Automobiles are one of the most significant inventions in the modern world. It is hard to imagine a world without them. The branches of engineering which deal with automobiles are known as automobile engineering. There are over four trillion (five hundred billion kilometres) of them in operation in the world today. They are the main mode of transportation for most people and play a major role in economy. The automobile industry ranked first in value of product in the United States in the 1920s and today provides one out of every six jobs. It has revolutionized the way Americans live and work, created new industries and services, influenced both industrial design and the development of better roads and transportation systems.

The automobile is the most complex mechanical system ever developed. It consists of thousands of parts that have specific design functions. Its complexity is the result of breakthroughs in materials, engineering and computer technology. Modern automobiles are designed to meet stringent safety and performance standards, to reduce noise and vibration and to be energy efficient. They are propelled by internal-combustion engines using a volatile fuel. These engines and fuels produce air pollution and carbon dioxide, a greenhouse gas, that contributes to climate change.

One of the most important reasons to own a car is that it saves time. It takes a lot of time to walk or ride a bicycle across town. Driving a car also saves time on shopping trips and visiting friends. Another advantage of owning a car is that it allows you to go on vacations and weekend getaways. The automobile has changed the world and made it much more accessible to most people.

Exactly who invented the automobile is a matter of controversy. Early accounts often gave credit to Karl Benz, who created the first true automobile in 1885/1886. Later research, however, has shown that a number of other people played an important part in the development of the automobile.

The American automobile industry was able to develop and market its products more rapidly than European manufacturers because of the greater need for automotive transportation in the vast country with its large hinterland of scattered, isolated settlements. Cheap raw materials and the absence of tariff barriers encouraged the manufacture of cars over a broad geographic area. The pioneering mass-production techniques of Henry Ford enabled the automobile to be sold at an affordable price.

As the number of cars grew, so did the demand for parts and fuel. An entire new industry of ancillary industries developed to supply these needs. Industries like petroleum and gasoline, rubber, steel and plastics grew and services such as gas stations and convenience stores sprang up. The automobile changed the economy and lifestyle of the United States and of many other nations.

By the 1970s automobile design had become more concerned with consumer aesthetics than with engineering improvement. The era of the annually restyled road cruiser had ended, as federal and state standards for safety, emissions of pollutants, and energy consumption took hold; as escalating gasoline prices raised concerns about global oil supplies; and as manufacturers sought higher unit profits by selling more automobiles.