Traffic Safety
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Traffic Safety |
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Departments >Traffic Safety > Safety Articles | |||||||||||||||||||||||||||
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Traffic
& Pedestrian Safety News Articles FIRE TRUCKS AND GREEN LIGHTS Did you ever notice that when a fire truck travels down County Road 42 with lights flashing and siren wailing that it always seems to get a green light at those many traffic signals? Coincidence? No, it's part of a citywide traffic signal preemption system Apple Valley has installed. If you have ever watched an Apple Valley fire truck, police vehicle or an ALF ambulance responding to an emergency, you may have seen a rapidly flashing bright white light among the many other red and blue flashing lights on the vehicle. This is the "emitter" part of the preemption package. It flashes at a precise rapid rate and has a specific light composition, unlike the other lights. On all traffic signals in Apple Valley, there are "preemption detectors" facing each street approach that look for the light from the emitter. The detector system can sense the specific light rate and composition from as far away as a quarter-mile. Once the light signal is received, a special traffic signal cycle sequence is started. Within certain guidelines, the green lights being shown, if not for the direction of the approaching emergency vehicle, are terminated with a yellow clearance light and then red. Following guidelines, the traffic signal controller then goes through a sequence to get a green light to the approaching emergency vehicle as soon as possible. While green lights may be shortened, no vehicle or pedestrian clearance period ever is. The light will stay green for the emergency vehicle as long as the detector senses the special light and for a brief period after detection. What if two emergency vehicles come from different directions? It's first come, first served! To alert emergency vehicle drivers to this possibility, a white floodlight is mounted on each traffic signal for each approach. When the special light is sensed coming from one direction, the floodlight is lit and remains steady. The floodlights for all other approaches will begin flashing. These floodlights also assist all motorists. If you see the flashing white light on the signal, watch for emergency vehicles coming from another direction. If you see a steady white light, check your rear view mirror and prepare to get out of the way. If you think it would be nice to have one of those emitters on your vehicle to get you to work quicker, forget it. The law specifically limits the use to official emergency vehicles responding to an emergency. Even emergency vehicles cannot use them except in response, meaning they will sit in traffic next to you on their return trip. Most traffic signal controllers record the preemption use and police, fire, and ambulance users must record their use of the systems. And the emitter units are only sold for official use. Statistics have shown the traffic signal preemption system has not only
reduced accidents but also response time by providing green lights to
responding emergency vehicles. This is just one more way technology has
made life safer for Apple Valley residents. Content updated on: 03-May-2004
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