A reversible lane (British English: tidal flow) is a lane in which traffic may travel in either direction, depending on certain conditions. Typically, it is meant to improve traffic flow during rush hours, by having overhead traffic lights and lighted street signs notifying drivers which lanes are open or closed to driving or turning.

Reversible lanes are also commonly found in tunnels and on bridges, and on the surrounding roadways – even where the lanes are not regularly reversed to handle normal changes in traffic flow. The presence of lane controls allows authorities to close or reverse lanes when unusual circumstances (such as construction or a traffic mishap) require use of fewer or more lanes to maintain orderly flow of traffic.