Automobiles are a form of transport that uses an internal combustion engine powered by a volatile fuel. The car is often four-wheeled and has seating for a driver and a small number of passengers, but may also have a cargo capacity or be specialized for particular purposes (such as automobiles used for racing). Modern cars are complex technical systems, employing many subsystems with specific design functions that have evolved from breakthroughs in engineering, such as electronic computers and high-strength plastics and alloys of steel and nonferrous metals. Automobiles have become the dominant mode of passenger transportation in most countries, covering more than three trillion miles (five trillion kilometers) per year. This has brought economic benefits, but has also contributed to air pollution and to the need for strict laws concerning traffic safety and environmental regulation.
Karl Benz is credited with inventing the first modern automobile, around 1885. Until then, most were built by hand and were expensive. But Henry Ford introduced assembly line techniques that made it possible to produce cars in quantity at a lower price. This opened the market to middle-class families.
The automobile revolutionized travel, making it faster and more convenient than walking or riding a bicycle. It also contributed to leisure activities and created new businesses, such as hotels, restaurants and amusement parks. However, cars are also responsible for millions of deaths in accidents each year, they pollute the environment and they consume large quantities of energy.