Contraflow lane reversal

Contraflow lane reversal is the altering of the normal flow of traffic, typically on a controlled-access highway (such as a freeway or motorway), to either aid in an emergency evacuation (the most common usage of the term in the United States) or, as part of routine maintenance activities, to facilitate widening or reconstruction of one of the highway's carriageways (the most common usage in the United Kingdom).

Usually, the term is used to refer to reversal of lanes which are normally configured for travel in one direction; routinely changing the configuration of reversible lanes (such as during rush hour) is not normally considered contraflow lane reversal.

In an emergency evacuation, contraflow lane reversal roughly doubles the number of lanes available for evacuation traffic. Crossover sections are used to move outgoing traffic to these lanes. All incoming traffic is blocked until the end of the evacuation.

Contraflow lane reversal is usually done on freeways and other controlled-access roadways; however, some examples listed below (particularly in South Carolina) are divided and undivided roadways. Use of contraflow lane reversal is generally considered to be an emergency measure, as the contraflow lanes (and any associated ramps at interchanges) lack proper signage, signals, and other traffic control devices needed to orderly conduct traffic in the opposite direction. Generally, a significant number of police officers or other officials are needed to manually direct traffic during a lane reversal (especially at interchanges, where ramp traffic in the wrong direction must intersect with other roadways operating normally).

Beginning in the 1990s, many states in the Southeastern United States adopted hurricane evacuation routes from coastal areas using contraflow lane reversals on Interstate Highways. State highway departments have coordinated on plans for traffic direction with state highway patrol agencies, constructed highway median crossovers, and installed signage for drivers and barriers and swing arms to inhibit wrong-way collisions.

...
Wikipedia