Automobiles are one of the most ubiquitous and universal of modern technologies, with a global industry producing over 73 million cars in 2017. An automobile is a four-wheeled motor vehicle designed primarily for passenger transportation. It is propelled by an internal combustion engine fueled most often by gasoline (petrol), but also by diesel, electricity, kerosene and other fuels. The modern automobile has many subsystems with specific design functions. These include:
The development of the automobile was accelerated by the availability of cheap raw materials in the United States, the absence of tariff barriers between states, and the manufacturing tradition that led to industrialization. By the 1920s, American manufacturers had produced a variety of models that competed for the hearts and wallets of consumers. Production soared during the two world wars and afterward.
During the 1950s, automotive manufacturers began adding new features. These included power steering and brakes, and automatic transmission. The automobile has become the dominant mode of personal transportation and has greatly changed the lifestyles of those who own and drive them. It has stimulated outdoor recreation and contributed to the growth of tourism-related businesses, such as gas stations and motels. It has ended rural isolation and brought urban amenities, such as schools and medical care, to suburban areas. It has brought economic and social change to the cities and towns in which it is a major form of transport, while at the same time creating environmental problems, such as air pollution, noise pollution and traffic congestion.