Automobiles are wheeled passenger vehicles that use an internal combustion engine. There are about 1.4 billion automobiles in operation worldwide, providing transportation for passengers and freight. The automotive industry includes the manufacture and development of cars, trucks, motorcycles, and other vehicular transport vehicles. The branches of engineering that deal with these vehicles are known as auto engineering or automotive engineering.

The advent of the automobile transformed American life in many ways. The automobile opened new work possibilities, enabling people to move from job to job. Moreover, the car brought them closer to their families and friends. They could go on vacations, travel to see relatives and visit other places of interest.

Initially, the automobile was a luxury item, affordable only to a small percentage of Americans. However, with the onset of the middle class in the 1920s, the demand for automobiles increased. As a result, manufacturers established more factories to meet the demand.

Henry Ford introduced a revolutionary assembly line concept that allowed mass production of automobiles. This reduced the cost of vehicles and enabled them to be sold to a large market. Other innovations in automobile design and manufacturing soon followed. These included the use of steel as a structural material, hydraulic brakes, and syncromesh transmission. The first self-starting engines and closed all-steel bodies also came into use.

As automobile ownership grew, dozens of industries and jobs emerged to supply the needs of the industry. New industries and services like gas stations and convenience stores sprang up. Other businesses specializing in tire and glass production and road construction grew as well.

The automobile was a major force in changing social structures as well. Families were able to vacation together, and urban dwellers were able to rediscover pristine landscapes in rural areas. In addition, teenagers gained independence and freedom from parental supervision and dating couples were able to take longer drives to more intimate destinations.

However, the automobile brought with it its own set of problems. Traffic congestion, accidents, and fatalities caused demands for licensing and safety regulations at the state level. Increasing gasoline consumption contributed to air pollution and was a drain on dwindling world oil reserves. Engineering in the postwar era often sacrificed economy and safety for style and appearance, and by the 1960s American-made cars had an average of twenty-four defects per unit. This was in contrast to Japanese-made cars that were delivering high quality vehicles at competitive prices.