In many countries, diamond markings are used to designate traffic lanes that are set aside for special traffic. Narrow diamond lanes that run near the curb are usually bicycle lanes, and diamond lanes on freeways are typically reserved for high-occupancy passenger cars and certain special classes of vehicles.
In addition to carpools, vehicles that are usually entitled to drive in the diamond lanes are taxis, buses and low- or zero-emissions vehicles. Motorcycles are also usually allowed access to diamond lanes, as are emergency vehicles of every type. Unauthorized vehicles caught driving in the diamond lane, especially during peak traffic hours, are subject to fines.