Automobiles are four-wheeled vehicles that seat one to six people, have a steering wheel and brakes, and are powered by internal combustion engines that use gasoline. They have revolutionized modern life, making it possible to travel far distances with ease and in a way that was never before possible. They have also transformed urban planning, and government services such as police, fire, ambulance, and highways. They have shaped leisure activities, such as shopping and vacation trips, and created new businesses like hotels and amusement parks. They have also caused harm to the environment because of air pollution and they require a great deal of land, which is used for building highways and related industries.

The automobile was a powerful force for change in twentieth-century America, becoming the backbone of a new consumer goods-oriented society. It ranked first in value of product and provided a large percentage of jobs in American industry. It was the chief customer of the petroleum and steel industries, and it drove a host of ancillary industries.

The automotive industry is constantly challenged by changing laws and requirements for vehicle safety, emissions control, fuel economy, and more. Moreover, consumers demand new designs and technology from their vehicles that make them more attractive and easier to drive. New technical developments are recognized by many automakers as the key to success, and a number of companies have committed themselves to research and development in order to keep up with competitors and satisfy customers.