Automobiles, also referred to as motor cars, are vehicles with four wheels. They are used for transportation and for commercial purposes. Modern automobiles are complex technical systems that use thousands of parts. Designed to carry passengers, cars are usually made to seat one to eight people. The main components of a modern car include the engine, the body, and the powertrain.

In the early nineteenth century, Edward Butler built the first three-wheeler with steerable front and rear wheels and a horizontal single-cylinder gasoline engine. This machine was an important step forward in automotive knowledge, especially since it was a first step toward creating a self-propelling carriage. Bicycle builder Sylvester Howard Roper created a similar contraption in 1867.

Cars became a popular mode of transportation in the United States during the twentieth century. This demand was due to higher per capita income and the development of the automobile industry. As a result, automobiles became the primary family transportation, with about 70 million passenger cars being manufactured each year worldwide.

Since the beginning of the twentieth century, automobile manufacturers have been required to conform to stricter standards to reduce fuel consumption and emissions. Standards also were established to ensure the safety of drivers. Automakers hired scientists and engineers to improve the engines, control systems, and bodies of their vehicles.

Automobiles have also become the target of theft. During the 1970s, oil shortages and embargoes caused the price of gasoline to skyrocket. However, the auto industry rebounded during the 1990s. At the same time, Japanese and European automakers gained more than a foothold in the U.S. market. These companies earned a reputation for manufacturing better quality cars.

Despite their popularity, automobiles have been known to cause a large number of personal injuries. The best way to minimize these injuries is to require automakers to design safer cars. But, despite the efforts of automakers and the government, there are still many accidents. Some people believe that the greatest contributor to the high rates of car crash injuries is the driver.

Automobiles are a major cause of air pollution. Their production has led to high levels of carbon dioxide and other harmful pollutants. Fortunately, automobile manufacturers are continually improving their engines, controls, and bodies to lower their environmental impact.

Aside from improving the drivetrain and emission-control systems, automobile manufacturers are also implementing new research and development procedures to increase stability and performance. Many of these advances are a result of the global competition amongst manufacturers. New designs and technical advancements are recognized as key factors to a successful competition.

Today, automobiles are the primary form of transport in the United States. It is estimated that the average American travels about three trillion miles each year. Therefore, they play a vital role in our society. Despite their popularity, cars are expensive to purchase and can cause tremendous personal injury. To address these issues, the National Highway Traffic Safety Administration (NHTSA) was granted authority to enforce safety regulations. In addition, states were given responsibility to coordinate and implement programs to help drivers.