Wrong-way Concurrency
As highways in the United States and Canada are usually signed with a cardinal direction, it is possible for two highways signed with opposite, conflicting directions to be running along the same stretch of physical roadway. The road itself is likely to be actually pointed in a third direction.
For example, near Wytheville, Virginia, there is a concurrency between Interstate 77 (which runs and is signed north-south) and Interstate 81 (which runs primarily northeast-southwest but is also signed north-south). The road itself is oriented east-west and carries the two Interstates signed in opposite directions. So one might simultaneously be on I-77 north and I-81 south, while actually traveling due west. Another well-traveled example is the I-580 and I-80 concurrency in the Bay Area of California, known locally as the Eastshore Freeway, which travels north-south along the shoreline of San Francisco Bay.
At least two roads run concurrently with their own opposite direction. A short stretch of Broadway in Pawtucket, Rhode Island, carries both directions of Route 114, and a short stretch of eastbound Interstate 376, as well as the ramps leading to it, in Pittsburgh, Pennsylvania, carries both directions of U.S. Route 19 Truck.
An unusual example of a three-directional concurrency occurs near the town of Starks, Illinois. To take advantage of an underpass beneath a railroad, US Route 20, Illinois Route 72 and Illinois Route 47 all converge. The net result is that a driver can be traveling east on US 20, west on IL 72, and south on IL 47 (the actual compass direction) all at the same time.
Canada also possesses at least four wrong-way concurrencies: an 11 km (6.8 mi) stretch of Saskatchewan Highways 2 and 11 between Chamberlain and Findlater, a 7 km (4.3 mi) stretch of British Columbia Highways 5 and 97 in Kamloops, a 10 km (6.2 mi) segment of New Brunswick Route 8 and Route 117 in Miramichi and 5.5 km (3.4 mi) segment of Highway 6 and Highway 21 west of Owen Sound, Ontario.
Read more about this topic: Concurrency (road)