A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid electric vehicles and plug-in hybrids. For legal purposes motor vehicles are often identified within a number of vehicle classes including cars, buses, motorcycles off highway vehicles, light trucks and regular trucks. These classifications vary according to the legal codes of each country. ISO 3833:1977 is the standard for road vehicles types, terms and definitions. As of 2010 there were more than one billion motor vehicles in use in the world excluding off-road vehicles and heavy construction equipment. Global vehicle ownership per capita in 2010 was 148 vehicles in operation per 1000 people. The United States has the largest fleet of motor vehicles in the world, with 239.8 million in 2010. Vehicle ownership per capita in the U.S. is also the highest in the world with 769 vehicles in operation per 1000 people. The People’s Republic of China has the second largest fleet in the world, with slightly more than 78 million vehicles and since 2009 became the world’s largest new car market. In 2011, a total of 80 million cars and commercial vehicles were built, led by China, with 18.4 million motor vehicles manufactured.