road, strip of land used for transportation. The history of roads has been related to the centralizing of populations in powerful cities, which the roads have served for military purposes and for trade, the collection of supplies, and tribute. In the Middle East, in N Mesopotamia, scientists have found evidence of a network of roads dating back to perhaps 3000 BC In Persia, between 500 and 400 BC, all the provinces were connected with the capital, Susa, by roads, one of them 1,500 mi (2,400 km) long. The ancient Greeks, cherishing the independence of their city-states and opposing centralization, did relatively little road making.
The Roman roads, however, are famous. In Italy and in every region that the Romans conquered, they built roads so durable that parts of them yet remain serviceable. The Roman roads were generally straight, even over steep grades. The surface, made of large slabs of hard stone, rested on a bed of smaller stones and cement about 3 ft (91 cm) thick.
From the fall of the Roman Empire until the 19th cent., European roads generally were neglected and hard to travel. People usually walked, rode horses, or were carried in sedan chairs. Goods were transported by pack animals. In France, Louis XIV and Napoleon built good roads for military purposes. Elsewhere on the Continent roads were not much improved before the middle of the 19th cent. In Great Britain two Scottish engineers, Thomas Telford and John L. McAdam, were responsible for the development of the macadam road (see pavement). The expansion of the Industrial Revolution brought this and other road improvements to the Continent, although the emphasis was on railroad construction until after the invention of the automobile.
In the Americas the Inca empire was remarkable for its fine roads. In what is now the United States, however, the waterways were the normal mode of travel for Native Americans, and their trails, though numerous, were often simply footpaths. These were used by white settlers and were eventually widened to make wagon trails. The increasing use of stagecoaches led to some improvement, and the turnpike, or toll road, was introduced at the beginning of the 19th cent. Although the planning and building of road arteries, notably the National Road, marked the early years of the century, canals and then railroads took precedence.
The invention and mass production of the automobile made the road became paramount again. Hard-surfaced highways were stretched across the entire land in a relatively few years. The building of roads became a major branch of engineering, and even the most difficult obstacles were surmounted. Roads have helped greatly to equalize and unify large heterogeneous nations. In the United States the Interstate Highway System consists of 42,793 mi (68,869 km) of roads (all but a few miles of which are completed) connecting every major city. Other well-known road networks which serve to unify large areas include Germany's Autobahn, the Trans-Canada Highway, and the Pan-American Highway. An ambitious, 23-nation agreement to link Asia with a network of highways was signed in 2004.
See G. Hindley, A History of Roads (1972); P. H. Wright et al., Highway Engineering (2004); E. Swift, The Big Roads: The Untold Story of the Engineers, Visionaries, and Trailblazers Who Created the American Superhighways (2011).