Today, for example, 98 percent of the urban passenger-miles covered in this country are by private automobile, and urban travel accounts for half the fuel consumed by automobiles. Even if the use of public transit were 15 times greater and consumed no fuel at all, the overall savings in fuel would amount to only 15 percent if total travel demand remained the same.15 However, with the more fuel-efficient automobiles assumed in all scenarios except scenario IV, the difference in efficiency between private automobiles and rail or even bus transit per passenger-mile is small. The savings in energy consumption that might be achieved by fixed-rail mass transit depend directly on patterns of settlement and land use that run counter to the recent locational trends described above. Such changes could probably be realized only over a period of time well beyond that addressed in this study. Today buses, van pools, and car pools, because they can make flexible use of an already existing network of roads and highways, are the most effective means of reducing energy consumption in commuter travel.16

BUILDINGS AND APPLIANCES

The demand for energy by residential and commercial buildings is expected to grow more slowly from 1975 to 2010 than in the past few decades, as population growth slows and some demands become saturated. Rising energy prices, aided by mandatory building and appliance standards, could foster wider use of such well-known measures as heat pumps, better insulation for buildings, larger heat-exchange surfaces for air conditioners and refrigerators, and passive solar building design. Through these and similar conservation measures, the energy demand for buildings in 2010 could be below today’s level of 16.8 quads, despite a projected 30 percent increase in population and 63 percent increase in residential buildings.17

Existing technology could be incorporated in new buildings and appliances to reduce energy consumption substantially. For example, gas and oil heating systems have been built to use 30 percent less gas or oil than conventional designs, through improved combustion and heat transfer. Electric heat pumps for space heating deliver about 3 times more heat than electric resistance heaters per unit of electricity consumption, and can also be reversed for cooling. The energy consumption of refrigerators can be economically reduced (even at present electricity prices) by 50 percent through better design and construction. Well-insulated new single-family houses need 40 percent less heating than the average house built before 1970.18 An experimental program of retrofitting existing housing has demonstrated that in a New Jersey community nearly



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