Automobiles are a major part of the modern world, and the most common way for people to get around. There are about 1.4 billion of them in use in the world. They travel over three trillion kilometers (five trillion miles) every year. Many people can’t imagine a life without them. The automobile revolutionized industrial manufacturing and changed many of the ways we live our lives. It created jobs in industries that supply car parts and fuel, and it gave people more freedom to move around and meet people. It also brought changes for the environment and for public safety. People drive more than ever before, and safety systems are becoming increasingly sophisticated.
Generally, automobiles have four wheels and carry one to eight people. They run primarily on roads and are powered by an internal-combustion engine using a volatile fuel. They can be driven manually or by an automatic transmission system. The most common fuel is gasoline, but some burn diesel fuel, wood gas, or a mixture of ethanol and gasoline — known as flex-fuel.
The first automobiles were powered by steam engines attached to wagons, which were slow and difficult to control. Electric cars were used in the late 1800s, but they had a limited range and required long periods of time to recharge. The gasoline-powered automobile became the dominant form of automotive transportation by 1920. The production-line method of making inexpensive automobiles, which was introduced by Henry Ford, greatly increased the number that could be produced.