<P> A high - occupancy vehicle lane (also known as an HOV lane, carpool lane, diamond lane, 2 + 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 . </P> <P> Regional and corporate - sponsored vanpools, carpools, and rideshare communities give commuters a way to increase occupancy . For places without such services, online rideshare communities can serve a similar purpose . Slugging lines are common in some places, where solo drivers pick up a passenger to share the ride and allow use of the HOV lane . High - occupancy toll lanes (HOT lanes) have been introduced in the United States to allow solo driver vehicles to use the lane on payment of a variable fee, which usually varies with demand . </P>

What is the purpose of the hov lane