TABLE F.1 Cost of Mass Reduction

MassR $/lb Incremental $/lb
10% $0.43 $0.43
20% $0.86 $1.30
30% $1.30 $2.16
40% $1.73 $3.02

Table 2.2 in Chapter 2 summarizes the weight reductions and costs that are used in 2the committee’s scenarios. It includes carbon fiber in 2050 for context, even though the committee considers it unlikely that costs will drop sufficiently for widespread use in vehicles. For the midrange cases, 5 percentage points of the weight reduction were countered by weight increases due to increased vehicle features in 2030, and 10 percentage points in 2050. Predicted reductions of new car weight are 18-22 percent in 2030 and 28-37 percent in 2050. For light trucks, they are 17-20 percent in 2030 and 23-33 percent in 2050.

The cost estimates in Table 2.2 do not include secondary weight reductions. In general, secondary weight reductions are free or even reduce costs, as they reduce component size. However, available estimates for secondary weight reductions generally include powertrain size reduction, in addition to chassis and suspension weight reductions. As the cost benefits of powertrain size reductions are being calculated elsewhere in the analysis and the amount of secondary weight reduction for the chassis and suspension alone is uncertain, no adjustments were made to lightweight material costs.

Safety Implications

The 2011 NRC report said the following: “Vehicle mass can be reduced without compromising size, crashworthiness, and [noise/vibration/harshness] …” NRC (2011, p. 100).

The NHTSA/EPA Final Rule stated that “the agencies believe that the overall effect of mass reduction in cars and LTVs may be close to zero, and may possibly be beneficial in terms of the fleet as a whole.”2 This statement was based on an analysis which looked at historical experience and tried to separate out size and weight differences and how they affect real world safety performance based on vehicle designs of the 1990s, which were not optimized with innovative designs using improved, lighter weight, stronger materials, and improved structural design (NHTSA/EPA (2010b).

NHTSA/EPA issued the proposed rule “2017 and Later Model Year Light-Duty Vehicle Greenhouse Gas Emissions and Corporate Average Fuel Economy Standards” (NHTSA/EPA, 2011c), which discussed an updated statistical analysis (Kahane, 2011). NHTSA created a common, updated database for statistical analysis that consists of crash data of model years 2000-2007 vehicles in calendar years 2002-2008, as compared to the database used in prior NHTSA analyses, which was based on model years 1991-1999 vehicles in calendar years 1995-2000. The study found that decreasing weight (while maintaining footprint) generally decreased fatalities in rollovers and collisions with fixed objects for all vehicles. In the other type of crashes, weight reduction in smaller vehicles tended to increase fatalities and in larger vehicles tended to decrease fatalities. NHTSA/EPA concluded, however: “The effect of mass reduction while maintaining footprint is a complicated topic and there are open questions whether future designs will reduce the historical correlation between weight and size. It is important to note that while the updated database represents more current vehicles with technologies more representative of vehicles on the road today, they still do not fully represent what vehicles will be on the road in the 2017-2025 timeframe.”3

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2 NHTSA/EPA, Final Rule, Federal Register, Volume 75, Number 88, May 7, 2010, p. 25383.

3 NHTSA/EPA, Proposed Rules, Federal Register, Volume 76, Number 231, December 1, 2011, p. 74955.



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