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A controlled-access highway is a type of highway which has been designed for high-speed vehicular traffic, with all traffic flow and ingress/egress regulated. Common English terms are freeway (in the US) and motorway (in the UK). Terms in other languages sometimes seen in English include (スペイン語:autopista or autovía) (depending on whether it has toll or not), (フランス語:autoroute), (ドイツ語:Autobahn), or (イタリア語:autostrada). Other similar terms include ''expressway'', ''Interstate'', and ''parkway''. They may also be called limited-access highways, although this term can also refer to a class of highway with somewhat less isolation from other traffic. Conversely, some of the United States use "controlled access" to describe a non-limited-access road, entrances to which are controlled by the state. 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. Entrances and exits to the highway are provided at interchanges by slip roads (ramps), which allow for speed changes between the highway and arterial roads 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 the sources of potential conflicts with other directions of travelers dramatically improves safety,〔http://archive.etsc.eu/documents/copy_of_PR%20Motorways%20safety-02.18-final.pdf〕 and capacity. Controlled-access highways evolved during the first half of the 20th century. Italy opened its first ''autostrada'' in 1924 connecting Milan to Varese (A8). Germany began to build its first ''autobahn'' controlled-access highway without speed limits (then referred to as a ''dual highway'') in 1932 between Cologne and Bonn (now A555). It then rapidly constructed a nationwide system of such roads in anticipation of their use in the Second World War. The first North American ''freeways'' (known as parkways) opened in the New York City area in the 1920s. Britain, heavily influenced by the railways, did not build its first ''motorway'', the Preston By-pass (M6), until 1958. Most technologically advanced nations feature an extensive network of freeways or motorways to provide high-capacity urban travel, or high-speed rural travel, or both. Many have a national-level or even international-level (e.g. European E route) system of route numbering. ==Definition== There is no formal definition of the English language words "motorway", "freeway" and "expressway", or of the equivalent words in other languages such as "autoroute", "Autobahn", "autostrada", "autocesta", that are accepted worldwide—in most cases these words are defined by local statute or design standards. Descriptions that are widely used include: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Controlled-access highway」の詳細全文を読む スポンサード リンク
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