Concurrency (road)
A concurrency in a road network is an instance of one physical roadway bearing two or more different route numbers.
However, any route that becomes unsigned in the middle of the concurrency will still be signed on most maps and road atlases.
I-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 I-76 designation.
[8] The longest Interstate Highway concurrency is I-80 and I-90 for 278 miles (447 km) across Indiana and Ohio.
[11] In the United States, concurrencies are simply marked by placing signs for both routes on the same or adjacent posts.
The federal Manual on Uniform Traffic Control Devices prescribes that when mounting these adjacent signs together that the numbers will be arranged vertically or horizontally in order of precedence.
The renumbering to 410 never came to pass,[16] and consequently Highway 403 was signed concurrently along the Queen Elizabeth Way in 2002, remedying the discontinuity.
Nonetheless, many surface street signs referring to that section of freeway with the QEW/Highway 403 concurrency still only use the highway's original designation of QEW, although the MTO has updated route markers on the QEW to reflect the concurrency.
In Sweden and Denmark, the most important highways use only the European route numbers that have cardinal directions.
The official road map enables a maximum of five concurrent routes of the intrastate numbering system.
It is a one-mile (1.6 km) segment consisting of eight lanes providing high-speed access between the two highways.
Since highways in the United States and Canada are usually signed with assigned cardinal directions based on their primary orientation, it is possible for a stretch of roadway shared between two highways to be signed with conflicting, even opposite, cardinal directions in a wrong-way concurrency.
A vehicle might simultaneously be on I-77 northbound and I-81 southbound, while actually traveling due westbound.
US 127 also has another exit 139 with the southern end of the US 127 business loop in Mount Pleasant, Michigan.
This can involve scaling back the terminus of one designation to the end of a concurrent section.
[27] Some consolidation schemes involve the use of incorporating two single-digit numbers onto one marker, as along the US 1/9 concurrency in northern New Jersey.
