Coordinated Traffic Signals

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Driving down Columbia Avenue in Castlegar, one cannot help but wonder if the Traffic Light Gods are conspiring against them. This morning driving from South to North while taking the girls for a treat at Tim Hortons I hit every red light from 24th Street to 15th Street. It seemed that just as I was approaching the lights, a single car pulling up to the side street stop line would actuate the signal controls, and I’d be stuck idling away. Now you might rightly say, “Why didn’t you turn off your engine Mr Greenie?”. Research has shown that at any stop longer than 10 seconds, you use less fuel stopping and restarting the car than letting it idle. Maybe it was my fury at the City having an anti-idling campaign, yet employing technology that made it almost mandatory to idle every couple of blocks as one car gracefully pulled out of the side street after a less than second wait.

Having grown up in Sydney, Australia, it seems that I was spoilt with the best traffic signal management system in the world. Called SCATS (links to pdf), the “Sydney Coordinated Adaptive Traffic System” is an urban traffic control system designed to dynamically adjust traffic signal phasing to real time conditions, gathering data from the loop detectors in the road and from human traffic controllers using video surveillance of the network. This isn’t just an Australian thing, the system has been installed in hundreds of cities across the world.

I’m not suggesting that the City of Castlegar needs to go to great expense in procuring the best system in the world, but the network is blessed with a relative simplicity with an almost uniform speed-limit of 50km/hr and no traffic lights off the North-South axis of Columbia Avenue which at almost all times holds the majority of traffic flow. It is almost guaranteed that a drive from one end to the other will be punctuated by traffic light stops at more intersections than not. I count a total of nine traffic signals in Castlegar, which will add about 5 minutes to the driving time, over a distance of 5.9km from 28th Street to the Library.

The US Department of Transportation states:

There are more than 330,000 traffic signals in the United States. It is estimated that over 75% of these signals could be improved by updating equipment or by simply adjusting and updating the timing plans. It is further estimated that poor traffic signal timing accounts for 5-10% of all traffic delay on highways or 295.8 million vehicle-hours of delay on major roadways alone. Traffic signal re-timing is one of the most cost effective ways to improve traffic flow and is one of the most basic strategies to help mitigate congestion. Optimizing traffic signals can produce benefit cost ratios as high as 40 to 1. The costs for retiming traffic signals generally range from around $500 to $3,000 per intersection.

In 2007 the National Transportation Operations Coalition prepared a report card of traffic signals in the US.

The report card shows how local jurisdictions such as cities, counties and states can reap large rewards, such as mitigating congestion and lessening fuel consumption, by making small changes in the way they manage and operate their traffic signal systems.

You can download the Executive Summary or the Technical Report.


Coordinating the traffic signals in Castlegar would potentially shave minutes of a trip from one end to the other, reducing idling, travel times, city worker time in vehicles, and intersection accidents, as well as some of the aggressive driving habits that partly result from frustrations with the system. I’m not sure what the cost of these adjustments would be, but there are tangible benefits to tweaking the system. In terms of long term sustainability, it is a small gesture, I’d rather focus on policies that reduce the number of vehicles on the road altogether – but while vehicles rule the road in the town, we should make every effort to maximize the efficiency of the system we have.


Published by Mike Thomas

Mike Thomas P.Eng. ENV SP, is the author of and Director of Engineering at the City of Revelstoke in the Interior of British Columbia, Canada.

2 replies on “Coordinated Traffic Signals”

  1. I, too, find it irksome having to stop at every stoplight along with all the other drivers, just to let one motorist into the main stream of traffic..

    IMO if a driver keeps to the speed limit, when the lights turn green that driver should be able to go right down Columbia Avenue with very few stops.

    If the driver goes even a little over the posted speed limit, then the driver should have to stop at every traffice light.

    My brother-in-law, Alex McKinnon, formerly of Castlegar, tells the story of when he was in Vancouver and was stopped by the police for shooting a red traffic light. On being asked where he lived, he said Castlegar. The cop then said, “Oh, you only have one traffice light there. I’ll let you off this time but be careful in furture”.
    That WAS some time ago.

  2. @Janice – it does take a bit of work to coordinate the lights, but it serves the community better than a system that seems, from my admittedly limited research, to delay through traffic at most lights.

    Great story re Alex!

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