Selective vehicle detection was the name of a bus priority system used by London Buses to allow traffic signals to selectively favour buses' movement through intersection by changing traffic light sequences and timings as buses approach.
Following a successful large-scale trial in 1987, London Transport began introducing selective vehicle detection to shorten red lights or extend green lights in the 1990s.[1] This delivered journey time savings, as well as increased service reliability and reduced costs, as a smaller number of vehicles were required to deliver the same frequency.[2] For example, it was estimated that route 15 could have a journey time 4 minutes shorter, due to the number of selective vehicle detection points passed.[2] The system worked using 'bus detectors' either mounted on lampposts by the side of the road or ground loops, which detect transmission made by transmitters aboard buses.[3]
Selective vehicle detection was replaced by the iBus system in the late 2000s which tracks all London's buses, allowing passengers to be provided with audio-visual announcements and improved information on bus arrivals, as well as triggering bus priority at traffic lights.[3][4] iBus uses the Global Positioning System instead of physical roadside equipment.[3][4] All buses in London were fitted with the iBus system by 2009.[5]
