Meaning of ROAD in English
the traveled way on which people, animals, or wheeled vehicles move. In modern usage the term road describes a rural, lesser traveled way, while the word street denotes an urban roadway. Highway refers to a major rural traveled way; more recently it has been used for a road, in either a rural or urban area, where points of entrance and exit for traffic are limited and controlled. The earliest roads developed from the paths and trails of prehistoric peoples; their construction was concurrent with the appearance of wheeled vehicles, which was probably in the area between the Caucasus Mountains and the Persian Gulf sometime before 3000 BC. Road systems were developed that connected the civilizations of Mesopotamia and Egypt and facilitated trade. The first major road was the Persian Royal Road, which extended from the Persian Gulf to the Aegean Sea over a distance of 1,775 miles (2,857 km) and was used from about 3500 to 300 BC. The Amber Routes were the earliest European roads and extended from Greece and Tuscany to the Baltic Sea. In East Asia the Chinese built a road system that linked its major cities and had a combined length of about 2,000 miles (3,200 km). The techniques used to build these early roads varied. In northern Europe, where wet land was often a problem, logs were laid on branches and then overlaid with transverse rows of logs to carry traffic over marshy areas. On the island of Malta ruts were carved in sandstone to hold carts on the roads. Civilizations around the Indus Valley built roads of brick cemented together with bitumen (an asphalt substance) and provided drains for water runoff. The Maurya Empire, one of the civilizations of this region, created a ministry of public works to keep its road system in good condition. The Romans also recognized the importance of roads in maintaining an empire; at the empire's peak it had some 53,000 miles (85,000 km) of road, extending from Britain in the north to North Africa in the south and from the Atlantic coast of the Iberian peninsula in the west to the Persian Gulf in the east. (See also Roman road system.) The Romans were the first to construct roads scientifically. Their roads were characteristically straight, and the best ones were composed of a graded soil foundation that was topped by four courses (layers): a bedding of sand or mortar; rows of large, flat stones; a thin layer of gravel mixed with lime; and finally a thin wearing surface of flintlike lava. Roman roads varied in thickness from 3 to 5 feet (0.9 to 1.5 m), and their design remained the most sophisticated until the advent of modern road-building technology in the late 18th and early 19th centuries. As Rome declined its roads fell into disrepair, and, other than some interest in municipal street paving in the 15th and 16th centuries, there was little road-building activity in the West for more than 1,500 years. The Silk Road, which connected the Roman Empire with India and China, was used intermittently during this period (it was frequently closed owing to warfare and raids by nomads). In South America, however, the Incas were building a sophisticated network of well-planned roads through their empire in the Andes Mountains. By the 16th century, when the Spaniards arrived, the Incas had two long, parallel roads (one along the coast and the other in the mountains) with numerous cross connections. When interest in road building revived in Europe in the late 18th century, engineers began designing roads that incorporated lighter surfaces, relying on the subsurface for load support. Roads could thus be built relatively cheaply and quickly. The most influential of the early engineers was John Loudon McAdam, inventor of the macadam road surface. His design comprised a compacted subgrade of crushed rock to support the load, and a surface covering of light stone to absorb wear and shed water to the drainage ditches. By the end of the 19th century the widespread use of the bicycle created a demand for roads with smoother surfaces. A pavement of natural rock asphalt was used in Paris as early as 1854, and portland cement concrete was used in Scotland in 1865. Road surfaces in the latter part of the century utilized a macadam construction. This process used a compacted stone base bound together with either a hydraulic (water-base) natural cement or a stone base impregnated with asphalt tar, called a tarmac surface. Two classifications of pavement (the hardened surface layer laid on top of a natural-earth or crushed-stone subgrade) have been developed: flexible and rigid. Flexible pavement is usually made of an asphaltgravel aggregate that is laid in one or more courses over the subgrade. The aggregate can be mixed at the road-building site or at a central plant, and its quality varies with the production method used. A cheap method of pavement, called surface treatment, is made by spraying hot asphalt or tar on a compacted stone base and then placing small stone chips on the tar; it is suitable for lightly traveled roads and can be built up in layers. Pavements made with a high-temperature plant mix are suitable for the heaviest loads and are made by laying the asphalt while it is hot and rolling it before it cools. A flexible pavement has the advantage of being easy to build and repair; its asphalt binder is both waterproof and plastic, so that it resists water damage and can readily expand and contract with temperature variations. Rigid pavement, made of portland cement concrete, generally has greater strength but is susceptible to cracking. The cement, mixed with water and various grades of crushed stone called aggregate, is poured onto the built-up and graded foundation as a plastic mass. It shrinks as it dries, causing tensile stresses. The concrete also contracts and expands with temperature change, so that cracking is a constant problem. To remedy this, concrete sections are jointed, and grooves are cut part way through the slabs so that cracks will occur at regular intervals. Expansion is absorbed by transverse joints consisting of small openings with steel-rod dowels for reinforcement. The best solution so far has been by pouring a continuous concrete slab in which a mesh of steel bars is embedded. The bars, running lengthwise through the concrete, absorb the tension of shrinkage and hold shut any cracks that form. Modern highway design entails careful study of soil types, the topography of the intended route, and the drainage systems around the roadway. Where necessary, measures are taken to provide additional drainage facilities to prevent water from eroding the road base or freezing in cracks. The techniques of cutting and filling (excavating in one place and depositing it nearby to form a level roadbed) and switchbacking (zigzagging up a slope) have been used for centuries to obtain easy gradients in varied terrains. But it became necessary to design broad, banked curves to keep vehicles from leaving the roadway and to limit and control access to and egress from the highway, as well as to separate the lanes of traffic, in order to reduce the possibility of collisions. The prototype of the modern superhighway was the Bronx River Parkway, which was completed in 1925 in New York City. It was a limited-access, high-speed highway designed to carry a large volume of traffic without disturbing the natural landscape. In the 1920s the Italians began the autostrada, and the Germans followed not long after with the autobahn. Military use was an important design feature of these highways, which could accommodate heavy traffic at speeds of 100 miles (160 km) per hour. In the United States the federal government created the national Interstate Highway System after World War II. It incorporated the toll-road network with other limited-access highways and linked all of the nation's major cities. Most industrialized countries in the world built similar systems to facilitate automobile and truck traffic.
Britannica English vocabulary. Английский словарь Британика. 2012