# Factor of Two: Halving the Fuel Consumption of New U.S. Automobiles by 2035

Lynette Cheah, Christopher Evans, Anup Bandivadekar & John Heywood

October 2007

Laboratory for Energy and Environment Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge, MA 02139, USA Publication No. LFEE 2007-04 RP2 Acknowledgements This project was funded by Environmental Defe nse. The authors thank John DeCicco and Freda Fung from Environmental Defense for thei r valuable feedback and comments during this research.3 Abstract This report examines the vehicle design and sales mix changes necessary to double the average fuel economy of new U.S. cars and light-trucks by model year 2035. To achieve this factor of two target, three technology options that are ava ilable and can be implemented on a large scale are evaluated: (1) channeling future vehicle techni cal efficiency improvements to reducing fuel consumption rather than improving vehicle performance, (2) increasing the market share of diesel, turbocharged gasoline and hybrid electric gasoline propulsion systems, and (3) reducing vehicle weight and size. Our illustrative scenarios demons trate the challenges of this factor-of-two improvement -- major changes in all these three optio ns would need to be implemented before the target is met. Over the next three decades, cons umers will have to accept little further improvements in acceleration performance, a large fraction of new light-duty vehicles sold must be propelled by alternative powertrains, and vehicle weight must be reduced by 20-35% from today. The additional cost of achieving this factor-of-two target would be about 20% more than a baseline scenario where fuel consumption does not change from today’s va lues, although these additional costs would be recouped within 4 to 5 years from the resulting fuel savings. Thus, while it is technically feasible to halve the fuel consumption of new vehicles in 2035, aggressive changes are needed and additional costs will be incurred. Results from this study im ply that continuing the current trend of ever increasing performance and size will have to be re versed if significantly lower vehicle fuel consumption is to be achieved.4 Table of Contents

Abstract ....................................................................................................................... ............................ 3 Table of Contents .............................................................................................................. ...................... 4 Introduction ................................................................................................................... .......................... 5 Background and Approach........................................................................................................ .............. 6 Option #1: Emphasize reducing fuel consumption ............................................................................... 11 Option #2: Use alternative, mo re efficient powertrains ........................................................................ 1 4 Option #3: Reduce vehicle weight and size ...................................................................................... .... 15 Results – Illustrative scenarios............................................................................................... ............... 19 Material cycle impact assessment ............................................................................................... .......... 25 Cost assessment................................................................................................................ ..................... 26 Conclusions .................................................................................................................... ....................... 33 Appendix A: Notes on fuel consumption .......................................................................................... .... 35 Appendix B: Summary of assumptions............................................................................................. .... 36 Appendix C: Future vehicle ch aracteristics at 0-100% ERFC .............................................................. 38 Appendix D: Market penetration of alternative powertrains................................................................. 41 Appendix E: Vehicle weight reduction ........................................................................................... ...... 43 Appendix F: Material cycle impact assessment ................................................................................... . 48 Refere nces ..................................................................................................................... ........................ 505 Introduction The automobile, while it has enable d remarkable mobility in the lives of Americans, is reliant upon petroleum to fuel our transportation needs. This dependence presents a challenging energy and environmental problem, as the transportation sector is responsible for two-thirds of total petroleum consumption and a third of the nation’s carbon emissions. Amid growing concerns over energy security, and the impacts of global climate cha nge, Congress is debating legislative proposals to increase the fuel economy of new passenger vehicles over the next two decades. In this study, we will examine the necessary changes to the automobile in order to double the fuel economy, or halve the fuel consumption of new light duty vehicles, comprising cars, wagons, SUVs, pickups and vans, by 2035. Meeting this target would cut down emissions and gasoline use by 50% over a vehicle’s driven lifetime. With a steady ra te of progress toward the target, the fuel used by all light duty vehicles on the road would be reduced by roughly a third in the year 2035. This factor-of-two target ca lls for an increase in the sales-weighted average fuel economy from 21 miles per gallon (mpg) today to 42 mpg by 2035 as shown in Figure 1. In terms of fuel consumption, this is equivalent to halving the av erage amount of fuel vehicles consume to travel a given distance, or reducing today’s 11.2 liters per 100 kilometers (L/100km ) to 5.6 L/100km by
2035. 1 To achieve this target, we will evaluate comb inations of available fuel-saving technologies and then consider their associated increased cost s of production. The impact on greenhouse gas (GHG) emissions, in particular carbon dioxide (CO 2 ), on a life-cycle basis is also evaluated. By illustrating scenarios of how fuel consumption reductions can be attained in automobiles, we hope this study will provide a useful reference for both policymakers and the automotive industry.

1 Adjusted, combined 55/45 city/highway EPA laboratory test fuel economy and fuel consumption numbers will be used throughout this paper (see Appendix A for details).6 0 5 10 15 20 25 30 35 40 45

1970 1980 1990 2000 2010 2020 2030 2040Fuel economy (mpg) orFuel consumption (L/100km)_

Historical fuel economy

Historical fuel consumption Target fuel economy

Target fuel consumption

Figure 1: Sales-weighted average new vehicle fu el economy (FE) and fuel consumption (FC)

Background and Approach
About 17 million new vehicles are introduced ont o the roads in the U.S. each year. Almost half of new vehicles sold are passenger cars, while the others are light trucks. More than 95% of vehicles operate on gasoline, using conventional, naturally-aspirated, spark-ignited internal combustion engines. Today, the average new car c onsumes 9.6 liters of petr oleum per 100 kilometers of travel (equivalent to fuel economy of 25 mpg), and can accelerate from 0 to 100 kilometers per hour (0 to 60 mph) in under 10 seconds. The car wei ghs 1,620 kg (3,560 lb), mostly embodied in iron and steel, and offers 31⁄4 cubic meters (114 cubic feet) of interior room for both the passengers and their cargo. The average light truck weighs 2,140 kg (4,720 lb) and consumes 12.8 liters of fuel per 100 km (18 mpg).7 One approach to improve vehicle fuel effi ciency is to improve conventional vehicle technology. For example, gasoline direct injecti on, variable valve lift and timing, and cylinder deactivation can individually realize efficiency improvements by 3-10%, and are already being deployed in gasoline spark-ignition engines. Furt her efficiency improvements from dual clutch and continuously variable transmissions are likely to occur in the near future, as well as reductions in aerodynamic drag, and rolling resistance. [Kasseris and Heywood, 2007] Another approach is to use alternative powertr ains, by which we mean turbocharged gasoline engines, high speed turbocharged diesel engines, and hybrid-electric systems. These alternatives provide additional fuel efficiency over naturally-aspir ated (N.A.) gasoline engines. A turbocharger, by increasing the amount of air flow into the engine cy linders, allows an engine to be downsized while delivering the same power. Diesel engines operate by auto-igniting diesel fuel injected directly into a cylinder of heated, pressurized air. This allows a high compression ratio, enables combustion with excess air, and eliminates throttling losses to offer increased engine efficiency. Finally a hybridelectric system provides the ability to store energy in a battery and run off of both an engine and electric motor. This offers improved efficiency by : (i) decoupling the engine from the drivetrain at lighter loads where the efficiency is low, (ii) turnin g the engine off while idling, and (iii) storing much of the vehicle’s kinetic energy with regenerative braking—all of which (iv) allow secondary benefits from downsizing to a smaller, lighter engine. [Kromer and Heywood, 2007]8 1.00

0.62 0.90

0.55 0.84

0.53 0.70

0.35

0.00 0.20 0.40 0.60 0.80 1.00 1.20

2006 2035Relative fuel consumption_ N.A. gasoline (reference) Turbocharged gasoline Diesel Hybrid-electric gasoline

(a) For passenger cars

0.63 1.00

0.54 0.83

0.50 0.74

0.35 0.70

0.00 0.20 0.40 0.60 0.80 1.00 1.20

2006 2035Relative fuel consumption_ N.A. gasoline (reference) Turbocharged gasoline Diesel Hybrid-electric gasoline

(b) For light trucks Figure 2: Current and future relative fuel consumption of alternative powertrains [Kasseris and Heywood 2007, Kromer and Heywood 2007]9 Figure 2 shows the current and future fuel c onsumption benefit of using these alternative powertrains in the average passenger car and light truck 2 , with today’s naturally-aspirated (N.A.) gasoline internal combustion engine as the referenc e. The hybrid vehicle model assessed is a full hybrid 3 with a parallel architecture, which for cars, is similar to a Toyota Camry hybrid. It offers the highest potential fuel savings, although the robust performance of diesels over a variety of operating conditions may make them more suitable than hybr ids in heavy towing applications. Over the next three decades, if all improvements to conventional vehicle technology are focused on reducing fuel consumption, significant benefit can be realized ac ross all powertrain options, including vehicles that continue to use the conventional N.A. gasoline engine. Next, vehicle weight reduction can reduce the ove rall energy required to accelerate to a given speed. Reductions in weight can be achieved by a comb ination of (i) material substitution; (ii) vehicle redesign; and (iii) vehicle downsizing. Material substitution involves replacing heavier iron and steel used in vehicles with weight-saving materials like aluminum, magnesium, high-strength steel, and plastics and polymer composites. Redesign reduces the size of the engine and other components as vehicle weight decreases, or through packagi ng improvements which reduce exterior vehicle dimensions while maintaining the same passenger and cargo space. Finally, downsizing can provide further weight reduction by shifting sales away from la rger and heavier to smaller and lighter vehicle categories. When considering various ways of achieving th e target of halving fuel consumption in vehicles, we have chosen to focus on options that are essentially available today, and which do not require significant changes to our fueling infrastructure. For this reason, plug-in hybrid electric, battery electric or hydrogen fuel cell vehicles will not be considered, although they are potentially

2 The best-selling car and light truck, the Toyota Camry CE mid-size sedan and Ford F150 pickup truck, were selected as representative models for this analysis. 3 It is recognized that there are diff erent types of hybrid-electric drives av ailable in the market, offering a range of fuel consumption benefits. Full hybrid systems have more powerful electric drives that assist the engine, and allow limited driving without use of the engine.10 important technologies for realizing vehicle fuel consumption reductions. Fuel alternatives are also deliberately excluded, although some alternative fuels can offer reductions in petroleum use and greenhouse gas emissions. Thus, as shown in Figure 3, the following three options will be explored based on their current feasibility, availability, and market-readiness: (1) Emphasis on reducing fuel consumption – dedicating future vehicle efficiency improvements to reducing fuel consumption, as opposed to improving vehicle performance; (2) Use of alternative powertrains – increasing market penetration of more efficient turbocharged gasoline engines, diesel engi nes, and hybrid electric-gasoline drives; (3) Vehicle weight and size reduction – additional weight and size reduction for further fuel efficiency gains.

Emphasis on reducing fuel consumption Market penetration of alternative powertrains Additional weight reduction Emphasis on reducing fuel consumption Market penetration of alternative powertrains Additional weight reduction

Figure 3: The vehicle design and marketing options to reduce fuel consumption

It is useful to clarify that we are working backwards to understand the degree of changes that are necessary in order to achieve the desired target, and are not forecasting what the future vehicle or market might look like in 2035. We will now discuss each of the three options in more detail.11 Option #1: Emphasize reducing fuel consumption The first option is to emphasize reducing fu el consumption over improving the vehicle’s horsepower and acceleration, while assuming that vehi cle size remains constant. This is an explicit design decision to dedicate future advances in vehicle efficiency into reducing fuel consumption rather than improving performance. Over the past two deca des, more emphasis has been placed on the latter, while the average new vehicle’s fuel consumption has remained almost stagnant. If the performance trend of the past two decades continues, the av erage new car in 2035 could potentially boast 320 horsepower and a 0-to-60 mph acceleration time of 6.2 seconds, outperforming today’s BMW Z4 Roadster. It is questionable whether this level of perform ance is necessary, or ev en safe for the average driver on regular roads, regardless of whether the fu ture consumer truly wants or expects this. Speed and horsepower have always had strong marketing appeal and dema nd might well continue. It is important to recognize, however, that a trade-off is being made between increasing performance, size, and weight over reducing fuel consumption in futu re vehicles. While holding size constant, we will define and quantify this trade-off as the degree of emphasis on reducing fuel consumption (ERFC), where:



### e performanc and size constant with possible reduction n consumptio fuel Future realized reduction n consumptio fuel Future % = ERFC

At 100% ERFC, all of the steady improvements in conventional technology over time are assumed to realize reduced fuel consumption, wh ile vehicle performance remains constant. This includes an assumption that vehicle weight will re duce by 20%. In contrast, without any emphasis on reducing fuel consumption (0% ERFC), the fuel c onsumption of new vehicles will remain at today’s12 values, no weight reduction will occur, and all of the efficiency gains from steady technology improvements are channeled to better the hor sepower and acceleration performance instead. By simulating the future vehicles described usi ng AVL’s ADVISOR software, the current and future new vehicle characteristics at different levels of ERFC are obtained and summarized in Table 1. The trade-off between acceleration performance and fuel consumption for the average car and light truck of a fixed size is depicted in Figure 4 below.

0% ERFC 1,616 kg 50% ERFC

1,454 kg 100% ERFC

1,293 kg 50% ERFC 1,923 kg 0% ERFC 2,137 kg 100% ERFC

1,710 kg

4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0

5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 

### Fuel consumption (L/100km)0-60mph acc. time (s)_

Current car Current light truck Future car Future light truck

Figure 4: Trade-off between acceleration time and fuel consumption in average new vehicles in 2035. Current vehicle characteristics plotted for reference.13 Year % ERFC Fuel consumption (L/100km) [relative] Horsepower [relative] 0-60 mph acceleration time (s) Vehicle weight (kg) [relative]
2006 - 9.6 [1.00] 198 [1.00] 9.5 1,616 [1.00] 0% 9.6 [1.00] 324 [1.64] 6.2 1,616 [1.00] 50% 7.8 [0.81] 239 [1.21] 7.2 1,454 [0.90] 2035 100% 6.0 [0.62] 151 [0.76] 9.5 1,293 [0.80]

(a) For cars

Year % ERFC Fuel consumption (L/100km) [relative] Horsepower [relative] 0-60 mph acceleration time (s) Vehicle weight (kg) [relative]
2006 - 12.8 [1.00] 239 [1.00] 9.9 2,137 [1.00] 0% 12.8 [1.00] 357 [1.49] 7.1 2,137 [1.00] 50% 10.4 [0.82] 275 [1.15] 8.1 1,923 [0.90] 2035 100% 8.1 [0.63] 191 [0.80] 9.8 1,710 [0.80]

(b) For light trucks

Table 1: Summary of current an d future naturally-aspirated gas oline vehicle characteristics 4

When full emphasis is placed on reducing fuel consumption (100% ERFC) the fuel consumption of a future new car declines by 35% fro m today’s value, from 9.6 to 6.0 L/100km. About a quarter of this fuel consumption reduction is accr edited to the 20% reduction in vehicle weight. This weight assumption is based on what is feasible in 2035, given the priority placed on achieving lower fuel consumption (see Appendix E). If only half of the efficiency gains are used to emphasize lowering fuel consumption, or at 50% ERFC, then only half of the total plausible reduction in fuel consumption will be realized by 2035. Note that the future vehicle curb weight is assumed to scale linearly with %ERFC, so vehicle weight at 50% ERFC reduces by 10% from today.

4 These numbers are assessed for spark-ig nited, naturally-aspirated gasoline vehicles with an internal combustion engine. The data for alternative powertrains will be different.14 The weight, performance, and fuel consumption of future vehicles are therefore dependent upon how improvements to convent ional automotive technology are utilized. This design decision, expressed as the emphasis on reducing fuel consumption (ERFC), is the first of the three options we will consider using to achieve the desired factor-of-two target.
Option #2: Use alternative, more efficient powertrains Today, less than 5% of the new vehicle in the U.S. market are turbocha rged gasoline, diesels, or hybrids, but their market shares are expected to grow. In the U.S., hybrid sales have grown from 6,000 in year 2000, when the first Honda Insight hybrid was introduced, to 213,000 in 2006. [Heavenrich 2006] More diesel passenger vehicle models are also expected to be made available in the U.S. from 2008. Increasing the market penetration of these alternative powertrains, especially the more efficient hybrids, can bring us closer to the desi red factor-of-two reduction in fuel consumption. The overall benefit obtained from alternative powertrains depends upon how quickly these new technologies can penetrate the existing vehicle fleet . In Europe, the share of diesel cars grew at an average rate of 9% per year to capture about half of the market today, motivated by innovations in common rail injection and lower taxation of diesel fuel over gasoline. Other automotive technologies such as front or 4-wheel drive and automatic transmissi on have diffused into the U.S. market at a rate of 7 to 11% per year in the past, over periods of 15 to 20 years. Based on these rates, we have assumed that the maximum compounded annual growth rate of alternative powertrains in the U.S. market is 10% per year. This corresponds to a maximum 85% sh are of alternative powertrains in new vehicle sales in 2035. In other words, if turbocharged g asoline engines, diesels and hybrids are aggressively promoted, only 15% of new vehicles introduced onto the roads in 2035 will remain powered by conventional, naturally-aspirated g asoline internal combustion engines. For simplification, the relative proportion of turbocharged gasoline to diesel vehicles that penetrate the fleet is initially fixed. Assuming that the more efficient hybrids remain more popular than other powertrains in the U.S. market, the sh are of turbocharged gasoline and diesel vehicles are15 each fixed at five-sevenths of the hybrid market share. Thus, in the extreme scenario of 85% alternative powertrains in 2035, hybrids account for 35% of the new vehicle market, while turbocharged gasoline and diesel vehicles each account for 25% of the market. This constraint will be relaxed later in order to gauge the sensitivity of allowing a different market mix of alternative powertrains.
Option #3: Reduce vehicle weight and size The third option is to reduce fuel consumption with vehicle weight reduction, beyond what has been assumed at different levels of ERFC. As me ntioned above, weight reduction can occur through a combination of (i) material substitution, (ii) vehicle redesign, and (iii) vehicle downsizing. Of the lightweight material candidates availabl e for material substitution, aluminum and highstrength steel (HSS) are more cost-effective at la rge production volume scales, and their increasing use in vehicles is likely to continue. Cast aluminum is best suited to replace cast iron components, stamped aluminum for stamped steel body pa nels and HSS for structural steel parts. Plastics and polymer composites are also expected to replace some steel in the vehicle, but to a smaller degree given the higher costs of these materials. With aggressive u se of these substitute materials, up to 20% reduction in vehicle weight can be achieved, and the co rresponding material breakdown of the average new future vehicle is shown in Figure 5 and Table 2. Redesigning the vehicle includes optimal sizing of vehicle subsystems that depend on total vehicle weight. As vehicle weight decreases, the performance requirements of the engine, suspension, and brake subsystems are lowered and these can be downsized accordingly. Vehicle redesign may also include “creative packaging” or downsizing the exteri or dimensions of the vehicle while maintaining the same interior (passenger and cargo) space. We wi ll assume that the weight savings obtained from vehicle redesign are half of that achieved by material substitution.16 (a) For cars (b) For light trucks

0 500 1,000 1,500 2,000 2,500

2006 2035Mass breakdown (kg)_ Other materials Other metals Glass Rubber Plastics/composites Aluminum Iron Steel -20%

0 500 1,000 1,500 2,000 2,500

2006 2035Mass breakdown (kg)_ Other materials Other metals Glass Rubber Plastics/composites Aluminum Iron Steel -20%

Figure 5: Material composition of the average ne w gasoline vehicle after material substitution

Material Cars Trucks In 2006, kg In 2035, kg In 2006, kg In 2035, kg Steel 929 670 1,228 885 Iron 168 82 222 108 Aluminum 142 323 188 427 Rubber 76 61 101 80 Plastics/composites 131 137 173 181 Glass 50 40 67 53 Other metals 55 44 73 58 Other materials 65 52 86 69 Total 1,616 1,408 2,137 1,862 Table 2: Material composition of the average new gasoline vehicle after material substitution

Beyond material substitution and vehicle re design, we assume that an additional 10% reduction in the sales-weighted average new vehicle weight is possible through vehicle downsizing.17 The current difference in weight achieved fro m downsizing a car by one U.S. EPA size-class 5 ranges from 8-11%. Specifically, only the heavier vehicle cl asses will be targeted for downsizing, while the smaller and lighter vehicles are not downsized any further. This accounts for the challenges in producing vehicles that are lighter than the lightest vehicles today, and also improves vehicle compatibility from a road safety perspective. Figure 6 shows the sales distribution of new cars today and in year 2035. After material substitution and vehicle redesign with out downsizing, the entire future car sales distribution shifts to the lighter weight ranges with no change in its sh ape. With downsizing, smaller and lighter vehicles will dominate the marketplace, resulting in a lower av erage weight. The share of light trucks in the 2035 new vehicle fleet is assumed to remain at today’s value of 55%. Based on these assessments of aggressive mate rial substitution, vehicle redesign, and downsizing, a maximum weight reduc tion of 35% is possible by 2035. Given the need and demand for weight-adding safety features and passenger and cabin space, it is unlikely that average vehicle weight will decline beyond this. Thus, the minimum averag e new car weight would be around one metric ton (1,050 kg)—down from 1,620 kg today—and the minimu m average new light truck weight would be 1,390 kg, a reduction of 750 kg from today’s average of 2,140 kg.

5 The US EPA car size classes are defined by interior (passenger + cargo) volume. A small car, like the Toyota Corolla has less than 110 ft 3 interior volume, a midsize car, like th e Toyota Camry, has between 110-120 ft 3 . A large car, such as the Chev rolet Impala, exceeds 120 ft 3

.18 0 1,000 2,000 3,000 4,000 5,000 6,000

0 500 1,000 1,500 2,000 2,500 3,000 3,500 Curb weight (kg)Sales ('000) 2006 2035 before downsizing 2035 after downsizing 1,620 kg 1,050 kg 1,170 kg

(a) For cars

0 1,000 2,000 3,000 4,000 5,000 6,000

0 500 1,000 1,500 2,000 2,500 3,000 3,500 Curb weight (kg)Sales ('000) 2006 2035 before downsizing 2035 after downsizing

2,137 kg 1,550 kg 1,380 kg

(b) For light trucks Figure 6: Current and future new vehicle sales distri bution, before and after vehicle downsizing. Average new vehicle curb weight denoted in kilograms.19 Using AVL ADVISOR simulations of representative vehicles we estimated the fuel consumption benefit provided by a given reduction in vehicle curb weight. For every 100 kg weight reduction, the adjusted fuel consumption can decr ease by 0.3 L/100km for cars, and 0.4 L/100km for light trucks (see Figure 7). 6 In other words, for every 10% we ight reduction, the vehicle’s fuel consumption reduces by 6 to 7%.

Average light truck FC = 0.004m + 3.223

Average car FC = 0.003m + 2.081

0.0 2.0 4.0 6.0 8.0 10.0 12.0

1,000 1,200 1,400 1,600 1,800 2,000 2,200 2,400 Curb weight, m (kg)Fuel consumption, FC (L/100km)

Figure 7: Weight-fuel consumption relationship for future vehicles

Results – Illustrative scenarios Studying the three described options, we realize that exercising each opti on individuall y is not sufficient to achieve the target. Table 3 expresses the effectiveness of each option in reducing fuel consumption, if each is exercised independently to its limit. None of them will result in the desired 50% fuel consumption reduction on their own. In order to halve the fuel consumption of new vehicles by 2035, scenarios which combine the effect s of these options must be developed.

6 These are fuel consumption values obtained using co mbined U.S. EPA city / hi ghways drive cycles. See Appendix E for more details on the fuel saving impact of vehicle weight reduction.20 Option Limit Resulting fuel consumption reduction at the limit (1) Degree of emphasis on reducing fuel consumption (ERFC) 100% ERFC 36% (2) Increase use of alternative powertrains Captures up to 85% of the market 23% (3) Vehicle weight reduction Up to 35% total vehicle weight reduction 19%

Table 3: The effectiveness of the 3 techni cal options in reducing fuel consumption

Three bounding, or limiting, scenarios are summarized in Table 4 and Figure 8 as Scenarios I, II and III. These scenarios were obtained by exercisi ng two of the three options to their limits, and then using the third option, if needed, until the target is reached. The resulting effects on the 2035 average new vehicle characteristics are shown as “outputs,” in Table 4. These three scenarios bound the shaded solution space depicted in Figure 8, for both cars and light trucks. Scenarios that lie within the shaded area, which combine greater emphasis on vehicle performance, less weight reduction, and less market penetration of alternative powertrains than each of the three bounding conditions, will also achieve the prescribed target. The bounding scenarios illustrate the necessary tr ade-off between vehicle performance, weight, and degree of alternative powertrain penetration. In Scenario I, new vehicles in 2035 realize all of the efficiency improvements in conventional vehicle technology over the next three decades in reduced fuel consumption. They have the same acceleration as vehicles today. On average, vehicles in this scenario weigh one-third less than today, through a combination of aggressive material substitution, redesign, and a 10% reduction in size. One out of every three new vehicles sold are propelled by alternative powertrains, while the remaining are powered by N.A. gasoline engines; 10% are turbocharged gasoline, 10% are diesel, and 14% are hybrid. In Scenario II, alternative powertrains pene trate much more aggressively into the fleet, achieving an 85% market share of new vehicle sales in 2035. Hybrids account for 35% of new vehicle21 sales, while diesel and turbocharged gasoline power trains each account for one-quarter each. Only 15% of new vehicles sales are comprised of conven tional N.A. gasoline vehicles. Almost all of the conventional technology improvements remain direct ed towards reducing fuel consumption, and the average weight of new vehicles reduces by roughly 20%. Finally, Scenario III describes a 2035 sales mix where a moderate level of emphasis is placed on reducing fuel consumption through improvement s in vehicle technology. Instead, about 60% of these improvements are directed towards faster acceleration, lowering the new car average 0-100 kmph acceleration time from 9.5 to 7.6 seconds. In or der to meet the fuel consumption target, this scenario requires aggressive penetration of alte rnative powertrain vehicles and maximum weight reduction. Only 15% of new vehicle sales are conventional N.A. gasoline; 35% are hybrids, and the remaining 50% is split evenly between turbocharged gasoline and diesel. Similar to Scenario I, the average vehicle weight is one-third less than today’ s average in 2035 as a result of aggressive material substitution, vehicle redesign, and downsizing.22 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

900 1,000 1,100 1,200 1,300 1,400 1,500 1,600 1,700 1,800 2035 average new car weight (kg)Marketshare of alt. powertrains (%)__

Iso-performance lines (0-60t) Solution space > 85% alternative powertrains

poorer acceleration performance > 35% weight reduction 7.6s 8.0s 8.5s

9.0s

9.4s

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

900 1,000 1,100 1,200 1,300 1,400 1,500 1,600 1,700 1,800 2035 average new car weight (kg)Marketshare of alt. powertrains (%)__

Iso-performance lines (0-60t) Solution space > 85% alternative powertrains

poorer acceleration performance > 35% weight reduction 7.6s 8.0s 8.5s

9.0s

9.4s

(a) For cars

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

900 1,000 1,100 1,200 1,300 1,400 1,500 1,600 1,700 1,800 2035 average new light truck weight (kg)Marketshare of alt. powertrains (%)__ > 85% alternative powertrains

poorer acceleration performance > 35% weight reduction

Iso-performance lines (0-60t) Solution space 8.4s 9.0s 9.5s

9.8s

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

900 1,000 1,100 1,200 1,300 1,400 1,500 1,600 1,700 1,800 2035 average new light truck weight (kg)Marketshare of alt. powertrains (%)__ > 85% alternative powertrains

poorer acceleration performance > 35% weight reduction

Iso-performance lines (0-60t) Solution space 8.4s 9.0s 9.5s

9.8s

(a) For light trucks Figure 8: Results – Solution space for Scenarios I, II and III23INPUTS OUTPUTS (vehicle characteristics)Degree of each option 2035 average new car 2035 average new light truck2035 powertrain mixScenarios%ERFCGasNAGasturboDiesel Hybrid% total.weightreductionfrom today0-60mphacc. timeFC ,L/100kmVehicleweight0-60mphacc. timeFC,L/100kmVehicleweight2006 values -- 95% 1% 2% 2% -- 9.5s 9.6 1,616 kg 9.9s 12.8 2,137 kgI. Strong emphasis onreducing FC and vehicleweight100% 66% 10% 10% 14% 35% 9.4s4.8 1,054 kg 9.8s6.4 1,394 kgII. Strong emphasis onreducing FC andaggressive penetration ofalternative powertrains96% 15% 25% 25% 35% 19% 9.2s4.8 1,318 kg 9.6s6.4 1,743 kgIII. Aggressive weightreduction and penetrationof alternative powertrains61% 15% 25% 25% 35% 35% 7.6s4.9 1,060 kg 8.4s6.3 1,402 kgIV. Scenario withaggressive hybridpenetration75% 15% 15% 15% 55% 20% 8.1s4.8 1,302 kg 8.8s6.3 1,722 kgTable 4: Results – Scenarios that halve thefuel consumption of new vehicles in 203524 These three bounding scenarios reveal trade-offs n ecessary to halve the fuel consumption of all new vehicles within the constraints of this assessment: (i) The factor-of-two target can be met with lower levels of market penetration of alternative powertrains, only with full em phasis on reducing fuel consumption and maximum possible weight reduction including some downsizing (Scenario I). (ii) To realize a factor-of-two reduction in fuel consumption with a moderate amount of weight reduction and no downsizing, alterna tive propulsion systems must penetrate the marketplace at a high rate while maintaini ng today’s vehicle performance (Scenario II). (iii) If performance of vehicles is to be im proved significantly above today’s level, maximum market penetration of alternative propulsion systems and a large degree of weight reduction and downsizing need s to be achieved (Scenario III). To illustrate the effects of an alternative power train mix, a fourth scenario is developed, in which the requirement for a fixed ratio of turbocha rged gasoline and diesel to hybrid powertrains has been relaxed. This final scenario relies heavily on hybrid electric-gasoline vehicles, which offer the greatest fuel consumption benefit relative to the othe r powertrains. In this Scenario IV, slightly more than half of new vehicles sold are hybrids. The re maining new vehicles are spread evenly between the naturally-aspirated gasoline, tur bocharged gasoline, and diesel vehicles. Vehicle weight has come down by 20%, mostly achieved with the use of light weight materials, while the new vehicle fleet’s size distribution remains unchanged. With such aggre ssive penetration of hybrids, vehicle acceleration performance can improve slightly from today. Th e average new car accelerates from 0-100 kmph in 8.1 seconds, and the light truck does the same in 8. 8 seconds. So when a high percentage of hybrids (55%) are relied on to achieve most of the fuel c onsumption reduction, we need less weight reduction, can avoid size reduction, and even allow a m odest improvement in vehicle performance. All four scenarios reveal that achieving a fact or-of-two reduction in fuel consumption by 2035 is possible, but requires aggressive action beginni ng today. The following sections will now compare25 the four scenarios on the basis of material cycle energy and greenhouse gas (GHG) emissions impact, and their cost-effectiveness.
Material cycle impact assessment The material cycle refers to the energy and environmental impact of producing the materials embodied in the vehicles. It includes the material extraction and processing steps, and does not include transportation of the materials, or manufacturing and assembly of the vehicle. It is important to consider this impact, because the scenarios all involve some use of alternative lightweight materials, and hybrid-electric vehicles with lithium-ion ba tteries, each of which require greater amounts of energy and GHG emissions to produce, relative to today’s conventional N.A. gasoline vehicle. The material production impact of these changes is calculated by keeping track of the material composition of future vehicles, and the energy intens ity of these materials. Energy intensity data is obtained from Argonne National Laboratory’s Gree nhouse gases, Regulated Emissions, and Energy use in Transportation (GREET 2.7) model. The tw o metrics compared across the scenarios are the energy consumed and metric tons of carbon dioxide (CO 2 ) emitted during the material cycle, and the results obtained are reported in Table 5.

Material cycle impact per gasoline car Total material cycle impact of the new vehicle fleet Scenario Energy (GJ/veh) CO 2 emissions (ton/veh) Energy (EJ) CO 2 emissions (mil tons)

2006 88.2 6.80 1.78 137

I 92.1 6.90 2.35 176 II 97.1 7.34 2.51 189 III 91.8 6.88 2.37 177 IV 97.7 7.38 2.54 190

Table 5: Material cycle impact of the average new car and of the new vehicle fleet in 203526 All four scenarios that halve the fuel consump tion of future new vehicles result in higher energy use and CO 2 emissions during the material production phase, since the lighter weight vehicles in these scenarios use more energy-intensive light weight materials. For example, the production energy requirement of primary aluminum is about 5 times that of the primary steel which it replaces in the future lightweight vehicle. Despite so, since th e material cycle is responsible for only 10% of the vehicle’s total life-cycle energy use and GHG emissions today 7 , a model year 2035 car that consumes two times less fuel than today’s car will e nd up using 43% less energy over its lifetime. It is also observed that the calculated material cycle impact is not very different across the scenarios. The total energy consumed in producing materials embodied in the new vehicles is about 2.3-2.5 exajoules (EJ, or 10 18 joules), and the amount of GHG emissions in the form of CO 2 ranges 175-190 million metric tons. Scenarios II and IV co mprise the heaviest vehicles, and therefore have higher material cycle impacts since these vehicles em body more materials than in the other scenarios.

Cost assessment Implementing improvements and new technologies to reduce fuel consumption will increase the cost of producing vehicles, and in turn, the reta il price paid by consumers. We now evaluate the cost of halving the fuel consumption of new vehi cles in 2035, and compare this against the resulting savings in fuel use and greenhouse gas emissions. We have developed estimates of the additional production cost 8 of improvements in future vehicles from a literature survey of future t echnology assessments. [DOT, 2006b; EEA, 2002; NRC,

7 The vehicle’s material cycle, manufacturing and assembly , use phase, and end-of-life treatment are included in its life-cycle. The fuel cycle is excluded. 8 We assume that production costs account for all of the costs associated with producing a vehicle at the manufacturing plant gate. This includes vehicle manufacturing, and corporate and production overhead. It excludes distribution costs and manufacturer and dealer profit margins (s ee Vyas et al, 2000).272002; NESCCAF, 2004; TNO, IEEP, LAT, 2006; Weiss et al, 2000] The average cost of a naturallyaspirated (N.A.) gasoline vehicle today is assume d to be $14,000 for car s and $14,500 for trucks. 9 Improvements in engine, transmission, rolling fric tion and drag are expected to occur over the next three decades. If there is a strong emphasis on reducing fuel consumption, these improvements will occur alongside weight reduction and engine downsizing. Therefore, with a full emphasis on reducing fuel consumption in the future, we estim ate that the cost of a 2035 N.A. gasoline car will increase by $1,400, and trucks by $1,600, relative to a current N. A. gasoline vehicle (Table 6).

Cost Increase Vehicle Technology Assumptions Cars, US$2007 Light trucks, US$ 2007
2035 N.A. Gasoline Engine and transmission improvements; engine downsizing and 20% weight reduction; reduced drag and rolling friction $1,400 $1,600

Table 6: Increase in cost relative to a curren t naturally aspirated (N.A.) gasoline vehicle Alternative powertrains and further weight re duction can lower fuel consumption further at additional cost. As shown in Table 7 below, it is estimated that turbocharging a 2035 gasoline car would cost an extra $500, bringing the total cost of a turbocharged 2035 car to $14,000 + $1,400 + $500 = $15,900. Weight reduction can occur by material substitutio n, redesign and downsizing of vehicle components, and by reducing the size of a vehicle. Table 8 shows the cost estimates assumed for each type of weight reduction.

9 All costs given in 2007 U.S. dollars. Base costs of N.A. gasoline vehicles taken as the U.S. base retail price of a Toyota Camry CE mid-size sedan and Ford F150 pickup truck, reduced by a factor of 1.4 that is consistent with our production cost assumptions; see Appendix B for details. [www.edmunds.com, acce ssed July, 2007; Vyas et al, 2000]28 Additional Cost Relative to 2035 N.A. Gasoline Vehicle Vehicle Technology Assumptions Cars, US$ 2007 Light trucks, US$ 2007 Alternative Powertrains

2035 Turbocharged gasoline Turbocharged spark-ignition gasoline engine $500 $600 2035 Diesel High-speed, turbocharged diesel; meets future emission standards $1,200 $1,500
2035 Hybrid gasoline Full hybrid; cost includes electric motor, Li-ion battery $1,800 $2,300

Table 7: Additional cost relativ e to a 2035 N.A. gasoline vehicle

Type of weight reduction % vehicle weight reduction 10 [%] Additional cost relative to a 2035 N.A. gasoline vehicle [US$ 2007 / kg] First tier material substitution 14% $3 Component downsizing, ve hicle redesign 7% $0 Subtotal 20% $2 Second tier material substitution 7% $5 Component downsizing, vehicle redesign 3% $0 Subtotal 10% $3.5 Vehicle size reduction 10% $0 Total 35% $2

Table 8: Estimated costs of vehicle weight red uction relative to a 2035 N.A. gasoline vehicle

Weight reduction by material substitution is est imated to cost $3 per kilogram up to a 14% reduction in vehicle weight, and is accompanied by an additional 7% weight reduction from vehicle redesign and component downsizing that is cost-n eutral. Multiplicatively combining these reductions yields a 20% reduction in vehicle weight, which is equivalent to the reduction assumed for full emphasis on reducing fuel consumption (100% ER FC). A second tier of more costly material substitution can yield an additional 7% reduction in vehicle weight at an estimated cost of $5 per kilogram, enabling an extra 3% reduction from further cost-neutral redesign and component

10 The percentage reductions for each of the weight reduction methods shown in this table have been combined multiplicatively.29 downsizing. Finally, an additional 10% reduction is available by reducing the average size of vehicle the vehicle fleet. While size reduction is assumed to be cost-neutral with respect to production costs, shifting to smaller vehicles implies some qualitativ e costs to the consumer from forgone interior volume. These assumptions allow an overall 20% reduction in vehicle weight from material substitution at a cost of roughly $3.5 per kilogram , and a 19% reduction in weight from cost-neutral reductions in redesign, component downsizing, and vehicle size reduction. Multiplicatively combining these reductions yields a 35% total reduction in vehicl e weight at an overall cost of roughly $2 per kilogram. Given these cost estimates, the benefits of the different technology options can be compared by calculating the gross cost of reducing one metr ic ton of GHG emissions, expressed in dollars per ton of CO 2 equivalent ($/ton CO 2 e). The gross cost does not account for the value of fuel savings generated from lower fuel consumption when cal culating the cost reducing of GHG emissions:



### savings emissions GHG (FC) n consumptio fuel reducing of Cost emissions GHG of ton one reducing of Cost =
The cost of reducing fuel consumption is the su m of: (a) the cost of incremental improvements to conventional vehicle technology that reduce fuel consumption; plus any extra cost for (b) upgrading to an alternative powertrain, and/or (c) additio nal weight reduction. The cost of incremental improvements in conventional vehicle technology that lower fuel consumption is estimated by multiplying the extra cost of the 2035 N.A. gaso line vehicle relative to today by the emphasis on reducing fuel consumption (%ERFC). It is assumed th at the efficiency gains provided by changing to an alternative powertrain, or by additional weight reduction, are fully realized in lowering fuel consumption. The remaining portion of the 2035 N.A. gasoline vehicle cost is attributed to other benefits, such as increasing size, weight or improving performance.

ERFC Vehicle Gasoline N.A. future of cost Extra FC reducing of Cost % × = + Alternative Powertrain Cost + Weight Reduction Cost %ERFC)

- (1 Vehicle Gasoline N.A. Future of Cost Extra benefits other of Cost × =30 Where the extra cost of the futu re N.A. gasoline vehicle is assumed in Table 6 above, and the alternative powertrain and weight reduction costs ar e shown in Tables 7 and 8. The total extra cost, relative to a vehicle in 2006 is given by: Total Extra Cost = Cost of Reducing FC + Cost of Other Benefits Using this approach, the results obtained are show n in Table 9 below. It is assumed that all of the efficiency improvements in conventional vehicl e technology are directed towards reducing fuel consumption and that vehicle weight is reduced by 20% between today and 2035. GHG emissions savings are calculated relative to what they would be if the fuel consumption of a 2035 vehicle remains unchanged from 2006, assuming a lifetime vehicle travel of 240,000 km over 15 years. 11

Vehicle technology Gross cost of GHG reduction, in US$ 2007 / ton CO 2 e Undiscounted payback period, in years Cars Light trucks Cars Light trucks N.A. Gasoline 55 50 4 4 Turbocharged Gasoline 60 55 4 4 Hybrid Gasoline 70 70 5 5 Diesel 80 70 6 5 Table 9: The cost of reducing one ton of G HG emissions in 2035 cars and light trucks

The estimated gross cost of reducing GHG emissions ranges from $50 to $80 per ton CO 2 e 12 , yielding a variation in cost of roughly 50% across an average of $65 per ton CO 2 e. An improved 2035 N.A. gasoline vehicle realizes the most cost-effec tive reductions in GHG emissions and fuel use when all future efficiency improvements are realized in reduced fuel consumption (100% ERFC). In cars, diesel engines are less cost-effective than turbocharg ed or hybrid gasoline powertrains, but in trucks,

11 Based on the average of lifetime car and light truck travel from the U.S. Department of Transportation vehicle survivability and mileage travel schedule. [DOT, 2006a: pp. 22, 25] 12 Or $165 to $175 per ton of carbon-equivalent GHG emissions (tC); $1.00 / tCO 2 e is approximately equal to $3.66 / tC.31 diesels are about as cost-effective as hybrids. Assuming a constant fuel cost of $1.85 per gallon 13 , the value of the undiscounted fuel savings recoups the in itial gross cost of each of the different vehicle technologies within 4 to 6 years. It is also important to recognize that the resu lts in Table 9 have em bedded a 20% reduction in vehicle weight by 2035. When separated out fro m the alternative powertrain and other vehicle improvements, weight reduction on its own is estimated to have a gross cost between $75 and $80 per
ton CO 2 e for cars, and between $65 and $70 for trucks. T hus, while reducing vehicle weight realizes extra savings in fuel use and GHG emissions, these bene fits come at a higher marginal cost that raises the cost of reducing a ton of CO 2 overall, although these costs are still recouped within 5 to 6 years by the value of the fuel savings gene rated from reducing vehicle weight. Next, the results from Table 9 are extrapolated across all new vehicles in 2035 to develop an estimate of the total societal costs of halving fuel consumption of the 2035 model year. Table 10 shows the aggregate extra cost of all new 2035 model year vehicles in each of the three bounding scenarios that halve new vehicle fuel consumpti on by 2035. Over 15 years of lifetime operation, vehicles in the 2035 model year will save 290 billion liters of fuel and offset a total of 850 Mt of GHG emissions. This is roughly equivalent to half of the total of motor g asoline fuel used in the U.S. in 2006. [EIA, 2007a]

13 The fuel price of $1.85 / gallon is taken as the aver age of the EIA’s Annual Energy Outlook long-term forecast for motor gasoline, excluding $0.40 / gallon in federal, state, and local taxes. [EIA, 2007b]32 Scenario Extra cost to halve FC of 2035 model year vehicles, in billions $US As % of baseline cost Undiscounted fuel savings pay-back period, in years Gross cost of GHG reduction, $US / ton CO 2 e I $54 16% 4 $65 II $56 17% 5 $70 III $63 19% 5 $76 IV $58 17% 5 $72 FC = fuel consumption Table 10: Societal costs, benefits, and cost-effectiven ess of halving fuel consumption in 2035 model year vehicles across the four scenarios (all values in 2007 U.S. dollars). The extra cost of halving fuel consumption shown in Table 10 is the combined cost of all efficiency improvements necessary to halve fuel consumption in new vehicles in 2035. Depending on the scenario, the extra cost ranges from $54 to $63 billi on. This is equivalent to an additional 16% to 19% of the estimated baseline production cost of th e 2035 model year when average fuel consumption remains unchanged from 2006. Assuming a 15 year life-cycle, a fuel cost of $1.85 per gallon, and a discount rate of 3% 14 , the value of the fuel savings provided by vehicles in the 2035 model year is estimated at $120 billion, which would yield a total ne t societal gain of some $60 to $70 billion after subtracting the extra costs of halving fuel cons umption. The undiscounted pay-back period to recoup the initial extra cost of halving fuel consumption is some 4 to 5 years. These estimates do not take into account the rebound effect of increased vehicle travel as it becomes cheaper to drive a vehicle with lower fu el consumption. Most studies have placed the longterm rebound effect between 10% to 25%. [Green ing et al., 2000] Van Dender and Small (2005) however, recently found that between 1997 and 2001 , the long-term rebound effect was half of its value over the entire 1966 to 2001 period, and is likely to diminish below 10% as rising income reduces the relevance of fuel costs in travel decisions.

14 The 3% discount rate is the same as the “social rate of time preference” us ed by the U.S. Office of Management and Budget in regulatory analysis. [OMB, 2003: 33]33 Without accounting for fuel savings, the cost of reducing a ton of GHG emissions ranges from $65 to $76 across the three scenarios, as shown in the same Table 10. For comparison, the Intergovernmental Panel on Climate Change (IPCC) estimates that GHG reductions costing between of $20 to $80 per ton of CO 2 e before 2030, and between $30 to $150 by 2050, will be required in order to stabilize atmospheric GHG emissions at 550 ppm CO 2 -equivalent by 2100. [IPCC 2007]

Conclusions This analysis has examined th e necessary changes required to double the fuel economy, or halve the fuel consumption of new vehicles within the next three decades. The results reveal the following key conclusions:

1. Available technologies can get us there. With the set of light-duty vehicle options that we have chosen, all of which are available in the nearer term, it is possible to halve the fuel cons umption of new vehicles by 2035. This requires: (i) incremental improvements in the engine and transm ission; (ii) aerodynamic drag, rolling resistance and weight and size reduction; and (iii) deployme nt of more efficient alternative powertrains.

2. However, significant changes are required and there are trade-offs. The material cycle impact is similar across th e scenarios examined, and there is little trade-off in this respect. However, this study reveals the trade-offs between the performance, cost, and fuel consumption reduction benefit that we are seeking. For example, Scenario I is the most cost-effective, but maintains today’s performance. Conversely, Scen ario III offers the best performance improvement of all scenarios presented, but is more expensiv e with aggressive weight reduction and use of alternative powertrains. We would have to pay mo re for scenarios which direct future efficiency improvements towards increasing vehicle horsepower and acceleration performance, rather than towards reducing fuel consumption.34 3. The production cost of fu ture vehicles will increase. Halving the fuel consumption of the 2035 m odel year will increase the production cost of future vehicles with roughly the same size, weight , and performance as today. Excluding distribution costs, dealer and manufacturer profits, the extra cost of the 2035 model year vehicles is estimated at $54 to $63 billion, or about 20% more than the baselin e cost. This corresponds to a cost of $65 to $76 per ton of CO 2 e emissions, when accounting for emissions savi ngs over the lifetime of vehicles in the 2035 model year. So while it is technically possible to halve the fuel consumption of new vehicles in 2035, the nature and magnitude of the changes required to meet this goal run counter to the trend towards larger, heavier, more powerful vehicles over the last 25 year s. Instead, these scenarios depict a transportation future where automakers might face costs up to 20% higher to produce potentially smaller vehicles with performance similar to today’s. Automakers may be hesitant to make such large-scale changes in the product mix unless consumers are willing to fo rego their continuing pursuit of ever higher performance, larger vehicle size and other amenities. Su ch a future will challenge the auto industry to make the capital investments necessary to realize a lternative technologies at a substantial scale, and requires the government to address the market failures that promote size, weight, and acceleration at the expense of higher vehicle fuel consumption and its associated impacts related to energy security and global warming. These are striking changes from the status quo. Halving fuel consumption in 2035 vehicles will require a fundamental shift in the mindset and motivation of a broad base of consumer, industry, and governmental stakeholders. It will require a new set of policies that pushes industry to utilize new technologies, while at the same time creating market demand to pull efficiency gains toward reducing fuel consumption and aligning the interests of dive rse stakeholder groups to realize this worthy and ambitious goal.35 Appendix A: Notes on fuel consumption

 The fuel efficiency of a vehicle may be expressed in terms of travel distance obtained per unit of fuel input, which is the fuel economy ; or its inverse – the amount of fuel used or consumed per unit of distance traveled, which is the fuel consumption . Fuel economy (FE) is commonly expressed in miles per U.S. gallon (mpg), and fuel consumption (FC) in liters of fuel used per 100 kilometers traveled (L/100km). A useful conversion factor to remember is:



### ) ( 2

. 235 ) 100 / ( mpg FE km L FC =

 In this study, the objective is to achieve a factor-of-two reduction in the sales-weighted average fuel consumption of the new vehicle fleet . This refers to the average fuel consumption of the 21.6 million new vehicles expected to be sold or introduced on the roads in year 2035, and not that of the entire stock of vehicles in u se, or already on the ro ad in that year. The sales-weighted average fuel consumption considers the powertrain mix in the market, and the fuel consumption benefit of using altern ative, and more efficient powertrains.

 The fuel consumption used is that obtained by combining both a city (FTP-75) and a highway (HWFET) drive cycle results. The Federal Test Procedure (FTP-75) is used by the Environmental Protection Agency (EPA) to certify the fuel economy and emissions performance of consumer vehicles for city driv ing. The highway fuel economy test (HWFET) driving cycle is used to simulate highway driving and estimate typical highway fuel economy. 0.55 and 0.45 weighting factors are used to account for the relative amounts of city and highway vehicle operation. The combined liters per 100 km travel is calculated as follows: 

### ) * 45

. 0 ( ) * 55

. 0 ( HWY CITY COMBINED 

### FC FC FC + =

 0.9 and 0.78 correction factors are used by EPA to adjust the results from dynamometer testing to reflect on-road operation for the city and highway drive cycles respectively. All fuel consumption figures that are reported in this st udy refers to the adjusted combined fuel consumption, and this is calculated as follows: 

### ) 78

. 0 / * 45

. 0 ( ) 90

. 0 / * 55

. 0 ( HWY CITY COMBINED 

### FC FC FC Adjusted + =

 When comparing the fuel consumption of a diesel vehicle versus a gasoline vehicle, the diesel fuel used by the diesel vehicle is converted into a gasoline equivalent, in order to make it an even comparison on an energy-basis. This gasolin e equivalent value is calculated based on the lower heating value of gasoline (42.6 kJ/g) and the density of gasoline (749 g/L). The lower heating value of diesel is 43.0 kJ/g, and th e density of diesel is 850 g/L. [AVL 2004]36 Appendix B: Summary of assumptions General assumptions

 The market share of light trucks (versus cars) in the new light vehicle fleet in 2035 is 55%, the same as today.

 Vehicle sales will grow at an annual rate of 0.8% per year, compounded. This estimate is based upon projections of population and income growth. For comparison, the EIA’s Annual Energy Outlook 2007 projects an average light-duty vehicle sales growth of 0.9% from 2005 to 2010.

 The average vehicle’s fuel consumption, horse power and weight will vary proportionately with the level of emphasis on reducing fuel consumption (% ERFC). Alternative powertrains

 Based on historical technology diffusion and market forecasts, there are limits to the market penetration of alternative powertrain (hybrid 35%, diesel 25%, turbocharged gasoline 25%)

 The relative proportion of the 3 different alternative powertrains’ market share is fixed.

 The market penetration of the alternative power trains will be the same in the car and light truck segments. Vehicle weight and material composition

 The maximum vehicle weight reduction is 35% from today’s values, i.e., the minimum salesweighted average weight is 1,051 kg for cars, 1,390 kg for light trucks.

 Vehicle weight reduction will take place thr ough a combination of material substitution, vehicle redesign and downsizing.

 Material substitution will account for up to 20% weight reduction. At the maximum, aluminum will replace 80% of the iron in the vehi cle, and more than half of conventional steel. HSS will replace 15% of steel, and plastics/com posites another 2%. All other materials will weigh a third less than 2006 values.

 Redesigning or reconfiguring the vehicle can ach ieve half of the weight reduction benefit obtained with material substitution.

 Weight reduction by downsizing is achieved by shifting vehicle sales away from the heavier vehicle categories without making the smallest ve hicles any smaller, and can result in a further 10% weight reduction.

 For every additional 100 kg weight reduction, the adjusted combined 55/45 U.S. EPA city/highway fuel consumption will reduce by 0.31 L/100km for cars, and 0.36 L/100km for light trucks. The adjustment factors used are 10% for the city drive cycle, and 22% for the highway drive cycle.

 Diesel vehicles weigh 3% more than gasoline vehi cles, and hybrids 0.5% more. While slightly heavier, diesel vehicles have the same material composition as gasoline vehicles.

 Hybrid vehicle in 2035 will use a lithium-ion ba ttery (this affects the material composition).

 Material production energy (MJ/kg) values ar e obtained from Argonne National Laboratory's GREET 2.7 program, and they do not change over time. Cost assessment

 Base costs of current N.A. gasoline vehicles calculated using a retail price factor of 1.4, assuming that production costs include vehicle manufacturing, and corporate and production overhead (see Vyas et al., 2000; Table 1, p. 2). Calculated as follows:

estimate cost in captured price retail of Fraction ing manufactur vehicle to relative price retail Total 4

. 1 ) 14

. 0 11

. 0 13

. 0 10

. 0 1 ( 00

. 2

= + + + + =37 Fuel and GHG savings benefits are calculated assuming:

 Fuel savings calculated based on an average lif etime vehicle travel of 240,000 km. Taken from the U.S. Department of Transportation’ s vehicle survivability and mileage travel schedule [DOT, 2006].

 GHG savings calculated assuming an emissions intensity of 2,950 grams of CO 2 -equivalent per liter of gasoline, calculated on a well-to-w heels basis (i.e. includes emissions produced from burning fuel during vehicle operation, and upstream emissions from extraction, refining, and distribution of the fuel).

 Value of fuel savings calculated assuming a consta nt fuel cost of $1.85 / gallon, taken as the average of the EIA’s long-term fo recast for motor gasoline, minus $0.40 / gallon in local, state, and government taxes. [EIA, 2007b]

 Value of fuel savings discounted at 3%, taken as the “social rate of time preference” used by the U.S. Office of Management and Budget for regulatory analysis. [OMB, 2003: 33]38 Appendix C: Future vehicle characteristics at 0-100% ERFC Table 1 in this report features the current and future average new car characteristics at different levels of emphasis on re ducing fuel consumption (ERFC). The characteristics of the future vehicle are developed by making some assumptions on the curb weight of the vehicle at different levels of ERFC, and using ADVISOR vehicle simula tions to verify and determine the acceleration performance. With a predefined vehicle mode l over a prescribed speed-time trace, ADVISOR software helps to calculate the torque, speed, and power passing through different vehicle components, and predicts the vehicle’s fuel c onsumption and acceleration performance. We begin with an understanding of the 1 00% ERFC vehicle described by Kasseris and Heywood (2007), which is a vehicle that has achieve d the full fuel consumption reduction potential in the future, but with no change to its accelerati on performance (see Table C.1). While performance has not improved, this vehicle consumes 35% less fuel per unit distance traveled, partly because it weighs 20% lighter than its counterpart today.

Vehicle characteristics Representative car (Toyota Camry) Representative light truck (Ford F150) Today Future Today Future Curb weight 1,435 kg 1,148 kg 1,995 kg 1,596 kg Displacement volume 2.4 liters 1.4 liters 4.2 liters 2.5 liters Maximum power 119.2 kW (160 hp) 95.4 kW (128 hp) 150.6 kW (202 hp) 120.5 kW (162 hp) Vehicle power/weight ratio 83.1 W/kg 83.1 W/kg 75.5 W/kg 75.5 W/kg Engine power density 0.74 kW/kg 0.93 kW/kg 0.74 kW/kg 0.93 kW/kg 0-60 mph acceleration time 9.4s 9.2s 9.8s 9.8s Fuel consumption 8.8 L/100km 5. 5 L/100km 13.6 L/100km 8.6 L/100km Table C.1. Characteristics of curre nt and future gasoline N.A. vehicles with full emphasis placed on reducing fuel consumption (100% ERFC) [Kasseris and Heywood 2007]

By our definition of ERFC, if there is no em phasis placed on reducing fuel consumption (0% ERFC), the fuel consumption of the future vehicl e will remain at today’s values. Assuming that the vehicle’s curb weight remains at today’s value as well 15 , the representative future car will weigh 1,435 kg, and these inputs in ADVISOR will result in a 0- 60 mph acceleration time of 6.6 seconds, requiring maximum power of 195 kW (261 hp). The next key assumption is that both the fuel consumption reduction benefit and the future vehicle’s curb weight will scale linearly with % ERFC. At 50% ERFC, or when half the maximum fuel reduction potential is realized, the future ve hicle will consume 0.5 times 35%, or 17% less fuel per unit distance traveled, and weighs 10% lighter than the 2006 vehicle. ADVISOR acceleration performance results for this 50% ERFC car is 7. 1 seconds, requiring a maximum power of 144 kW (193 hp). These results for the future representative car a nd light truck at different levels of ERFC are detailed in Table C.2 and Figure C.1 below. While th ese are obtained for single, representative car and light truck models, the Toyota Camry and the Ford F150, the relative ratios of the vehicle’s fuel consumption, weight, and maximum power will be applied to the sales-weighted average vehicle characteristics to obtain the values reported in Table 1.

15 See Appendix E for more details on the vehicle curb weight assumptions.39 Year % ERFC Fuel consumption (L/100km) [relative] Horsepower [relative] 0-60 mph acceleration time (s) Vehicle weight (kg) [relative] 2006 - 8.8 [1.00] 160 [1.00] 9.4 1,435 [1.00] 0% 8.8 [1.00] 261 [1.64] 6.6 1,435 [1.00] 50% 7.1 [0.81] 193 [1.21] 7.1 1,292 [0.90] 2035 100% 5.5 [0.62] 122 [0.76] 9.3 1,148 [0.80] (a) The representative car model, the Toyota Camry Year % ERFC Fuel consumption (L/100km) [relative] Horsepower [relative] 0-60 mph acceleration time (s) Vehicle weight (kg) [relative] 2006 - 13.6 [1.00] 202 [1.00] 9.8 1,995 [1.00] 0% 13.6 [1.00] 302 [1.49] 8.1 1,995 [1.00] 50% 11.2 [0.82] 232 [1.15] 8.4 1,796 [0.90] 2035 100% 8.6 [0.63] 162 [0.80] 9.8 1,596 [0.80] (b) The representative light truck model, the Ford F150 Table C.2. Current and future naturally-aspirated gasoline vehicl e characteristics at different levels of emphasis placed on reducing fuel consumption (% ERFC)

0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80

0% 25% 50% 75% 100% % ERFCFuture values relative to 2006_ Horsepower Weight Fuel consumption

Figure C.1. Future car characteristic s at different levels of emphasis pl aced on reducing fuel consumption (% ERFC)

The level of emphasis that is placed on reducing fuel consumption (ERFC) will also affect the relative fuel consumption of the different powertr ains in 2035. At full ERFC, performance does not change from today’s values, and the maximum level of fuel consumption benefit is achieved in all powertrains. With 0% ERFC, the fuel consumption of different powertrains relative to one another will be the same as that at 100% ERFC, with th e fuel consumption of the gasoline N.A. vehicle remaining at today’s values. These ratio s are depicted in Figure C.2 below.40 0.62 1.00 1.00

0.55 0.89 0.90

0.53 0.85 0.84

0.35 0.56 0.70

0.00 0.20 0.40 0.60 0.80 1.00 1.20

2006 2035 (0% ERFC) 2035 (100% ERFC)Relative fuel consumption_ N.A. gasoline (reference) Turbocharged gasoline Diesel Hybrid-electric gasoline

(a) For passenger cars

1.00 1.00

0.63 0.83 0.85

0.54 0.74 0.79

0.50 0.70

0.56

0.35

0.00 0.20 0.40 0.60 0.80 1.00 1.20

2006 2035 (0% ERFC) 2035 (100% ERFC)Relative fuel consumption_ N.A. gasoline (reference) Turbocharged gasoline Diesel Hybrid-electric gasoline

(b) For light trucks Figure C.2: Current and future relative fuel consumptio n of alternative powertra ins at different % ERFC [Kasseris and Heywood 2007, Kromer and Heywood 2007]41 Appendix D: Market penetration of alternative powertrains Increasing the market share of alternative, more efficient powetrains that use turbochargers, diesel engines, or hybrid-electric drives is one of the three options discussed in this study. We have assumed a maximum market penetration limit of 85% in 2035 for these alternative powertrains, based on a review of historical automotive diffusion, as al ready explained in the main body of this paper. Following from this, at least 15% of new vehicles sold in 2035 will continue to use the conventional spark-ignited naturally-aspirated gasoline engi ne. The powertrain mix at the assumed maximum market penetration is listed in Table D.1, and th e effective compounded annual growth rate (CAGR) to achieve this market share is listed in the right-most column.

Powertrain technology 2006 mark et share (%) Maximum 2035 market share (%) 2006-2035 CAGR 16 (%)

Turbocharged gasoline 1.0% 25.0% 11.9% Diesel 2.3% 25.0% 8.6% Hybrid-electric gasoline 1.6% 35.0% 11.1% Total 4.9% 85.0% 10.4% Table D.1. Current and assumed ma ximum future market penetratio n of alternative powertrains

The proportion of turbocharged gasoline, diesels, and hybrid electric-gasoline vehicles in the market is initially assumed to be fixed at (5:5:7) fo r Scenarios I, II and III. That is, for every 12 new vehicles sold with alternative powertrains, 5 will utilize turbochargers, another 5 will run on diesel fuel, and the remaining 7 will be hybrids. So hybrids are expected to outperform diesel and turbocharged gasoline engines slightly in the U.S. market. It is recognized that the actual future powertrain mix is hard to predict, and there is some flexibility to be applied to this ratio. For instance, in Scenario IV, where there is even more aggressive penetration of hybrids, a ratio of (3:3:11) is used. Available market forecasts of alternative powertrai ns are reviewed below to examine the validity of these assumptions. Forecasts of alternative powertrain technology diffusion Available projections of alternative powertrains’ market share in the U.S. are all upward, but vary widely, as seen in Table D.2 and Figure D.1. Most project the sales of alternative powertrains 5- 10 years into the future, and only the Energy In formation Administration (EIA) of the U.S. DOE publishes projections beyond 2015. These market penetration forecas ts project annual growth rates of 4% to 25% (compounded). In these projections, the proportion of hybrids to diesels in the future U.S. market remains fairly close, ranging from 0.6 to 1.6 (see Table D.3). Factors against diesels are poor customer acceptance of diesels in the passenger cars segment, diesel fuel price premium, and the negative perception that diesels are noisier and dirtier. For hybrids, UBS/Ricardo [2007] reports that the hybrid technologies will face manufacturing cost penalties, and Frost & Sullivan [2005] believes that hybrids will remain in a “premium-priced envi ronmental-oriented driver niche”.

16 Compounded annual growth rate (CAGR) = [( Future market share / today’s market share) (1 / # of years) ]-142 Powertrain technology Duration Market share (%) CAGR (%) Source
2006-2030 1.0-2.3% 3.7% EIA 2007 Turbocharged gasoline 2004-2015 2.5-5.0% 6.5% Frost & Sullivan 2005 2006-2030 2.3-6.0% 4.1% EIA 2007 2004-2012 3.0-7.5% 12.1% J.D. Power 2005 2004-2015 2.4-10.0% 13.9% Frost & Sullivan 2005 Diesel

2005-2012 2.0-8.3% 22.4% UBS/Ricardo 2007 2006-2030 1.6-7.6% 6.6% EIA 2007 2005-2012 1.3-4.2% 18.2% J.D. Power 2006 2005-2012 1.4-6.7% 24.8% UBS/Ricardo 2007 Hybrid-electric gasoline 2004-2015 0.5-8.0% 28.7% Frost & Sullivan 2005 Table D.2. Market share projections of alternative powert rains in the U.S.

Diesel (F&S)
Hybrids (F&S) Hybrid (UBS) Turbo (F&S) Diesel (JDP) Diesel (UBS)

0% 2% 4% 6% 8% 10% 12%

2005 2010 2015 2020 2025 2030US light vehicle market penetration Hybrid (EIA) Diesel (EIA) Turbo (EIA)

Figure D.1. Market share projecti ons of alternative powertrains in the U.S. [various sources]

Year Market share of hybrids (%) Market share of diesels (%) Hybrid:diesel ratio Source

2006 (Today) 1.6% 2.3% 0.72 EIA 2007 2012 4.2% 7.5% 0.56 J.D. Power 2006 2012 6.7% 8.3% 0.80 UBS/Ricardo 2007 2012 3.5% 2.5% 1.40 EIA 2007 2015 8.0% 10.0% 0.80 Frost & Sullivan 2005 2015 4.2% 2.7% 1.55 EIA 2007 2030 7.6% 6.0% 1.27 EIA 2007 Table D.3. Comparison of join t diesel and hybrid vehicle ma rket forecasts in the U.S.43 Appendix E: Vehicle weight reduction Weight reduction assumptions In this study, there are four key assumptions made that concern vehicle weight. Firstly, at 100% ERFC, it is assumed that a 20% reduction vehicle curb weight can take place in the future with no change in the level of vehicle performance, size a nd safety from today’s values. This assumption is not a projection of what the weight of the future ve hicle will be, but the level of weight reduction that is feasible. This weight reduction can be achieved by 2035 with advances in lightweight materials and manufacturing technologies, which will be discussed shortly. The second assumption is that the future vehicl e curb weight will scale linearly with % ERFC, as detailed in the right-most column of Table 1 in th e main body of this report. There is no change in vehicle weight at 0% ERFC, and a 20% reduction in vehicle weight at 100% ERFC. This assumption provides reasonable agreement with an extrapolation of historical vehicle performance. Using An and DeCicco’s Performance-Fuel economy (PFI) index 17 [An and DeCicco 2007], which tracks and projects the rate of technical progress in vehicles, the PFI values of the average new car at all levels of ERFC match the expected PFI value in 2035, and are shown in Figure E.1.

0.00 0.50 1.00 1.50 2.00 2.50

1970 1980 1990 2000 2010 2020 2030 2040(hp/lb).mpgHistorical 0% ERFC 50% ERFC 100% ERFC

Figure E.1. Performance-fuel eco nomy index of the average car

The third assumption is that there will be a lim it to the amount of weight reduction possible by 2035, and this is set at about a third (35%) fro m today’s values. Given the need and demand for weight-adding safety features and passenger and ca bin space, it is unlikely that the sales-weighted average new car weight can decline below 1,050 kg . In 2005, there were only three new car models that weighed less than 1,000 kg – the 2-seaters Honda Insight and Toyota MR2 Spider, and the Toyota Echo. Finally, it is assumed that the adjusted combin ed city/highway (55/45) fuel consumption will decline by 0.31 L/100km for every 100 kg of weight reduction for a car, and by 0.36 L/100km for a light truck. This is based on vehicle simulations of the best-selling vehicle models, the Toyota Camry, and Ford F150 pickup, using AVL ADVISOR, and includes the effects of expected technical

17 PFI = (horsepower/curb weight) x fuel economy, and has units of (hp/lb).mpg.44 improvements in the future vehicles , and engine downsizing. The drive cycles used are the U.S. EPA’s Federal Test Procedure (FTP) for the city and the Highway Fuel Economy Driving Schedule (HWFET) for the highway. How up to 35% weight reduction is achieved Reduction in the sales-weighted average ne w vehicle weight can be achieved by a combination of (i) material substitution; (ii) redesigning the vehicle to minimize weight; and (iii) downsizing of the new vehicle fleet by shifting sales away from larger and heavier vehicles. The first two approaches are preferred since they offer little change in the level of interior and cargo space utility, which are popular attributes to consumers, and are more effective in achieving weight reduction. The weight reduction achieved from downsizing an automobile by one USEPA sizeclass is 8-11%, while the weight savings from aggres sive use of lightweight materials can be 20-45%, as demonstrated in some concept vehicles (see Ta ble E.2). As such, it is assumed that the initial desired weight reduction will be achieved by mate rial substitution or new vehicle designs that optimize weight. Vehicle downsizing will be used on ly if higher degrees of weight reduction, i.e. downsizing will take place if 20- 35% weight reduction from today’s values, are required. The amount of weight reduction apportioned to the three me thods is summarized in Table E.3, and this is elaborated on in the following sections.

Vehicle Vehicle segment Curb we ight (kg) Weight savings (%) Stodolsky et al (1995) aluminum-int ensive car Midsize sedan -- 19% DaimlerChrysler Dodge Intrepid ESX2 concept composite- and aluminum-intensive car Midsize sedan 1,021 kg 37% IISI ULSAB-AVC concept high-strength steel intensive car Midsize sedan 998 kg 38% Ford P2000 concept aluminum -intensive car (similar to Ford Taurus) Midsize sedan 912 kg 44% Table E.2. Concept lightwe ight automobiles that emb ody lightweight materials

Weight reduction method For 20% weight reduction For up to 35% weight reduction (i) Material substitution 14% 20% (ii) Vehicle redesign 7% 10% (iii) Vehicle downsizing 0% 10% Total weight reduction 20% 35% Table E.3. Weight reduction methods

Material substitution Alternative lightweight materials, like high strength steels (HSS), aluminum, magnesium, or glass- and carbon fiber-reinforced polymer composite s can be used to replace heavier iron and steel components. Of the candidates, aluminum and HSS are more cost-effective at large production volume scales and their increasing use in vehicles is likel y to continue. Cast aluminum is most suited to replace cast iron components, stamped aluminum for stamped steel body panels and HSS for structural steel parts. Polymer composites are also expected to replace some steel in the vehicle, but to a smaller degree given high cost inhibitions. A comparison of the lightweight material options is summarized in Table E.4.45 Material Current use Merits Challenges Aluminum 130 kg/vehicle, 80% are cast parts e.g. engine block, wheels - Can be recycled - Manufacturers familiar with metal forming - High cost of Al - Stamped sheet is harder to form than steel - Softer and more vulnerable to scratches - Harder to spot weld, use more labor-intensive adhesive bonding High-strength steel 180 kg/vehicle, in structural components e.g. pillars, rails, rail reinforcements Makes use of existing vehicle manufacturing infrastructure,there is OEM support for nearterm use - More expensive at higher volume scale - Lower strength-to-weight ratio compared to other lightweight materials Magnesium 3.5 kg/vehi cle, mostly thinwalled cast parts e.g. instrument panels and cross car beams, knee bolsters, seat frames, intake manifolds, valve covers Low density, offering good strength-to-weight ratio - Higher cost of magnesium components - Production of magnesium in sheet and extruded forms Glass-fiber reinforced polymer composite Rear hatches, roofs, door inner structures, door surrounds and brackets for the instrument panel - Ability to consolidate parts and functions, so less assembly is required - Corrosion resistance - Good damping and NVH control - Long production cycle time, more expensive at higher volume scale - Cannot be recycled

Carbon-fiber reinforced polymer composite Drive shaft Highest strength-to-weight ratio,offering significant weightsaving benefit - As above - High cost of fibers ($17-22/kg)

Table E.4. Comparison of alternative lightweight automotive materials

The amount of weight savings resulting from us ing alternative materials in any vehicle component depends on the application and design inte nt. For instance, for a body panel designed for strength and resistance to plastic deformation, 1 kg of aluminum can replace 3-4 kg of steel. For a structural component designed for stiffness in order to restrict deflection, 1 kg of aluminum replaces only 2 kg of steel. Based on material substitution case studies, the assumed weight savings from replacing steel and iron for the most likely alterna tive materials are listed in Table E.5. For a 35% reduction in vehicle weight, lightweight materials w ill be used to achieve the first 20% of weight reduction, and the amount of iron and steel that need to be replaced then is described in the last column.

Material substitution Relati ve density Weight savings per unit weight of iron or steel replaced % iron or steel replaced
Cast aluminum for iron 0.38 35% 78%

Wrought Al for steel 0.34 45% 47% HSS for steel 1.00 25% 14% Plastics for steel 0.20 25% 2% Table E.5. Material substitution required to achieve a 20% reduction in the average vehicle weight46 Vehicle redesign to minimize weight Redesigning or reconfiguring the vehicle can also offer some weight savings. For example, a marked decline in vehicle weight in the early 1980s was partly achieved by changing some vehicles from a heavier body-on-frame to lighter-weight unibo dy designs. Although most cars are already using a unibody design, the potential is for the larg er sport-utility vehicles to do the same. Secondary weight savings can also be realized by downsizing subsystems that depend on the total vehicle weight. As the vehicle weight decr eases, the performance requirements of the engine, suspension, and brake subsystems are lowered and th ese can be downsized accordingly. For example, if the average future car’s body weight is reduced by 100 kg using material substitution, the engine weight can be lowered by about 7 kg, assuming a future engine power density of 0.9 kW/kg. Another way to minimize weight with crea tive design and packaging is to minimize the exterior dimensions of the vehicle while maintaini ng the same interior space, or to remove features from the vehicle. Figure E.2., which plots the interi or volume of various midsize sedans offered in model year 2007/2008 with their curb weights, illustrates the potential weight savings of this. While these options are available, it is acknowledge d that the need for safety features, either by regulation or consumer demand, may hinder lig htweight vehicle design. The amount of weight savings possible by vehicle redesign is therefore moderated, and assumed to be half the benefit achieved with material substitution.

108 110 112 114 116 118 120

1,000 1,500 2,000 2,500 3,000 

### Curb weight (kg)Interior volume (cu-ft)_

Various models Sales-weighted average Approximate weight gains from redesigning a sedan

while maintaining same interior volume: 12-35%

Figure E.2. Potential weight savings from redesigning model year 2007/8 midsize sedans while maintaining same interior volume

Downsizing of the new vehicle fleet By shifting sales away from larger and heavie r vehicle categories, further reduction in the sales-weighted average new vehicle weight can be obtained. The difference in weight achieved from downsizing an average vehicle by one U.S. EPA si ze class ranges 8-11% for cars, and 5-25% for other vehicle segments (see Figure E.3). When considering this change in the vehicle sales distribution, we will shift sales from the heavier vehicle categories to the lighter weight cate gories, but will not reduce the sales from the lighter weight categories. This is shown in Figure E.4, where the sales distributions are pinned on the left, while the curves are shifted leftward to the lighter weight categories. This accounts for the challenges in producing vehicles that are lighter than the lightes t vehicles in both the car and light truck segments, and also improves vehicle compatibility from a road safety perspective. Downsizing from the light47 truck segment to the car segment is not considered , with the assumption that the market split between these two segments will remain at 55:45 (light trucks:cars).

0 500 1,000 1,500 2,000 2,500 3,000

Small Midsize LargeCurb weight (kg)_ Car Wagon Pickup SUV Van

Figure E.3. MY2000-2005 sales-weighted average U.S. ve hicle weights by EPA size class [data from EPA]

0 1,000 2,000 3,000 4,000 5,000 6,000

0 500 1,000 1,500 2,000 2,500 Curb weight (kg)Sales ('000) Before downsizing After downsizing 1,050 kg
1,170 kg

0 1,000 2,000 3,000 4,000 5,000 6,000

0 500 1,000 1,500 2,000 2,500 Curb weight (kg)Sales ('000) Before downsizing After downsizing 1,390 kg 1,550 k

(a) Cars (b) Light trucks Figure E.4. Sales distribution before and aft er downsizing of the new 2035 vehicle fleet

Implications on safety We have not considered any compromise in sa fety standards when reducing the weight and size of the vehicle for two reasons. First, it is possi ble to design and build small vehicles with similar crashworthiness as larger and heavier ones. By rein forcing the structural stiffness of the vehicle at critical points, including side airbags, and introduc ing crumple zones to absorb energy in case of a collision, automakers are already making smaller cars that protect their occupants better. For example, the MINI Cooper scored 4 out of 5 stars in the U. S. National Highway Traffic Safety Administration frontal and side crash ratings. Second, aside from th e crashworthiness of the vehicle, there are other facets to the safety discussion to be considered, in cluding rollover risk, aggre ssiveness of vehicles to other road users, and vehicle crash compatibility. Co nsidering the effect of overall road safety, some of the larger and heavier SUVs and pickups can actua lly pose greater safety risks for their drivers and other road users [Ross et al, 2006]. Hence, there is little compromise in safety as vehicle weight and size is reduced, and safety might actually improve if the heaviest vehicles could be made lighter.48 Appendix F: Material cycle impact assessment The material composition used for the aver age gasoline (both naturally-aspirated and turbocharged), diesel, and hybrid-electric cars are summarized in Table F.1. The same composition is used for light trucks, although they weigh a third more than cars. The gasoline and diesel vehicles’ material breakdown are obtained from the DOE’s Transportation Energy Data Book. The hybrid vehicle’s material breakdown is based on the H onda Insight, the Toyota Prius and Argonne National Laboratory’s GREET 2.7 database. In 2035, diesel ve hicles are assumed to weigh 3.0% more than gasoline vehicles, and hybrid-electric vehicles only 0.5% more. Future hybrid vehicles are expected to use a lithium-ion battery with specific energy of 100 Wh/kg. [Kromer and Heywood 2007] Table F.2 shows the material composition of the average gasoline car after each of the three described steps of weight reduction – material s ubstitution, vehicle rede sign and downsizing – to achieve a net 35% reduction in vehicle weight. For vehicle redesign and downsizing, the material composition is assumed to remain unchanged, while total vehicle weight decreases. The energy intensity of the materials used in the vehicles are obtained from the GREET 2.7 database, and summarized in Table F.3. This ta ble also includes the energy required to recover materials from scrap (secondary energy), and the percen tage of materials used in each vehicle that are secondary or recovered. We will assume that the ma terial energy intensity data reported in GREET 2.7 does not vary over time and is applicable to future vehicles.

Gasoline Diesel Hybrid-electric Material kg % mass kg % mass kg % mass
Steel Conventional steel 693 42.9% 713 42.9% 729 44.9% High-strength steel 194 12.0% 200 12.0% 204 12.6% Stainless steel 29 1.8% 30 1.8% 30 1.9% Other steels 14 0.8% 14 0.8% 14 0.9% Iron 168 10.4% 173 10.4% 69 4.2% Aluminum Cast 113 7.0% 117 7.0% 137 8.5% Wrought 29 1.8% 29 1.8% 45 2.8% Rubber 76 4.7% 78 4.7% 56 3.4% Plastics/composites 131 8.1% 135 8.1% 191 11.7% Glass 50 3.1% 52 3.1% 42 2.6% Other metals Copper 26 1.6% 26 1.6% 32 2.0% Zinc 4 0.3% 4 0.3% 0 0.0% Magnesium 5 0.3% 5 0.3% 5 0.3% Nickel 0 0.0% 0 0.0% 10 0.6% Other metals 20 1.3% 21 1.3% 5 0.3% Other materials 65 4. 0% 67 4.0% 55 3.4% Total 1,616 100.0% 1,664 100.0% 1,624 100.0% Table F.1. Materi al composition of different cars49 (i) after material substitution (ii) after vehicle redesign (iii) after downsizing Material kg % mass kg % mass kg % mass
Steel Conventional steel 235 18.2% 212 18.2% 191 18.2% High-strength steel 273 21.1% 246 21.1% 221 21.1% Stainless steel 20 1.5% 18 1.5% 16 1.5% Other steels 0 0.0% 0 0.0% 0 0.0% Iron 35 2.7% 31 2.7% 28 2.7% Aluminum Cast 200 15.4% 180 15.4% 162 15.4% Wrought 222 17.2% 200 17.2% 180 17.2% Rubber 52 4.0% 47 4.0% 42 4.0% Plastics/composites 141 10.9% 127 10.9% 114 10.9% Glass 34 2.7% 31 2.7% 28 2.7% Other metals Copper 17 1.3% 16 1.3% 14 1.3% Zinc 3 0.2% 3 0.2% 2 0.2% Magnesium 3 0.3% 3 0.3% 3 0.3% Nickel 0 0.0% 0 0.0% 0 0.0% Other metals 14 1.1% 13 1.1% 11 1.1% Other materials 45 3. 4% 40 3.4% 36 3.4% Total 1,294 100.0% 1,166 100.0% 1,050 100.0% Table F.2. Material composition of the aver age gasoline car after weight reduction steps

Material Primary Energy (MJ/kg) Secondary Energy, or energy required to recover materials from scrap (MJ/kg) % of secondary material used in each vehicle

Steel Conventional steel 48.8 34.9 70.0% High-strength steel 48.8 34.9 70.0% Stainless steel 37.2 - - Other steels 48.8 34.9 70.0% Iron 39.5 - - Aluminum Cast 204.7 46.5 59.0% Wrought 237.2 53.5 11.0% Rubber 44.2 - - Plastics/composites 60.5 - - Glass 20.9 - - Other metals Copper 111.6 - - Zinc 118.6 - - Magnesium 379.1 - - Nickel 151.2 37.2 44.0% Other metals 120.0 - - Other materials 100.0 - - Table F.3. Material energy intensity or production en ergy requirement [GREET 2.7]50 References



###  AVL, ADVISOR 2004: User’s Guide , April 2004



###  ACEA, New passenger car registrations, breakdown by share of diesel , European Automobile Manufacturers Association statistics, 2007



###  An, F., J. DeCicco, Trends in Technical Efficiency Trade-O ffs for the U.S. Light Vehicle Fleet , SAE Paper No. 2007-01-1325, 2007, Warrendale, PA: Society of Automotive Engineers.



###  Board on Energy and Environmental Systems, Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards , National Research Council, National Academy Press, Washington, D.C., 2002



###  Burnham, A. et al, Development and Applications of GREET 2.7 – The Transportation VehicleCycle Model , Argonne National Laboratory report ANL/ESD/06-5, November 2006



###  Davis, S. and S. Diegel, Transportation Energy Data Book: Edition 26 , Oak Ridge National Laboratory, ORNL-6978, 2007



###  Department of Transportation (DOT), Vehicle Survivability and Travel Mileage Schedules , National Highway Traffic Safety Administrati on, Technical Report DOT HS 809 952, January 2006a. Accessed July 2007 from http://www-nrd.nhtsa.dot.gov/pdf/nrd30/NCSA/Rpts/2006/809952.pdf



###  Department of Transportation (DOT), Final Regulatory Impact Analysis: Corporate Average Fuel Economy and CAFE Reform for MY 2008-2011 Light Trucks , 2006. Accessed September 29, 2006, from http://www.nhtsa.dot.gov/staticfiles/DOT/NHTSA /Rulemaking/Rules/Associated%20Files/2006_ FRIAPublic.pdf



###  Dhingra, R. et al, Life-cycle environmental evaluation of aluminum and composite-intensive vehicles , report from the Center for Clean Produc ts and Clean Technologies, University of Tennessee, 5 March 1999



###  Energy and Environmental Analysis Inc. (EEA), Analysis and Forecast of the Performance and Cost of Conventional and Electric-Hybrid Vehicles , 2002. Accessed 19 February 2007, from http://www.energy.ca.gov/fuels/petroleum_de pendence/documents/2002-04-09_HYBRID.PDF



###  Energy Information Administration (EIA), Short-Term Energy Outlook – July 2007 , 2007a. Accessed July 2007 from http://www.eia.doe.gov/emeu/steo/pub/contents.html



###  Energy Information Administration (EIA), Annual Energy Outlook 2007 with Projections to 2030 , Report #DOE/EIA-0383, 2007. Accessed July 2007 from http://www.eia.doe.gov/oiaf/aeo/index.html and http://www.eia.doe.gov/oiaf/aeo/supplement/supref.html#trans , Tables 47, 58



###  Frost & Sullivan, Strategic Analysis of North American Automotive Light Diesel Technologies , research report, 30 September 2005



###  Frost & Sullivan, Strategic Analysis of North American Advanced Automoti ve Gasoline Engine Technologies , research report, 9 June 2005



###  Greening, L. et al, Energy efficiency and consumption – the rebound effect – a survey , Energy Policy, 28 (2000) pp. 389-401



###  J.D. Power and Associates, Sales of Hybrid-Electric Vehicles Expected to Grow 268 Percent by 2012 , press release, 4 January 2006



###  J.D. Power and Associates, Hybrid and Diesel Vehicles Expect ed to Represent 11 Percent of Market Share in Next Seven Years , press release, 28 June 2005



###  Kasseris, E. and J. B. Heywood, Comparative Analysis of Automo tive Powertrain Choices for the Next 25 Years , SAE Paper No. 2007-01-1605, SAE World Congress & Exhibition, Detroit, MI, USA, April 200751 

###  Kromer, M. A. and J. B. Heywood, Electric Powertrains: Opportunities and Challenges in the U.S. Light-Duty Vehicle Fleet , Laboratory for Energy and the Environment report #LFEE 2007-03 RP, Massachusetts Institute of Technology, June 2007, Accessed August, 2007 from http://lfee.mit.edu/pub lic/LFEE_2007-03_RP.pdf



###  Heavenrich, R., Light-Duty Automotive Technology and Fuel Economy Trends: 1975 through 2006 , U.S. Environmental Protection Agency, EPA420-S-06-003, July 2006



###  IPCC (2007), Climate Change 2007: Miti gation of Climate Change . Working Group III contribution to the Intergovernmental Panel on Climate Change Fourth Assessment Report: Summary for Policy Makers, para. 23, p. 29. Accessed July 2007 from http://www.mnp.nl/ipcc/pages_media/ar4.html



###  Northeastern States Center for a Clean Air Future (NESCCAF), Reducing Greenhouse Gas Emissions from Light-Duty Motor Vehicles , 2004. Accessed July 2007 from http://www.nescaum.org/documen ts/rpt040923ghglightduty.pdf/



###  Office of Management and Budget (OMB), Ci rcular No. A-4: Regulatory Analysis, 2003. Accessed August 2007 from http://www.whitehouse.gov/omb/circulars/a004/a-4.pdf



###  Ross, M. et al, Vehicle design and the physics of traffic safety , Physics Today, 59, 49–54, 2006



###  Small, K. A. and K. Van Dender, Fuel Efficiency and Motor Vehicle Travel: The Declining Rebound Effect , The Energy Journal, vol. 28, no. 1, pp. 25-51, 2007



###  Stodolsky, F. et al, Lightweight materials in the light-duty passenger vehicle market: Their market penetration potential and impacts , The Second World Car Conference, Riverside, CA, March 1995



###  TNO Science and Industry, Institute for European Environmental Policy (IEEP), & Laboratory of Applied Thermodynamics (LAT), Review and analysis of the reduction potential and costs of technological and other measures to re duce CO2-emissions from passenger cars , 2006. Retrieved 2 March 2007, from http://www.lowcvp.org.uk/assets/reports/TNO %20IEEP%20LAT%20et% 20al%20report_co2_red uction.pdf



###  UBS and Ricardo, Diesels set to out-strip hybrids in accelerating US growth , joint press release, 24 May 2007



###  Vyas, A., D. Santini, R. Cuenca, Comparison of indirect cost multipliers for vehicle manufacturing”, Argonne National Laboratory , April 2000. Accessed July 2007 from http://www.transportati on.anl.gov/pdfs/TA/57.pdf



###  Weiss, M. A. et al, On the Road in 2020: A life-cycle analysis of new automobile technologies , 2000, Cambridge, United States: Laboratory for Energy and the Environment (LFEE). Accessed July 2007 from http://web.mit.edu/energy lab/www/pubs/el00-003.pdf



###  World Auto Steel, ULSAB-AVC Overview Report , International Iron and Steel Institute, 2001