342 FORMS OF ENERGY In 1895 the first pneumatic automobile tires were introduced. Improvements then piled up rapidly. More cylinders were added; demountable rims were introduced; tires were improved; kerosene lights were replaced by carbide headlights which were, in turn, replaced by electric lights run by a generator. Then the storage battery was added and with it the self-starter. Closed bodies were designed. Fig. 142. Evolution uf the automobile. (Courtesy of the United States National Museum.) Increased production required the construction of marvelous new tools and machines, which made possible much better products at less cost. New alloys were used to permit higher-speed and lighter-weight engines and cars. Fuels and the efficiency of engines were improved, although more and more cylinders were added to provide smoother running and greater power. Highway Expansion Was Stimulated by the Invention of the Automobile. In 1900 there were only 150 miles of dustless paved highways in the United States. When the weather was dry, dust rose in clouds from the horse-driven vehicles; and when it rained, the wheels sank hubdeep in mud. The development of highway transportation is one of the most profound and far-reaching contributions to modern life. It has added immeasurably to the national wealth and has added social and cultural enrichment to the lives of the people. Highways have made possible
THE AUTOMOBILE 343 consolidations of schools and churches and quick movement of farm crops to city markets. Improved highways have been recognized as an investment rather than an expense because they reduce the operating cost of automobiles by savings in gasoline, tires, depreciation, and repairs and make f^ Fig. 143. 1850 — Dark ages of the road. (Courtesy of the Public Roads Administration.) possible quicker and usually year-round transportation. Improved highways also open up land and markets, and give isolated communities transportation. Over 40,000 towns in the United States are served only by trucks and busses. Highways also have important military value. The United States had 360,000 miles of surfaced highways in 1920 and 1,172,000 miles in 1940. There is still room for much highway development. Less than one half of the rural roads are hard-surfaced. Express highways through cities and by-passes which distribute routes around cities are needed to avoid congestion. Traffic congestion reduces gasoline mileage 50 per cent and causes many bent fenders and still more frayed nerves, as well as a considerable loss in time. Few city streets were designed to handle the present automobile traffic. Because railroads were developed before highways, there are now 240,000 railroad grade crossings to be rendered safe. Modern road-building is a careful scientific process; maps are made, traffic surveys, including the number, type, and weight of vehicles.