An automobile (or car) is a motor vehicle that runs primarily on roads, seats one to eight people and has four wheels. There are about a billion automobiles in use worldwide. An automobile is powered by an internal combustion engine that can be fed gasoline, diesel, kerosene or other fuels. An automobile’s main functions are transportation of passengers and cargo. It may also have other utilities such as power steering, traction control, air conditioning and cruise control.
Many countries have laws that govern how and where cars can be driven. Some of these regulations require safety equipment such as seat belts and airbags. Other regulations may require drivers to have licenses and insurance. There are also rules that regulate the speed limits that a driver can travel at. Many cities have traffic lights to slow or stop automobiles, and there are often laws about parking in certain areas.
The invention of the automobile has had a profound impact on modern life. It changed the way cities were built and reshaped rural life. It encouraged participation in outdoor recreation and spawned new industries such as tourist attractions, hotel chains and service stations. It caused a revolution in manufacturing, including the development of the assembly line. It provided jobs in the automobile industry itself and also in ancillary industries that produced parts and supplies such as tires, steel and petroleum products. It made it possible for people to live far from their place of work and have a much more flexible lifestyle than was previously possible.
Automobiles are important tools for personal freedom and self-expression. They have enabled political activism such as the 1916 trip across the United States by Nell Richardson and Alice Burke, who decorated their car with “votes for women” banners. They have also helped people to communicate with each other and with the world, and have enabled travel that would not be feasible by any other means.
There are a number of disadvantages to automobiles, however. They can cause air pollution if too many are used in a small area, and they are a major source of global warming. They can also be dangerous if they crash, and they can get stuck in traffic jams when too many vehicles try to go in the same direction. Many places have public transportation systems such as buses, trains (steam-powered, diesel-powered, monorail or light rail), trams and subways that can move more quickly and cheaply than an automobile can.
Modern automobiles are complex technical systems that depend on a large number of subsystems with specific design functions. Research and development engineers are constantly working to improve the bodies, chassis, engines, transmissions, controls, electrical equipment and other components of these vehicles. They are also researching ways to make them more environmentally friendly and safer. Some of these improvements are the result of advances in technology, such as electronic computers and high-strength plastics; others are the result of legislative mandates, such as air-pollution standards and seat-belt requirements.