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).

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.

A construction worker or police officer directs traffic with a "Stop/Slow Paddle", which is a sign displaying "STOP" on one side and "SLOW" on the other.

In some cases, traffic may be shifted onto one half, making it a temporary two-lane freeway corridor.

An example of this is Interstate 10 in Arizona, in which eastbound traffic is reduced to one lane and shifted onto the westbound half of the road.

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 by jersey barriers, or in rare circumstances, traffic cones.

After the race concludes, PA 115 becomes one-way northbound between Pocono Raceway and I-80 until everyone has left the track.