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Contraflow lane reversal is the altering of the normal flow of traffic, typically on acontrolled-access highway (such as a freeway or motorway), to either aid in anemergency evacuation (the most common usage of the term in theUnited States) or, as part ofroutine maintenance activities, to facilitate widening or reconstruction of one of the highway'scarriageways (the most common usage in theUnited 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 ofreversible lanes (such as duringrush hour) is not normally considered contraflow lane reversal.[1] On undivided highways, evacuation contraflow may be called evacuation reverse flow.[2]
There are similar setups with slightly different usages, although the terms may be commonly used interchangeably.
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 inSouth 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 propersignage,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 atinterchanges, where ramp traffic in the wrong direction must intersect with other roadways that are operating normally).
From the 1990s, many states in theSoutheastern United States adoptedhurricaneevacuation routes from coastal areas using contraflow lane reversals onInterstate Highways. State highway departments have coordinated on plans for traffic direction with statehighway patrol agencies, constructed highway median crossovers, and installed signage for drivers and barriers and swing arms to inhibit wrong-way collisions.[3]
Most evacuation plans involve only a single state; however, the states ofLouisiana andMississippi have developed coordinated plans to evacuate theNew Orleans metropolitan area by usingInterstate 55 andInterstate 59.
Current contraflow evacuation plans exist for:
Florida had contraflow evacuation plans in place until 2017. The plans were abandoned for emergencyshoulder use.[16] North Carolina has twice evaluated contraflow onI-40 fromWilmington toI-95 atBenson but rejected it.[17]
When roads are undergoingconstruction amid heavy traffic, one lane of traffic may be blocked and another lane reversed.
Single track roads are often closed during reconstruction.
Aconstruction worker orpolice officer directs traffic with a "Stop/Slow Paddle", which is a sign displaying "STOP" on one side and "SLOW" on the other. The sign is turned, and the other side proceeds.Traffic signals are also sometimes used, especially during bridge construction or any situation in which a lane must be closed during times when construction crews are not at work. Other cases include treating the street as a temporary one-way street in areas in which several nearby parallel streets are available as a detour for the opposing side.
If road construction necessitates the complete closure of one half of a road with four or more lanes, two lanes of traffic may be shifted to the other roadway. If the road being constructed is a highway, the used half is called asemi-highway.
Whencontrolled-access highways undergo reconstruction, both sides are often reduced to one lane. In some cases, traffic may be shifted onto one half, making it a temporarytwo-lane freeway corridor. An example of this isInterstate 10 inArizona, in which eastbound traffic is reduced to one lane and shifted onto the westbound half of the road.[18] Another technique is to treat the rightmosthard shoulder as a travel lane. On a six-lane freeway (i.e., one containing three lanes in each direction), a third lane may be kept open for the busier direction, or the shoulder may be opened to allow for four lanes of traffic but with little or no shoulder space; emergency breakdown areas may be added. In these situations, temporary "YIELD" or "STOP" signs are usually posted on merge ramps on freeways, expressways, and uncontrolled roads with interchanges. In such cases, opposing directions are separated byjersey barriers, or in rare circumstances,traffic cones.
At the beginning and end of major sporting events, the center turn lanes of roads around a stadium or arena may be used to accommodate event traffic. Because these lanes are typically not subject to lane control, this can be considered a limited form of contraflow reversal.
Once a year, upon completion ofNASCAR races atNew Hampshire Motor Speedway inLoudon, New Hampshire, a form of contraflow lane reversal, referred to as "borrow a lane," is conducted onInterstate 93 inConcord, New Hampshire. In this case, the left lane of northbound Interstate 93 is temporarily "borrowed" to use as a third southbound lane. Southbound traffic has the option of transferring to the "borrowed" lane north of theInterstate 393 interchange and can travel southbound in the left northbound lane to allow a bypass of heavy race traffic entering I-93 southbound from I-393 at Exit 15. The two lanes of traffic in the normal southbound lanes, and traffic in the bypass "borrowed" lane rejoin on the southbound side of the interstate just south of theInterstate 89 interchange inBow.[19]
Contraflow lane reversal is also used forNASCAR Cup Series andIndyCar Series races atPocono Raceway inLong Pond, Pennsylvania. For these races, two-lanePennsylvania Route 115 becomes one-way southbound betweenInterstate 80 and the track the morning of the race until everyone has arrived at the track. After the race concludes, PA 115 becomes one-way northbound between Pocono Raceway and I-80 until everyone has left the track.[20][21]