This article describes the Pedestrian Crosswalk Warning System, also known as the Smart Crosswalk, which has been developed by the American company LightGuard Systems, and uses Hewlett-Packard light-emitting diodes (LEDs). The aim of the system is to warn drivers, approaching a pedestrian crossing, that the crossing is occupied by pedestrians; such a warning is very valuable, as pedestrians are often almost invisible at night or even in bad daylight weather conditions. At a typical crossing, amber LED modules are permanently embedded into the street surface along each side of the crossing facing oncoming traffic. The beam of the LED is set at about 8° to provide visibility to motorists up to about 500m from the crossing. Automatic bollards at each end of the crossing activate the system only when a pedestrian steps onto the crossing. After deciding that it is safe to cross, the pedestrian moves forward, and breaks an infrared signal passing between two bollards, to activate the LEDs; the LEDs continue to flash long enough to allow the pedestrian to cross safely. The system gives drivers at up to 45mph enough time to slow down and if necessary, stop. Independent tests show that drivers accept this system. Across a two-lane street, it costs under US$20,000, compared with about US$100,000 for a signalised pedestrian crossing.
Samenvatting