Automobiles are powered by an internal combustion engine, which uses fuel—such as gasoline, diesel or kerosene—to run. The power from the engine goes to the wheels through a transmission system. The automobile has become one of the most important inventions in the 20th century, changing people’s lifestyles and enabling them to travel more easily. It has also helped the economy and contributed to a shift toward consumer goods. It has spawned new industries, including hotels and restaurants. The automobile has many advantages over other forms of transport, such as trains and buses. People who own cars can go to work whenever they want, instead of having to depend on public transport and adjust their schedules around other people’s schedules. They can visit friends and family, go to the mall or the movies, and do whatever else they want. The disadvantages of the automobile include high operating costs and environmental harm, especially from the exhaust produced by gas-burning engines.

Karl Benz is credited with inventing the first modern automobile in the late 1880s. Other inventors and engineers followed in his footsteps, including Henry Ford, who revolutionized the production process to make it cheaper to produce the cars. As a result, more people could afford to buy and operate them.

Originally, most automobiles were designed and built for specific purposes. Those intended for off-road use require durable systems that can withstand extreme overload and operating conditions, while those designed for limited-access road systems must be optimized for passenger comfort options and high-speed handling. Other factors that influence the design and construction of an automobile include passenger capacity, engine performance, weight distribution and suspension characteristics.

Special automobiles include fire trucks, police cars and ambulances. These vehicles are designed with various features to fulfill their specific functions, such as a hydraulic system to lift heavy loads, an engine that can perform under severe conditions and a body constructed from lightweight materials, such as steel section pillars and aluminum panels. Other vehicles designed for certain tasks are cranes at building construction sites, road rollers in roads and warehouses, and fork-lifts in industrial plants.

As the automobile industry reached market saturation in the 1920s, technological innovation began to decline. However, automobile manufacturers continued to improve their cars and engines by modifying existing components or by developing entirely new ones. For example, improved transmissions and clutches allowed more torque to be delivered to the rear wheels, enhancing vehicle stability and performance. The development of the electric motor also enabled cars to accelerate faster and climb hills more easily.

During World War II, the automobile became a vital part of America’s defense effort. In addition to producing civilian automobiles, American manufacturers turned out several million military vehicles and other war materiel. The automobile industry was the single biggest user of steel and petroleum products, as well as the chief customer for many ancillary industrial products. It also prompted the creation of highways, which required extensive land acquisition.