It seems everyone has a beef about traffic lights, and St. Albert's transportation co-ordinator Dean Schick has heard all the criticisms.
Schick is the city's go-to guy for traffic light issues.
"Everyone who drives is a transportation engineer," Schick grins.
Schick has an encyclopaedic knowledge of the city's intersections. He can cite from memory the order of intersections, their lane configurations and their timing sequences. But what he can't do is synchronize the lights to please everybody.
"As much as we would like to say that we can provide co-ordination for all directions of movement at all times, it cannot be done," Schick said.
The most common traffic light complaints the transportation department receives are wait times on side streets, traffic light co-ordination and a lack of left-turn arrows.
Schick and his boss, manager of transportation and urban development Brian Hartman, have answers to those questions, but understanding those answers requires an understanding of the system.
The system
St. Albert adheres to industry best practices as defined by the International Municipal Signal Association.
The city has 52 intersections that are "fully signalized."
These signals operate on cycle lengths, which is the time it takes for a signal to go from green to amber to red and back to green for a particular direction of travel. All traffic movements, such as vehicles, left turns and pedestrians, must be allowed a portion of the total cycle length time. Put another way, if Schick wants to increase the green time for a particular direction, he has to take it away from another direction.
To co-ordinate signals along a roadway corridor, the cycle lengths for each intersection must be the same, Schick says.
In St. Albert, the cycle lengths are typically 110 to 120 seconds during the peak periods, 100 seconds during off-peak periods and 75 seconds at night. This keeps the flow of traffic moving efficiently and safely, Schick says.
For any given intersection, one direction of travel will be deemed the priority while the other will be subordinate. St. Albert Trail is the priority along its entire length. During weekday mornings, the timings are set to prioritize flow southbound into Edmonton. This is reversed during the afternoon commute time.
On weekends, the signals along the trail are more balanced to make crossing easier and facilitate those visiting the farmers' market or doing other commerce, Schick said.
Gadgets
Intersections with traffic lights have devices to detect the presence of a vehicle. The standard detection device is an electromagnetic loop in the pavement. But these aren't always reliable, leading to the implementation of other devices like microwave detectors and the latest in technology — video.
Detection allows the presence of vehicles to alter the signal sequences. For example, a vehicle that appears in a left-turn lane can trigger a priority arrow that otherwise wouldn't appear. Or a vehicle arriving when the light is green can extend the green time by a few seconds.
Video cameras are the best available detection technology as they can cover a wider area and can also perform other functions like traffic counts and vehicle classifications, which helps Schick design the signal timings appropriately.
It costs about $30,000 to equip an intersection with video for all directions. In recent months, the city has increased the number of intersections equipped with video detection from three to 26.
"The cameras are not recording any information," Schick said. "They are just really a live video stream that the controllers use to activate the signals."
Drill sergeant
St. Albert currently has a pair of master controllers to better co-ordinate signals. One of these controllers co-ordinates the lights along St. Albert Trail while the other co-ordinates lights on Boudreau Road/Giroux Road.
Within these networks, each intersection has its own individual controller, just like any other set of traffic lights, but these controllers all communicate via wireless radio signal with the master controller to ensure their time of day settings are in synch and that they're running the correct program.
"Think of [the master controller] as a drill sergeant keeping everybody in line," Hartman said.
Unlike larger cities like Edmonton, St. Albert doesn't have a master control centre with a bank of screens where a technician can remotely monitor intersections and adjust the signal timings.
To tap into St. Albert's system, Schick must travel to an intersection and log in with his laptop.
Answers
The answers to some of the most common traffic light complaints can be found on a new section of the city website at www.stalbert.ca/traffic-signal-timings-and-coordination-faq.
On the co-ordination issue, the simple answer is that it's impossible to provide free flowing traffic in all four directions at once, Schick said, because each intersection is part of a network. That's why engineers have to set priorities.
"I can guarantee you, at any given time, I'm only making 50 per cent happy, at best, at an intersection," Schick said.
Regarding left-hand turn arrows: these are only activated when there's sufficient demand to justify taking away green time for through traffic.
"There's this public perception that, if you have it installed already, why not hit the switch, put the power to it and give me a left turn advance?" Hartman said. "Think about it. If everybody gets a left turn advance, what about the people going straight through?"
Case study
For the answer to the side street complaint, let's take the intersection of Arlington Drive and Hebert Road as a case study.
Area residents who've been commuting through that intersection regularly over the years may have noticed a change a while back. It used to be that approaching Hebert from Arlington would bring an instant green light, something those drivers liked, Hartman said.
However, traffic that proceeded west toward St. Albert Trail would then hit a succession of red lights before reaching St. Albert Trail. So he and Schick decided a better approach would be to stop these vehicles at Arlington and Hebert, have them "queue up like cows," then release them in a group. They set the wait time at 65 seconds.
The change brought a flood of complaints.
"When you're used to getting instant gratification, 65 seconds seems like forever," Hartman admitted.
However, his department timed the signal so that, after having waited, the released herd of cows would get all green lights on its way to the trail, thereby saving time overall.
"We said, 'Give us 65 seconds and we'll guarantee you [all greens afterward].' We never got a call back from any of those people," Hartman said.
Universal
The principle behind side street access onto busy streets is that the lower priority vehicles will trigger a light change, but only when the next available sequence comes around. It's like waiting for a chairlift at a ski hill, said Alex Mawanay, senior traffic engineer for the City of Edmonton.
"You've got to wait until the next time the chairlift becomes available with your name on it, because otherwise we're screwing up the co-ordination on the main street," Mawanay said.
Edmonton has four engineers and one technician who design signal timings. That city receives complaints that are very similar to those that dominate in St. Albert: lack of co-ordination, lack of left-turn signals and insufficient time for left turns or through traffic, Mawanay said.
"Perfect co-ordination does not work in the real world and that's what people's expectations are," he said. "It doesn't matter what city you go to, all the engineers will tell you the same thing. Co-ordination isn't as simple as it looks."
