The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
and that, combined with a growing concern about greenhouse
warming and the role of CO2 as a
greenhouse gas, has once again focused attention on the efficient
use of transportation fuel. Vehicle efficiency involves
technological improvements in fuel economyimproving the miles
per gallon of vehicles. The more efficient a vehicle is, the less
fuel it burns to travel a given distance. The less fuel it burns,
the lower are the amounts of CO2
emitted. These methods of emission reduction and their
cost-effectiveness are evaluated in the following sections for
light-duty vehicles, heavy-duty trucks, and domestic air carriers.
The emphasis is on light-duty vehicles because they represent the
largest and most thoroughly studied sector. Table 23.1 shows the
amount of fuel used by each type of vehicle for different modes of
operation. The information presented here indicates that light-duty
vehicles consume the largest quantity of transportation fuel, with
heavy-duty trucks second and aircraft third.
The recent trend in fuel economy from 1975 to 1989 for the new
U.S. passenger car fleet is presented in Figure 23.1a (Amann,
1989). Figure 23.1b shows the fuel economy index (FEI) for the
period from 1930 to 1990. The FEI is an index of powertrain
efficiency including weight and performance. Studies by Leone and
Parkinson (1990) and by Greene (1989) indicate that the trend in
the period from 1975 to 1982 was a response to increased fuel
prices and fuel economy regulations. As discussed below in the
''Barriers to Implementation" section, there is some disagreement
on the relative impact of fuel prices and regulations on the supply
of fuel-efficient vehicles. The vehicles manufactured during that
period were, on the average, 450 kg (1000 pounds) lighter within
each market segment, were degraded in performance and other
attributes, and incorporated various fuel-efficient technologies.
Figure 23.2 indicates how consumer preferences for vehicles changed
from 1972 to 1986. As shown, some consumers accepted the smaller
vehicles offered to improve energy efficiency, while others
resisted the change in performance and either did not buy cars or
shifted to light-duty trucks and vans.
Because market conditions and fuel prices cause consumer
preferences for fuel-efficient vehicles to change over time, one
should distinguish between the trends in overall vehicle fuel
economy and powertrain efficiency. Therefore it is important to
look not only at miles per gallon but also at the FEI. The FEI is
used to control for other vehicle changes, as shown in Figure 23.1b
for the period from 1930 to 1990. This parameter, used to judge
passenger cars for many decades, provides a better indicator of
powertrain efficiency than does fuel economy alone by controlling
for both weight and performance.