High Occupancy Vehicle (HOV) lanes are designated highway lanes restricted to vehicles with minimum passenger occupancy—typically two or more people, though some require three or more during peak periods. HOV lanes incentivize carpooling by offering faster travel times during congested periods. Eligible vehicles usually include carpools, vanpools, buses, and sometimes motorcycles, taxis, and green vehicles regardless of occupancy. HOV enforcement involves visual observation by police or camera systems. Violations typically incur significant fines. HOV lanes can be separated by barriers, marked lanes, or shoulder lanes operating during specific hours. Effectiveness depends on congestion levels in regular lanes, enforcement, and traveller willingness to carpool. Some HOV lanes have been converted to HOT lanes (allowing single-occupant vehicles for a toll) to better utilize capacity. HOV lanes represent transportation demand management—trying to move more people in fewer vehicles rather than just expanding road capacity.