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 RP 
 

2

Acknowledgements 

This project was funded by Environmental Defense. The authors thank John DeCicco and 

Freda Fung from Environmental Defense for their 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 available and can be implemented on a large scale are 

evaluated: (1) channeling future vehicle technical 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 demonstrate the challenges of this factor-of-two 

improvement -- major changes in all these three options would need to be implemented before the 

target is met. Over the next three decades, consumers 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 values, 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 imply that continuing the current trend of ever 

increasing performance and size will have to be reversed 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, more efficient powertrains ........................................................................ 14 

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 characteristics 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 

References ............................................................................................................................................. 50
 

5

Introduction 

The automobile, while it has enabled 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 change, 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 rate 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 calls 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 average 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 combinations of available fuel-saving technologies 

and then consider their associated increased costs of production. The impact on greenhouse gas (GHG) 

emissions, in particular carbon dioxide (CO2), 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 2040

Fuel economy (mpg) or

Fuel consumption (L/100km)_

Historical fuel economy

Historical fuel consumption

Target fuel

economy

Target fuel

consumption

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

Background and Approach 

About 17 million new vehicles are introduced onto 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 consumes 9.6 liters of petroleum 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 weighs 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 efficiency is to improve conventional vehicle 

technology. For example, gasoline direct injection, 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. Further 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 powertrains, by which we mean turbocharged gasoline 

engines, high speed turbocharged diesel engines, and hybrid-electric systems. These alternatives 

provide additional fuel efficiency over naturally-aspirated (N.A.) gasoline engines. A turbocharger, by 

increasing the amount of air flow into the engine cylinders, 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) turning 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 2035

Relative 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 2035

Relative 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 consumption benefit of using these alternative 

powertrains in the average passenger car and light truck2

, with today’s naturally-aspirated (N.A.) 

gasoline internal combustion engine as the reference. The hybrid vehicle model assessed is a full 

hybrid3

 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 hybrids 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 across all powertrain options, including vehicles that 

continue to use the conventional N.A. gasoline engine. 

Next, vehicle weight reduction can reduce the overall energy required to accelerate to a given 

speed. Reductions in weight can be achieved by a combination 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 packaging 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 larger and heavier to smaller and lighter vehicle 

categories. 

When considering various ways of achieving the 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 different types of hybrid-electric drives available 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 engines, 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 fuel consumption over improving the vehicle’s 

horsepower and acceleration, while assuming that vehicle 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 decades, 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 average 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 performance is necessary, or even safe for the average 

driver on regular roads, regardless of whether the future consumer truly wants or expects this. Speed 

and horsepower have always had strong marketing appeal and demand 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 future vehicles. While holding size constant, we will 

define and quantify this trade-off as the degree of emphasis on reducing fuel consumption (ERFC), 

where: 

Future fuel consumption reduction possible with constant size and performance

Future fuel consumption reduction realized % ERFC =

At 100% ERFC, all of the steady improvements in conventional technology over time are 

assumed to realize reduced fuel consumption, while vehicle performance remains constant. This 

includes an assumption that vehicle weight will reduce by 20%. In contrast, without any emphasis on 

reducing fuel consumption (0% ERFC), the fuel consumption of new vehicles will remain at today’s 
 

12

values, no weight reduction will occur, and all of the efficiency gains from steady technology 

improvements are channeled to better the horsepower and acceleration performance instead. 

By simulating the future vehicles described using 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] 

2035 50% 7.8 [0.81] 239 [1.21] 7.2 1,454 [0.90] 

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] 

2035 50% 10.4 [0.82] 275 [1.15] 8.1 1,923 [0.90] 

100% 8.1 [0.63] 191 [0.80] 9.8 1,710 [0.80] 

(b) For light trucks 

Table 1: Summary of current and future naturally-aspirated gasoline vehicle characteristics4

When full emphasis is placed on reducing fuel consumption (100% ERFC) the fuel 

consumption of a future new car declines by 35% from today’s value, from 9.6 to 6.0 L/100km. About 

a quarter of this fuel consumption reduction is accredited 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-ignited, 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 conventional 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 turbocharged 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 desired 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 transmission 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% share of alternative powertrains in new vehicle 

sales in 2035. In other words, if turbocharged gasoline 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 gasoline 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 share of turbocharged gasoline and diesel vehicles are 
 

15

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 mentioned above, weight reduction can occur through a 

combination of (i) material substitution, (ii) vehicle redesign, and (iii) vehicle downsizing. 

Of the lightweight material candidates available for material substitution, aluminum and highstrength steel (HSS) are more cost-effective at large 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 panels 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 use of these substitute materials, up to 20% reduction 

in vehicle weight can be achieved, and the corresponding 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 exterior dimensions of the vehicle while maintaining 

the same interior (passenger and cargo) space. We will 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 2035

Mass 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 2035

Mass breakdown (kg)_

Other materials

Other metals

Glass

Rubber

Plastics/composites

Aluminum

Iron

Steel

-20%

Figure 5: Material composition of the average new 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 redesign, 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 from downsizing a car by one U.S. EPA size-class5 ranges 

from 8-11%. Specifically, only the heavier vehicle classes 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 without downsizing, the entire future car sales distribution shifts to 

the lighter weight ranges with no change in its shape. With downsizing, smaller and lighter vehicles 

will dominate the marketplace, resulting in a lower average 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 material substitution, vehicle redesign, and 

downsizing, a maximum weight reduction 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 average new car weight would be around one metric ton 

(1,050 kg)—down from 1,620 kg today—and the minimum 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 ft3 interior volume, a midsize car, like the Toyota Camry, has between 110-120 ft3. A 

large car, such as the Chevrolet Impala, exceeds 120 ft3

. 
 

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 distribution, 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 decrease 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% weight 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 option individually 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 effects of these options must be developed. 

 

6

 These are fuel consumption values obtained using combined U.S. EPA city / highways 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 technical 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 exercising 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 trade-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 penetrate much more aggressively into the fleet, 

achieving an 85% market share of new vehicle sales in 2035. Hybrids account for 35% of new vehicle 
 

21

sales, while diesel and turbocharged gasoline powertrains each account for one-quarter each. Only 

15% of new vehicles sales are comprised of conventional N.A. gasoline vehicles. Almost all of the 

conventional technology improvements remain directed 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 improvements 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 order to meet the fuel consumption target, this 

scenario requires aggressive penetration of alternative 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 III 
INPUTS OUTPUTS (vehicle charact

Degree of each option 2035 average new car 2035 

2035 powertrain mix Scenarios % 

ERFC 

Gas 

NA 

Gas 

turbo 

Diesel Hybrid 

% total. 

weight 

reduction 

from today 

0-60mph 

acc. time 

FC , 

L/100km 

Vehicle 

weight 

0-60mp

acc. tim

2006 values -- 95% 1% 2% 2% -- 9.5s 9.6 1,616 kg 9.9s I. Strong emphasis on reducing FC and vehicle weight 

100% 66% 10% 10% 14% 35% 9.4s 4.8 1,054 kg 9.8s 

II. Strong emphasis on reducing FC and aggressive penetration of alternative powertrains 

96% 15% 25% 25% 35% 19% 9.2s 4.8 1,318 kg 9.6s 

III. Aggressive weight reduction and penetration of alternative powertrains 

61% 15% 25% 25% 35% 35% 7.6s 4.9 1,060 kg 8.4s 

IV. Scenario with aggressive hybrid penetration 

75% 15% 15% 15% 55% 20% 8.1s 4.8 1,302 kg 8.8s 

Table 4: Results – Scenarios that halve the fuel consumption of new vehicles in 2035 
 

24

These three bounding scenarios reveal trade-offs necessary 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 emphasis 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, alternative propulsion systems must penetrate the 

marketplace at a high rate while maintaining today’s vehicle performance (Scenario II). 

(iii) If performance of vehicles is to be improved significantly above today’s level, 

maximum market penetration of alternative propulsion systems and a large degree of 

weight reduction and downsizing needs to be achieved (Scenario III). 

To illustrate the effects of an alternative powertrain mix, a fourth scenario is developed, in 

which the requirement for a fixed ratio of turbocharged 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 other powertrains. In this Scenario IV, slightly more 

than half of new vehicles sold are hybrids. The remaining new vehicles are spread evenly between the 

naturally-aspirated gasoline, turbocharged gasoline, and diesel vehicles. Vehicle weight has come 

down by 20%, mostly achieved with the use of lightweight materials, while the new vehicle fleet’s 

size distribution remains unchanged. With such aggressive penetration of hybrids, vehicle acceleration 

performance can improve slightly from today. The 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 consumption reduction, we need less weight reduction, 

can avoid size reduction, and even allow a modest improvement in vehicle performance. 

All four scenarios reveal that achieving a factor-of-two reduction in fuel consumption by 2035 

is possible, but requires aggressive action beginning today. The following sections will now compare 
 

25

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 batteries, 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 intensity of these materials. Energy intensity data is 

obtained from Argonne National Laboratory’s Greenhouse gases, Regulated Emissions, and Energy 

use in Transportation (GREET 2.7) model. The two metrics compared across the scenarios are the 

energy consumed and metric tons of carbon dioxide (CO2) emitted during the material cycle, and the 

results obtained are reported in Table 5. 

Scenario Material cycle impact per gasoline car Total material cycle impact of the new vehicle fleet 

Energy 

(GJ/veh) 

CO2 emissions 

(ton/veh) 

Energy 

(EJ) 

CO2 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 2035 
 

26

All four scenarios that halve the fuel consumption of future new vehicles result in higher 

energy use and CO2 emissions during the material production phase, since the lighter weight vehicles 

in these scenarios use more energy-intensive lightweight 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 the material cycle is responsible for only 10% of the 

vehicle’s total life-cycle energy use and GHG emissions today7

, a model year 2035 car that consumes 

two times less fuel than today’s car will end 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 1018 joules), and the amount of GHG emissions in the form of CO2 ranges 

175-190 million metric tons. Scenarios II and IV comprise the heaviest vehicles, and therefore have 

higher material cycle impacts since these vehicles embody 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 retail price paid by consumers. We now evaluate the 

cost of halving the fuel consumption of new vehicles in 2035, and compare this against the resulting 

savings in fuel use and greenhouse gas emissions. 

We have developed estimates of the additional production cost8

 of improvements in future 

vehicles from a literature survey of future technology 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 (see Vyas et al, 2000). 
 

27

2002; NESCCAF, 2004; TNO, IEEP, LAT, 2006; Weiss et al, 2000] The average cost of a naturallyaspirated (N.A.) gasoline vehicle today is assumed to be $14,000 for cars and $14,500 for trucks.9

Improvements in engine, transmission, rolling friction 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 estimate 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 current naturally aspirated (N.A.) gasoline vehicle 

Alternative powertrains and further weight reduction 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 substitution, 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, accessed 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 relative to a 2035 N.A. gasoline vehicle 

Type of weight reduction 

% vehicle weight 

reduction10 

[%] 

Additional cost relative to a 

2035 N.A. gasoline vehicle 

[US$ 2007 / kg] 

 

First tier material substitution 14% $3 

Component downsizing, vehicle 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 reduction relative to a 2035 N.A. gasoline vehicle 

Weight reduction by material substitution is estimated 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-neutral. 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% ERFC). 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 qualitative 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 vehicle 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 metric ton of GHG emissions, expressed in dollars per 

ton of CO2 equivalent ($/ton CO2e). The gross cost does not account for the value of fuel savings 

generated from lower fuel consumption when calculating the cost reducing of GHG emissions: 

GHG emissions savings

Cost of reducing fuel consumption (FC) Cost of reducing one ton of GHG emissions =

The cost of reducing fuel consumption is the sum 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) additional 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. gasoline vehicle relative to today by the emphasis on 

reducing fuel consumption (%ERFC). It is assumed that 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. 

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

Cost + Weight Reduction Cost 

Cost of other benefits = Extra Cost of Future N.A.Gasoline Vehicle × (1 - %ERFC)
 

30

Where the extra cost of the future N.A. gasoline vehicle is assumed in Table 6 above, and the 

alternative powertrain and weight reduction costs are 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 shown in Table 9 below. It is assumed that all of 

the efficiency improvements in conventional vehicle 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 CO2e 

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 GHG emissions in 2035 cars and light trucks 

The estimated gross cost of reducing GHG emissions ranges from $50 to $80 per ton CO2e

12, 

yielding a variation in cost of roughly 50% across an average of $65 per ton CO2e. An improved 2035 

N.A. gasoline vehicle realizes the most cost-effective 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 turbocharged 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 / tCO2e 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 gallon13, the 

value of the undiscounted fuel savings recoups the initial gross cost of each of the different vehicle 

technologies within 4 to 6 years. 

It is also important to recognize that the results in Table 9 have embedded a 20% reduction in 

vehicle weight by 2035. When separated out from 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 CO2e for cars, and between $65 and $70 for trucks. Thus, while reducing vehicle weight realizes 

extra savings in fuel use and GHG emissions, these benefits come at a higher marginal cost that raises 

the cost of reducing a ton of CO2 overall, although these costs are still recouped within 5 to 6 years by 

the value of the fuel savings generated 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 consumption 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 gasoline fuel used in the U.S. in 

2006. [EIA, 2007a]

 

13 The fuel price of $1.85 / gallon is taken as the average 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 CO2e 

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-effectiveness 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 billion. This is equivalent to an additional 16% to 

19% of the estimated baseline production cost of the 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 net societal gain of some $60 to $70 billion after 

subtracting the extra costs of halving fuel consumption. 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 fuel consumption. Most studies have placed the longterm rebound effect between 10% to 25%. [Greening 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” used 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 CO2e before 2030, and between $30 to $150 by 2050, will be required in order 

to stabilize atmospheric GHG emissions at 550 ppm CO2-equivalent by 2100. [IPCC 2007] 

Conclusions 

This analysis has examined the 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 consumption of new vehicles by 2035. This requires: (i) 

incremental improvements in the engine and transmission; (ii) aerodynamic drag, rolling resistance 

and weight and size reduction; and (iii) deployment of more efficient alternative powertrains. 

2. However, significant changes are required and there are trade-offs. 

The material cycle impact is similar across the 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, Scenario III offers the best performance improvement 

of all scenarios presented, but is more expensive with aggressive weight reduction and use of 

alternative powertrains. We would have to pay more 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 future vehicles will increase.

Halving the fuel consumption of the 2035 model 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 baseline cost. This corresponds to a cost of $65 to $76 

per ton of CO2e emissions, when accounting for emissions savings 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 years. 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 forego their continuing pursuit of ever higher 

performance, larger vehicle size and other amenities. Such a future will challenge the auto industry to 

make the capital investments necessary to realize alternative 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 diverse 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: 

( )

235.2 ( /100 ) FE mpg

FC L km =

 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 use, or already on the road in that year. The 

sales-weighted average fuel consumption considers the powertrain mix in the market, and the 

fuel consumption benefit of using alternative, 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 driving. 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: 

(0.55* ) (0.45* ) FCCOMBINED = FCCITY + FCHWY

 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 study refers to the adjusted combined fuel 

consumption, and this is calculated as follows: 

(0.55* / 0.90) (0.45* / 0.78) Adjusted FCCOMBINED = FCCITY + FCHWY

 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 gasoline 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 the 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, horsepower 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 powertrains 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 through 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 vehicle, and more than half of conventional steel. 

HSS will replace 15% of steel, and plastics/composites another 2%. All other materials will 

weigh a third less than 2006 values. 

 Redesigning or reconfiguring the vehicle can achieve 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 vehicles 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 vehicles, 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 battery (this affects the material composition). 

 Material production energy (MJ/kg) values are 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: 

Fraction of retail price captured in cost estimate

Total retail price relative to vehicle manufacturing 1.4

(1 0.10 0.13 0.11 0.14)

2.00 = + + + + =
 

37

Fuel and GHG savings benefits are calculated assuming: 

 Fuel savings calculated based on an average lifetime 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 CO2-equivalent 

per liter of gasoline, calculated on a well-to-wheels 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 constant fuel cost of $1.85 / gallon, taken as the 

average of the EIA’s long-term forecast 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 reducing 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 simulations to verify and determine the acceleration 

performance. With a predefined vehicle model 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 consumption and acceleration performance. 

We begin with an understanding of the 100% ERFC vehicle described by Kasseris and 

Heywood (2007), which is a vehicle that has achieved the full fuel consumption reduction potential in 

the future, but with no change to its acceleration 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 current 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 emphasis placed on reducing fuel consumption (0% 

ERFC), the fuel consumption of the future vehicle will remain at today’s values. Assuming that the 

vehicle’s curb weight remains at today’s value as well15, 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 vehicle 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 and light truck at different levels of ERFC are 

detailed in Table C.2 and Figure C.1 below. While these 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 vehicle 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%

% ERFC

Future values relative to 2006

_

Horsepower

Weight

Fuel consumption

Figure C.1. Future car characteristics at different levels of emphasis placed 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 powertrains 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 the fuel consumption of the gasoline N.A. vehicle 

remaining at today’s values. These ratios are depicted in Figure C.2 below. 
 

40

0.62

1.00 1.00

0.55

0.89 0.90

0.53

0.84 0.85

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 consumptio

n_

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 consumption of alternative powertrains 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 already 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 engine. The powertrain mix at the assumed maximum 

market penetration is listed in Table D.1, and the effective compounded annual growth rate (CAGR) to 

achieve this market share is listed in the right-most column. 

Powertrain technology 2006 market share (%) Maximum 2035 market 

share (%) 

2006-2035 CAGR16 (%) 

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 maximum future market penetration 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) for 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 powertrains 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 Information Administration (EIA) of the U.S. DOE 

publishes projections beyond 2015. These market penetration forecasts 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 environmental-oriented driver niche”. 

 

16 Compounded annual growth rate (CAGR) = [(Future market share / today’s market share)(1 / # of years)]-1 
 

42

Powertrain technology Duration Market share (%) CAGR (%) Source 

Turbocharged gasoline 2006-2030 1.0-2.3% 3.7% EIA 2007 

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 powertrains 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 2030

US light vehicle market penetratio

n

Hybrid (EIA)

Diesel (EIA)

Turbo (EIA)

Figure D.1. Market share projections 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 joint diesel and hybrid vehicle market 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 and safety from today’s values. This assumption is 

not a projection of what the weight of the future vehicle 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 vehicle curb weight will scale linearly with % ERFC, 

as detailed in the right-most column of Table 1 in the 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) index17 [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 economy index of the average car 

The third assumption is that there will be a limit to the amount of weight reduction possible by 

2035, and this is set at about a third (35%) from today’s values. Given the need and demand for 

weight-adding safety features and passenger and cabin 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 combined 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 new 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 aggressive use of lightweight materials can be 20-45%, 

as demonstrated in some concept vehicles (see Table E.2). As such, it is assumed that the initial 

desired weight reduction will be achieved by material substitution or new vehicle designs that 

optimize weight. Vehicle downsizing will be used only 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 methods is summarized in Table E.3, and this is 

elaborated on in the following sections. 

Vehicle Vehicle segment Curb weight (kg) Weight savings (%) 

Stodolsky et al (1995) aluminum-intensive 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 lightweight automobiles that embody 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 composites 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 likely 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/vehicle, 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 using alternative materials in any vehicle 

component depends on the application and design intent. 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 alternative materials are listed in Table E.5. For a 35% 

reduction in vehicle weight, lightweight materials will 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 Relative 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 weight 
 

46

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 unibody designs. Although most cars are already using 

a unibody design, the potential is for the larger 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 decreases, the performance requirements of the engine, 

suspension, and brake subsystems are lowered and these 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 creative design and packaging is to minimize the 

exterior dimensions of the vehicle while maintaining the same interior space, or to remove features 

from the vehicle. Figure E.2., which plots the interior 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 acknowledged that the need for safety features, either 

by regulation or consumer demand, may hinder lightweight 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 heavier 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 size 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 categories, 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 lightest vehicles in both the car and light truck segments, 

and also improves vehicle compatibility from a road safety perspective. Downsizing from the light 
 

47

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 Large

Curb weight (kg)_

Car Wagon Pickup SUV Van

Figure E.3. MY2000-2005 sales-weighted average U.S. vehicle 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

1,050 kg After downsizing

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 after downsizing of the new 2035 vehicle fleet 

Implications on safety 

We have not considered any compromise in safety standards when reducing the weight and 

size of the vehicle for two reasons. First, it is possible to design and build small vehicles with similar 

crashworthiness as larger and heavier ones. By reinforcing the structural stiffness of the vehicle at 

critical points, including side airbags, and introducing 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 the crashworthiness of the vehicle, there are other 

facets to the safety discussion to be considered, including rollover risk, aggressiveness of vehicles to 

other road users, and vehicle crash compatibility. Considering the effect of overall road safety, some 

of the larger and heavier SUVs and pickups can actually 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 average 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 Honda Insight, the Toyota Prius and Argonne National 

Laboratory’s GREET 2.7 database. In 2035, diesel vehicles 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 substitution, vehicle redesign 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 table also includes the energy required to recover 

materials from scrap (secondary energy), and the percentage of materials used in each vehicle that are 

secondary or recovered. We will assume that the material energy intensity data reported in GREET 2.7 

does not vary over time and is applicable to future vehicles. 

Material Gasoline Diesel Hybrid-electric 

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. Material composition of different cars 
 

49

Material (i) after material substitution (ii) after vehicle redesign (iii) after downsizing 

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 average 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 energy requirement [GREET 2.7] 
 

50

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