A
high-occupancy vehicle lane (also known as an
HOV lane,
carpool lane,
diamond lane, and
transit lane or
T2 or T3 lanes in Australia and New Zealand) is a restricted
traffic lane reserved at
peak travel times or longer for the exclusive use of vehicles with a driver and one or more passengers, including
carpools,
vanpools, and
transit buses. The normal minimum occupancy level is 2 or 3 occupants. Many jurisdictions exempt other vehicles, including motorcycles, charter buses, emergency and law enforcement vehicles, low-emission and other
green vehicles, and/or
single-occupancy vehicles paying a toll. HOV lanes are normally created to increase average vehicle occupancy and persons traveling with the goal of reducing
traffic congestion and
air pollution, although their effectiveness is questionable.