2013-08-30 / In the Know

In the Know

System assists in emergencies
By B. Michael Thurlow Special contributor

Now that the Dunstan intersection improvements are complete I wanted to explain one of the key components of the project that helps emergency vehicles quickly and efficiently respond to calls through that and other intersections around town.

The key is the town’s traffic pre-emption system. I’m sure many of you have noticed the small red strobe lights that sit on top of various traffic signal mast arms at all the major intersections in town.

Those are indicator lights that let the public and responding emergency apparatus know that the traffic pre-emption system has been activated.

Pre-emption systems are activated by police cruisers, ambulances, and fire apparatus as they approach the intersection.

A receiver on the mast arm notifies the traffic signal controller that an emergency vehicle is approaching.

The controller turns the signals yellow, then red in all directions except the one the emergency vehicle is approaching from, giving that approach a green light to help clear the traffic at the intersection and to legally allow cars to proceed through an intersection to help clear a path for first responders.

Before the advent of these systems first responders had little choice when approaching an intersection that had a red light but to move over the yellow line into oncoming traffic to navigate around grid-locked traffic that had no place to yield.

Now the systems work so well that most of the time the lights have changed to green in the direction of travel of the emergency vehicle by the time it gets to the intersection.

That means it can remain in the normal travel lane and go with the flow of traffic that is much safer for everyone.

This system becomes extremely important at the newer intersections such as Dunstan because modern traffic designers love to use raised islands for aesthetics and to slow and channel traffic.

Because the Dunstan intersection is actually three separate intersections all in one, it is nearly impossible to respond through there when traffic is heavy without the aid of the pre-emption system.

Traffic is simply gridlocked and has no way to yield to the approaching emergency vehicles, nor does it give the first responders the flexibility to move around traffic and into an oncoming lane when necessary due to the raised islands.

State law requires all drivers to pull as far to the right as possible and come to a complete stop when emergency apparatus is approaching.

In most cases that is the proper and correct thing to do. But when you are stuck at a major intersection (particularly one with raised islands such as Dunstan), and you don’t have room to pull out of the way, then it is permissible, once the preemption system gives you the green light, to continue through the intersection either straight or from a turn lane in an effort to clear the intersection before pulling over to yield for the emergency vehicle. That way you clear the intersection prior to the arrival of the apparatus and leave an open travel lane for them to proceed.

Shortly after the emergency vehicles pass the traffic signals will return to their normal cycle and the red strobe lights will stop flashing.

One additional thing to be cautious about is, apparatus sometimes responds from different directions so even though you saw one vehicle go through, there may be others coming from a different direction.

Always use caution and never go through any red signal light.

Please also remember summer is coming to an end and school is back in session so don’t forget to yield to school buses when the lights are flashing as they pick up and discharge students.

Also make sure to obey the speed limits, particularly in the school zones.

There are few things more traumatic than responding to a crash involving young children.

If you have any questions about this article or any fire department issue you may contact me at mthurl@ ci.scarborough.me.us or 730-4201. B. Michael Thurlow is fire chief for Scarborough.

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