A concurrency in a road network is an instance of one physical roadway bearing two or more different route numbers. When two roadways share the same right-of-way, it is sometimes called a common section or commons. Other terminology for a concurrency includes overlap, coincidence, duplex, triplex, multiplex, dual routing or triple routing.
An extreme example: I-40, I-85 Business, US 29, US 70, US 220, and US 421 formerly ran concurrently in Greensboro, North Carolina. In 2008, I-40 was rerouted off this road but was put back on it later that same year with US 220 being rerouted instead. US 421 was also rerouted in 2009.
The Queen Elizabeth Way concurrent with Highway 403 in Ontario
A section of Ontario Highway 400 runs concurrent with a branch of the Trans-Canada Highway.
Concurrency of the city beltway, a European road, and three first-class roads in Hradec Králové, Czech Republic
Interstate 70 in Pennsylvania
Interstate 70 (I-70) is a state highway that is located in the Commonwealth of Pennsylvania in the United States. It runs east to west across the southwest part of Pennsylvania and serves the southern fringe of the Pittsburgh metropolitan area.
I-70 through Buffalo Township in Washington County
I-70 (on top) merges with I-79 going through Washington, Pennsylvania, shown in 2008 before reconstruction and flyover construction
I-70 eastbound approaching the PA 88 exit in Speers
View east along the surface portion of I-70 and west along US 30 in Breezewood
