An automobile, also commonly called a "car," is a four-wheel vehicle propelled by an internal combustion engine or an electric motor and that is designed primarily for carrying a small number of passengers on roads. Automobiles differ from vans and buses, which are capable of transporting larger numbers of passengers, and from trucks, which are intended mainly for carrying freight.
Automobiles can offer great convenience to their users. Moreover, much importance is often attached to them, especially more expensive ones, as fashion or prestige items. This, plus their relatively low cost and ease of acquisition, has led to a massive growth in the number of automobiles worldwide, now numbering roughly 1.47 billion, of which about 285 million are in the United States.
This extreme proliferation of automobiles and other road vehicles has come at massive cost to the natural environment. They have been responsible for a major share of greenhouse gas emissions and are also highly destructive of wildlife because of habitat fragmentation, roadkill, air pollution and even noise pollution. They have also been having a severe effect on public health and the quality of life, including resulting in a number of injuries and deaths from traffic accidents comparable to the numbers of injuries and deaths from all wars in the 20th century and an ever-increasing amount of disease and death from air pollution.