Automobiles are motor vehicles that provide a means of transportation for people and goods. They are usually four-wheeled and propelled by an internal combustion engine using a volatile fuel. They are designed to be driven on public roads and may carry between one and eight passengers. The modern automobile is a complex technical system with many subsystems that have specific design functions. The most important of these are the engine, transmission, powertrain, and chassis. The latter includes the wheels, suspension system, and braking system.

The development of the automobile has been a major factor in changing the way we live. It has revolutionized both work and leisure, making it possible for urban dwellers to escape to the countryside and for rural dwellers to visit urban areas. Automobiles also have provided the freedom to move to different jobs, schools, and recreational activities without being dependent on a bus schedule or other forms of public transport.

There are 1.4 billion passenger cars in operation worldwide. Many of these are in the United States, where three trillion miles (five trillion kilometres) are driven each year. Compared with earlier vehicles, the modern car is very comfortable and easy to operate. The automotive industry has pioneered new technology, including electric ignition and self-starting, independent suspension, and the use of computerized control systems. The manufacturing methods introduced by Henry Ford revolutionized industrial production and brought the automobile within reach of middle-class families.

During the first decades of the 20th century, America began to build more automobile plants. The number of automobiles in the country grew rapidly, and the American middle class expanded. This allowed more people to purchase cars, and they were used for everything from grocery shopping to commuting to work and visiting friends. The automobile has given people the freedom to live where they choose and spend their time doing what they want with family and friends.

Automobiles have had negative impacts on society as well. Traffic congestion slows cars and reduces efficiency, and air pollution from automobiles can cause sickness. In addition, they can be dangerous to their occupants and other road users, especially when they are involved in accidents. Nevertheless, the automobile continues to dominate the world’s transportation system and is a symbol of the promise and the problems of modern life.

The main components of an automobile are the engine, transmission, powertrain, chassis, and body. The choice and arrangement of these elements depends on the type of automobile and its intended use. For example, a car designed for economy driving will have a simpler engine and less equipment than a sporty model built for high speeds. The chassis of an automobile provides the base for its suspension and braking systems, as well as its protection from the elements and impact damage. The body of an automobile, analogous to the skeleton of the human body, houses the seats, doors, windows, and other accessories. Some automobiles have special bodies for carrying cargo or serving other purposes.