applications may be considerably enhanced in the future if (as is likely) the cost of liquid fuels rises more rapidly than the cost of electricity (on a percentage basis). This advantage is not fully reflected in the scenario projections presented here, which assume that the price of electricity rises almost as rapidly as the price of liquid fuel.

Air Travel

The efficiency of the passenger aircraft fleet could be improved 40 percent by 2010.6 This would require aircraft industry investments in development; airline purchases of more efficient airplanes; scheduling and pricing policies that increase load factors (passengers per plane trip); and additional improvements in traffic management. Some of these developments are already occurring as a result of recent airline deregulation and the consequent fleet expansion and rise in load factors.

An interagency task force of the federal government estimates that the research and development required to introduce fuel-conserving jet and turboprop engines, lighter structures with associated control systems, and improved design for laminar-flow control and aerodynamics, all of which would cost $670 million, could make possible savings of 2 billion barrels of oil between 1980 and 2005—$25 billion at 1976 oil prices.7 The airlines’ incentive to invest in fuel-efficient aircraft and management practices depends on favorable long-term prospects for air traffic and profit, as well as on forecasts of the price of fuel and attendant policies.

If the design and load factor improvements described were introduced, new aircraft in 2010 might consume 3180 Btu per passenger-mile, as against 7630 Btu in 1975. If a passenger load factor 44 percent above the 1975 values is included,8 then even at quadrupled energy prices (scenario A), the per capita air travel demand would increase 58 percent. The total energy consumed in scenario A would be 1.0 quad, compared to a 1975 consumption of 1.2 quads.9 For a doubling of energy prices (scenario B), demand would increase from 745 to 1800 passenger-miles per capita, and total energy consumption would be 1.6 quads.

Truck and Rail Freight

Freight-hauling trucks built in the future can be made 30 percent more fuel-efficient by using turbocharged diesel engines, improved axles, radial tires, and declutching fans.10 Some of these options are now being installed in freight trucks. Lighter tractors designed for aerodynamic efficiency would represent an additional 10 percent gain. The fuel economy of the truck fleet can be improved by installing diesel engines in medium- and

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