The article describes an application of passive infrared vehicle detectors to intersection control. These detectors examine the thermal radiation emitted by targets, and can offer lane discrimination at long range, due to their precise optical definition, but their response is relatively slow. They were originally used to detect moving vehicles, but they can also be used for presence detection, by multiplying detection channels and using sophisticated digital signal processing. The multichannel presence detector, IR 224, can detect vehicles entering an area, extending for several meters in front of the stop line of a signal-controlled intersection; this enables a green phase call or request signal to be given to the controller. Green phases can be extended with the aid of a simple dynamic vehicle detector, IR 200, where cycle timing is less critical, or a more sophisticated detector, IR 210, for more accurate timing. Static and dynamic detectors can be combined for a single lane with one pair of detectors. The IR 222 is a detector, suitable for count and presence information, which can be mounted on a roadside structure or gantry at a given distance from a traffic signal.
Abstract