Automobiles are four-wheeled vehicles designed primarily for passenger transportation and propelled by internal combustion engines that use fuel. These vehicles are usually powered by petroleum or natural gas, but they can also be powered by electricity. They have become indispensable tools for many of us, making modern life virtually inconceivable without them.

The automobile has brought changes for industry and technology as well as everyday life. For example, it created new jobs in the manufacture of cars and their parts, such as tires and rubber, as well as services like gas stations and convenience stores. The automobile has also increased freedom of movement, allowing people to work or travel more easily. It ended rural isolation and brought urban amenities, including schools and medical care, to small towns and villages. It also facilitated participation in outdoor recreation, such as camping and fishing. It also allowed people to visit relatives and friends more easily.

Today, there are more than one billion cars in operation worldwide. In the United States alone, we drive more than three trillion miles (five trillion kilometres) each year on average. This huge demand encouraged rapid growth of automobile manufacturers, who flooded the market with hundreds of different models. Engineering, however, was often subordinated to questionable aesthetics and nonfunctional styling, and quality deteriorated. The result has been escalating air pollution, high oil consumption and the draining of dwindling world oil reserves. These conditions have prompted the imposition of government standards for safety, emission levels and energy consumption.