Automobiles are motor vehicles for transportation with four wheels and an internal combustion engine fueled most commonly by gasoline, a liquid petroleum product. They also use an electric motor for some functions. Most cars have a transmission which transfers the power of the engine to the driving wheels. Cars have brakes to stop the vehicle in emergencies and to prevent it from rolling while parked. Some cars have regenerative brakes which convert the energy that is lost through braking back into electricity.
The automobile revolutionized many aspects of modern life in the United States and elsewhere. It created jobs in the industry, provided a new way of transporting goods and people, and enabled leisure travel that was previously unfeasible for most. This change triggered the development of many new industries, services and businesses like restaurants, motels and hotels. It also led to new laws and regulations. It has caused environmental damage from exhaust and the use of valuable land for highway construction and related industries.
The automobile has many advantages over other means of public and private transportation, but there are a few disadvantages as well. One is the expense of owning and operating a car, but this can be offset by savings on fuel and other maintenance costs. Another is the increased risk of accidents due to reckless drivers and traffic congestion, but this can be reduced by obeying all road rules and driving safely. Finally, there is the inconvenience of having to wait for public transit or finding parking in busy areas.