How do the lights detect vehicles?
Vehicles can be detected in two ways. Often loop detectors are used and these are buried in the carriageway on the approach to the signals or crossing. Loop detectors sense when a large metallic object such as a car engine passes over them. Alternatively above ground detection mounted above the signals may be used which sense the movement of approaching vehicles. Pneumatic pads/sensors were used many years ago but their use has long since been made obsolete by loop detectors and above ground detection.
