Changing traffic signals

Question of the Month: (January 2011)

"I have read and heard people say that a person can make a traffic signal change from red to green by flashing their headlamps a certain way. Is this true?"

What you are most likely referring to is the ability to change a red light to green if that signal is equipped with what is known as a "traffic signal preemption system." Opticom from the 3M Company, is the brand of preemption system used throughout Kootenai County. This system is programmed to allow emergency vehicles equipped with emitters to force a green traffic light in their direction of travel, making for a faster and safer response to a call.

The emergency responder can switch on the Opticom transmitter located in their vehicle which then emits a light or infrared signal programmed to flash between 600 and 900 times a minute. The Opticom receiver, mounted on the same cross bars which support the signal lights, picks up the correct frequency from the vehicle and changes the lights appropriately: green in the direction of travel and red for all others. Those turning red will briefly turn yellow first, allowing pedestrians and drivers in or near the intersection to safely proceed.

To alert the emergency vehicle driver that the signal has been preempted and will remain green until they are safely through the intersection, a spot light mounted next to the receiver, and facing the oncoming emergency vehicle, will illuminate brightly.

After turning green, all signals are held while the emitter and receiver are in "contact." According to Gordon Dobler, the City Engineer for Coeur d'Alene, within seconds of the vehicle passing through the intersection and the signal lost, the traffic light controlling the busiest lane of travel will turn green and a normal pattern of signally will resume.

As a driver, if you notice the confirmation spotlight illuminated, be aware that an emergency vehicle is about to go through the same intersection in the same direction as you. Visually locate them while making sure to clear the intersection and safely pull over to the right and stop or slow down to allow them to pass.

So, to answer the question, because the signal is programmed at a frequency much faster than is possible to replicate manually, it is virtually impossible to change a signal by flashing one's headlights.

Lt. John Ward of Kootenai County Fire & Rescue (KCFR), in charge of the fire district's radio and communication systems, explained that Post Falls Fire first began equipping its signals and emergency vehicles with traffic signal preemption systems in the early to mid-1990s. Soon after, the installation of the preemptive system was required for all future traffic signals and was included in the overall expense. The city of Coeur d'Alene began including traffic signal preemptive technology in all its new signals beginning in 1994, according to Gordon Dobler. KCFR, Northern Lakes Fire, Coeur d'Alene Fire, Kootenai County Emergency Medical Services System (which provides the ambulance services throughout Kootenai County), and Coeur d'Alene police all currently use the preemption system. Idaho State Police, Post Falls police and the Kootenai County Sheriff Department do not use Opticom at this time, along with other smaller communities with few, if any, traffic signals.

I spoke with personnel from the Northern Lakes and Timberlake Fire Districts who stated that several traffic signals along major roadways have the signals installed. Along Highway 95, traffic signal preemption technology is installed at the intersections of Highway 53, Hayden Avenue, Garwood and Ohio Match Road. The signal at Highway 41 and Boekel Road also allows for Opticom to be used to preempt the signal.

According to both Ward and Dobler, the importance of the Opticom system in heavily traveled areas is two-fold. The first point shared by both was that it provides for a much faster response to those requiring assistance from responders needing to travel through intersections controlled by traffic signals.

The second and overriding factor is the increased safety for responders and citizens alike. When emergency vehicles enter into an intersection with a red signal, often times the driver must travel in the opposing traffic lane to get around the log jam of cars, creating a potentially dangerous situation. By changing the light to green and drivers pulling through the intersection and safely pulling off to the right side of the road, the emergency responders can remain in their lane of travel and continue on the call with minimal delay.

With thousands and thousands of calls each year, emergency responders greatly appreciate the experienced drivers who recognize the need to clear intersections and pull over so emergency vehicles can pass safely. This, along with the use of traffic signal preemptive devices can greatly reduce the risk of collisions in the busiest of intersections within Kootenai County.

Stay safe out there!

Jim Lyon is the public education specialist/information officer with Kootenai County Fire and Rescue (KCFR). If you have a question about emergency services in your area, please submit your question to "Ask Firefighter Jim" at askffjim@kootenaifire.com. Visit our Web page at www.kootenaifire.com for additional information and to read archives of previously answered questions under the link, "Prevention."

Did you know...

Occasionally drivers pulled over to allow an emergency vehicle running "code" to go through an intersection see them slow down and turn off their lights and sirens as soon as they pass through. I assure you this was not done to avoid waiting for the light on a non-emergency call. Most likely, they were "downgraded" or canceled which means that the first person who arrived to the call they are responding to has determined that running code was unnecessary and requested them to slow down or cancel. This again, is done for the safety of all those concerned.