- published: 22 Sep 2015
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A controlled-access highway is a highway designed exclusively for high-speed vehicular traffic, with all traffic flow and ingress/egress regulated. They are known by various terms worldwide, including Autobahn, autopista, autoroute, autostrada, snelweg, freeway, motorway, and sometimes less precise terms such as highway, expressway, parkway, or turnpike.
A controlled-access highway provides an unhindered flow of traffic, with no traffic signals, intersections or property access. They are free of any at-grade crossings with other roads, railways, or pedestrian paths, which are instead carried by overpasses and underpasses across the highway. Entrance and exit to the highway are provided at interchanges by slip roads (ramps), which allow for speed changes between the highway and arterial thoroughfares and collector roads. On the highway, opposing directions of travel are physically separated by a central reservation (median), such as a strip of grass or boulders, or by a traffic barrier.
Controlled-access highways, as they exist today, evolved during the first half of the twentieth century. The Long Island Motor Parkway, opened in 1908 as a private venture, was the world's first limited-access roadway. Germany began to build its famous Reichsautobahn controlled-access highway network (then referred to as a Dual Highway) following the First World War. It rapidly assembled a nationwide system of such roads in anticipation of their use in World War II. Italy followed shortly thereafter, opening its first Autostrada in 1925. The first North American freeways (known as parkways) opened in the New York City area in the 1920s. Britain, heavily influenced by the railway,[citation needed] did not build its first motorway until the mid-1950s.