Automobiles, also referred to as cars, are wheeled passenger vehicles that carry people and cargo. They are powered by internal combustion engines and have a chassis with suspension that is usually designed to support the weight of the car and its passengers. There are many different types of automobiles, but they all share similar characteristics including their internal combustion engines and their chassis with suspension. These vehicles have become the main mode of transportation for most Americans, traveling more than three trillion miles (five billion kilometres) every year. The automobile has transformed society by making it possible for middle-class families to own their own vehicles. It has spawned new industries such as those that manufacture parts and vehicles, and it has influenced the design of roads and highways. It has also prompted changes in law enforcement and safety regulations and fueled an enormous increase in consumption of petroleum products, steel, and other industrial resources.

The development of the automobile has been a continuous process. While the basic components of an automobile have remained the same, the improvements in vehicle performance and reliability have been made through technical advances. Research and development engineers and scientists have been employed by every manufacturer to improve the body, chassis, engine, transmission, drivetrain, control systems, and safety systems of automobiles.

Today, there are more than 1.4 billion automobiles in operation worldwide. Of these, nearly 500 million are in the United States. Most of these are passenger cars, which carry one to six people and travel on roads. Automobiles are the principal means of family transportation in the country and have revolutionized the way people live. They make it possible to go long distances with ease and in relative comfort, opening up a wide range of leisure activities and services such as hotels, restaurants, amusement parks, and recreation areas. They have enabled people to commute to work and school by themselves instead of depending on others for transportation. They have also fueled new industries such as those that manufacture parts and automobiles and have influenced the design of roads and highways and changes in law enforcement and safety regulations.

An automobile’s components must be flexible enough to perform in a variety of situations and conditions. The arrangement, choice and type of these components will depend on the use of the automobile. For example, a car that is used for daily driving will probably have a four-cylinder engine because this allows the automobile to achieve high fuel economy. However, a sporty car that is designed for high speeds may require more power and a bigger engine.

The scientific and technical building blocks of the automobile date back centuries. Leonardo da Vinci was developing designs for cars in the 1500s, and the modern car developed gradually during the 19th century. Exactly who invented the first automobile is a matter of debate, but the invention of the internal combustion engine allowed mass production and the affordable price of automobiles for most middle-class families.