These lanes function similar to Express Lanes or conventional HOV lanes on Interstates and other commuter freeways in metropolitan areas. HOV eligible motorists may use these lanes free of charge, either through a preregistered account (such as with Peach Pass in Georgia), with an E-ZPass Flex transponder (such as in Northern Virginia), or simply by having the necessary number of passengers (Fastrak Lanes on I-15 in San Diego). Single occupent motorists are charged a variable rate depending upon time of day and traffic congestion. Tolls are paid electronically through transponders or toll-by-plate technology at AET gantries.