Automobiles are one of the most common forms of modern transportation. Often referred to as cars, they are four-wheeled vehicles used primarily for passenger transportation and propelled by internal combustion engines using volatile fuels. Modern automobiles are complex technical systems, incorporating subsystems with specific design functions.

The automobile has changed society in many ways. It has made travel more convenient and allowed people to move more easily between jobs and neighborhoods. It has also led to the development of new industries such as gas stations, restaurants and hotels. It has also caused problems such as pollution, traffic congestion and the draining of the world’s oil supply.

During the first decade of the 20th century, America’s middle class grew and more people could afford an automobile. This created a large market for the car industry and it became a significant driver of economic growth for the country. In the 1920s it was the biggest consumer of steel, a major user of petroleum and a vital source of employment. It also revolutionized the ancillary industries, such as those that manufacture parts for the car.

Cars have become the dominant mode of passenger transportation in developed countries, with more than 1.4 billion vehicles currently on the road. Most are sedans, with four doors and a trunk. They are available in a range of sizes from small (subcompacts like the Nissan Versa and Kia Rio), through mid-size (Honda Civic and Toyota Corolla) to luxury models (Lexus and Mercedes-Benz).

Aside from their primary function as a means of transport, the automobile has provided a symbol of independence and status. It has been used for political protest, such as the 1916 trip across the country by Nell Richardson and Alice Burke to advocate for women’s right to vote. It has also been a way to make a statement, as evidenced by the photos of the “flirty-dash” girls.

In the postwar era, however, engineering began to be subordinated to questionable aesthetics in American cars, and quality declined. Questions arose concerning nonfunctional styling, the safety and durability of the cars and their cost. In addition, there were growing concerns about the impact of automobiles on the environment. Exhaust fumes from gasoline-powered automobiles contributed to air pollution and drained the world’s dwindling oil supply.

The decision whether to own an automobile or not depends on a person’s lifestyle and needs, as well as the availability of alternative modes of transportation. In urban areas, where narrow streets and traffic jams make driving less efficient than public transit, the automobile may not be as necessary. Similarly, in rural areas, where public transit is not easily accessible, it might be easier to live without a car. But for most people, an automobile is essential for work and leisure. It gives them freedom, independence and convenience. In these cases, it makes sense to own a vehicle. For others, however, there are other alternatives that can offer the same mobility and flexibility of an automobile without all the costs and responsibilities.