Automobiles are motor vehicles that operate on roads and transport people. They differ from bicycles and motorcycles in that they are designed to carry one to eight passengers and are powered by an internal combustion engine. Historically, automobiles have used gasoline, but they can also be powered by steam, electricity or other sources of fuel. Automobiles are so widespread today that they shape the design of cities and influence the operation of police, fire, ambulance and utility services, as well as such personal activities as vacation travel and dining. They have transformed social and leisure activities as they provide the power of rapid, long-distance movement to their owners and open up new opportunities for shopping and other activities.
Automobile design has been driven by the need to meet market needs, particularly in relation to price and functionality. The American carmaker Henry Ford revolutionized industrial manufacturing with his use of the assembly line, which reduced production time and made his Model T affordable for middle-class Americans. Throughout the twentieth century, other companies used assembly lines to produce their cars and other automotive components. By the late 1960s, automobiles were beginning to lose popularity as government agencies established safety standards and emissions regulations, and fuel prices rose.
The automobile is a highly complex system that combines several mechanical systems and electrical components. The major systems include the engine, transmission, electrical, cooling and lubrication systems and the chassis, which supports the wheels, tires and body. The arrangement and choice of these systems depends on the type of automobile and its intended uses. For example, a car designed for commuting to work or school will typically have the highest level of fuel efficiency, while an automobile built for speed may need a powerful engine, a more advanced suspension system and more sophisticated steering and handling abilities.
Few inventions have had as much impact on the world as the automobile. Today, in the United States alone, they are so widespread that modern life seems inconceivable without access to a vehicle. With three trillion miles (five trillion kilometres) being driven each year on average, they have dramatically changed the way that we live and work. They have shaped urban design, government services such as police and fire departments, and created new industries such as gas stations and hotels. They have opened up new opportunities for recreation and shopping, and they have enabled families to move out of the city and into suburban areas. In some places, this has resulted in sprawl, a pattern of low-density development that degrades the landscape and creates traffic congestion.