Controlled-access highway

A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway, and expressway. Other similar terms include throughway or thruway and parkway. Some of these may be limited-access highways, although this term can also refer to a class of highways with somewhat less isolation from other traffic. In countries following the Vienna Convention, the motorway qualification implies that walking and parking are forbidden. A fully 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. Entrances and exits to the highway are provided at interchanges by slip roads (ramps), which allow for speed changes between the highway and arterials and collector roads. On the controlled-access highway, opposing directions of travel are generally separated by a median strip or central reservation containing a traffic barrier or grass. Elimination of conflicts with other directions of traffic dramatically improves safety, while increasing traffic capacity and speed. Controlled-access highways evolved during the first half of the 20th century. Italy was the first country in the world to connect cities with controlled-access highways reserved for fast traffic and for motor vehicles only. Italy opened its first autostrada in 1924, A8, connecting Milan to Varese. Germany since 1907 planned and in 1913 had started to built the AVUS in Berlin, but this 'Automobile traffic and training road' was a closed circuit with two long straights where vehicles could reach their top speed twice before returning to the entrance. Opened in 1921 and mainly used for testing and racing for two decades, the AVUS was connected in 1940 to the nationwide network...