impact Analysis 

2-64

crediting for the mass difference in our compliance program. It is not our intention to create a 

tradeoff between the right truck to serve a need (e.g. one with more or fewer axles) and

compliance with our final standards. Therefore, we are not including provisions to credit (or 

penalize) vehicle performance based on the subtraction (or addition) of specific vehicle 

components configuration containing dual tires with steel wheels. 

The agencies continue to believe that the 400 pound weight target is appropriate for 

setting the final combination tractor CO2 emissions and fuel consumption standards. The 

agencies agree with the commenter that 400 pounds of weight reduction without the use of 

single wide tires may not be achievable for all tractor configurations. The agencies have 

extended the list of weight reduction components in order to provide the manufacturers with 

additional means to comply with the combination tractors and to further encourage reductions 

in vehicle weight. The agencies considered increasing the target value beyond 400 pounds 

given the additional reduction potential identified in the expanded technology list; however, 

lacking information on the capacity for the industry to change to these light weight 

components across the board by the 2014 model year, we have decided to maintain the 400 

pound target. The agencies intend to continue to study the potential for additional weight 

reductions in our future work considering a second phase of truck fuel efficiency and GHG 

regulations.

Table 2-25: Weight Reductions

WEIGHT REDUCTION TECHNOLOGY WEIGHT REDUCTION

(LB PER TIRE/WHEEL)

Single Wide Drive

Tire with ...

Steel Wheel 84

Aluminum Wheel 139

Light Weight 

Aluminum Wheel

147

Steer Tire or Dual 

Wide Drive Tire with 

...

High Strength Steel 

Wheel

8

Aluminum Wheel 21

Light Weight 

Aluminum Wheel

30

Weight Reduction Technologies AluminumWeight 

Reduction (lb.)

High Strength Steel 

Weight Reduction (lb.)

Door 20 6

Roof 60 18

Cab rear wall 49 16

Cab floor 56 18

Hood Support Structure 15 3

Fairing Support Structure 35 6

Instrument Panel Support Structure 5 1

Brake Drums – Drive (4) 140 11

Brake Drums – Non Drive (2) 60 8

Frame Rails 440 87

Crossmember - Cab 15 5
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Crossmember – Suspension 25 6

Crossmember – Non Suspension (3) 15 5

Fifth Wheel 100 25

Radiator Support 20 6

Fuel Tank Support Structure 40 12

Steps 35 6

Bumper 33 10

Shackles 10 3

Front Axle 60 15

Suspension Brackets, Hangers 100 30

Transmission Case 50 12

Clutch Housing 40 10

Drive Axle Hubs (8) 160 4

Non Drive Front Hubs (2) 40 5

Driveshaft 20 5

Transmission/Clutch Shift Levers 20 4

EPA and NHTSA are specifying the baseline vehicle weight for each regulatory

vehicle subcategory (including the tires, wheels, frame, and cab components) in GEM in 

aggregate based on weight of vehicles used in EPA’s aerodynamic test program, but allow 

manufacturers to specify the use of light-weight components. GEM then quantifies the 

weight reductions based on the pre-determined weight of the baseline component minus the 

pre-determined weight of the component made from light-weight material. Manufacturers 

cannot specify the weight of the light-weight component themselves, only the material used in 

the substitute component. The agencies assume the baseline wheel and tire configuration 

contains dual tires with steel wheels, along with steel frame and cab components, because 

these represent the vast majority of new vehicle configurations today. The weight reduction 

due to replacement of components with light weight versions will be reflected partially in the 

payload tons and partially in reducing the overall weight of the vehicle run in GEM. The 

specified payload in GEM will be set to the prescribed payload plus one third of the weight 

reduction amount to recognize that approximately one third of the truck miles are travelled at 

maximum payload, as discussed below in the payload discussion. The other two thirds of the 

weight reduction will be subtracted from the overall vehicle weight prescribed in GEM. The 

impact of vehicle mass reductions on a Class 8 combination tractor modeled in GEM over the 

composite test cycle is shown in Figure 2-3. The figure depicts both the weighted CO2 results 

and the percent CO2 reduction for a sample Class 8 combination tractor at various weight 

reduction levels.
Regulatory Impact Analysis 

2-66

Figure 2-3: Weight Reduction Impact on Combination Tractor

The agencies have estimated costs for the wheel and tire weight reduction

technologies. Those costs are shown in Table 2-26. The costs shown include a low 

complexity ICM of 1.18 and flat-portion of the curve learning would be considered 

appropriate for these technologies.

Table 2-26 Estimated Weight Reduction Technology Costs for Class 7 & 8 Tractors for the 2014MY 

(2009$)

CLASS 7 TRACTORS CLASS 8 TRACTORS

Single Wide Tire (per tractor) $336 $672

Aluminum Steer Wheel $546 $546

Aluminum Wheels - dual $1,637 $2,727

Aluminum Wheel – Single wide $654 $1,308

Weight reductions will be reflected in GEM in two parts. The reason for evaluating the 

impact of weight reduction in this way is because weight reduction is most effective in trucks 

that are at maximum payload. Weight reduction in trucks at maximum payload allows the 

truck to carry additional freight. This additional freight reduces the fuel consumption on a 

ton-mile basis to a much greater extent than does reducing the weight of the truck alone. The 

agencies estimated that one tire of truck miles are travelled at maximum payload. For this 

assessment, the agencies assumed the overall mass of the vehicle will be reduced by an 

amount equal to two-thirds of the mass reduction to account for the vehicles miles which are 

travelled at less than maximum payload. Second, the specified payload will be increased by

the weight reduction amount discounted by two thirds to recognize that approximately one 

third of the truck miles are travelled at maximum payload. 

0.0%

0.2%

0.4%

0.6%

0.8%

1.0%

88.6

88.8

89.0

89.2

89.4

89.6

0 200 400 600 800 1000

C

O

2

REd

uctio

n (%)

W

eig

hte

d

C

O

2 (g

/to

n -mile)

Weight Reduced (lb)

Weight Reduction Impact 

on Class 8 Combination Truck

Weighted CO2 CO2 Reduction
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2.5.4 Extended Idle 

Class 8 heavy-duty diesel truck extended engine idling expends significant amounts of 

fuel in the United States. Department of Transportation regulations require a certain amount 

of rest for a corresponding period of driving hours, as discussed in Chapter 1. Extended idle 

occurs when Class 8 long haul drivers rest in the sleeper/cab compartment during rest periods 

as drivers find it more convenient and economical to rest in the truck cab itself. In many 

cases it is the only option available. During this rest period a driver will generally idle the 

truck in order to provide heating or cooling or run on-board appliances. During rest periods 

the truck’s main propulsion engine is running but not engaged in gear and it remains in a 

stationary position. In some cases the engine can idle in excess of 10 hours. During this 

period of time, fuel consumption will generally average 0.8 gallons per hour.91 Average 

overnight fuel usage would exceed 8 gallons in this example. When multiplied by the number 

of long haul trucks without idle control technology that operate on national highways on a 

daily basis, the number of gallons consumed by extended idling would exceed 3 million 

gallons per day. Fortunately, a number of alternatives (idling reduction technologies) are 

available to alleviate this situation. 

2.5.4.1 Idle Control Technologies

Idle reduction technologies in general utilize an alternative energy source in place of 

operating the main engine. By using these devices the truck driver can obtain needed power 

for services and appliances without running the engine. A number of these devices attach to 

the truck providing heat, air conditioning, or electrical power for microwave ovens, 

televisions, etc. 

The idle control technologies (along with their typical hourly fuel rate) available today

include the following:92

 Auxiliary Power Unit (APU) powers the truck’s heating, cooling, and electrical 

system. The fuel use of an APU is typically 0.2 gallons per hour.

 Fuel Operated Heater (FOH) provides heating services to the truck through 

small diesel fired heaters. The fuel use is typically 0.04 gallons per hour.

 Battery Air Conditioning Systems (BAC) provides cooling to the truck.

 Thermal Storage Systems provide cooling to trucks.

Another alternative involves electrified parking spaces (EPS), with or without 

modification to the truck. An EPS system operates independently of the truck’s engine and 

allows the truck engine to be turned off as the EPS system supplies heating, cooling, and 

electrical power. The EPS system provides off-board electrical power to operate either:
Regulatory Impact Analysis 

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1. A single system electrification which requires no on-board equipment by providing 

an independent heating, cooling, and electrical power system, or 

2. A dual system which allows driver to plug in on-board equipment.

In the first case, power is provided to stationary equipment that is temporarily attached 

to the truck. In the second, the truck is modified to accept power from the electrical grid to 

operate on-board truck equipment. The retail price of idle reduction systems varies depending 

on the level of sophistication. For example, on-board technologies such as APUs can retail for 

over $7,000 while options such as EPS require negligible up-front costs for equipment for the 

truck itself, but will accrue fees with usage.5

2.5.4.2 CO2 Emissions and Fuel Consumption Idle Reduction Benefit 

CO2 emissions and fuel consumption during extended idling are significant 

contributors to emissions and fuel consumption from Class 8 sleeper cabs. The federal test 

procedure does evaluate idle emissions and fuel consumption as part of the drive cycle and 

related emissions measurement. However, long duration extended idle emissions and fuel 

consumption are not fully represented during the prescribed test cycle. To address the fact 

that real-world fuel and emissions savings can occur with idle reduction technologies that 

cannot be reflected on the test cycle, the agencies are adopting a credit mechanism for 

manufacturers who provide for idle control using an automatic engine shutdown (AES) 

system on the tractor. This credit recognizes the CO2 reductions and fuel consumption 

savings attributed to idle control systems and allows truck manufacturers flexibility in product 

design and performance capabilities, compared to an alternative where the agencies would 

allow credits for specific idle control technologies. 

For a manufacturer to qualify for the credit, the agencies are requiring that a truck 

have an automatic engine shutdown system enabled at time of purchase that shuts off the 

engine after five minutes of idling when it is in a parked position. To provide power while the 

engine is off, truck owners can obtain additional verified idle reduction technologies (IRT) on 

a new truck at the time of purchase from the manufacturer or install verified technology after 

purchase. This approach also allows for operational strategies such as electrified parking 

spaces, team drivers, and overnights spent in hotels to achieve real-world reductions of idling 

emissions and fuel consumption, while being assured through a tie-back to a verifiable 

technology - engine shutdown. With an AES system, it is reasonable to assume that one or 

several of the idle control technologies described above will also be employed in order to 

allow the driver to rest in the truck during the mandated rest periods.

The idle reduction credit value is based on the CO2 emission and fuel consumption 

reduction from the technology when compared to main engine idling, as shown in Table 2-27. 

The agencies assume that the main engine consumes approximately 0.8 gal/hr during idling.93 

ACEEE argued that the agencies should use a fuel consumption rate of 0.47 gallon/hour for 

main engine idling based on a paper written by Kahn. MEMA argued that the agencies 

should use a main engine idling fuel consumption rate of 0.87 gal/hr, which is the midpoint of 

a DOE calculator reporting fuel consumption rates from 0.64 to 1.15 gal/hr at idling

conditions, and between 800 and 1200 rpm with the air conditioning on and off, respectively. 

Having reviewed these comments and the sources provided, the agencies continue to believe 
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that 0.8 gal/hr is the best estimate for a main engine idling fuel consumption rate. In the Kahn 

paper cited by ACEEE, the author states that while idling fuel consumption is 0.47 gal/hr on 

average for 600 rpm, CO2 emissions increase by 25 percent with A/C on at 600 rpm, and 

increase by 165 percent between 600 rpm and 1,100 rpm with A/C on.94 In addition, the 

presentation by Gaines, which is also mentioned, provides idling fuel consumption rates 

ranging between 0.6 and 1.2 gallon/hour. Drivers typically idle at speeds greater than 600 

rpm for heating or cooling, to provide power for accessories such as interior lights, and 

protect the engine from damage. Finally, both the Gaines study and the NAS report cited in 

the RIA use 0.8 gallon/hour. Therefore, the agencies are adopting a main engine idle fuel 

consumption rate of 0.8 gallon/hour. Using a factor of 10,180 grams of CO2 per gallon of 

diesel fuel, the CO2 emissions from the main engine at idle is 8,144 g per hour. 

The agencies assumed the average Class 8 sleeper cab spends 1,800 hours in extended 

idle per year to determine the idling emissions per year.95 MEMA recommended using 2,500 

hours per year for APU operation, citing the SmartWay website which uses 2,400 hours per 

year (8 hours per day and 300 days per year), and an Argonne study which assumed 7 hours 

per day and 303 days per year, which equals 2,121 hours per year. MEMA also cited the 

FMCSA 2010 driver guidelines, which reduce the number of hours driven per day by one to 

two hours, which would lead to 2,650 to 2,900 hours per year in total.

The agencies reviewed these and other studies to quantify idling operation. The 2010 

NAS study assumes between 1,500 and 2,400 idling hours per year.96 Gaines uses 1,800 

hours per year.97 Brodrick, et al. assumes 1,818 hours per year (6 hours per day for 303 days 

per year) based on an Argonne study and Freightliner fleet customers.98 An EPA technical 

paper states between 1,500 and 2,400 hours per year.99 Kahn uses 1,830 hours as the baseline 

extended idle case.100 Based on the literature, the agencies are finalizing as proposed the use

of 1,800 hours per year as reasonably reflecting the available range of information.

The agencies then assumed the average Class 8 sleeper cab travels 125,000 miles per 

year (500 miles per day and 250 days per year) and carries 19 tons of payload (the 

standardized payload finalized for Class 8 tractors) to calculate the baseline emissions as 6.2 

grams of CO2 per ton-mile. The agencies proposed that the fuel consumption of a dieselfueled APU would be used to quantify the fuel consumption and CO2 emissions reduction of 

engines using an AES. The agencies assumed APUs consume approximately 0.2 gallon of 

diesel fuel per hour.101 ACEEE argued that the agencies should use a fuel rate of 0.23 

gal/hour for the APU (based on Gaines presentation). In response, the agencies reviewed the 

NAS study which lists 12 APUs and their associated fuel consumption, which ranged between 

0.04 and 0.40 gal/hour. The average in the NAS report is 0.2 gal/hour.102 Due to the range of 

fuel consumption of APUs and the precision of the available test information, the agencies are 

finalizing as proposed an APU fuel consumption of 0.2 gal/hr, which is consistent with 

ACEEE’s comment. 

The CO2 emissions from the APU equate to 1.5 grams per ton-mile. Therefore, the 

agencies are finalizing an idle reduction credit of 5 g CO2 per ton-mile (0.5 gal/1,000 tonmile) which represents the difference in emissions and fuel consumption between the main 
Regulatory Impact Analysis 

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engine idling and operation of an APU. Credits are based on the requirement that all Class 8 

sleeper cabs shall be equipped with an automatic engine shutdown. The credit reflects a 

technology’s fuel consumption in conjunction with a shutdown. 

Table 2-27: Idle Emissions Reduction Calculation

The agencies are finalizing an approach that allows manufacturers to provide an AES 

with a limited life to address concerns about resale value of trucks with an automatic engine 

shutoff. EMA/TMA specifically requested that manufacturers be allowed to program an 

“expiration date”, based on time or mileage, into the AES feature, after which it could be 

reprogrammed. EMA/TMA argued that the extended idle reduction technologies must have 

features that can be modified for unforeseen uses in the secondary market. EMA/TMA also 

requested that GEM be updated to accommodate an expiration date and its associated impact 

of emission reductions. As part of this provision, the agencies will discount the value of the 

AES based on the number of miles in which it is preset relative to the lifetime of the tractor. 

The agencies calculated the lifetime miles of a combination tractor based on EPA’s MOVES 

model as 1,258,788 miles. The lifetime value is weighted to take into account the survival 

rate of heavy-duty trucks, as shown in Table 2-28.

Table 2-28: Lifetime Miles of 2015 MY Combination Tractor 

AGE COMBINATION TRACTOR VMT 

PER YEAR

1 130,832 

2 119,001 

3 108,164 

4 97,441 

5 87,476 

6 78,930 

7 70,940 

8 63,474 

9 56,865 

10 50,887 

11 45,567 

12 40,906 

13 36,679 

14 32,876 

Idle Fuel 

Consumption 

(gal/hour)

Idle CO2

emissions 

per hour

Idle 

Hours 

per 

Year

Idle CO2

Emission 

per year 

(grams)

Miles 

Per 

Year

Payload 

(tons)

GHG 

Emissions 

Due to 

Idling 

(g/tonmile)

GHG 

Reduction 

(g/tonmile)

Fuel 

Consumption 

Reduction 

(gal/1,000 

ton-mile)

Baseline 0.8 8,144 1,800 14,659,200 125,000 19 6.2

Idle 

Reduction 

Technology

0.2 2,036 1,800 3,664,800 125,000 19 1.5 5 0.5
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2-71

15 29,406 

16 26,408 

17 23,657 

18 21,230 

19 18,977 

20 17,013 

21 15,221 

22 13,679 

23 12,232 

24 10,927 

25 9,764

26 8,718 

27 7,785 

28 6,966 

29 6,233 

30 5,562 

The equation to derive the GEM input for IRT for systems with an AES expiration is 

shown in Equation 2-1.

Equation 2-1: Discounted IRT Equation for GEM Input

GEM IRT Input = 5 g CO2/ton-mile * (miles at expiration / 1,259,000 miles)

2.5.4.3 Automatic Engine Shutdown Overrides

The agencies explained in the proposal that we were unaware of reasons why extended 

idle reduction technologies could not be applied to all tractors with sleeper cabs, but 

welcomed comments. The agencies received comments from ATA, DTNA, EMA/TMA, 

Cummins, TRALA and CARB, generally in support of the AES technology but with strong 

concerns that override capabilities must be allowed to address safety, emergency, servicing 

and maintenance issues. Upon consideration of these comments, the agencies are adopting six

override provisions . The California Air Resources Board (CARB) currently has an antiidling rule for all medium-and heavy-duty vehicles, with several override provisions.103

 The 

agencies find that four of CARB’s override provisions are appropriate for the scope of this 

program – addressing long-term idling of Class 8 sleeper cab tractors - and are adopting 

similar provisions in this final HD National Program. CARB’s anti-idling rule allows 

overrides for four of the situations named below: regeneration, engine/vehicle servicing, low 

coolant temperature and PTO operation. In addition, the agencies are adopting two override 

provisions that are not from CARB’s rule: low battery state-of-charge and extreme ambient 

temperatures; which were requested by several of the industry commenters listed above.

The stringency of the final HD rules is predicated on all Class 8 sleeper cab tractors

employing AES to reduce long-term idling of the main engine during mandated driver rest 

periods. The amount of reduced emissions and fuel savings by employing this IRT is 
Regulatory Impact Analysis 

2-72

described above, and presumes a default value based on the use of a diesel APU in lieu of 

main engine idle. While not mandating any IRT beyond the AES, the agencies anticipate an 

appropriate device or system would typically be installed as needed to provide an alternate 

source of power while the main engine is off, for the comfort and safety of the driver during 

mandated rest periods. As described above and in the preamble in Section III.A.2, truck 

manufacturers may obtain the AES credit without identifying an alternate power source. 

Having considered this issue further in response to comments, the agencies believe that the 

override provisions adopted in the final rules are necessary because they prevent undesirable 

engine operation, provide for service, maintenance or inspections, and protect driver safety 

should a tractor not have an alternate power source, or an adequate one for extreme 

conditions.

Two of the final override provisions requested by ATA, DTNA and EMA/TMA allow

the automatic shutdown to be delayed for reasons related to engine servicing: when an 

exhaust emission control device undergoes regeneration, and when the engine/vehicle is 

undergoing servicing, maintenance or inspection. It is expected that the duration of each 

instance of these events would typically range from 30 to 60 minutes. It is not known 

whether or how often a regeneration event would occur during a driver rest period, as the 

frequency of these events depends on driving patterns and manufacturer settings. Nonetheless, 

regeneration and engine/vehicle servicing are both activities during which the agencies 

recognize that an automatic shutdown would be undesirable. 

In response to comments received from EMA/TMA the agencies are adopting an AES 

override in the case that the vehicle’s main battery state-of-charge is too low to restart the 

engine. In the event that the battery is drained excessively while the engine is off, and a 

backup battery is not functioning, the agencies recognize that allowing override of the AES 

may assist a driver in such an emergency situation. A main engine may be unable to start if 

its battery state of charge falls below a specified threshold. The agencies are aware that 

manufacturers already do program the engine controller to recognize a low battery situation 

and provide alerts or other signals as warranted. This override simply allows the main engine 

to idle temporarily if a backup system is not available to provide this power.

Another override that the agencies are adopting is for extreme ambient temperatures, 

which was also requested by commenters including ATA, DTNA, EMA/TMA, Cummins and 

TRALA. In the case where the cabin temperature cannot be maintained within a reasonable 

range due to extreme hot or cold ambient conditions, this provision will allow main engine 

idle for cabin heating or cooling purposes. If there is no auxiliary heating or cooling system 

installed, or if it is inadequate or fails, the agencies recognize that allowing override of the 

AES may assist in providing for driver safety, and possibly avoid adverse health impacts from 

unreasonable cabin conditions in unexpected situations. The agencies have not found 

regulations defining or governing acceptable tractor cabin or sleeper berth temperatures.104 In

general, temperatures below 50 degrees F can result in impaired dexterity. Temperature is not 

the sole indicator of unreasonable conditions, since environmental effects such as humidity

and solar radiation, and individual conditions such as weight, cardiovascular health, and 

clothing also contribute to the safety of an individual.105 Tractors with “arctic” packages are 

available on the market, with insulation properties that reduce demand from heating and 

cooling sources. Nonetheless, the agencies recognize that our rules do not specify cab design, 
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nor do they mandate an auxiliary power source. Preliminary testing indicates that some 

devices may have trouble cooling or heating the cabin to the desired temperature for a 

duration of 10 hours with ambient temperatures at 100 or zero degrees F, respectively.

106

 

Thus, this override allows the main engine to idle if an auxiliary system is not able to provide 

needed heating or cooling.

The fifth override provision adopted is for the case where the engine coolant 

temperature is too low to protect the engine. ATA commented that this is one of the 

flexibilities the agencies should consider. Manufacturers specify acceptable temperature 

ranges for engine coolants, which if not heated sufficiently, may be too viscous to properly 

circulate. With engine block heaters and insulated lines, coolant temperature is normally

maintained within acceptable levels, often above 60 degrees C (140 degrees F). The agencies 

are adopting this AES override for low coolant temperature, in the case that the main engine 

must be allowed to idle according the manufacturer's engine protection guidance. The 

agencies expect this provision will be effectuated rarely, and the duration of main engine idle 

will be short for each instance, with coolant temperatures rising quickly to acceptable 

levels.107

The sixth override provision adopted is for the case where the main engine must idle 

to operate a power take-off. ATA commented that this is one of the flexibilities the agencies 

should consider. The agencies understand that certain sleeper cab Class 8 tractors employ a 

power take-off to perform work such as pumping liquid cargo or tipping a container, or for 

cargo refrigeration. This override is offered because the fuel and emissions reductions 

targeted in this program are primarily those from extended idle during mandated driver rest 

periods, rather than periods performing useful work.

2.5.5 Vehicle Speed Limiters 

As discussed above, the power required to move a vehicle increases as the vehicle 

speed increases. Travelling at lower speeds provides additional efficiency to the vehicle 

performance. Most vehicles today have the ability to electronically control the maximum 

vehicle speed through the engine controller. This feature is used today by fleets and owners 

to provide increased safety and fuel economy. Currently, these features are designed to be 

able to be changed by the owner and/or dealer. 

The impact of this feature is dependent on the difference between the governed speed 

and the speed that would have been travelled, which is dependent on road type, state speed 

limits, traffic congestion, and other factors. The agencies will be assessing the benefit of a 

vehicle speed limiter by reducing the maximum drive cycle speed on the 65 mph Cruise mode 

of the cycle. The maximum speed of the drive cycle is 65 mph, therefore any vehicle speed 

limit with a setting greater than this will show no benefit for purposes of these regulations, but 

may still show benefit in the real world in states where the interstate truck speed limit is 

greater than the national average of 65.5 mph.

The benefits of this simple technology are widely recognized. The American 

Trucking Association (ATA) developed six recommendations to reduce carbon emissions 
Regulatory Impact Analysis 

2-74

from trucks in the United States. Their first recommendation is to enact a national truck speed 

limit of 65 mph and require that trucks manufactured after 1992 have speed governors set at 

not greater than 65 mph.108 The SmartWay program includes speed management as one of 

their key Clean Freight Strategies and provides information to the public regarding the benefit 

of lower highway speeds.109

Some countries have enacted regulations to reduce truck speeds. For example, the 

United Kingdom introduced regulations in 2005 which require new trucks used for goods 

movement to have a vehicle speed limiter not to exceed 90 km/hr (56 mph).110 The Canadian 

Provinces of Ontario and Quebec developed regulations which took effect in January 2009 

that requires on-highway commercial heavy-duty trucks to have speed limiters which limit the 

truck’s speed to 105 km/hr (65 mph).

111

Many truck fleets consider speed limiter application a good business practice in their 

operations. A Canadian assessment of heavy-duty truck speed limiters estimated that 60 

percent of heavy truck fleets in North America use speed limiters.112 Con Way Freight, Con 

Way Truckload, and Wal-Mart currently govern the speeds of their fleets between 62 and 65 

mph.113

A potential disbenefit of this technology is the additional time required for goods 

movement, or loss of productivity. The elasticity between speed reduction and productivity

loss has not been well defined in industry. The Canadian assessment of speed limiters cited 

above found that the fuel savings due to the lower operating speeds outweigh any productivity

losses. A general consensus among the OEMs is that a one percent decrease in speed might 

lower productivity by approximately 0.2 percent.114

In this final rule, the agencies are allowing the use of vehicle speed limiters as a way

of complying with the Class 7 and 8 combination tractor vehicle standards – that is, a VSL

value is an optional input in GEM. For purposes of these regulations, the agencies are 

assuming that there is no additional capital cost associated with a vehicle speed limiter. There 

are also no hardware requirements for this feature, only software control strategies. Nearly all 

heavy-duty engines today are electronically controlled and are capable of being programmed 

for a maximum vehicle speed. The only new requirement for truck manufacturers that the 

agencies are imposing through this rulemaking is to offer a vehicle speed limiter which is 

protected from tampering and cannot be changed by the fleet or truck owner. This technology

is required to be used for the full useful life of the vehicle to obtain the GHG emissions 

reduction.

The vehicle speed limiter is technically applicable to all truck classes which operate at 

high speeds. However, due to the structure of the first phase of the Heavy-Duty truck 

program, it is only applicable to the Class 7-8 tractors. The benefits of the vehicle speed 

limiter are assessed through the use of alternate High Speed Cruise cycles. The baseline cycle 

contains a constant 65 mph cruise. 

As discussed in much more detail in Section II.B.3.g of the final rule, the agencies are 

providing some adjustments to the VSL requirements for the final rulemaking to 

accommodate flexibilities desired by the trucking industry. The agencies will continue to 
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2-75

allow VSL credit for manufacturers who provide “soft top” and expiration features to be 

programmed into PCMs in order to provide additional flexibility for fleet owners and so that 

fleets who purchase used vehicles have the ability to have different VSL policies than the 

original owner of the vehicle.

The agencies are finalizing an approach which allows manufacturers to provide a 

vehicle speed limiter with a limited life to address concerns about resale value of trucks with a 

VSL. The agencies will discount the value of the vehicle speed limiter based on the number 

of miles in which it is preset relative to the lifetime of the tractor. The agencies calculated the 

lifetime miles of a combination tractor based on EPA’s MOVES model as 1,259,000 miles. 

The lifetime value is weighted to take into account the survival rate of heavy duty trucks, as 

shown above in Table 2-28. In using a soft top feature, a manufacturer will be required to 

provide to the agencies a functional description of the “soft top” control strategy including 

calibration values, the speed setting for both the hard limit and the soft top and the maximum 

time per day the control strategy could allow the vehicle to operate at the “soft top” speed 

limit at the time of certification and identify the use of the “soft top” VSL on the vehicle label. 

This information will be used to derive a factor to discount the VSL input used in GEM 

modeling to determine the fuel consumption and GHG emissions performance of the vehicle. 

The equation to derive the GEM input for VSL for systems with an expiration is the 

following, as shown in Equation 2-2.

Equation 2-2: Discounted VSL Equation

VSL input for GEM = Expiration Factor * [Soft Top Factor* Soft Top VSL + (1-Soft Top Factor) * 

VSL] + (1-Expiration Factor)*65 mph

The expiration factor is equal to the number of miles at expiration divided by 

1,259,000 miles

The soft top factor is equal to the maximum number of hours that a vehicle may travel 

at the soft top VSL in a 10 hour day divided by 7.3 hours for sleeper cabs or 3.9 hours for day

cabs based on the agencies’ drive cycle weighting factors. The number of hours spent 

travelling at each cycle is included in Table 2-29.

Table 2-29: Soft Top Factor Calculations

Sleeper Cab Day Cab

VMT weighting of 65 mph cycle 0.86 0.64

VMT weighting of 55 mph cycle 0.09 0.17

VMT weighting of Transient cycle 0.05 0.19

Average speed of 65 mph cycle 65 65

Average Speed of 55 mph cycle 55 55

Average Speed of Transient cycle 15.3 15.3

Miles per day travelled at 65 mph 474.2 252.4

Miles per day travelled at 55 mph 49.6 67.0

Miles per day travelled at transient 27.6 74.9
Regulatory Impact Analysis 

2-76

Total miles per day 551 394

Hours per day spent at 65 mph 7.3 3.9

Hours per day spent at 55 mph 0.9 1.2

Hours per day spent at transient 1.8 4.9

Total hours per day 10.0 10.0

2.5.6 Automated Manual Transmission

Most heavy-duty trucks use manual transmissions with 8 to 18 gear ratios available. 

The most common transmissions for line haul applications have 10 ratios with an overdrive 

top gear. Torque-converter automatic transmissions, similar to those used in passenger cars, 

are used in some stop/go truck applications but are more expensive and do not have 

anefficiency advantage in line-haul applications. Automated manual transmissions have been 

available on the market for over 10 years now and are increasing in market share. Automated 

manuals have a computer to decide when to shift and use pneumatic or hydraulic mechanisms 

to actuate the clutch and hidden shift levers. An automated manual can shift as quickly as the 

best driver, and the shift schedule can be tailored to match the characteristics of the engine 

and vehicle. This reduces variability of fuel consumption and CO2 emissions between drivers, 

with all drivers achieving results closer to those of the best drivers. In application, there 

would be a fuel economy improvement proportional to the number of non-fuel-conscious 

drivers in a fleet.115 

2.5.7 Class 7 and 8 Tractor Baseline Assessment

The agencies developed the baseline tractor for each subcategory to represent an 

average 2010 model year tractor. The approach taken by the agencies was to define the 

individual inputs to GEM. For example, the agencies evaluated the industry’s tractor 

offerings and conclude that the average tractor contains a generally aerodynamic shape (such 

as roof fairings) and avoid classic features such as exhaust stacks at the b-pillar which 

increase drag. The agencies consider a baseline truck as having “conventional” 

aerodynamics. The baseline rolling resistance coefficient for today’s fleet is 7.8 kg/metric ton 

for the steer tire and 8.2 kg/metric ton for the drive tire, based on sales weighting of the top 

three manufacturers based on market share.116 However, today there is a large spread in 

aerodynamics in the new tractor fleet. Trucks are sold that may reflect classic styling, or are 

sold with conventional or SmartWay aerodynamic packages.

Table 2-30 Class 7 and 8 Baseline Attributes

CLASS 7 CLASS 8

Day Cab Day Cab Sleeper Cab

Low 

Roof

Mid 

Roof

High 

Roof

Low Roof Mid Roof High Roof Low Roof Mid Roof High 

Roof

Aerodynamics (Cd)

Baseline 0.77 0.87 0.73 0.77 0.87 0.73 0.77 0.87 0.70

Steer Tires (Crr kg/metric ton)
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2-77

Baseline 7.8 7.8 7.8 7.8 7.8 7.8 7.8 7.8 7.8

Drive Tires (Crr kg/metric ton)

Baseline 8.2 8.2 8.2 8.2 8.2 8.2 8.2 8.2 8.2

Weight Reduction (lb)

Baseline 0 0 0 0 0 0 0 0 0

Extended Idle Reduction (gram CO2/ton-mile reduction)

Baseline N/A N/A N/A N/A N/A N/A 0 0 0

Vehicle Speed Limiter

Baseline -- -- -- -- -- -- -- -- --

Engine

Baseline 2010 MY 

11L 

Engine

2010 

MY 11L 

Engine

2010 

MY 11L 

Engine

2010 MY 

15L 

Engine

2010 MY 

15L 

Engine

2010 MY 

15L 

Engine

2010 MY 

15L 

Engine

2010 MY 

15L 

Engine

2010 MY 

15L 

Engine

2.5.8 Class 7 and 8 Tractor Standards Derivation

As discussed in more detail in Section II.B and III.A of the preamble, EPA and 

NHTSA project that CO2 emissions and fuel consumption reductions can be achieved through 

the increased penetration of aerodynamic technologies, low rolling resistance tires, weight 

reduction, extended idle reduction technologies, and vehicle speed limiters. The agencies 

believe that hybrid powertrains in line-haul applications will not be cost-effective in the time 

frame of the rule. The NAS report stated that the effectiveness of hybrid powertrains installed 

in tractors is 10 percent, but 6 percent of it was attributed to idle reduction which is already 

addressed in the HD program, at a cost of $25,000.117 The agencies also are not including

drivetrain technologies in the standard setting process, as discussed in Section II.B.3.h.iv of 

the preamble, and instead are choosing to allow the continuation of the current truck 

specifying process that is working well today.

The agencies investigated the possibility of essentially forcing SmartWay technologies 

(aerodynamics, tires, and extended idle) into 100 percent of Class 7 and Class 8 tractors. 

However, as discussed below, the agencies realize that there are some restrictions which 

prevent 100 percent penetration. Therefore, the agencies took the approach of evaluating each 

technology and finalizing what we deem as the maximum feasible penetration into each 

tractor regulatory category. The next sections describe the effectiveness of the individual 

technologies, the costs of the technologies, the penetration rates of the technologies into the 

regulatory categories, and finally the derivation of the final standards.

2.5.8.1 Technology Effectiveness

The agencies’ assessment of the technology effectiveness was developed through the 

use of the GEM . Table 2-31 describes the model inputs for the range of Class 7 and 8 

tractor technologies. 
Regulatory Impact Analysis 

2-78

Table 2-31: GEM Inputs 

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low / 

Mid Roof

High Roof Low / 

Mid Roof

High Roof Low Roof Mid Roof High Roof

Aerodynamics (Cd)

Frontal Area (m2) 6.0 9.8 6.0 9.8 6.0 7.7 9.8

Bin I 0.77 /

0.87 0.79

0.77 /

0.87 0.79

0.77 0.87

0.75

Bin II 0.71 /

0.82 0.72

0.71 /

0.82 0.72

0.71 0.82

0.68

Bin III 0.63 0.63 0.60

Bin IV 0.56 0.56 0.52

Bin V 0.51 0.51 0.47

Steer Tires (Crr kg/metric ton)

Baseline 7.8 7.8 7.8 7.8 7.8 7.8 7.8

Level I 6.6 6.6 6.6 6.6 6.6 6.6 6.6

Level II 5.7 5.7 5.7 5.7 5.7 5.7 5.7

Drive Tires (Crr kg/metric ton)

Baseline 8.2 8.2 8.2 8.2 8.2 8.2 8.2

Level I 7.0 7.0 7.0 7.0 7.0 7.0 7.0

Level II 6.0 6.0 6.0 6.0 6.0 6.0 6.0

Weight Reduction (lbs.)

Control 400 400 400 400 400 400 400

Extended Idle Reduction (gram CO2/ton-mile reduction)

Control N/A N/A N/A N/A 5 5 5

Vehicle Speed Limiter

Control N/A N/A N/A N/A N/A N/A N/A

2.5.8.2 Class 7 and 8 Tractor Application Rates

Vehicle manufacturers often introduce major product changes together, as a package. 

In this manner the manufacturers can optimize their available resources, including 

engineering, development, manufacturing and marketing activities to create a product with 

multiple new features. In addition, manufacturers recognize that an engine and truck will 

need to remain competitive over its intended life and meet future regulatory requirements. In 

some limited cases, manufacturers may implement an individual technology outside of a 

vehicle’s redesign cycle. For consistency with these industry practices, the agencies have 

created a set of vehicle technology packages for each regulatory subcategory.

With respect to the level of technology required to meet the standards, NHTSA and 

EPA established technology application caps. The first type of cap was established based on 

the application of common fuel consumption and CO2 emission reduction technologies into 
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2-79

the different types of tractors. For example, idle reduction technologies are limited to Class 8 

sleeper cabs based on the assumption that day cabs are not used for overnight hoteling. Idle 

reduction technologies such as APUs and cabin heaters can reduce workday idling associated 

with day cabs. However, characterizing idling activity for this segment in order to quantify

the benefits of idle reduction technology is complicated by the variety of duty cycles found in 

the sector. Idling in tractors used for pick-up and delivery construction, refuse, and other 

types of vocational vehicles varies significantly. Given the great variety of duty cycles and 

operating conditions of vocational vehicles and the timing of these rules, it is not feasible at 

this time to establish an accurate baseline for quantifying the expected improvements which 

could result from use of idle reduction technologies. A second type of constraint was applied 

to most other technologies and limited their penetration based on factors such as market 

demands.

The impact of aerodynamics on a truck’s efficiency increases with vehicle speed. 

Therefore, the usage pattern of the truck will determine the benefit of various aerodynamic 

technologies. Sleeper cabs are often used in line haul applications and drive the majority of 

their miles on the highway travelling at speeds greater than 55 mph. The industry has focused 

aerodynamic technology development, including SmartWay certified tractors, on these types 

of trucks. Therefore the agencies are finalizing the most aggressive aerodynamic technology

penetration in this regulatory subcategory. All of the major manufacturers today offer at least 

one truck model that is SmartWay designated. The 2010 NAS Report found that 

manufacturers indicated that aerodynamic improvements which yield 3 to 4 percent fuel 

consumption reduction or 6 to 8 percent reduction in Cd values, beyond technologies used in 

today’s SmartWay trucks are achievable.118 The final standards are predicted on an 

aerodynamic penetration rate for Class 8 sleeper cab high roof cabs of 20 percent of Bin IV, 

70 percent Bin III, and 10 percent Bin II. The small percentage of Bin II tractor aerodynamics 

is for applications that do not qualify as vocational tractors but may still not be able to use 

features such as chassis skirts which are prone to damage in off-road applications.

Tire rolling resistance is only one of several performance criteria that affect tire 

selection. The characteristics of a tire also influence durability, traction control, vehicle 

handling and comfort. A single performance parameter can easily be enhanced, but an 

optimal balance of all the criteria must be maintained. Tire design requires balancing 

performance, since changes in design may change different performance characteristics in 

opposing direction. Similar to the discussion regarding lesser aerodynamic technology 

penetration in tractor segments other than sleeper cab high roof, the agencies believe that low 

rolling resistance tires should not be applied to 100 percent of all tractor segments. The 

agencies are instead basing the standards on application rates that vary by subcategory to 

reflect the on/off-road application of some tractors which require a different balancing of 

traction versus rolling resistance, but do not qualify for the off-road vocational tractor 

exemption.

Weight reductions can be achieved through single wide tires replacing dual tires and 

lighter weight wheel material or through the use of other light weight components as specified 

in Table 2-23. Single wide tires can reduce weight by over 160 pounds per axle. Aluminum 
Regulatory Impact Analysis 

2-80

wheels used in lieu of steel wheels will reduce weight by over 80 pounds for a dual wheel 

axle. Light weight aluminum steer wheels and aluminum single wide drive wheels and tires 

package will provide a 670 pound weight reduction over the baseline steel steer and dual drive 

wheels. In comments to the agencies, Volvo and ATA stated that not all fleets can use single 

wide tires and as a result they stated the weight reduction requirement should be reduced. In 

response, the agencies are finalizing as direct GEM inputs additional light weight components 

that can be used to achieve the 400 pound weight reduction for tractors. Additional weight 

reduction opportunities exist with the use of aluminum or light weight steel in steps, clutch 

housings, and other components listed in Table 2-23. 

Idle reduction technologies provide significant reductions in fuel consumption and 

CO2 emissions. There are several different technologies available to reduce idling, like

auxiliary power units, diesel fired heaters, and battery powered units. Each of these 

technologies has a different level of fuel consumption and CO2 emissions. Therefore, the 

emissions reduction value varies by technology. Also, our discussions with manufacturers 

indicate that idle technologies are sometimes installed in the factory, but it is also a common 

practice to have the units installed after the sale of the truck. Therefore, we would like to 

continue to incentivize this practice while providing some certainty that the overnight idle 

operations will be eliminated. Therefore, we are allowing the installation of only an 

automatic engine shutoff, without override capability, to qualify for idle emission reductions. 

We are finalizing a 100 percent penetration rate for this technology (and several override 

options not proposed, to account for driver safety and comfort concerns raised in the 

comments) and have estimated that 30 percent of the current fleet already employs this 

technology meaning that 70 percent are estimated to add this technology.

Consistent with proposal, vehicle speed limiters may be used as a technology to meet 

the standard, but this technology was not used as part of the technology package on which the 

standard is based. The comments received from stakeholders did not address the agencies’ 

concerns discussed in the proposal, specifically the risk of requiring VSL in situations that are 

not appropriate from an efficiency perspective because it may lead to additional truck trips to 

deliver the same amount of freight.H The agencies continue to believe that we are not in a 

position to determine how many additional trucks would benefit from the use of a VSL with a 

setting of less than 65 mph (a VSL with a speed set at or above 65 mph will show no CO2

emissions or fuel consumption benefit on the drive cycles included in this program). We will 

monitor the industry’s use of VSL in this program and may consider using this technology in 

standard setting in the future. 

Table 2-32 provides the final application rates for each technology by regulatory

subcategory.

 

H

See 75 FR at page 74223
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2-81

Table 2-32: Application Rates

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low/Mid 

Roof

High Roof Low/Mid 

Roof

High Roof Low Roof Mid Roof High Roof

Aerodynamics (Cd)

Bin I 40% 0% 40% 0% 30% 30% 0%

Bin II 60% 30% 60% 30% 70% 70% 10%

Bin III 60% 60% 70%

Bin IV 10% 10% 20%

Bin V 0% 0% 0%

Steer Tires (Crr kg/metric ton)

Baseline 40% 30% 40% 30% 30% 30% 10%

Bin I 50% 60% 50% 60% 60% 60% 70%

Bin II 10% 10% 10% 10% 10% 10% 20%

Drive Tires (Crr kg/metric ton)

Baseline 40% 30% 40% 30% 30% 30% 10%

Bin I 50% 60% 50% 60% 60% 60% 70%

Bin II 10% 10% 10% 10% 10% 10% 20%

Weight Reduction (lbs.)

Control 100% 100% 100% 100% 100% 100% 100%

Extended Idle Reduction (gram CO2/ton-mile reduction)

Control Not 

Applicable

Not 

Applicable

Not 

Applicable

Not 

Applicable

100% 100% 100%

Vehicle Speed Limiter

Control -- -- -- -- -- -- --

The agencies used the technology inputs and technology application rates in GEM to 

develop the fuel consumption and CO2 emissions standards for each subcategory of Class 7/8 

combination tractors. The agencies derived a scenario truck for each subcategory by

weighting the individual GEM input parameters included in Table 2-31 by the application 

rates in Table 2-32. For example, the Cd value for a Class 8 Sleeper Cab High Roof scenario 

case was derived as (10 percent x 0.66) + (70 percent x 0.58) + (20 percent x 0.50), which is 

equal to a Cd of 0.57. Similar calculations were done for tire rolling resistance, weight 

reduction, idle reduction, and vehicle speed limiters. To account for the two engine standards, 

EPA and NHTSA are finalizing the use of a 2014 model year fuel consumption map in GEM 

to derive the 2014 model year tractor standard and a 2017 model year fuel consumption map 

to derive the 2017 model year tractor standard.119 The agencies then ran GEM with a single 

set of vehicle inputs, as shown in Table 2-33, to derive the final standards for each 

subcategory. The final standards and percent reductions are included in Table 2-34.

Table 2-33 Inputs to the GEM model for Class 7 and 8 Tractor Standard Setting

CLASS 7 CLASS 8
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Day Cab Day Cab Sleeper Cab

Low Roof Mid Roof High Roof Low Roof Mid Roof High Roof Low Roof Mid Roof High 

Roof

Aerodynamics (Cd)

0.73 0.84 0.65 0.73 0.84 0.65 0.73 0.84 0.59

Steer Tires (Crr kg/metric ton)

6.99 6.99 6.87 6.99 6.99 6.87 6.87 6.87 6.54

Drive Tires (Crr kg/metric ton)

7.38 7.38 7.26 7.38 7.38 7.26 7.26 7.26 6.92

Weight Reduction (lb)

400 400 400 400 400 400 400 400 400

Extended Idle Reduction (gram CO2/ton-mile reduction)

N/A N/A N/A N/A N/A N/A 5 5 5

Vehicle Speed Limiter

-- -- -- -- -- -- --

Engine

2014/17 MY 

11L Engine

2014/17 

MY 11L 

Engine

2014/17 

MY 11L 

Engine

2014/17

MY 15L 

Engine

2014/17 

MY 15L 

Engine

2014/17 

MY 15L 

Engine

2014/17 

MY 15L 

Engine

2014/17 

MY 15L 

Engine

2014/17 

MY 15L 

Engine
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Table 2-34 Tractor Standards and Percent Reductions

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low

Roof

Mid Roof High Roof Low

Roof

Mid Roof High 

Roof

Low 

Roof

Mid 

Roof

High 

Roof

2014 Model Year (voluntary for NHTSA program)

2014 MY 

Voluntary Fuel 

Consumption 

Standard 

(gallon/1000 

ton-mile)

10.5 11.7 12.2 8.0 8.7 9.0 6.7 7.4 7.3

2014 MY CO2

Standard 

(grams 

CO2/ton-mile)

107 119 124 81 88 92 68 76 75

Percent 

Reduction

8% 7% 10% 8% 7% 11% 15% 14% 21%

2017 Model Year and later

2017 MY Fuel 

Consumption 

Standard 

(gallon/1000 

ton-mile)

10.2 11.3 11.8 7.8 8.4 8.7 6.5 7.2 7.1

2017 MY CO2

Standard 

(grams 

CO2/ton-mile)

104 115 120 80 86 89 66 73 72

Percent 

Reduction

10% 10% 13% 10% 10% 13% 17% 17% 23%

2.5.9 Class 7-8 Tractor Technology Costs

The technology costs associated with the tractor defined in Table 2-33 for each of the 

tractor subcategories are listed in Table 2-35.
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Table 2-35 Estimated Class 7-8 Tractor Technology Costs, Inclusive of Markups and Penetration Rates, 

Applicable in the 2014MY (2009 dollars)

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low & 

Mid Roof

High Roof Low & 

Mid Roof

High Roof Low Roof Mid Roof High Roof

Aerodynamics 

Bin III & Bin IV $675 $924 $675 $924 $962 $983 $1,627

Steer Tires 

Low Rolling Resistance $68 $68 $68 $68 $68 $68 $68

Drive Tires 

Low Rolling Resistance $63 $63 $126 $126 $126 $126 $126

Weight Reduction 

Weight Package $1,200 $1,536 $1,980 $1,980 $3,275 $3,275 $1,980

Extended Idle Reduction

Auxiliary Power Unit N/A N/A N/A N/A $3,819 $3,819 $3,819

Vehicle Speed Limiter

Control N/A N/A N/A N/A N/A N/A N/A

2.6 Class 2b-8 Vocational Vehicles

2.6.1 Tires 

As discussed in more detail in Section III.D of the preamble, the range of rolling 

resistance of tires used on vocational vehicles (Class 2b – 8) today is large. The competitive 

pressure to improve rolling resistance of these tires has been less than that found in the Class 

8 line haul tire market. Due to the drive cycles typical for these applications, tire traction and 

durability are weighed more heavily in a purchaser’s decision than rolling resistance. 

Therefore, the agencies believe that a regulatory program that incentivizes the optimization of 

tire rolling resistance, traction and durability can bring about GHG emission and fuel 

consumption reductions from this segment. It is estimated that low rolling resistance tires 

used on Class 3 – 6 trucks would improve fuel economy by 2.5 percent84 relative to tires not 

designed for fuel efficiency.

Tires used on vocational vehicles (Class 2b – 8) typically carry less load than a Class 8 

line haul vehicle. They are also designed for resistance to scrubbing and curb damage. 

Because they carry less load and high scrubbing, tires used on vocational vehicles are can 

retreaded as many as five times. 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

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Since the NPRM, the agencies have conducted additional research on tire rolling 

resistance for medium- and heavy-duty applications. EPA has conducted tire rolling resistance 

testing to help inform the final rulemaking.122

The testing measured the RRC of tires representing 16 different vehicle applications 

for Class 4 – 8 vocational vehicles. The testing included approximately 5 samples each of 

both steer and drive tires for each application. The tests were conducted by two independent 

tire test labs, Standards Testing Lab (STL) and Smithers-Rapra (Smithers). 

Overall, a total of 156 medium- and heavy-duty tires were included in this testing, 

which was comprised of 88 tires covering various commercial vocational vehicle types, such 

as bucket trucks, school buses, city delivery vehicles, city transit buses and refuse haulers 

among others; 47 tires intended for application to tractors; and 21 tires classified as light-truck 

(LT) tires intended for Class 4 vocational vehicles such as delivery vans. 

The test results for 88 commercial vocational vehicle tires (19.5” and 22.5” sizes) 

showed a test average RRC of 7.4 kg/metric ton, with results ranging from 5.4 to 9.8. To 

comply with the proposed vocational vehicle fuel consumption and GHG emissions standards 

using improved tire rolling resistance as the compliance strategy, a manufacturer would need 

to achieve an average tire RRC value of 8.1 kg/metric ton.

123

 The measured average RRC of

7.4 kg/metric ton is thus better than the average value that would be needed to meet 

vocational vehicle standards. Of those eighty-eight tires tested, twenty tires had RRC values 

worse than 8.1 kg/metric ton, two were at 8.1 kg/metric ton, and sixty-six tires were better 

than 8.1 kg/metric ton. Additional data analyses examining the tire data by tire size to 

determine the range and distribution of RRC values within each tire size showed each tire size 

generally had tires ranging from approximately 6.0 to 8.5 kg/metric ton, with a small number 

of tires in the 5.3 – 5.7 kg/metric ton range and a small number of tires in a range as high as 

9.3 – 9.8 kg/ton. Review of the data showed that for each tire size and vehicle type, the 

majority of tires tested would enable compliance with vocational vehicle fuel consumption 

and GHG emission standards. 

Finally, the 21 LT tires intended for Class 4 vocational vehicles were comprised of 

two sizes; LT225/75R16 and LT245/75R16 with 11 and 10 samples tested, respectively. 

Some auto manufacturers have indicated that RRC values for tires fitted to these Class 4 

vehicles typically have a higher RRC values than tires found on commercial vocational 

vehicles because of the smaller diameter wheel size and the ISO testing protocol.124 The test 

data showed the average RRC for LT225/75R16 tires was 9.1 kg/metric ton and the average 

for LT245/75R16 tires was 8.6 kg/metric ton. The range for the LT225/75R16 tires spanned 

7.4 to 11.0125 and the range for the LT245/75R16 tires ranged from 6.6 to 9.8 kg/metric ton. 

Overall, the average for the tested LT tires was 8.9 kg/metric ton.

Analysis of the EPA test data for all vocational vehicles, including LT tires, shows the 

test average RRC is 7.7 kg/metric ton and with a standard deviation of 1.2 kg/metric ton. 

Review of the data thus shows that for each tire size and vehicle type, there are many tires 

available that would enable compliance with the proposed standards for vocational vehicles 
Regulatory Impact Analysis 

2-86

and tractors except for LT tires for Class 4 vocational vehicles where test results show the 

majority of these tires are worse than 8.1 kg/metric ton. 

The agencies also reviewed the RRC data from the tires that were tested at both the 

STL and Smithers laboratories to assess inter-laboratory and test machine variability. The 

agencies conducted statistical analysis of the data to gain better understanding of lab-to-lab 

correlation and developed an adjustment factor for data measured at each of the test labs. 

When applied, this correction factor showed that for 77 of the 80 tires tested, the difference 

between the original RRC and a value corrected RRC was 0.01 kg/metric ton. The values for 

the remaining three tires were 0.03 kg/metric ton, 0.05 kg/metric ton and 0.07 kg/metric ton. 

Based on these results, the agencies believe the lab-to-lab variation for the STL and Smithers 

laboratories would have very small effect on measured RRC values. Further, in analyzing the 

data, the agencies considered both measurement variability and the value of the measurements 

relative to proposed standards. The agencies concluded that although laboratory-to-laboratory

and test machine-to-test machine measurement variability exists, the level observed is not 

excessive relative to the distribution of absolute measured RRC performance values and 

relative to the proposed standards. Based on this, the agencies concluded that the test protocol 

is reasonable for this program, but are making some revisions to the vehicle standards.

For vocational vehicles, the rolling resistance of each tire will be measured using the 

ISO 28850 test method for drive tires and steer tires planned for fitment to the vehicle being 

certified. Once the test RRC values are obtained, a manufacturer will input the RRC values for 

the drive and steer tires separately into the GEM where, for vocational vehicles, the vehicle 

load is distributed equally over the steer and drive tires. Once entered, the amount of GHG 

reduction attributed to tire rolling resistance will be incorporated into the overall vehicle 

compliance value. The following table provides the revised target RRC values for vocational 

vehicles for 2014 and 2017 model years that are used to determine the vehicle standards.

Table 2-36: Vocational Vehicle – Target RRC Values for GEM Input

2014 MY 2017 MY

Tire Rolling Resistance 

(kg/metric ton)

7.7 kg/metric ton 7.7 kg/metric ton

These target values are being revised based on the significant availability of tires for 

vocational vehicles applications which have performance better than the originally proposed 

8.1 kg/metric ton target. As just discussed, 63 of the 88 tires tested for vocational applications 

had RRC values better than the proposed target. The tires tested covered fitment to a wide 

range of vocational vehicle types and classes; thus agencies believe the original target value 

of 8.1 kg/metric ton was possibly too lenient after reviewing the testing data. Therefore, the 

agencies believe it is appropriate to reduce the proposed vehicle standard based on 

performance of an RRC target value of 7.7 kg/metric ton for non-LT tire type. As discussed 

previously, this value is the test average of all vocational tires tested (including LT) which 

takes a conservative approach over setting a target based on the average of only the non-LT 

Vocational tires tested. For LT tires, based on both the test data and the comments from 

AAPC and Ford Motor Company, the agencies recognize the need to provide an adjustment. 

In lieu of having two sets of Light Heavy-Duty vocational vehicle standards, the agencies are 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

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finalizing an adjustment factor which applies to the RRC test results for LT tires. The 

agencies developed an adjustment factor dividing the overall vocational test average RRC of 

7.7 by the LT Vocational Average of 8.9. This yields an adjustment factor of 0.87. For LT 

vocational vehicle tires, the measured RRC values will be multiplied by the 0.87 adjustment 

factor before entering the values in the GEM for compliance. 

The agencies have estimated the costs of low rolling resistance tires as shown in Table 

2-37. These costs include a low complexity ICM of 1.18 and flat-portion of the curve

learning would be considered appropriate for these technologies. 

Table 2-37 Estimated Costs for Low Rolling Resistance Tires on Vocational Vehicles in the 2014MY 

(2009$)

LIGHT-HEAVY & 

MEDIUM-HEAVY HEAVY-HEAVY

Low rolling resistance steer tires $68 $68

Low rolling resistance drive tires $94 $126

Package cost (including penetration rates) $81 $97

2.6.2 Other Evaluated Technologies for Vocational Vehicles

2.6.2.1 Aerodynamics 

Aerodynamic drag is an important aspect of the power requirements for Class 2b 

through 8 vocational vehicles. Because aerodynamic drag is a function of the cube of vehicle 

speed, small changes in the aerodynamics of a vocational vehicle reduces drag, fuel 

consumption, and GHG emissions. The great variety of applications for vocational vehicles 

result in a wide range of operational speed profiles (i.e., in-use drive cycles), with many

weighted toward lower speeds where aerodynamic improvement benefits are less pronounced. 

In addition, vocational vehicles have a wide variety of configurations (e.g., utility trucks with 

aerial devices, transit buses, and pick-up and delivery trucks) and functional needs (e.g., 

ground clearance, towing, and all weather capability). This specialization can make the 

implementation of aerodynamic features impractical and, where specialty markets are limited, 

make it unlikely that per-unit costs will lower with sales volume.

This technology is not expected as a result of the final standards.

2.6.2.2 Hybrid Powertrains

A hybrid electric vehicle (HEV) is a vehicle that combines two or more sources of 

propulsion energy, where one uses a consumable fuel (i.e. gasoline or diesel), and one is 

rechargeable (during operation, or by another energy source). Hybrid technology is 

established in the U.S. market and more manufacturers are adding hybrid models to their 

lineups. Hybrids reduce fuel consumption through three major mechanisms:
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2-88

 Powertrain control strategy can be developed to operate the engine at or near its 

most efficient point most of the time.

 The internal combustion engine can be optimized through downsizing or 

modifying the operating cycle. Power loss from engine downsizing can be 

mitigated by employing power assist from the secondary power source.

 Some of the energy normally lost as heat while braking can be captured and stored 

in the energy storage system for later use.

 The engine is turned off when it is not needed, such as when the vehicle is coasting 

or stopped, such as extending idle conditions.

Hybrid vehicles utilize some combination of the above mechanisms to reduce fuel

consumption and CO2 emissions. A final mechanism to reduce fuel consumption, available 

only to plug-in hybrids, is by substituting the petroleum fuel energy with energy from another 

source, such as the electric grid. Plug-in hybrids may be most suitable for some applications 

which travel short distances such as local pickup and delivery. 

The effectiveness of fuel consumption and CO2 reduction depends on the utilization of 

the above mechanisms and how aggressively they are pursued. One area where this variation 

is particularly prevalent is in the choice of engine size and its effect on balancing fuel 

efficiency and performance. Some manufacturers choose not to downsize the engine when 

applying hybrid technologies depending on the power from the hybrid system components. In 

these cases, performance is improved, while fuel efficiency improves significantly less than if 

the engine was downsized to maintain the same performance as the conventional version. 

While this approach of not downsizing the engine has been used in passenger cars

occasionally, it is more likely to be used for trucks where towing, hauling and/or cargo 

capacity is an integral part of their performance requirements. In these cases, if the engine is 

downsized, the battery can be quickly drained during a long hill climb with a heavy load, 

leaving only a downsized engine to carry the entire load. Because cargo capability is critical 

truck attribute, manufacturers are hesitant to offer a truck with downsized engine which can 

lead to a significantly diminished towing performance with a low battery, and therefore 

engines are traditionally not significantly downsized for these vehicles.

In addition to the purely hybrid technologies, which decreases 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 CO2 emissions 

and fuel consumption. Optimization of the auxiliary functions, together with the hybrid 

technologies, is collectively referred to as vehicle or accessory load electrification because 

they generally use electricity instead of engine power. Fuel efficiency gains achieved only 

through electrification are considered in a separate section although these improvements may

be combined with the hybrid system.

A hybrid drive unit is complex and consists of discrete components such as the electric 

traction motor, transmission, generator, inverter, controller and cooling devices. Certain types 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

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of drive units may work better than others for specific vehicle applications or performance 

requirements. Several types of motors and generators have been developed for hybrid-electric 

drive systems, many of which merit further evaluation and development on specific 

applications. Series HEVs typically have larger motors with higher power ratings because the 

motor alone propels the vehicle, which may be applicable to Class 3-5 applications. In parallel 

hybrids, the power plant and the motor combine to propel the vehicle. Motor and engine 

torque are usually blended through couplings, planetary gear sets and clutch/brake units. The 

same mechanical components that make parallel heavy-duty hybrid drive units possible can 

be designed into series hybrid drive units to decrease the size of the electric motor(s) and 

power electronics. 

An electrical energy storage system is needed to capture energy from the generator, to 

store energy captured during vehicle braking events, and to return energy when the driver 

demands power. This technology has seen a tremendous amount of improvement over the last 

decade and recent years. Advanced battery technologies and other types of energy storage are 

emerging to give the vehicle its needed performance and efficiency gains while still providing 

a product with long life. The focus on the more promising energy storage technologies such as 

nickel metal-hydride (NiMH) and lithium technology batteries along with ultra capacitors for 

the heavy-duty fleet should yield interesting results after further research and applications in 

the light-duty fleet.

Heavy-duty hybrid vehicles also use regenerative braking for improved fuel economy, 

emissions, brake heat, and wear. A conventional heavy vehicle relies on friction brakes at the 

wheels, sometimes combined with an optional engine retarder or driveline retarder to reduce 

vehicle speed. During normal braking, the vehicle’s kinetic energy is wasted when it is 

converted to heat by the friction brakes. The conventional brake configuration has large 

components, heavy brake heat sinks, and high temperatures at the wheels during braking, 

audible brake squeal, and consumable components requiring maintenance and replacement. 

Hybrid electric systems recover some of the vehicle’s kinetic energy through regenerative 

braking, where kinetic energy is captured and directed to the energy storage system. The 

remaining kinetic energy is dissipated through conventional wheel brakes or in a driveline or 

transmission retarder. Regenerative braking in a hybrid electric vehicle can require integration 

with the vehicle’s foundation (friction) braking system to maximize performance and safety. 

Today’s systems function by simultaneously using the regenerative features and the friction 

braking system, allowing only some of the kinetic energy to be saved for later use. Optimizing 

the integration of the regenerative braking system with the foundation brakes will increase the 

benefits and is a focus for continued work. This type of hybrid regenerative braking system 

improves fuel economy, GHG emissions, brake heat, and wear.

In addition to electric hybrid systems, EPA is experimenting with a Class 6 hydraulic 

hybrid that achieves a fuel economy increase superior to that of an electric hybrid.126 In this 

type of system, deceleration energy is taken from the drivetrain by an inline hydraulic 

pump/motor unit by pumping hydraulic fluid into high pressure cylinders. The fluid, while not 

compressible, pushes against a membrane in the cylinder that compresses an inert gas to 5,000 

PSI or more when fully charged. Upon acceleration, the energy stored in the pressurized tank 
Regulatory Impact Analysis 

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pushes hydraulic fluid back into the drivetrain pump/motor unit, allowing it to motor into the 

drivetrain and assist the vehicle’s engine with the acceleration event. This heavy-duty truck 

hybrid approach has been demonstrated successfully, producing good results on a number of 

commercial and military trucks. 

Nevertheless, considering the diversity of the heavy-duty fleet along with the various 

types of hybridization, the results are diverse as well. The percentage savings that can be 

expected from hybridization is very sensitive to duty cycle. For this reason, analyses and 

efforts to promote hybrids often focus on narrow categories of vehicles. For vocational 

vehicles other than tractor-trailers, hybrid technologies are promising, because a large fraction 

of miles driven by these trucks are local and under stop-and-go conditions. One study claims 

hybridization could almost double fuel economy for Class 3-5 trucks and raise Class 6-7 fuel 

economy by 71 percent in city driving, at costs that will decline rapidly in the coming years 

with the incremental cost of the hybrid vehicles depending on the choice of technology and 

the year, the later being a surrogate for progress towards economies of scale and experience 

with the technology80. Another Argonne National Lab study considering only truck Classes 2 

and 3 indicates possible fuel efficiency gains of 40 percent84. The Hybrid Truck Users Forum 

has published a selection of four types as good candidates for hybridization; Class 4-8 

Specialty Trucks, including utility and fire trucks; Class 4-6 urban delivery trucks, including

package and beverage delivery; Class 7 and 8 refuse collection; and Class 7 and 8 less-thanload urban delivery trucks. The average fuel economy increase over the five cycles is 93 

percent for the Class 3-4 truck and 71 percent for the Class 6-7 vehicle. 

Stop-and-go truck driving includes a fraction of idling conditions during which the 

truck base engine consumes fuel but produces no economically useful output (e.g., movement 

of goods, or repositioning of the truck to a new location). Hybrid propulsion systems shut off 

the engine under idling conditions or situations of low engine power demand. Trucks that 

have high fractions of stop-and-go freight transport activities within their driving cycles, such 

as medium-duty package and beverage delivery trucks, may be appropriate candidates for 

hybridization. Long-haul trucks have a lower proportion of short-term idling or low engine 

power demand in their duty cycles because of traffic conditions or frequency stops compared 

to medium-duty trucks in local services. Based on the results of hybridization effects 

modeling, medium-duty trucks in local service (e.g., delivery) can reduce energy use by 41.5 

percent127. Another 2009 report states that a 10 percent fuel consumption decrease could be 

achieved if idle reduction benefits were realized and a 5 percent improvement considering for 

on-road only 

128

. 

In heavy-duty hybrid research, the industry role will be represented by the heavyhybrid team members (e.g. Allison Transmission, Arvin-Meritor, BAE Systems, and Eaton 

Corporation). The Department of Energy is pursuing heavy hybrid research through the 

Freedom CAR and Vehicle Technologies Program. The Department of Transportation 

(Federal Transit Administration) is playing a role in demonstration of these vehicles for the 

transit bus market. The Department of Defense is working with heavy hybrid equipment 

suppliers to develop and demonstrate hybrid vehicles for military applications, and has 

already made significant investments in hybrid technology to reduce fuel consumption and 

improve their ability to travel silently in combat situations. The Environmental Protection 

Agency has participated in the heavy hybrid arena through its work on mechanical hybrids for 
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certain applications as discussed previously. The U.S. Department of Energy’s 21st Century

Truck Partnership (21CTP) has established challenging goals for improving fuel economy and 

pollutant emissions from heavy-duty vehicles including a diverse set of vehicles ranging from 

approximately 8,500 lb GVW to 100,000+ lb GVW60. 

Despite the significant future potential for hybrids discussed above, there are no 

simple solutions applicable for each heavy-duty hybrid application due to the large vocational 

vehicle fleet variation. A choice must be made relative to the requirements and priorities for 

the application. Challenges in motor subsystems such as gear reductions and cooling systems 

must be considered when comparing the specific power, power density, and cost of the motor 

assemblies. High speed motors can significantly reduce weight and size, but they require 

speed reduction gear sets that can offset some of the weight savings, reduce reliability and add 

cost and complexity. Air-cooled motors are simpler and generally less expensive than liquidcooled motors, but they will be larger and heavier, and they require access to ambient air, 

which can carry dirt, water, and other contaminants. Liquid-cooled motors are generally

smaller and lighter for a given power rating, but they may require more complex cooling 

systems that can be avoided with air-cooled versions. Various coolant options, including 

water, water-glycol, and oil, are available for liquid-cooled motors but must be further 

researched for long term durability. Electric motors, power electronics, electrical safety, 

regenerative braking, and power-plant control optimization have been identified as the most 

critical technologies requiring further research to enable the development of higher efficiency

hybrid electric propulsion systems.

In addition, because manufacturers will incur expenses in bringing hybrids to market, 

and because buyers do not purchase vehicles on the basis of net lifetime savings (see Section 

VIII.A.4 of the preamble), the cost-effectiveness of hybrids may not in itself translate into 

market success, and measures to promote hybrids are needed until costs come down. 

Vocational vehicles have diverse duty cycles, and they are used to a far greater extent for 

local trips. Some of the technologies are much less effective for trucks that generally drive at 

low speeds and therefore have limited applicability. Conversely, these trucks are the best 

candidates for hybrid technology, because local trips typically involve a large amount of stopand-go driving, which permits extensive capture of braking and deceleration energy.

In summary, many technologies that apply to cars do not apply to heavy-duty trucks 

and there is a common perception that investments in passenger car (light-duty vehicle) 

technology can easily benefit heavy-duty trucks. This group of vehicles is very diverse and 

includes tractor-trailers, refuse and dump trucks, package delivery vehicles and buses. The 

life expectancy and duty cycles for heavy-duty vehicles are about ten times more demanding 

than those for light-duty vehicles, technologies and solutions for the fleet must be more 

durable and reliable. Although a new generation of components is being developed for 

commercial and military HEVs, more research and testing are required.

Due to the complexity of the heavy-duty fleet, the variation of hybrid system reported 

fuel efficiency gains and the growing research and testing – vehicle hybridization is not 
Regulatory Impact Analysis 

2-92

mandated nor included in the model for calculation of truck fuel efficiency and GHG output. 

Vehicle hybridization is feasible on both tractor and vocational applications but must be tested 

on an individual basis to an applicable baseline to realize the system benefits and net fuel 

usage and GHG reductions.

2.6.2.2.1 EPA Testing of a Hybrid Transit Bus

EPA conducted a hybrid transit bus test to gather experience in testing hybrids and 

evaluate the GHG emissions and fuel consumption benefits. This section provides an 

overview of the study and its results. However, as noted above, the agencies do not consider 

hybrid powertrains to be part of the basis for the standard during this first rulemaking. 

Following coastdown testing, in-use emissions testing was conducted on each bus 

using portable emissions measurement systems meeting subpart J of 40 CFR 1065. Each bus 

was operated over two routes, which were meant to simulate normal transit bus operation. The 

first route was comprised entirely of typical urban stop/go driving, with a number of bus stops 

along the 4.75 mile route. The second route was comprised of roughly half urban driving and 

half highway operation, reaching a maximum speed of approximately 60 MPH. This route 

was approximately 5.75 miles in length.

Fuel economy could be calculated using two methods: through integration of the 

instantaneous fuel rate broadcast by the ECU (ECU method) or through a carbon balance of 

the exhaust gases (Carbon Balance Method). Both methods provided repeatable results, 

however the ECU method tended to consistently yield approximately 5 percent lower fuel 

consumption on both vehicles. This bias appears to be due to small differences in predicted 

fuel flow versus measured exhaust carbon, particularly during deceleration where the ECU 

predicts a complete fuel cut-off. Since the carbon balance method yields more conservative 

results, all fuel consumption data presented has been calculating using this method.

Figure 2-4 presents a comparison of the fuel economy of both buses over the two test 

routes. Each vehicle was tested at least 3 times over each route, and in several cases up to 10 

repeats of each route were conducted. The error bars represent the standard deviation over the 

replicates of each route. Over both routes, the hybrid showed a significant fuel economy 

benefit over the conventional bus. Over route 1 (urban only), this benefit was greatest and 

approached 37 percent. Over route 2 (mixed urban/highway), fuel economy was still 

improved by over 25 percent. Much of this benefit is likely attributable to the regenerative 

braking and launch assist capability of the hybrid system since there is no idle shut-off of the 

engine. A secondary benefit to the regenerative braking system is a significant increase in 

brake service intervals, which was highlighted in discussions with a bus fleet operator.
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Figure 2-4 Hybrid and Conventional Bus Fuel Economy (mpg)

Figure 2-5 presents the CO2 emissions over each route on a work-specific basis. For 

comparison, Figure 2-6, presents CO2 normalized by the mileage travelled. Characterizing the 

CO2 reduction due to the hybrid system, both methods show significant decreases in 

emissions. The work-specific basis may provide a more accurate comparison in this case, 

since environmental effects are better accounted for (i.e. driver aggressiveness, traffic, etc). 

This is evident when comparing the variation over the course of testing, represented by the 

standard deviation. The variability on a work-specific basis is nearly half that of using the 

distance-based metric.

Fuel Economy vs Route

5.52 5.15

6.95 7.04

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Route 1 Route 2

Fuel Economy (mpg)

Conventional

Hybrid
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2-94

Figure 2-5 Hybrid and Conventional Bus CO2 Emission Rates (g/bhp-hr)

Figure 2-6 Hybrid and Conventional Bus CO2 Emission Rates (g/mile)

Figure 2-7 (a-d) compares the CO2 emissions rate (in g/s) during typical launch 

(starting from a stop) events in both buses. Both vehicles showed a spike in CO2 emissions 

when starting from a stop. However, this spike was much more attenuated with the hybrid 

bus, which demonstrates the ability of the launch assist system to reduce CO2 emissions. The 

magnitude of this attenuation varied depending on the exact event, however reductions of 

over 50 percent were not uncommon. Also worth noting is that near the 0.35 mile mark on 

Figure 2-7-d (lower-right), the CO2 emissions are near zero, suggesting that the vehicle is 

maintaining a speed of approximately 15 MPH solely on electric power.

CO2 Emissions vs Route

624 602

410 396

0

100

200

300

400

500

600

700

Route 1 Route 2

CO2 (g/bhp-hr)

Conventional

Hybrid

CO2 Emissions vs Route

1859

1995

1442 1467

0

500

1000

1500

2000

2500

Route 1 Route 2

CO2 (g/mile)

Conventional

Hybrid
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Figure 2-7 Hybrid and Conventional Bus CO2 Emission Rates (g/s)

a b

c d

Other observations through this testing suggest significant complexity in the 

calibration of the hybrid powertrain, presumably with the intent of reducing fuel consumption. 

One example is the set of engine speed-torque points over a given route (see Figure 2-8). The 

calibration of the hybrid powertrain (red) shows distinct patterns for where the engine 

operates. First, the engine is less frequently loaded at, or near idle speed. Second, the engine 

frequently operates at 1200 RPM, which is the lowest speed at which peak torque is available. 

Third, when more power is required (beyond 100 percent torque at 1200 RPM), the engine 

tends to operate along the maximum torque curve as RPM is increased. Keeping engine 

speed as low as possible reduces frictional losses, thus increasing efficiency. In contrast, the 

speed-torque points of the conventional bus show a much more random distribution and 

propensity for operating at lower engine loads. 

0

5

10

15

20

25

30

35

40

45

50

0 0.1 0.2

Distance (miles)

Speed (MPH) or CO2 (g/s)

Conv-MPH

Hybrid-MPH

Conv - CO2

Hybrid-CO2

0

5

10

15

20

25

30

35

40

45

50

0.1 0.2 0.3

Distance (miles)

Speed (MPH) or CO2 (g/s)

Conv-MPH

Hybrid-MPH

Conv - CO2

Hybrid-CO2

0

5

10

15

20

25

30

35

40

45

50

0 0.1 0.2

Distance (miles)

Speed (MPH) or CO2 (g/s)

Conv-MPH

Hybrid-MPH

Conv - CO2

Hybrid-CO2

0

5

10

15

20

25

30

35

40

45

50

0.2 0.3 0.4

Distance (miles)

Speed (MPH) or CO2 (g/s)

Conv-MPH

Hybrid-MPH

Conv - CO2

Hybrid-CO2
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Figure 2-8 Hybrid and Conventional Bus Operating Map Comparison

In summary, the hybrid powertrain has demonstrated significant opportunity in this 

testing for reduction of fuel consumption and CO2 emissions in transit bus applications. 

Testing over typical bus routes showed up to a 37 percent reduction in both fuel consumption 

and CO2 emissions. A summary of these finding is presented in Table 2-38. These reductions 

can be attributed to three features of the hybrid powertrain. First, electric launch assist 

facilitated through regenerative braking. Second, calibration of the engine to operate in the 

most efficient regions of the speed-torque map. Third, electric-only drive at lower speeds was 

witnessed occasionally. 

Table 2-38 Hybrid Powertrain Benefit

Conventional Hybrid Benefit

Avg CoV Avg CoV mpg or 

g/mile

percent

Route 1 MPG 5.15 8.2% 7.04 5.5% 1.89 37%

CO2 (g/mile) 1995 8.0% 1442 5.5% 553 28%

CO2 (g/bhp-hr) 624 3.7% 396 5.3% 228 37%

Route 2 MPG 5.52 8.0% 6.95 5.3% 1.43 26%

CO2 (g/mile) 1859 7.9% 1467 5.5% 392 21%

CO2 (g/bhp-hr) 602 4.0% 410 1.7% 192 32%

0

20

40

60

80

100

120

500 1000 1500 2000 2500

Engine Speed (RPM)

Engine Load (%)

Conventional

Hybrid
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2.6.2.3 Other Vocational Vehicle Technologies

The agencies assessed other vehicle technologies, such as idle reduction, advanced 

drivetrains, and weight reduction, and have concluded that they may have the potential to 

reduce fuel consumption and GHG emissions from at least certain vocational vehicles, but the 

agencies have not been able to estimate baseline fuel consumption and GHG emissions levels 

for each type of vocational vehicle and for each type of technology, given the wide variety of 

models and uses of vocational vehicles. 

Idle reduction technologies such as APUs and cabin heaters can reduce workday idling 

associated with vocational vehicles. However, characterizing idling activity for the vocational 

segment in order to quantify the benefits of idle reduction technology is complicated by the 

variety of duty cycles found in the sector. Idling in school buses, fire trucks, pick-up trucks, 

delivery trucks, and other types of vocational vehicles varies significantly. Given the great 

variety of duty cycles and operating conditions of vocational vehicles and the timing of these 

rules, it is not feasible at this time to establish an accurate baseline for quantifying the 

expected improvements which could result from use of idle reduction technologies. 

Similarly, for advanced drivetrains and advanced transmissions determining a baseline 

configuration, or a set of baseline configurations, is extremely difficult given the variety of 

trucks in this segment. The agencies do not believe that we can legitimately base standard 

stringency on the use of technologies for which we cannot identify baseline configurations, 

because absent baseline emissions and baseline fuel consumption, the emissions reductions 

achieved from introduction of the technology cannot be quantified. 

For some technologies, such as weight reduction and improved auxiliaries – such as 

electrically driven power steering pumps and the vehicle’s air conditioning system -- the need 

to limit technologies to those under the control of the chassis manufacturer further restricted 

the agencies’ options for incorporating the technologies into the final rules. For example, 

lightweight components that are under the control of chassis manufacturers are limited to a 

very few components such as frame rails. Considering the fuel efficiency and GHG emissions 

reduction benefits that will be achieved by finalizing these rules in the timeframe proposed, 

rather than delaying in order to gain enough information to include additional technologies, 

the agencies have decided to finalize standards that do not assume the use of these 

technologies and will consider incorporating them in a later action applicable to later model 

years.

2.7 Air Conditioning

Air conditioning (A/C) systems contribute to GHG emissions in two ways – direct 

emissions through refrigerant leakage, and indirect exhaust emissions due to the extra load on 

the vehicle’s engine to provide power to the air conditioning system. Hydrofluorocarbon 

(HFC) refrigerants, which are powerful GHG pollutants, can leak from the A/C system. This 

includes the direct leakage of refrigerant as well as the subsequent leakage associated with 

maintenance and servicing, and with disposal at the end of the vehicle’s life. No other vehicle 
Regulatory Impact Analysis 

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system has associated GHG leakage.129 The current widely-used refrigerant – R134a, has a 

high global warming potential (GWP) of 1430. 130 Due to the high GWP of this HFC, a small 

leakage of the refrigerant has a much greater global warming impact than a similar amount of 

emissions of CO2 or other mobile source GHGs. 

Heavy-duty air conditioning systems today are similar to those used in light-duty

applications. However, differences may exist in terms of cooling capacity (such as sleeper 

cabs have larger cabin volumes than day cabs), system layout (such as the number of 

evaporators), and the durability requirements due to longer truck life. However, the 

component technologies and costs to reduce direct HFC emissions are similar between the 

two types of vehicles. 

The quantity of indirect GHG emissions from A/C use in heavy-duty trucks relative to 

the CO2 emissions from driving the vehicle and moving freight is very small. Therefore, a 

credit approach for improved A/C system efficiency is not appropriate for this segment of 

vehicles because the value of the credit is too small to provide sufficient incentive to utilize 

feasible and cost-effective air conditioning leakage improvements. For the same reason, 

including air conditioning leakage improvements within the main standard would in many

instances result in lost control opportunities. Therefore, EPA is finalizing that truck 

manufacturers be required to meet a low leakage requirement for all air conditioning systems 

installed in 2014 model year and later trucks, with one exception. EPA is not establishing 

leakage standards for Class 2b-8 Vocational Vehicles at this time due to the complexity in the 

build process and the potential for different entities besides the chassis manufacturer to be 

involved in the air conditioning system production and installation, with consequent 

difficulties in developing a regulatory system. 

2.7.1 Refrigerant Leakage

Based on measurements from 300 European light-duty vehicles (collected in 2002 and 

2003), Schwarz and Harnisch estimate that the average HFC direct leakage rate from modern 

A/C systems was estimated to be 53 g/yr.131 This corresponds to a leakage rate of 6.9 percent 

per year. This was estimated by extracting the refrigerant from recruited vehicles and 

comparing the amount extracted to the amount originally filled (as per the vehicle 

specifications). The fleet and size of vehicles differs from Europe and the United States, 

therefore it is conceivable that vehicles in the United States could have a different leakage 

rate. The authors measured the average charge of refrigerant at initial fill to be about 747 

grams (it is somewhat higher in the U.S. at 770g), and that the smaller cars (684 gram charge) 

emitted less than the higher charge vehicles (883 gram charge). Moreover, due to the climate 

differences, the A/C usage patterns also vary between the two continents, which may

influence leakage rates. 

Vincent et al., from the California Air Resources Board estimated the in-use 

refrigerant leakage rate to be 80 g/yr.

132

 This is based on consumption of refrigerant in 

commercial fleets, surveys of vehicle owners and technicians. The study assumed an average 

A/C charge size of 950 grams and a recharge rate of 1 in 16 years (lifetime). The recharges 

occurred when the system was 52 percent empty and the fraction recovered at end-of-life was 

8.5 percent.
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Since the A/C systems are similar in design and operation between light- and heavyduty vehicles, and emissions due to direct refrigerant leakage are significant in all vehicle 

types, EPA is finalizing a leakage standard which is a “percent refrigerant leakage per year” 

to assure that high-quality, low-leakage components are used in each air conditioning system 

design. The agency believes that a single “gram of refrigerant leakage per year” would not 

fairly address the variety of air conditioning system designs and layouts found in the heavyduty truck sector. EPA is finalizing a standard of 1.50 percent leakage per year for HeavyDuty Pickup Trucks and Vans and Class 7/8 Tractors. The final standard was derived from 

the vehicles with the largest system refrigerant capacity based on the Minnesota GHG 

Reporting database.133 As shown in Figure 2-9, the average percent leakage per year of the 

2010 model year vehicles in the upper quartile in terms of refrigerant capacity was 1.60 

percent (for reference, in the 2010 Light-Duty GHG rule, the average was estimated to be 2.7 

percent, based on a leakage rate of 20.7 g/yr and a system capacity of 770 g). 

Figure 2-9 Distribution of Percentage Refrigerant Loss Per Year - Vehicles in Upper Quartile of A/C 

System Refrigerant Capacity (from 2010 Minnesota Reporting Data).

By requiring that all heavy-duty trucks achieve the leakage level of 1.50 percent per 

year, roughly half of the vehicles in the 2010 data sample would need to reduce their leakage 

rates, and an emissions reduction roughly comparable to that necessary to generate direct 

emission credits under the light-duty vehicle program would result. See 75 FR at 25426-247. 

0.0000

0.0200

0.0400

0.0600

0.0800

0.1000

0.1200

0.1400

0.1600

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50 2.60 2.70 2.80 2.90 3.00

Frequency

Annual Percentage Refrigerant Loss (%/yr)

-Annual Percentage Loss = Yearly Leak Rate / Refrigerant Capacity

-53 vehicles in data set (2010 model year only)

- System refrigerant capacity ranges from 810 g (Chevrolet Express)

to 1531 g (Ford E-Series w/dual evaporators)

- Yearly % leak rate ranges from 0.78%/yr (Chevrolet Express) to

2.77%/yr (Toyota Land Cruiser w/dual evaporator and coolbox)

Median = 1.44 %/yr

Average = 1.60 %/yr
Regulatory Impact Analysis 

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We believe that a yearly system leakage approach will assure that high-quality, low-leakage, 

components are used in each A/C system design, and we expect that manufacturers will 

reduce A/C leakage emissions by utilizing improved, leak-tight components. Some of the 

improved components available to manufacturers are low-permeation flexible hoses, multiple 

o-ring or seal washer connections, and multiple-lip compressor shaft seals. The availability of 

low leakage components in the market is being driven by the air conditioning credit program 

in the light-duty GHG rule (which applies to 2012 model year and later vehicles). EPA 

believes that reducing A/C system leakage is both highly cost-effective and technologically 

feasible. The cooperative industry and government Improved Mobile Air Conditioning 

(IMAC) program has demonstrated that new-vehicle leakage emissions can be reduced by 50

percent by reducing the number and improving the quality of the components, fittings, seals, 

and hoses of the A/C system.134 All of these technologies are already in commercial use and 

exist on some of today’s systems.

 

EPA requires that manufacturers demonstrate improvements in their A/C system 

designs and components through a design-based method. The method for calculating A/C 

Leakage is based closely on an industry-consensus leakage scoring method, described below. 

This leakage scoring method is correlated to experimentally-measured leakage rates from a

number of vehicles using the different available A/C components. Under this approach, 

manufacturers would choose from a menu of A/C equipment and components used in their 

vehicles in order to establish leakage scores, which would characterize their A/C system 

leakage performance and calculate the percent leakage per year as this score divided by the 

system refrigerant capacity. 

Consistent with the Light-Duty Vehicle Greenhouse Gas Emissions rulemaking, a 

manufacturer would compare the components of its A/C system with a set of leakagereduction technologies and actions that is based closely on that being developed through 

IMAC and the Society of Automotive Engineers (as SAE Surface Vehicle Standard J2727, 

August 2008 version).135 See generally 75 FR at 25426. The SAE J2727 approach was 

developed from laboratory testing of a variety of A/C related components, and EPA believes 

that the J2727 leakage scoring system generally represents a reasonable correlation with 

average real-world leakage in new vehicles. Like the IMAC approach, our proposed approach 

would associate each component with a specific leakage rate in grams per year identical to the 

values in J2727 and then sum together the component leakage values to develop the total A/C 

system leakage. However, in the heavy-duty truck program, the total A/C leakage score is 

then divided the value by the total refrigerant system capacity to develop a percent leakage 

per year value.

2.7.2 System Efficiency

A program could also be developed that includes efficiency improvements. CO2-

equivalent emissions and fuel consumption are also associated with air conditioner efficiency, 

since air conditioners create load on the engine. See 74 FR at 49529. However, the agencies 

are not setting air conditioning efficiency standards for heavy-duty trucks, as the fuel 

consumption and CO2 emissions due to air conditioning systems in heavy-duty trucks are 
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minimal (compared to their overall fuel consumption and emissions of CO2). For example, 

EPA conducted modeling of a Class 8 sleeper cab using GEM to evaluate the impact of air 

conditioning and found that it leads to approximately 1 gram of CO2/ton- mile. Therefore, a 

projected 24 percent improvement of the air conditioning system (the level projected in the 

light-duty GHG rulemaking), would only reduce CO2 emissions by less than 0.3 g CO2/tonmile, or approximately 0.3 percent of the baseline Class 8 sleeper cab CO2 emissions.
Regulatory Impact Analysis 

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2.8 Other Fuel Consumption and GHG Reducing Strategies

There are several other types of strategies available to reduce fuel consumption and 

GHG emissions from trucks. For the reader’s reference, EPA and NHTSA identify several of 

these technologies and strategies below, but we note that they are outside the regulatory

framework currently identified and will neither be required by final standards nor were they

considered in determining the stringency of the final standards. 

2.8.1 Auxiliaries 

The accessories on a truck engine, including the alternator, coolant and oil pumps are 

traditionally mechanically gear- or belt-driven by the base engine. In general, the effect of 

accessory power consumption in trucks is much less than in cars, but the mechanical 

auxiliaries operate whenever base engines are running, which can waste energy when the 

auxiliaries are not needed. The replacement of mechanical auxiliaries by electrically-driven 

systems can decouple mechanical loads from the base engine and reduce energy use. Since 

the average engine loads from mechanical auxiliaries are higher than those from a small 

generator that supplies electricity to electric auxiliaries, base engine fuel can be reduced. A 

reduction in CO2 emissions and fuel consumption can be realized by driving them electrically

and only when needed (“on-demand”). The heavy and medium trucks have several auxiliary 

systems:

 Air compressor,

 Hydraulic pumps,

 Coolant pump,

 Engine oil and fuel pumps,

 Fans, and

 Air conditioning compressor.

The systems listed above, although not inclusive, can be optimized by various 

methods reducing fuel consumption and GHG emissions:

 Electric power steering (EPS) – is an electrically-assisted steering system that has 

advantages over traditional hydraulic power steering because it replaces a 

continuously operated hydraulic pump, thereby reducing parasitic losses from the 

accessory drive.

 Electric water pumps and electric fans - can provide better control of engine cooling. 

For example, coolant flow from an electric water pump can be reduced and the 

radiator fan can be shut off during engine warm-up or cold ambient temperature 

conditions which will reduce warm-up time, reduce warm-up fuel enrichment, and 

reduce parasitic losses. Indirect benefit may be obtained by reducing the flow from the 

water pump electrically during the engine warm-up period, allowing the engine to heat 

more rapidly and thereby reducing the fuel enrichment needed during cold starting of 

the engine.
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 High efficiency alternators - provide greater electrical power and efficiency at road 

speed or at idle than conventional original equipment replacement alternators that 

typically operate at 55 percent efficiency. 

 If electric power is not available - there are still some technologies that can be applied 

to reduce the parasitic power consumption of accessories. Increased component 

efficiency is one approach, and clutches can be used to disengage the alternator and air 

compressor when they are not required. Many MD/HD engines incorporate clutched 

cooling fans which can be shut off during engine warm-up, thereby not requiring 

electric cooling fans. Air compressors that are rotating but not creating pressure 

absorb about half the power of a pumping compressor, and compressors normally only 

pump a small percentage of the time in long-haul trucks.

Several studies have documented the GHG reductions from electrification and/or 

optimization of truck auxiliaries. One study, based on a full-scaled test of a prototype truck 

that used a small generator to produce electricity, full electrification of auxiliaries reduces fuel 

use by 2 percent including extended idle and estimated potential reductions in modal GHG 

emissions are 1.4 percent. Another study recently completed by Ricardo discussed the 

advantages of electrification of engine accessories along with the potential to increase fuel 

economy citing examples such as variable flow water pumps and oil pumps136. Potential gains 

may be realized in the range of 1 to 3 percent but are highly dependent on truck type, size and 

duty cycle. In a NESCCAF study, the accessory power demand of a baseline truck was 

modeled as a steady state power draw of 5 kW, and 3 kW for more electrical accessories in 

individual vehicle configurations that included electric turbo compounding. The 2 kW savings 

versus average engine power of 100 to 200kW over a drive cycle nets roughly 1 to 2 percent

savings compared to a baseline vehicle.

Accurate data providing power consumption values for each discrete accessory over a 

range of operating conditions was not available due to the variation of the truck fleet. Based 

on research and industry feedback, a simplified assumption for modeling was made that the 

average power demand for mechanically driven accessories is 5 kW, and the average power 

demand for electrically driven accessories is 3 kW. This provides a 2 kW advantage for the 

electrically driven accessories over the entire drive cycle represented and is estimated to 

provide a 1.5 percent improvement in efficiency and reduction in CO2 emissions. As a 

comparison, the average load on a car engine over a drive cycle may be in the 10 to 20 kW 

range. At this level, a 2 kW reduction in accessory loads of a passenger vehicle makes a 

significant difference (approximately 10 percent). Given the higher loads experienced by

truck engines, accessory demand is a much smaller share of overall fuel consumption. 

Accessory power demand determined by discrete components will be not be included in the 

model at this time and a power draw of 5 kW for standard accessories and 3 kW for electrical 

accessories will be used. There is opportunity for additional research to improve upon this 

simple modeling approach by using actual measured data to improve the modeling 

assumptions.
Regulatory Impact Analysis 

2-104

2.8.2 Driver training 

Driver training that targets fuel efficiency can help drivers recognize and change 

driving habits that waste fuel and increase harmful emissions. Even highly experienced truck 

drivers can boost their skills and enhance driving performance through driver training 

programs.137

Driving habits that commonly waste fuel are high speed driving, driving at 

unnecessarily high rpm, excessive idling, improper shifting, too-rapid acceleration, 

unnecessarily frequent stops and starts, and poor route planning. Well-trained drivers can 

reduce fuel consumption by applying simple techniques to address vehicle and engine speed, 

shifting patterns, acceleration and braking habits, idling, and use of accessories.138 Some 

techniques include starting out in a gear that does not require using the throttle when releasing 

the clutch, progressive shifting (upshifting at the lowest possible rpm), anticipating traffic 

flow to reduce starts and stops, use of block shifting where possible (e.g., shifting from 2nd to 

5

th gear), using cruise control as appropriate, and coasting down or using the engine brake to 

slow the vehicle, instead of gearing down or using the brake pedal.

As discussed elsewhere in this chapter, idling can be eliminated by the use of auxiliary 

power units or other idle reduction solutions that provide power or heating and cooling to the 

cab at a much lower rate of energy consumption.

Better route planning that reduces unnecessary mileage and the frequency of empty

backhauls, and takes into account factors like daily congestion patterns is another facet of a 

comprehensive driver training program. Such planning can be assisted through the use of 

logistics companies, which specialize in such efficiencies.

In its report, Technologies and Approaches to Reducing the Fuel Consumption of 

Medium and Heavy-Duty Vehicles, the National Research Council cited studies that found, on 

average, a five percent improvement in vehicle fuel efficiency due to driver training.139 

EPA’s SmartWay Transport Partnership has documented the success of dozens of trucking 

companies’ use of driver training programs. One company reported saving an average of 42 

gallons per student, or 335,000 gallons of fuel per year; and, saving 837,000 gallons of fuel in 

the four years it has had its training program in place.

140

 Trucking fleets can provide 

additional motivation to reward drivers for improved performance with incentive programs, 

which may be monetary or provide other forms of benefits and recognition. Successful 

programs are those that perform ongoing reviews of driver techniques, and provide assistance 

to improve and/or retrain drivers. 

While EPA and NHTSA recognize the potential opportunity to reduce fuel 

consumption and greenhouse gas emissions by encouraging fuel-efficient driver habits, 

mandating driver training for all of the nation’s truck drivers is beyond the scope of this 

regulation. However, in developing this regulation, the agencies did consider technologies 

that can provide some of the benefits typically addressed through driver training. Examples 

include automatic engine shutdown to reduce idling, automated or automated manual 

transmissions to optimize shifting, and speed limiters to reduce high speed operation. EPA 

will also continue to promote fuel-efficient driving through its SmartWay program. In 
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addition to providing fact sheets on fuel efficient driving,141 SmartWay is collaborating with 

Natural Resources Canada’s FleetSmart program to develop a web-enabled “fuel efficient 

driver” training course for commercial truck drivers. Once the course is developed, it will 

complement the agencies’ regulatory program by making fuel efficient driver training 

strategies available to any commercial truck driver.

2.8.2.1 Replacement Tires

Original equipment (OE) tires are designed and marketed for specific applications and 

vehicles. Their characteristics are optimized for the specific application and vehicle. Because 

they are not sold as OE, replacement tires are generally designed for a variety of applications 

and vehicle types that have different handling characteristics. The tires marketed to the 

replacement tire market tend to place greater emphasis on tread wear, and therefore often have 

higher rolling resistance than OE tires. 

The market for replacement tires is individual vehicle owners and fleet owners and not 

the vehicle manufacturers. Many fleets report that the cost of fuel as opposed to driver pay is 

its number one cost. This has resulted in a greater demand for low rolling resistance 

replacement tires. Both heavy-duty and medium-duty truck fleets are looking for ways to 

reduce operational costs. 

In 2007, EPA’s SmartWay Transport Partnership introduced a means to distinguish 

tires based on their rolling resistance. Since 2007 the number of low rolling resistance tires 

available to vehicle owners and vehicle fleets has increased greatly, which is an indicator of 

an increase in demand. EPA expects this trend to continue. In addition, effective January 1, 

2010, California Air Resource Board requires that all tractor-trailers hauling dry van trailers 

on any California road be equipped with SmartWay verified low rolling resistance tires; other 

states may adopt this requirement. EPA expects this requirement will drive the demand for 

low rolling resistance tires even further. 

2.8.2.2 Retreaded Tires

The tread life of a tire is a measure of durability and some tires are designed 

specifically for greater durability. Commercial truck tires are designed to be retreaded, a 

process in which a new tread is bonded to the tire casing. The original tread of a tire will last 

anywhere from 100,000 miles to over 300,000 miles, depending on vehicle operation, original 

tread depth, tire axle position, and proper tire maintenance. Retreading can extend the tire’s 

useful life by 100,000 miles or more.142 In 2005, the Tire Industry Association estimated that 

approximately 17.6 million retreaded truck tires were sold in North America143.

To maintain the quality of the casing and increase the likelihood of retreading, a tire 

should be retreaded before the tread depth is reduced to its legal limit. At any time, a steer 

tire must have a tread depth of at least 4/32 of an inch and a drive tire must have a tread depth 

of at least 2/32 of an inch (49 CFR § 393.75). To protect the casing, a steer tire is generally 

retreaded once the tread is worn down to 6/32 of an inch and a drive tire is retreaded once the 
Regulatory Impact Analysis 

2-106

tread is worn down to 8/32 of an inch.144 Tires used on Class 8 vehicles are retreaded as 

many as three times. 

Both the casing and the tread contribute to a tire’s rolling resistance. It is estimated 

that 35 to 50 percent of a tire’s rolling resistance is the result of the tread.61 Differences in 

drive tire rolling resistance of up to 50 percent for the same casing with various tread 

compounds have been demonstrated. For example, a fuel efficient tread (as defined by the 

manufacturer) was added to two different casings resulting in an average increase in rolling 

resistance of 48 percent. When a nonfuel efficient tread (also defined by the manufacturer) 

was added to the same casings, the rolling resistance increased by 125 percent on average. 

This characterizes the effect of the tread on the rolling resistance of a tire. 

Because tires can be retreaded multiple times, changes in the casing due to wear, 

damage and material aging may impact rolling resistance to a greater degree than would occur 

in an original tire. Additionally, as evidenced above, if a tread compound different than the 

original tread is used, a retreaded tire can have higher or lower rolling resistance than the 

original tire. Since the agencies have no way of knowing whether the rolling resistance of 

retreaded tires will be higher or lower than the rolling resistance of the original tires, we 

similarly have no way of knowing whether low rolling resistance tire benefits will continue to 

accrue for a vehicle’s entire lifetime. 

There is a cost savings associated with retread tires. A new retread costs between 

$150 and $200, compared to a new tire which costs typically around $400. Since retreads are 

not typically used on the steer axle position, this represents a savings of $1,600 to $2,000 per 

tractor. 

2.8.3 Automatic Tire inflation and Tire Pressure Monitoring System

Underinflation of tires has the potential to reduce fuel economy by as much as two to 

three percent145. Although most truck fleets understand the importance of keeping tires 

properly inflated, it is likely that a substantial proportion of trucks on the road have one or 

more underinflated tires. An industry survey conducted in 2002 at two truck stops found that 

fewer than half of the tires checked were within five pounds per square inch (psi) of their 

recommended inflation pressure. Twenty-two percent of the vehicles checked had at least one 

tire underinflated by at least twenty psi, and four percent of the vehicles were running with at 

least one flat tire, defined as a tire underinflated by fifty psi or more. The survey also found 

mismatches in tire pressure exceeding five percent for dual tires on axle ends.146

A commercial vehicle tire condition study conducted by the Federal Motor Vehicle 

Safety Administration (FMCSA) in 2003 found similar indicators of poor tire inflation 

pressure maintenance in commercial fleets. The FMCSA concluded that only forty-four 

percent of all tires on commercial vehicles were inflated within 5 psi of the recommended 

pressure, while over seven percent of all tires in operation on commercial vehicles were 

underinflated by at least twenty psi. It was also determined that the rates of tires used in dual 

assemblies that differed in pressure by more than 5 psi was approximately twenty percent for 
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tractor duals and twenty-five percent for trailer duals. Finally, the FMCSA concluded that 

there were significant differences in tire inflation maintenance practices between private and 

for-hire fleets, smaller and larger fleets, and local bus and motor coach fleets.147

Proper tire inflation pressure can be maintained with a rigorous tire inspection and 

maintenance program or with the use of tire pressure and inflation systems. These systems 

monitor tire pressure; some also automatically keep tires inflated to a specific level. 

However, while the agencies recognize that such devices could have a beneficial effect on 

fuel economy, their use is not included in the regulatory framework. Notwithstanding the 

cited studies, the current level of underinflation of tires in the American truck fleet is not 

known,148 which means that neither a baseline value nor an estimate of the fuel savings from 

the use of automatic tire inflation systems can be quantified with certainty and thus is not 

included as part of the technology package on which standard stringency is predicated. 

Through its SmartWay program, however, EPA does provide information on proper tire 

inflation pressure and on tire inflation and tire inflation pressure monitoring systems.149

2.8.4 Engine Features 

Previous sections 2.3.2.2 through 2.3.2.8 describe the technologies that can be tested 

in an engine test cell for certification purpose and could be potentially implemented in 

production before the time frame of 2017. Some other technologies that cannot be easily

tested in an engine test cell, but can improve engine fuel economy, are still worth mentioning

for the reader’s reference. Examples include these technologies, such as driver rewards, load 

based speed control, gear down protection, and fan control offered by Cummins’s PowerSpec. 

The driver reward developed by Cummins monitors and averages the driver’s trip fuel 

economy and trip idle percent time at regular intervals, seeking to modify driver behavior by

offering incentives to use less fuel. Desirable driving habits, such as low percentage of idle 

time, and high MPG, are rewarded with higher limits on the road speed governor, cruise 

control or both. The load based speed control or other similar programs are designed to 

improve fuel economy, lower vehicle noise, and improve driver satisfaction by managing 

engine speed (rpm) based on real time operating conditions. During high power requirements, 

this type of technology enhances engine performance by providing the driver with an 

extended operating range. In addition to the fuel economy benefits from operating the engine 

at lower speeds, vehicle noise is lowered. 

Gear down protection offered by Cummins is to promote increased fuel efficiency by

encouraging the vehicle driver to operate as much as effectively possible in top gear where 

fuel consumption is lower. This can be done by limiting vehicle speed in lower gears. 

Maximizing time in top gear means the engine runs in a lower rpm range, where fuel 

efficiency is best with improved durability and without compromising performance. 

Difference between top gear and one gear down can be as much as 16 percent in fuel 

economy. More detailed descriptions of many technologies including those mentioned here 

can be viewed at Cummins’s website of 

http://www.powerspec.cummins.com/site/home/index.html. 
Regulatory Impact Analysis 

2-108

Although these technologies mentioned in this section are not able to be tested in an 

engine test cell environment, thus being unable to be directly used for benefits of certification 

purpose, the agencies encourage manufacturers to continue improving the current and 

developing new technologies, thereby reducing fuel consumption and greenhouse gases in a 

broader way.

2.8.5 Logistics

Logistics encompasses a number of interrelated, mostly operational factors that affect 

how efficiently the overall freight transport system works. These factors include choice of 

mode, carrier and equipment; packaging type and amount; delivery time; points of origin and 

destination; route choice, including locations of ports and distribution hubs; and transportation 

tracking systems. These factors are controlled by the organizations that ship and receive 

goods. Due to the specialized nature of logistics management, organizations increasingly rely 

upon internal or outsourced business units to handle this function; many transportation 

providers offer logistics management services to their freight customers. 

Because optimizing logistics is specific to each individual freight move, neither EPA 

nor NHTSA believed it is feasible to manage logistics through this regulation. However, 

implementing certain system-wide logistics enhancements on a national level could provide 

benefits. As described in the 2010 NAS Report,

150 a broader national approach could include 

enhanced telematics and intelligent transportation systems; changes to existing infrastructure 

to optimize modal choice; and increased truck capacity through changes to current truck 

weight and size limits. While such a broad transformation of our freight system is worthwhile 

to consider, implementing such system-wide changes falls outside the scope of this regulation. 

As the National Research Council noted,151 due to its complex nature, logistics management is 

not readily or effectively addressed through any single approach or regulation; a number of 

complementary measures and alternatives are needed. Such measures can include initiatives 

that enable companies to better understand, measure and track the benefits of logistics 

optimization from an environmental and economic standpoint. The SmartWay program 

provides uniform tools and methodologies that companies can use to assess and optimize 

transportation supply chains, and that can complement any future regulatory and 

nonregulatory approaches. 

2.8.6 Longer Combination Vehicles, Weight Increase 

Longer combination vehicles (LCVs) are tractor-trailer combinations that tow more 

than one trailer, where at least one of the trailers exceeds the “pup” size (typically 24-28 feet). 

Because LCVs are capable of hauling more freight than a typical tractor-trailer combination, 

using LCVs reduces the number of truck trips needed to carry the same amount of freight. On 

a fleetwide basis, this saves fuel, reduces greenhouse gas emissions, and reduces per-fleet 

shipping costs. A typical non-LCV may tow a single trailer up to 53 feet in length, or tow two 

pup trailers, or even be a straight truck with a pup trailer connected via a draw bar. In 

contrast, the typical LCV may consist of a tractor towing two trailers of 45-48 feet, and 

occasionally 53 feet in length (a “turnpike double”), or one of that size and one pup (a “Rocky

Mountain double”), or may tow three pups (a “triple”). 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

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Trucks consisting of a two-axle tractor combined with two one-axle trailers up to 28.5 

feet are permitted on all highways in the U.S. National Network, which consists of the 

interstate highway system and certain other roads. Individual states may permit longer LCVs 

to operate on roads that are not part of the National Network. They are allowed in 16 western 

states, but only on turnpikes in the five states east of the Mississippi that allow them; no new 

states were granted permitting authority for LCVs after 1991.

152

 Regulations vary among 

states; some allow LCVs with more than three trailers, but only by permit. Longer length 

turnpike doubles are typically restricted to tolled turnpikes. Such restrictions are based on 

considerations of the difficulty of operation and on expected weather conditions. Other 

regulations on the types of LCVs allowed are seen in other countries; in Australia, where 

weather tends to be stable and dry and cross-country roads tend to be extremely long and flat,

“road trains” of up to four trailers, usually with three axles per trailer, are permitted. 

Some proponents of liberalized size and weight regulations project substantial 

benefits, estimating that highway freight productivity could be doubled and costs reduced. 

Despite the potential benefits of LCVs, as the National Research Council noted in its recent 

report, there are considerations that may make LCVs less cost-effective and less safe, 

compared to traditional tractor-trailer configurations. For example, if infrastructure (e.g., 

bridges with sufficient capacity; roadways with adequate lane width and curb radii for turning 

to accommodate an LCV safely) are not available without traveling far from a more efficient 

route, or if there is insufficient opportunity for the LCV to make the most of the available 

volume in multiple trailers, then LCVs would not be cost-effective. 

The increased vehicular weight of LCVs is both a safety issue and a road maintenance 

issue (see discussion below on increasing vehicle weight and legal load limits). The 

additional weight of extra trailers increases braking and stopping distance, and adds difficulty 

in maintaining speed in grade situations.

With additional regard to safety, LCVs might have trouble with offtracking (when the 

truck’s front and rear wheels do not follow the same path, which can result in departing the 

lane boundaries—a particular problem with longer LCVs), and could increase the challenge of 

merging with and maneuvering in traffic. Lateral stability is a greater problem in LCVs, and 

leads to a greater chance of rollover, particularly when the individual trailers are shorter. 

Also, when a vehicle is passing a LCV on a two-lane road, the period of time spent in the 

opposing lane (up to 2-3 seconds) poses another safety problem.153 Such safety

considerations impact decisions regarding restrictions on the use of LCVs, even when they

may otherwise be a cost-effective freight choice.

Related, moves to increase commercial vehicle weight limits concern not only

relaxing limitations on the use of LCVs, but also increasing gross vehicle weight limits for 

single unit trucks and conventional tractor-trailer combinations, as well as increasing axle 

load limits and trailer lengths. Some analysts cite scenarios in which such relaxations result 

in increased highway freight productivity, while yielding significant reductions in shipping 

costs, congestion, and total vehicle miles traveled.154 Increasing the weight limits allows 

commercial freight vehicles to carry heavier loads, reducing the number of trucks required to 
Regulatory Impact Analysis 

2-110

transport freight, which could potentially result in overall emissions and fuel consumption 

reductions.

Federal law limits gross vehicle weight for commercial vehicles operating in the 

Interstate Highway System to a maximum of 80,000 lbs. (maximum 20,000 lbs. per single 

axle, 34,000 lbs. per tandem axle), with permits available for certain oversize or overweight 

loads and exceptions allowing 400 lbs. more for tractors with idle reduction devices. 

Additional vehicle weight limitations have been set by state and local regulations. These 

limitations arise from considerations of infrastructure characteristics, traffic densities, 

economic activities, freight movement, mode options, and approach to transportation design. 

In some cases, state limits are higher (less stringent) than federal limits.

155

 While these 

parameters are changeable, federal weight limits on vehicles have not changed since 1982, 

and limits set by states have been frozen since 1991.

In response to input from the freight transportation sector and other interested 

parties, the Department of Transportation, the Transportation Research Board, the General 

Accounting Office, and others have conducted studies examining the impacts of proposals 

related to liberalized weight limits. Regardless of the potential benefits of such action, the 

analyses predict premature degradation of infrastructure (e.g., bridges, pavement, grades) as a 

consequence. Increased costs required to maintain and upgrade the highway system would 

impose high burdens on already-strained public resources, raising serious questions about the 

desirability of relaxing weight limits, and about whether such expenditures provide adequate 

public good to justify them. Safety issues similar to those cited for LCVs enter into this 

debate, as do concerns with the effect on the efficiency of automotive travel, impacts on and 

net productivity of other shipping modes (particularly rail), and potential environmental and 

social costs.

The 2010 NAS Report156 recognized the complexities and potential trade-offs 

involved in increasing vehicle size and weight limits. While it is useful to discuss the 

potential emission and energy benefits of heavier and longer trucks, the far-reaching policy

ramifications extend well beyond the scope of this rulemaking.

2.8.7 Traffic Congestion Mitigation 

There are a wide range of strategies to reduce traffic congestion. Many of them are 

aimed at eliminating light-duty vehicle trips such as mass transit improvements, commute trip 

reduction programs, ridesharing programs, implementation of high occupancy vehicle lanes, 

parking pricing, and parking management programs. While focused on reducing light-duty 

vehicle trips, these types of strategies would allow heavy- and medium-duty vehicles to travel 

on less congested roads and thereby use less fuel and emit less CO2. 

A second group of strategies would directly impact CO2 emissions and fuel 

consumption from all types of vehicles. One example of these strategies is road pricing,

including increasing the price of driving on certain roads or in certain areas during the most 

congested periods of the day. A second example is reducing the speed limits on roads and 

implementing measures to ensure that drivers obey the lower speed limits such as increased 

enforcement or adding design features that discourage excessive speeds. 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-111

Some strategies would be designed to effect trips made by heavy- and medium-duty

trucks. These would include programs to shift deliveries in congested areas to off-peak hours. 

Another example is to modify land use so that common destinations are closer together, which 

reduces the amount of travel required for goods distribution. 

These types of congestion relief strategies have been implemented in a number of 

areas around the country. They are typically implemented either by state or local 

governments or in some cases strategies to reduce commuting trips and scheduling off-peak 

deliveries have been implemented by private companies or groups of companies. 

2.9 Summary of Technology Costs Used in this Analysis

Table 2-39 shows the technology costs used throughout this analysis for heavy-duty

engines, vocational vehicles and combination tractors for the years 2014-2020. Table 2-40

shows the technology costs used throughout this analysis for Class 2b and 3 diesel and 

gasoline trucks for the years 2014-2020. These tables reflect the impact of learning effects on 

estimated technology costs. Refer to Table 2-2 for details on the ICMs applied to each 

technology and Table 2-4 for the type of learning applied to each technology. The costs 

shown in the tables do not include the penetration rates so do not always reflect the 

technology’s contribution to the resultant package costs. One final note of clarification is that 

the terms “MHDDcomb” and “HHDDcomb” in the “Class” column refer specifically to 

engines placed in combination tractors (Class 7 and 8 day cabs and sleeper cabs).
Regulatory Impact Analysis 

2-112

Table 2-39 Technology Effectiveness and Costs, Inclusive of Markups, by Year for Heavy-duty DieselIand Gasoline Engines, Vocational Vehicles, and 

Combination Tractors (2009$)

Technology Applied 

to Truck type Class CO2eqEffectiveness 2014 2015 2016 2017 2018 2019 2020

Aftertreatment 

improvements Engine LHDD 1-4%

$117 $114 $111 $108 $105 $103 $101

Turbo efficiency 

improvements Engine LHDD 1-2%

$18 $18 $17 $17 $16 $16 $16

Piston improvements

Engine LHDD

0.5-2%

$3 $3 $3 $3 $2 $2 $2

Optimized water pump

Engine LHDD $91 $89 $86 $84 $82 $81 $79

Optimized oil pump

Engine LHDD $5 $4 $4 $4 $4 $4 $4

Optimized fuel pump

Engine LHDD $5 $4 $4 $4 $4 $4 $4

Valve train friction 

reductions Engine LHDD $109 $106 $104 $101 $98 $97 $95

Optimized fuel rail

Engine LHDD

2-7%

$12 $12 $11 $11 $11 $10 $10

Optimized fuel injector

Engine LHDD $15 $14 $14 $13 $13 $13 $13

EGR cooler improvements

Engine LHDD $4 $4 $3 $3 $3 $3 $3

Cylinder head 

improvements Engine LHDD

$11 $11 $10 $10 $10 $10 $10

2014 MY LHDD Engine 

Package Engine LHDD 5% $388 $378 $368

2017 MY LHDD Engine Engine LHDD 9% $358 $349 $343 $337

 

I The costs included in the table represent technology costs. The engineering costs of $6.8 million per diesel engine manufacturer per year for a five year period 

are not included in the table.
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

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Technology Applied 

to Truck type Class CO2eqEffectiveness 2014 2015 2016 2017 2018 2019 2020

Package

Aftertreatment 

Improvements Engine MHDD 1-4% In R&D In R&D In R&D In R&D In R&D In R&D In R&D

Turbo efficiency 

improvements Engine MHDD 1-2% $18 $18 $17 $17 $16 $16 $16

Piston improvements Engine MHDD

0.5-2%

$3 $3 $3 $3 $2 $2 $2

Optimized water pump Engine MHDD $91 $89 $86 $84 $82 $81 $79

Optimized oil pump Engine MHDD $5 $4 $4 $4 $4 $4 $4

Optimized fuel pump Engine MHDD $5 $4 $4 $4 $4 $4 $4

Valve train friction 

reductions Engine MHDD $82 $80 $78 $76 $74 $73 $71

Optimized fuel rail Engine MHDD

2-7%

$10 $10 $10 $9 $9 $9 $9

Optimized fuel injector Engine MHDD $11 $11 $10 $10 $10 $10 $10

EGR cooler improvements Engine MHDD $4 $4 $3 $3 $3 $3 $3

Cylinder head 

improvements Engine MHDD $6 $6 $6 $6 $6 $6 $6

2014 MY MHDD Engine 

Package Engine MHDD 5% $234 $228 $222

2017 MY MHDD Engine 

Package Engine MHDD 9% $216 $211 $207 $204

Aftertreatment 

Improvements Engine MHDDcomb 1-4% In R&D In R&D In R&D In R&D In R&D In R&D In R&D

Turbo efficiency 

improvements Engine MHDDcomb 1-2% $18 $18 $17 $17 $16 $16 $16

Piston improvements Engine MHDDcomb

0.5-2%

$3 $3 $3 $3 $2 $2 $2

Optimized water pump Engine MHDDcomb $91 $89 $86 $84 $82 $81 $79

Optimized oil pump Engine MHDDcomb $5 $4 $4 $4 $4 $4 $4

Optimized fuel pump Engine MHDDcomb $5 $4 $4 $4 $4 $4 $4

Valve train friction 

reductions Engine MHDDcomb

$82 $80 $78 $76 $74 $73 $71

Optimized fuel rail Engine MHDDcomb

2-7%

$10 $10 $10 $9 $9 $9 $9

Optimized fuel injector Engine MHDDcomb $11 $11 $10 $10 $10 $10 $10

EGR cooler improvements Engine MHDDcomb $4 $4 $3 $3 $3 $3 $3

Cylinder head 

improvements Engine MHDDcomb $6 $6 $6 $6 $6 $6 $6

Turbo mechanical- Engine MHDDcomb 2.5-5% -- -- -- $875 $852 $838 $824
Regulatory Impact Analysis 

2-114

Technology Applied 

to Truck type Class CO2eqEffectiveness 2014 2015 2016 2017 2018 2019 2020

compounding

2014 MY MHDD Engine 

Package Engine MHDDcomb 3% $234 $228 $222

2017 MY MHDD Engine 

Package Engine MHDDcomb 6% $1,091 $1,063 $1,045 $1,027

Aftertreatment 

Improvements Engine HHDD 1-4% In R&D In R&D In R&D In R&D In R&D In R&D In R&D

Turbo efficiency 

improvements Engine HHDD 1-2% $18 $18 $17 $17 $16 $16 $16

Piston improvements Engine HHDD

0.5-2%

$3 $3 $3 $3 $2 $2 $2

Optimized water pump Engine HHDD $91 $89 $86 $84 $82 $81 $79

Optimized oil pump Engine HHDD $5 $4 $4 $4 $4 $4 $4

Optimized fuel pump Engine HHDD $5 $4 $4 $4 $4 $4 $4

Optimized fuel rail Engine HHDD

2-7%

$10 $10 $10 $9 $9 $9 $9

Optimized fuel injector Engine HHDD $11 $11 $10 $10 $10 $10 $10

Cylinder head 

improvements Engine HHDD $6 $6 $6 $6 $6 $6 $6

EGR cooler improvements Engine HHDD $4 $4 $3 $3 $3 $3 $3

2014 MY HHDD Engine 

Package Engine HHDD 3% $234 $228 $222

2017 MY HHDD Engine 

Package Engine HHDD 5% $216 $211 $207 $204

Aftertreatment 

Improvements Engine HHDDcomb 1-4% In R&D In R&D In R&D In R&D In R&D In R&D In R&D

Turbo efficiency 

improvements Engine HHDDcomb 1-2% $18 $18 $17 $17 $16 $16 $16

Piston improvements Engine HHDDcomb

0.5-2%

$3 $3 $3 $3 $2 $2 $2

Optimized water pump Engine HHDDcomb $91 $89 $86 $84 $82 $81 $79

Optimized oil pump Engine HHDDcomb $5 $4 $4 $4 $4 $4 $4

Optimized fuel pump Engine HHDDcomb $5 $4 $4 $4 $4 $4 $4

Optimized fuel rail Engine HHDDcomb

2-7%

$10 $10 $10 $9 $9 $9 $9

Optimized fuel injector Engine HHDDcomb $11 $11 $10 $10 $10 $10 $10

Cylinder head 

improvements Engine HHDDcomb $6 $6 $6 $6 $6 $6 $6

EGR cooler improvements Engine HHDD $4 $4 $3 $3 $3 $3 $3

Turbo mechanicalcompounding Engine HHDDcomb 2.5-5% -- -- -- $875 $852 $838 $824
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

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Technology Applied 

to Truck type Class CO2eqEffectiveness 2014 2015 2016 2017 2018 2019 2020

2014 MY HHDD Engine 

Package Engine HHDDcomb 3% $234 $228 $222

2017 MY HHDD Engine 

Package Engine HHDDcomb 6% $1,091 $1,063 $1,045 $1,027

Engine friction reduction Engine HDG 1-3% -- -- $95 $95 $95 $95 $95

Coupled valve timing Engine HDG 1-4% -- -- $46 $45 $44 $43 $43

Stoich GDI-V8 Engine HDG 1-2% -- -- $452 $442 $433 $426 $420

HD Gasoline Engine 

Package – 2016 MY Engine HDG 5% -- --

$594 $582 $572 $565 $558

LRR steer tire 8.1 Truck Vocational LH 2-3%

$68 $68 $56 $56 $47 $46 $45

LRR drive tire 8.1 Truck Vocational LH $94 $94 $78 $78 $65 $64 $62

2014MY Vehicle Package Truck Vocational LH 3% $81 $79 $77 $75 $73 $72 $71

LRR steer tire 8.1 Truck Vocational MH 2-3% $68 $68 $56 $56 $47 $46 $45

LRR drive tire 8.1 Truck Vocational MH $94 $94 $78 $78 $65 $64 $62

2014MY Vehicle Package Truck Vocational MH 3% $81 $79 $77 $75 $73 $72 $71

LRR steer tire 8.1 Truck Vocational HH 2% $68 $68 $56 $56 $47 $46 $45

LRR drive tire 8.1 Truck Vocational HH $126 $126 $104 $104 $87 $85 $83

2014MY Vehicle Package Truck Vocational HH 2% $97 $94 $92 $90 $87 $86 $84

Aero-Bin III Truck Class7_DayCab LowRoof 1-2% $1,126 $1,097 $1,068 $1,041 $1,015 $997 $981

LRR steer tire Truck Class7_DayCab LowRoof 1-3%

$68 $66 $64 $63 $61 $60 $59

LRR drive tire Truck Class7_DayCab LowRoof $63 $61 $60 $58 $57 $56 $55

Weight reduction: Singlewide tire Truck Class7_DayCab LowRoof

<1%

$336 $327 $319 $311 $303 $298 $293

Weight reduction: 

Aluminum steer wheel Truck Class7_DayCab LowRoof $546 $532 $518 $505 $492 $484 $476

Weight reduction: 

Aluminum single-wide 

wheel

Truck Class7_DayCab LowRoof

$654 $637 $621 $605 $590 $580 $570

Air Conditioning Leakage Truck Class7_DayCab LowRoof <1% $22 $21 $21 $20 $20 $19 $19
Regulatory Impact Analysis 

2-116

Technology Applied 

to Truck type Class CO2eqEffectiveness 2014 2015 2016 2017 2018 2019 2020

2014MY Vehicle 

PackageJ Truck Class7_DayCab LowRoof 3-4% $2,364 $2,303 $2,244 $2,186 $2,131 $2,095 $2,059

Aero-Bin III Truck Class7_DayCab HighRoof 2-4% $1,155 $1,126 $1,097 $1,069 $1,041 $1,024 $1,007

Aero-Bin IV Truck Class7_DayCab HighRoof 3-5% $2,303 $2,303 $1,907 $1,907 $1,590 $1,552 $1,515

LRR steer tire Truck Class7_DayCab HighRoof 1-3%

$68 $66 $64 $63 $61 $60 $59

LRR drive tire Truck Class7_DayCab HighRoof $63 $61 $60 $58 $57 $56 $55

Weight reduction: Singlewide tire Truck Class7_DayCab HighRoof

<1%

$336 $327 $319 $311 $303 $298 $293

Weight reduction: 

Aluminum steer wheel Truck Class7_DayCab HighRoof $546 $532 $518 $505 $492 $484 $476

Weight reduction: 

Aluminum single-wide 

wheel

Truck Class7_DayCab HighRoof

$654 $637 $621 $605 $590 $580 $570

Air Conditioning Leakage Truck Class7_DayCab HighRoof <1% $22 $21 $21 $20 $20 $19 $19

2014MY Vehicle Package Truck Class7_DayCab HighRoof 6-7% $2,612 $2,551 $2,451 $2,394 $2,306 $2,266 $2,226

Aero-Bin III Truck Class8_DayCab LowRoof 1-2% $1,126 $1,097 $1,068 $1,041 $1,015 $997 $981

LRR steer tire Truck Class8_DayCab LowRoof 1-3%

$68 $66 $64 $63 $61 $60 $59

LRR drive tire Truck Class8_DayCab LowRoof $126 $123 $120 $116 $114 $112 $110

Weight reduction: Singlewide tire Truck Class8_DayCab LowRoof

<1%

$672 $654 $638 $621 $605 $595 $585

Weight reduction: 

Aluminum steer wheel Truck Class8_DayCab LowRoof $546 $532 $518 $505 $492 $484 $476

Weight reduction: 

Aluminum single-wide 

wheel

Truck Class8_DayCab LowRoof

$1,308 $1,275 $1,242 $1,210 $1,179 $1,160 $1,140

Air Conditioning Leakage Truck Class8_DayCab LowRoof <1% $22 $21 $21 $20 $20 $19 $19

2014MY Vehicle Package Truck Class8_DayCab LowRoof 3-4% $2,871 $2,797 $2,725 $2,656 $2,588 $2,544 $2,501

Aero-Bin III Truck Class8_DayCab HighRoof 2-4% $1,155 $1,126 $1,097 $1,069 $1,041 $1,024 $1,007

Aero-Bin IV Truck Class8_DayCab HighRoof 3-5% $2,303 $2,303 $1,907 $1,907 $1,590 $1,552 $1,515

LRR steer tire Truck Class8_DayCab HighRoof 1-3% $68 $66 $64 $63 $61 $60 $59

 

J All vehicle package costs in the table include the proposed application rates of the individual technologies used to establish the proposed standards. 
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

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Technology Applied 

to Truck type Class CO2eqEffectiveness 2014 2015 2016 2017 2018 2019 2020

LRR drive tire Truck Class8_DayCab HighRoof $126 $123 $120 $116 $114 $112 $110

Weight reduction: Singlewide tire Truck Class8_DayCab HighRoof

<1%

$672 $654 $638 $621 $605 $595 $585

Weight reduction: 

Aluminum steer wheel Truck Class8_DayCab HighRoof $546 $532 $518 $505 $492 $484 $476

Weight reduction: 

Aluminum single-wide 

wheel

Truck Class8_DayCab HighRoof

$1,308 $1,275 $1,242 $1,210 $1,179 $1,160 $1,140

Air Conditioning Leakage Truck Class8_DayCab HighRoof <1% $22 $21 $21 $20 $20 $19 $19

2014MY Vehicle Package Truck Class8_DayCab HighRoof 6-7% $3,119 $3,045 $2,933 $2,863 $2,763 $2,715 $2,668

Aero-Bin III Truck Class8_Sleeper

Cab LowRoof 3-5% $1,374 $1,338 $1,304 $1,271 $1,238 $1,217 $1,197

LRR steer tire Truck Class8_Sleeper

Cab LowRoof 1-3% $68 $66 $64 $63 $61 $60 $59

LRR drive tire Truck Class8_Sleeper

Cab LowRoof $126 $123 $120 $116 $114 $112 $110

Weight reduction: Singlewide tire Truck Class8_Sleeper

Cab LowRoof <1% $672 $654 $638 $621 $605 $595 $585

Weight reduction: 

Aluminum steer wheel Truck Class8_SleeperCab LowRoof $546 $532 $518 $505 $492 $484 $476

Weight reduction: 

Aluminum single-wide 

wheel

Truck Class8_Sleeper

Cab LowRoof

$1,308 $1,275 $1,242 $1,210 $1,179 $1,160 $1,140

Aux power unit (APU) Truck Class8_Sleeper

Cab LowRoof 5-6% $5,455 $5,314 $5,178 $5,046 $4,917 $4,834 $4,753

Air Conditioning Leakage Truck Class8_Sleeper

Cab LowRoof <1% $22 $21 $21 $20 $20 $19 $19

2014MY Vehicle Package Truck Class8_Sleeper

Cab LowRoof 12-13% $8,271 $8,057 $7,850 $7,650 $7,455 $7,329 $7,206

Aero-Bin III Truck Class8_Sleeper

Cab MidRoof 3-5% $1,404 $1,367 $1,332 $1,298 $1,265 $1,244 $1,223

LRR steer tire Truck Class8_Sleeper

Cab MidRoof 1-3% $68 $66 $64 $63 $61 $60 $59

LRR drive tire Truck Class8_Sleeper

Cab MidRoof $126 $123 $120 $116 $114 $112 $110

Weight reduction: Single- Truck Class8_Sleeper MidRoof <1% $672 $654 $638 $621 $605 $595 $585
Regulatory Impact Analysis 

2-118

Technology Applied 

to Truck type Class CO2eqEffectiveness 2014 2015 2016 2017 2018 2019 2020

wide tire Cab

Weight reduction: 

Aluminum steer wheel Truck Class8_SleeperCab MidRoof $546 $532 $518 $505 $492 $484 $476

Weight reduction: 

Aluminum single-wide 

wheel

Truck Class8_Sleeper

Cab MidRoof

$1,308 $1,275 $1,242 $1,210 $1,179 $1,160 $1,140

Aux power unit (APU) Truck Class8_Sleeper

Cab MidRoof 5-6% $5,455 $5,314 $5,178 $5,046 $4,917 $4,834 $4,753

Air Conditioning Leakage Truck Class8_Sleeper

Cab MidRoof <1% $22 $21 $21 $20 $20 $19 $19

2014MY Vehicle Package Truck Class8_Sleeper

Cab MidRoof 11-12% $8,291 $8,078 $7,870 $7,669 $7,474 $7,347 $7,224

Aero-Bin III Truck Class8_Sleeper

Cab HighRoof 3-5% $1,560 $1,520 $1,481 $1,443 $1,406 $1,382 $1,359

Aero-Bin IV Truck Class8_Sleeper

Cab HighRoof 4-7% $2,675 $2,675 $2,215 $2,215 $1,847 $1,803 $1,760

LRR steer tire Truck Class8_Sleeper

Cab HighRoof 1-3% $68 $66 $64 $63 $61 $60 $59

LRR drive tire Truck Class8_Sleeper

Cab HighRoof $126 $123 $120 $116 $114 $112 $110

Weight reduction: Singlewide tire Truck Class8_Sleeper

Cab HighRoof <1% $672 $654 $638 $621 $605 $595 $585

Weight reduction: 

Aluminum steer wheel Truck Class8_SleeperCab HighRoof $546 $532 $518 $505 $492 $484 $476

Weight reduction: 

Aluminum single-wide 

wheel

Truck Class8_Sleeper

Cab HighRoof

$1,308 $1,275 $1,242 $1,210 $1,179 $1,160 $1,140

Aux power unit (APU) Truck Class8_Sleeper

Cab HighRoof 5-6% $5,455 $5,314 $5,178 $5,046 $4,917 $4,834 $4,753

Air Conditioning Leakage Truck Class8_Sleeper

Cab HighRoof <1% $22 $21 $21 $20 $20 $19 $19

2014MY Vehicle Package Truck Class8_Sleeper

Cab HighRoof 15-16% $7,641 $7,458 $7,188 $7,016 $6,775 $6,658 $6,543
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-119

Table 2-40 Technology Effectiveness and Costs, Inclusive of Markups, by Year for HD Diesel and Gasoline Pickup Trucks & Vans (2009$)

Technology Applied to CO2eq 

Effectiveness 2014 2015 2016 2017 2018 2019

Low friction 

lubricants All 0-1% $4 $4 $4 $4 $4 $4

Engine friction 

reduction

HD

Gasoline 1-3% $116 $116 $116 $116 $116 $111

Stoich GDI V8 HD

Gasoline 1-2% $481 $470 $460 $460 $460 $425

8sp AT (relative 

to 6sp AT) All 1.7% $281 $275 $269 $269 $269 $248

Low RR Tires All 1-2% $7 $7 $7 $7 $7 $6

Aero1 All 1-2% $58 $57 $55 $55 $55 $53

Electric/Electrohydraulic Power 

steering

All 1-2% $115 $112 $109 $109 $109 $105

DSL engine 

improvements HD Diesel 4-6% $184 $180 $175 $171 $167 $156

DSL 

aftertreatment 

improvements

HD Diesel 3-5% $119 $116 $114 $114 $114 $109

Improved 

accessories HD Diesel 1-2% $93 $91 $89 $89 $89 $851

Mass Reduction 

(5%)

2b 

HDGasoline 1.6% $108 $106 $103 $103 $103 $99

Mass Reduction 

(5%)

2b 

HDDiesel 1.6% $121 $118 $115 $115 $115 $110

Mass Reduction 

(5%)

3 

HDGasoline 1.6% $115 $112 $109 $109 $109 $105

Mass Reduction 

(5%) 3 HDDiesel 1.6% $127 $124 $121 $121 $121 $116

Air 

Conditioning 

Leakage

All 2% $21 $21 $20 $19 $19 $18

Overall 2018 

MY Package 12-17% $1,048 $986
Regulatory Impact Analysis 

2-120

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*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-121

 

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*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

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98 Brodrick, C., T.Lipman, M. Farshchi, H. Dwyer, S. Gouse III, D.B. Harris, and F.King, Jr. Potential Benefits 

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Page 1405.
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101 National Academy of Science. Technologies and Approaches to Reducing the Fuel Consumption of Mediumand Heavy-Duty Vehicles. March 2010. 2010. Page 122 says the best in class APU consumes 0.18 gallon per 

hour.

102 National Academy of Science. Technologies and Approaches to Reducing the Fuel Consumption of Mediumand Heavy-Duty Vehicles. March 2010. Page 124.

103

 See Title 13, California Code of Regulations § 1956.8, Requirements to Reduce Idling Emissions From New 

and In-Use Trucks, available at http://www.arb.ca.gov/regact/hdvidle/frorev.pdf

104 See http://www.osha.gov/SLTC/trucking_industry/index.html and http://www.fmcsa.dot.gov/rulesregulations/administration/fmcsr/fmcsrruletext.aspx?reg=393.76, accessed May 2011

105 See http://www.ccohs.ca/oshanswers/phys_agents/heat_health.html, and 

http://www.coolantarctica.com/Antarctica%20fact%20file/science/cold_humans.htm, accessed May 2011

106

 Data Collected by the Texas Transportation Institute as part of NTRD Project N-42: Development of a NOx 

Verification Protocol and Actual Testing of Onboard Idle Reduction Technologies. Sponsored by Houston Area 

Research Council (HARC) and US EPA SmartWay Transport Program. May 2011

107 See 

http://www.leonardbus.com/PageZoneSiteResources/LeonardBus.com/Resources/file/PDF_info/MX7%20Cold

%20Starting.pdf; and 

https://evalue.internationaldelivers.com/service/bodybuilder/general/engine_feature/documents/NAVI_910DT_

CAP_021211_MY2010_REV1.pdf, accessed May 2011

108 American Trucking Association. Last viewed on January 29, 2010 at 

http://www.trucksdeliver.org/recommendations/speed-limits.html

109 U.S. EPA SmartWay Transport Partnership. Last viewed on January 28, 2010 at 

http://www.epa.gov/smartway/transport/documents/tech/reducedspeed.pdf

110 Department for Transport, Vehicle and Operator Services Agency. Last viewed on January 6, 2010 at 

http://www.dft.gov.uk/vosa/newsandevents/pressreleases/2006pressreleases/28-12-06speedlimiterlegislation.htm

111 Transport Canada. Summary Report – Assessment of a Heavy Truck Speed Limiter Requirement in Canada. 

Last viewed on January 6, 2010 at http://www.tc.gc.ca/eng/roadsafety/tp-tp14808-menu-370.htm

112 Transport Canada. Summary Report – Assessment of a Heavy-Truck Speed Limiter Requirement in Canada.

113 “Assessment of Fuel Economy Technologies for Medium- and Heavy-Duty Vehicles”, TIAX LLC, 

November 19, 2009. Page 4-98.

114 “Assessment of Fuel Economy Technologies for Medium- and Heavy-Duty Vehicles”, TIAX LLC, 

November 19, 2009. Page 4-98.

115 NESCCAF/ICCT. “Reducing Heavy-Duty Long Haul Combination Truck Fuel Consumption and CO2

Emissions.” October, 2009]

116 US Environmental Protection Agency's SmartWay Transport Partnership July 2010 e-update accessed July 

16, 2010, from http://www.epa.gov/smartwaylogistics/newsroom/documents/e-update-july-10.pdf

117 NAS Report. Page 146.

118 TIAX. Assessment of Fuel Economy Technologies for Medium- and Heavy-Duty Vehicles. November 

2009. Page 4-40.
*** E.O. 12866 Review – Draft – Do Not Cite, Quote, or Release During Review ***

2-127

 

119 As explained further in Section V below, EPA would use these inputs in GEM even for engines electing to 

use the alternative engine standard.

122 See Docket EPA-HQ-OAR-2010-0162

123 See 75 FR at 74244.

124 See comments to docket EPA-HQ-OAR-2010-0162-1761; Ford Motor Company

125 The agency notes the highest RRC values recorded for LT tires, of 11.0 and 10.9, were for two tires of the 

same size and brand. The nearest recorded values to these two tires were 9.8; substantially beyond the 

differences between other tires tested.

126 Kargul, J. J., 2010, "Clean Automotive Technology. Cost-Effective Solutions for a Petroleum and Carbon 

Constrained World," Presentation made to National Academy of Sciences, Review of 21st Century Truck 

Program, September 8, 2010

127 “Best practices Guidebook for Greenhouse Gas Reductions in Freight Transportation”, H. Christopher Fey, 

Po-Yao Kuo, North Carolina State University prepared for the U.S. Department of Transportation, October 4, 

2007.

128 “Reducing Heavy-Duty long haul Combination Truck Fuel Consumption and CO2 Emissions”, NESCCAF, 

ICCT, SwRI, TIAX LLC, October 2009.

129 The U.S. EPA has reclamation requirements for refrigerants in place under Title VI of the Clean Air Act.

130 The global warming potentials (GWP) used in the NPRM analysis are consistent with Intergovernmental 

Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). At this time, the IPCC Second Assessment 

Report (SAR) global warming potential values have been agreed upon as the official U.S. framework for 

addressing climate change. The IPCC SAR GWP values are used in the official U.S. greenhouse gas inventory 

submission to the climate change framework. When inventories are recalculated for the final rule, changes in 

GWP used may lead to adjustments. 

131 Schwarz, W., Harnisch, J. 2003. “Establishing Leakage Rates of Mobile Air Conditioners.” Prepared for the 

European Commission (DG Environment), Doc B4-3040/2002/337136/MAR/C1. 

132 Vincent, R., Cleary, K., Ayala, A., Corey, R. 2004. “Emissions of HFC-134a from Light-Duty Vehicles in 

California.” SAE 2004-01-2256. 

133 The Minnesota refrigerant leakage data can be found at 

http://www.pca.state.mn.us/climatechange/mobileair.html#leakdata.

134 Society of Automotive Engineers, “IMAC Team 1 – Refrigerant Leakage Reduction, Final Report to 

Sponsors,” 2006.

135 Society of Automotive Engineers Surface Vehicle Standard J2727, issued August 2008, http://www.sae.org.

136 “Review of Low Carbon Technologies for Heavy Goods Vehicles – Annex 1”, Ricardo prepared for 

Department of Transport, Technology Paper RD.09/182601.7, Jun 2009

137 U.S. Environmental Protection Agency Office of Transportation and Air Quality SmartWay Transport 

Partnership, A Glance at Clean Freight Strategies: Drivers Training EPA 420-F-04-008; February 2004.

138 Ibid.
Regulatory Impact Analysis 

2-128

 

139 National Research Council, Technologies and Approaches to Reducing the Fuel Consumption of Mediumand Heavy-Duty Vehicles, Committee to Assess Fuel Economy Technologies for Medium- and Heavy-Duty 

Vehicles; Washington, DC, National Academies Press, 2010.

140 Information from US EPA review of 2009 SmartWay Excellence Awards applications.

141 U.S. Environmental Protection Agency Office of Transportation and Air Quality SmartWay Transport 

Partnership, A Glance at Clean Freight Strategies: Drivers Training EPA 420-F-04-008; February 2004. 

142 “Buses & Retread Tires,” The Tire Retread & Repair Information Bureau, Pacific Grove, Ca., Accessed on 

January 27, 2010 at http://www.retread.org/packet/index.cfm/ID/284.htm. 

143 “What are Retreaders Doing to Improve Fuel Efficiency?” H. Inman, Tire Review, December 11, 2006, 

Accessed on February 18, 2010 at 

http://www.tirereview.com/Article/59777/what_are_retreaders_doing_to_improve_fuel_efficiency.aspx. 

144 “Better Fuel Economy? Start with a Strong Tire Program,” H. Inman, Fleet & Tire 2006, Tire Review, 

December 11, 2006, Accessed on February 18, 2010 at 

http://www.tirereview.com/Article/59776/better_fuel_economy_start_with_a_strong_tire_program.aspx. 

145 National Research Council, Technologies and Approaches to Reducing the Fuel Consumption of Mediumand Heavy-Duty Vehicles, Committee to Assess Fuel Economy Technologies for Medium- and Heavy-Duty 

Vehicles; Washington, DC, National Academies Press, 2010.

146 Technology and Maintenance Council of the American Trucking Associations, Tire Air Pressure Study, Tire 

Debris Prevention Task Force S.2 Tire & Wheel Study Group; May 2002.

147 “Commercial Vehicle Tire Condition Sensors,” Federal Motor Carrier Safety Administration. Report No. 

FMCSA-PSV-04-002, November 2003.

148 National Research Council, Technologies and Approaches to Reducing the Fuel Consumption of Mediumand Heavy-Duty Vehicles, Committee to Assess Fuel Economy Technologies for Medium- and Heavy-Duty 

Vehicles; Washington, DC, National Academies Press, 2010.

149 U.S. Environmental Protection Agency Office of Transportation and Air Quality SmartWay Transport 

Partnership, A Glance at Clean Freight Strategies: Automatic Tire Inflation Systems EPA 420-F-04-0010; 

February 2004. 

150 National Research Council, Technologies and Approaches to Reducing the Fuel Consumption of Mediumand Heavy-Duty Vehicles, Committee to Assess Fuel Economy Technologies for Medium- and Heavy-Duty 

Vehicles; Washington, DC, National Academies Press, 2010.

151 Ibid.

152 “Comprehensive Truck Weight and Size Study: Summary Report,” U.S. DOT Federal Highway Traffic 

Administration, August 2000.

153 “Comprehensive Truck Weight and Size Study: Summary Report,” U.S. DOT Federal Highway Traffic 

Administration, August 2000.

154 U.S. Department of Transportation. “Comprehensive Truck Size and Weight Study,” Volume 3. August 2000.

155 “Comprehensive Truck Weight and Size Study: Summary Report,” U.S. DOT Federal Highway Traffic 

Administration, August 2000.

156 National Research Council, Technologies and Approaches to Reducing the Fuel Consumption of Mediumand Heavy-Duty Vehicles, Committee to Assess Fuel Economy Technologies for Medium- and Heavy-Duty 

Vehicles; Washington, DC, National Academies Press, 2010.