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- road 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. Generally to avoid requiring handicapped persons from having to possess an operator's license to use one, or requiring tags and insurance, powered wheelchairs will be specifically excluded by law from being considered motor vehicles.
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 258 million in 2014. Vehicle ownership per capita in the US is also the highest in the world with 769 vehicles in operation per 1000 people.
