The automobile is a four-wheeled vehicle with an internal combustion engine that is primarily used for personal transportation. It is one of the most popular forms of personal property in the United States. Automobiles are complex technical systems with thousands of component parts. The automobile industry has evolved in recent decades due to advances in technology and air pollution laws, as well as global competition between automobile manufacturers.
Automobiles can be classified into different types, depending on their size and number of wheels. Motorcycles are classified as automobiles if they have four wheels and a seat for one or two passengers. Motorcycles are also classified as automobiles if they have a side car. Some people may argue that motorcycles are not automobiles, but this is a common misconception.
The development of automobiles radically changed American society. It made it possible for Americans to travel on vacation with their families and shop in towns. It also allowed teenagers to enjoy independence by driving their own cars. In the United States, automobile ownership doubled from one million in the 1890s to over 23 million by 1920. This growth of automobile ownership sparked an economic revolution. New roads and highways were built, creating thousands of jobs and increasing the number of registered drivers.
Automobiles are the most common form of transportation. But there are many types of vehicles. Motorcycles, for example, are electric vehicles. They are zero-emission, and have very high fuel economy equivalents. Other forms of vehicles include petroleum-electric hybrids and fuel cells. Two-wheeled motorcycles are also popular, and are known as autobikes. The angular momentum of the wheels ensures that the bike stays upright.