Interstate 80 near Berkeley, United States
A road is an identifiable route, way or path between two or more places. Roads are typically smoothed, paved, or otherwise prepared to allow easy travel; though they need not be, and historically many roads were simply recognizable routes without any formal construction or maintenance. In urban areas roads may pass through a city or village and be named as streets, serving a dual function as urban space easement and route.
The most common road vehicle is the automobile; a wheeled passenger vehicle that carries its own motor. Other users of roads include buses, trucks, motorcycles, bicycles and pedestrians. As of 2002 there were 590 million automobiles worldwide.
The first forms of road transport were horses, oxen or even humans carrying goods over dirt tracks that often followed game trails. The Roman Empire was in need for armies to be able to travel quickly; they built deep roadbeds of crushed stone as an underlying layer to ensure that they kept dry, as the water would flow out from the crushed stone, instead of becoming mud in clay soils. John Loudon McAdam designed the first modern highways of inexpensive paving material of soil and stone aggregate known as macadam during the Industrial Revolution. Coating of cobblestones and wooden paving were popular during the 19th century while tarmac and concrete paving became popular during the 20th.
Automobiles offer high flexibility and with low capacity, but are deemed with high energy and area use, and the main source of noise and air pollution in cities; buses allow for more efficient travel at the cost of reduced flexibility. Road transport by truck is often the initial and final stage of freight transport.