Four-wheeled automotive vehicle designed for passenger transportation and commonly propelled by an internal-combustion engine using a volatile fuel. The modern automobile consists of about 14,000 parts and comprises several structural and mechanical systems. These include the body, containing the passenger and storage space, which sits on the chassis, or steel frame; the internal-combustion gasoline engine, which powers the car by means of a transmission; the steering and braking systems, which control the car's motion; and the electrical system, which includes a battery, alternator, and other devices. Subsystems involve fuel, exhaust, lubrication, cooling, suspension, and tires. Though experimental vehicles were built as early as the 18th century, not until the 1880s did Gottlieb Daimler and Karl Benz in Germany begin separately to manufacture cars commercially. In the U.S., James and William Packard and Ransom Olds were among the first auto manufacturers, and by 1898 there were 50 U.S. manufacturers. Some early cars operated by steam engine, such as those made from c. 1902 by Francis E. Stanley and Freelan O. Stanley. The internal-combustion engine was used by Henry Ford when he introduced the Model T in 1908; Ford would soon revolutionize the industry with his use of the assembly line. In the 1930s European manufacturers began to make small, affordable cars such as the Volkswagen. In the 1950s and '60s U.S. automakers produced larger, more luxurious cars with more automatic features. In the 1970s and '80s Japanese manufacturers exported their small, reliable, fuel-efficient cars worldwide, and their increasing popularity spurred U.S. automakers to produce similar models. During a period of stable fuel prices and economic prosperity in the 1990s, sport-utility vehicles (SUVs) and minivans, with their greater cargo and passenger capacities, became highly popular. After the turn of the 21st century, rising fuel prices and concerns about vehicle emissions spurred a rising interest in electric and hybrid-electric automobiles. Some 50 million passenger cars are produced each year worldwide. China and the U.S. are the world's largest automobile markets; annual sales in China surpassed those in the U.S. for the first time in 2009. See also axle; brake; bus; carburetor; electric automobile; fuel injection; motorcycle; truck.