Automobiles are a vital part of modern life, but their dependence is also a source of concern. The automobile allows people to travel long distances, expand their social circles and work opportunities, and enjoy the luxuries of the modern world. Its use also creates problems, such as air pollution and traffic congestion. The automobile is a complex system of components and subsystems, and its development has been driven by new technical developments, such as electronic computers, high-strength plastics and alloys of steel and nonferrous metals.

The modern automobile combines engineering and design to offer the mobility and flexibility demanded by people of all lifestyles. It has become a symbol of American prosperity and a major influence on the design of cities, industries and public services.

In its basic form, the automobile is a four-wheeled vehicle with two doors that holds passengers and luggage. It is propelled by an internal-combustion engine, which uses a volatile fuel such as gasoline, diesel or kerosene to power pistons that turn the wheels. The engine can be powered by from two to eight cylinders, with the number of cylinders reflecting the size of the car and the amount of power it needs.

An automobile’s mechanical system includes the engine, transmission and electrical systems, cooling and lubrication systems, and the chassis. Its body, which can be made from a variety of materials, is designed to accommodate the passengers and cargo and to provide comfort and security. The vehicle also has a steering and suspension system, which control the direction of the wheels and the car’s attitude on a road.

Its braking system provides the stopping force that slows the automobile and is controlled by the brake pedal. The engine also generates electricity to run the electric motor that turns the wheels. An automobile’s engine can be powered by steam, a battery or an internal combustion engine. Steam engines were popular in the late 1800s, but they burned a large amount of coal and had a limited range. Batteries powered cars, which became more common than gasoline-powered automobiles, but they were slow and required time to recharge. The gasoline-powered engine eventually dominated the industry.

Historically, the United States had the largest market for automobiles, and its large land area ensured great demand. The country’s manufacturing tradition encouraged the production of a wide range of cars and the development of mass-production techniques. In addition, low tariff barriers and cheap raw materials encouraged the spread of automobile manufacture to a broad geographic area.

As the use of automobiles has expanded in recent years, many people have restructured their lives around them. This has included reorganizing work, leisure activities and home locations to suit automobile transportation needs, as well as establishing communities based on automobile accessibility. It has also facilitated the development of sprawl, a pattern of sluggish, low-density urban growth that degrades landscapes and causes traffic congestion that immobilizes automobiles. People who are not able to afford or don’t want the expense of an automobile can rely on public transportation.