Why do HOV lanes use the left lane on highways and the right lane on city streets?
Municipal HOV lanes operate in a different environment than highway HOV lanes. The primary purpose of municipal HOV lanes is to serve high-frequency local transit buses and taxis, which typically travel in the curb lane, making frequent stops. HOV lanes on 400-series highways are intended to serve multi-occupant vehicles, including inter-regional buses, moving at highway speeds and making longer-distance through trips. It is safer to locate a highway HOV lane on the left, to minimize weaving and lane change interactions with the general traffic lanes. Most interchange access is located on the right side of the highway, so it is safest and most practical to locate the HOV lane in the left lane.
