Automobiles are land vehicles that carry one or more passengers and have a motor to make them move. They are usually powered by gasoline, diesel fuel, or electric energy, but other power sources are possible. They are typically smaller than trucks (or lorries or cabs) and buses, and may have four or more wheels. The first automobiles were steam-powered, with the engine projecting forward; later the engines were housed under the carriage and drove the rear wheels. A major turning point in the history of automobiles was when the American Henry Ford developed methods for mass production that made them affordable to middle-class families. This, combined with the building of highways that linked cities and towns and regions to each other, transformed the landscape of twentieth-century America and brought modern life within reach for millions of people.
The design of an automobile depends on its intended use. For example, a vehicle built for off-road driving must have rugged systems that can withstand extreme overloads and operating conditions. On the other hand, a vehicle designed for high-speed driving on limited-access roads requires more passenger comfort options and optimized engine performance.
Most automobiles are powered by a piston-type internal combustion engine that burns either gasoline, diesel fuel, or kerosene to produce the mechanical energy to drive the wheels. Some cars are also powered by an electric motor, which turns electrical energy into motion, or regenerative brakes that convert the automobile’s kinetic energy back to electricity when it is stopped.