Transportation
Whereas transportation uses only one-fourth of U.S. total energy, it uses 60 percent of U.S. oil consumption. Cars built in other countries have long tended to be more efficient than those built in the U.S., partly because of the pressures of heavy taxes on gasoline and on large engines in those countries. In 1975 the U.S. Congress passed a law that mandated doubling the fuel efficiency of new cars by 1985. This law, together with gasoline shortages in 1974 and 1979 and considerably higher gasoline prices (especially since 1979), caused the average efficiency of all U.S. cars to improve about 40 percent between 1975 and 1990. However, much of this improvement has been offset by dramatic increases in the number of cars on the road. Automobile manufacturers have the technical capability today to build cars that are even more efficient than the efficiency mandated for the future by Congress, but to mass-produce cars with this efficiency would require vast capital investments. Increases in the price of gasoline and of parking have encouraged two other transportation modes: ride sharing (either van or car pools) and public transportation. These can be highly efficient, but the extensive character of many U.S. cities can make their use difficult