A high-occupancy toll lane (or HOT lane) is a type of traffic lane or roadway that is available to high-occupancy vehicles and other exempt vehicles without charge; other vehicles being required to pay a variable fee that is adjusted in response to demand. Unlike toll roads, drivers have an option to use general purpose lanes, on which a fee is not charged. Express toll lanes, which are less common, operate along similar lines, but do not exempt high-occupancy vehicles.