year are reduced by about 0.7 percent in 2020, 19 percent in 2035, and 60 percent in 2050 compared to the reference case.

Case 2 (ICEV Efficiency)

Case 2 is an “evolutionary,” not revolutionary, scenario. The committee assumes that currently available improvements in gasoline internal combustion engine technology are used to improve fuel economy (rather than power and acceleration).

A range of more efficient advanced gasoline technologies could be implemented in 2010-2035 as described in Chapter 4. In this scenario, a new “high-fuel-economy” gasoline vehicle is introduced, as well as a hybrid gasoline vehicle, and these capture growing market share over time. By 2035 (2050), 42 percent (85 percent) of new LDVs and 30 percent (60 percent) of the fleet are gasoline hybrids, and the remaining non-hybrid cars have high fuel economy. This is shown in Figure 6.17.

In 2010, the new gasoline vehicle is assumed to have an on-road fuel economy of 22.2 mpg, the hybrid 31.9 mpg. (These values are selected to match the reference case up to 2010.) The fuel economy of each vehicle is then assumed to improve as follows and discussed in Chapter 4:

  • 2.6 percent per year from 2010 to 2025,

  • 1.7 percent per year from 2026 to 2035, and

  • 0.5 percent per year from 2035 to 2050.

The on-road new car fuel economy over time is plotted in Figure 6.18. Note that this is similar to the reference case in Figure 6.4 up to about 2020. Beyond this, Case 2 is significantly more efficient; by 2050, gasoline ICEV and hybrid cars are about 35 percent more efficient than in the reference case, which incorporates the new CAFE standards.

The committee did not project increased market share for diesel engines in this scenario because of the uncertainty over the costs of meeting future tailpipe emission specifications and consumer acceptance, considering the poor history of diesels in U.S. automobiles. However, advanced diesel power

FIGURE 6.17 Case 2 assumed market penetration for gasoline ICEVs and advanced gasoline HEVs.

FIGURE 6.18 Case 2 assumed on-road fuel economy for new gasoline ICEVs and gasoline hybrid ICEVs over time.

trains could offer an additional 15 percent reduction in fuel consumption and CO2 emissions over advanced conventional spark ignition power trains and have cost advantages over hybrid electric vehicles (see, for example, Adrian, 2004). In a high-fuel-cost environment, they could become a growing fraction of LDV sales with the some shifts in government positions on diesels and a positive public relations program. Thus, to the extent that diesels can penetrate the market, this scenario may understate potential fuel savings.

The same vehicle stock model used in the reference case keeps track of the vehicle numbers and vintages of advanced gasoline cars and gasoline hybrids on the road in any year. This allows calculation of oil consumption and greenhouse gas emissions for each year.

Oil Displacement

Gasoline consumption for the case above is estimated in Figure 6.19. Improving fuel economy is a very effective way to cut gasoline use. Gasoline consumption in 2020 is only slightly reduced relative to the reference case, which includes rapidly improving fuel economy, but in 2035 it is down by 35 billion gallons per year (25 percent), and in 2050, by 64 billion gallons per year (40 percent).

Greenhouse Gas Reductions

Greenhouse gas emissions show a similar trend (Figure 6.20). Fuel economy improvements can yield increasing reductions in greenhouse gases. Greenhouse gas emissions are reduced by about 24 million tonnes of CO2 equivalent per year (1.7 percent) by 2020, 385 million tonnes (25 percent) by 2035, and 700 million tonnes (41 percent) by 2050.

Based on projected gasoline prices and cost estimates for improved fuel economy, it appears that gasoline hybrids and advanced gasoline vehicles would pay for themselves on a life-cycle cost basis, so no external subsidy should be needed. A simple calculation shows that increasing fuel economy from 30 to 45 mpg in a car that travels 15,000

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