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A concurrency in a road network is an instance of one physical road bearing two or more different highway, motorway, or other route numbers. When two freeways share the same right-of-way, it is sometimes called a common section or commons. Other terminology for a concurrency includes overlap, coincidence, duplex (two concurrent routes), triplex (three concurrent routes) multiplex (any number of concurrent routes), dual routing or triple routing. Concurrent numbering can become very common in countries that allow it. Where multiple routes must pass through a single mountain crossing, or through a major city, it is often economically and practically advantageous for them all to be accommodated on a single physical road. In some countries, however, concurrent numbering is avoided by posting only one route number on road signs; these routes disappear at the start of the concurrency and reappear when it ends. Criticism of concurrencies include environmental intrusion, as well as being considered a factor in road accidents. ==Overview== Most concurrencies are simply a combination of two route numbers on the same physical road. This is often practically advantageous as well as economically advantageous; it may be better for two route numbers to be combined into one along riverways or through mountain valleys. Some nations allow for concurrencies to occur, however some nations specifically do not allow it to happen. In those nations which do permit concurrencies, it can become very common. In these countries, there are a variety of concurrences which can occur. An example of this is the concurrency of I-70 and I-76 on the Pennsylvania Turnpike in western Pennsylvania. Interstate 70 merges with the Pennsylvania Turnpike so the route number can ultimately continue east into Maryland; instead of having a second physical highway built to carry the route, it is combined with the Pennsylvania Turnpike and the Interstate 76 designation. A triple Interstate concurrency is found north of Madison, Wisconsin, with I-39, I-90, and I-94. Wisconsin has another triple Interstate concurrency along the section of I-41, I-43, and I-894 in Milwaukee, Wisconsin. The concurrency of I-41 and I-43 on this roadway is an example of a wrong-way concurrency. The longest Interstate highway concurrency is I-80 and I-90 for across Indiana and Ohio. There is an example of an eight-way concurrency: I-465 around Indianapolis and Georgia State Route 10 Loop around downtown Athens, Georgia. Portions of the I-465 overlap with I-74, US 31, US 36, US 40, US 52, US 421, SR 37 and SR 67—a total of eight other routes. Seven of the eight other designations overlap between exits 46 and 47 to create an eight-way concurrency. 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「Concurrency (road)」の詳細全文を読む スポンサード リンク
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