Energy supplies can be extended by the conservation, or planned management, of currently available resources. There are three types of energy conservation practices. The first is curtailment; doing without. For instance, cutting back on travel to reduce the amount of gasoline burned. The second is overhaul; changing the way people live and the way goods and services are produced. For example, they are slowing further urbanization of society by using less energy-intensive materials in production processes and decreasing the amount of energy consumed by certain products such as cars. The third type is the more efficient use of energy; adjusting to higher energy costs. An example is investing in cars that go farther per gallon or insulating houses. Societies most commonly adopt this option because it requires less drastic changes in lifestyle.
             Increased energy efficiency helps the world energy balance, and productive conservation is no less an energy alternative than the energy sources. Substantial energy savings began to occur in the United States in the 1970s when the federal government imposed a nationwide automobile efficiency standard and offered tax deductions for insulating houses and installing solar energy panels. Some obstacles stand in the way of conserving energy. It requires hundreds of millions of people to do routine things such as turning off lights and keeping tires properly inflated. Also, the price of energy is very high. Low energy prices make it difficult to convince people to invest in energy efficiency. Over time, improvements in energy efficiency more than pay for themselves. They also, however, require large capital investments, which are not attractive when energy prices are low.
             Transportation uses 25 percent of the total energy consumed in the United States and also accounts for 66 percent of the oil used. In 1975 the U.S. Congress passed a law that mandated doubling the fuel efficiency of new cars by 1...