Automobiles, also called cars or motor vehicles, are four-wheeled motor transporters that can carry two to six passengers and some cargo. They are powered by internal combustion engines and use the energy stored in fossil fuels (petroleum, diesel oil or natural gas) to propel themselves along a road. They differ from trucks, which are designed primarily for the transportation of cargo, and buses, which can carry many passengers at once and have a more streamlined design.

Modern automobiles are complex machines with many parts that work together to power and control the vehicle. An engine, for example, turns the wheels and generates electricity to light the car and run its accessories. An automobile’s electrical system provides information for its navigation, speedometer, and other gauges. In addition, its computerized systems can detect dangerous conditions and warn the driver or activate automatic safety equipment to prevent accidents.

The automotive industry was a key force for change in twentieth-century America. It was the backbone of a new consumer goods-oriented society and the chief customer of steel, petroleum products, and other industrial materials. It employed millions of people worldwide in factories that built the cars and at dozens of spin-off industries, such as rubber production and motel chains catering to drivers.

Its social effects were also profound. With their freedom of movement, automobiles enabled people to shop in cities and go on weekend trips. They allowed city dwellers to rediscover pristine countryside and brought rural residents closer to the markets of urban centers. They helped young people escape from restrictive family structures and facilitated sexual attitudes that encouraged independence. The automobile was the main means of travel for the vast majority of Americans by 1980.

During the 1920s, American automaker Henry Ford revolutionized manufacturing methods by creating the assembly line, which used workers who specialize in one task and moved car parts through a conveyor belt to quickly produce the Model T. Ford’s methods reduced the price of his car until it was affordable for middle-class families.

The Model T was a popular car, with over 15 million produced by 1927. The automobile was a symbol of America’s drive to self-reliance and wealth, and it became the dominant form of personal transport until the 1970s, when questions about its pollution and the draining of world oil reserves began to surface. Increasingly, motorists demanded safety standards and fuel efficiency. Postwar, a variety of factors combined to stifle innovation in automobile production.

The automobile has a place in our society, but it can be a nuisance. Hundreds of thousands of people die in car accidents each year. Traffic jams and air pollution can make commutes stressful. Parking space is scarce. Automobiles pollute the atmosphere with carbon monoxide and other pollutants. The automobile, however, also gives millions of people the ability to live more convenient lives and spend more time doing the things they love, such as spending time with friends or family. The future of the automobile will likely be hybrid, electric, and autonomous.