Automobiles, also called cars, are four-wheeled vehicles that are designed primarily for passenger transportation and are propelled by an internal combustion engine using a volatile fuel. Modern automobiles are complex technical systems involving many subsystems with specific design functions.

A CAR OPENED UP WORLDS: Having your own car makes it possible to reach places quickly and easily. It is easier to get to work, to meet with friends or family and to go shopping. It is even possible to take a vacation far away. Without a car it would be hard to live in one town and work in another.

The first automobiles were steam engines attached to wagons in the late 1800s but gasoline powered automobiles became very popular by 1920. This was largely because of new manufacturing techniques pioneered by U.S. car maker Henry Ford. He developed an assembly line which enabled workers to remain in one place doing the same task and made the Model T so affordable that middle class Americans could afford it.

Most automobiles are powered by an internal combustion engine that uses gasoline, diesel fuel or kerosene to make a piston move in a cylinder and turn the wheels. They also use a system of friction brakes that slow the vehicle and regenerative brakes that convert some of the energy of movement into electricity to make the engine run again.

An important disadvantage of automobiles is that they release greenhouse gases into the atmosphere. This is especially true of gas-powered automobiles which release carbon dioxide when they burn fuel. Drivers can limit greenhouse emissions by purchasing a more fuel efficient automobile and by keeping their car properly maintained.