Vanessa is making her way downtown, and as she crosses over 105 Street, she wonders why the little walking person switches to a flashing hand so quickly. A fellow pedestrian turns around and returns to the curb when they notice the flashing hand.
Hector is waiting at a red light on Calgary Trail. Are these signals synchronized? Those smart traffic lights he heard about on social media would certainly get him home quicker.
Janis Chow helps the City in its careful balancing act that ensures Vanessa and Hector both get where they’re going. Chow is the City of Edmonton’s Traffic and Intelligent Transportation Systems specialist and General Supervisor of Signals and Streetlighting. She oversees who gets green, yellow and red lights and arrows, who gets the walk signs and the flashing hands…when…and for how long.
It’s a colourful job.
She knows that in Vanessa’s case, the timing of the crosswalk is based on the standard national walking speed so that most people can be certain they’ll make it across so long as they begin crossing before the flashing hand appears.
And to answer Hector’s question, the lights are synchronized on Calgary Trail to optimize flow at peak hours. Chow knows a thing or two about the smart signal pilot project, so she has an answer to his smart traffic light idea too.
Vanessa and Hector’s questions are very relevant to the work Chow and her team do to manage the over 1100 traffic signals in our city.
“The one question I don’t get as much is: What does it take to run an entire traffic signal operation, for pedestrians, cyclists and drivers, for all Edmontonians, no matter how they move?” she smiled.
“And that’s okay. That’s our team’s job. But we do want people to know that keeping all road users moving safely and efficiently is what is always top of mind for us.”
The City asked for any questions about traffic signals on social media. They came in from all directions. Here you will find Janis’ answers to those questions, organized into topics:
• Timing, flow
• Late night signals
• People walking, biking, rolling
• Smart traffic signals
• Some specific intersections
Q: Does the City sync the lights so that the traffic flows smoothly and doesn’t cause gridlock during peak times?
A: Yes. The City of Edmonton designs traffic lights for the best traffic flow along any corridor in the city. The traffic signals are designed to provide green lights based on the posted speed limit, and to prevent, wherever possible, drivers from getting two red lights in a row in any direction.
Q: How does the City decide the timing of traffic signals at different times of day? How easy is it to change the timing between seasons (if icy crossings take longer)?
A: The length of time a traffic signal stays green is determined by a number of factors such as the number of lanes, driver sightlines and volume of vehicles moving through the intersection. Different timing plans are operated throughout the day to account for changes in traffic volume. For example, 97 Street north of the river is timed in the morning peak for inbound traffic and in the afternoon peak for outbound traffic.
The City of Edmonton does not change the timings for winter, as timings are based on typical road conditions, including winter driving conditions.
Q: Does the traffic department monitor traffic patterns and continually adjust light timing? Or, how is it done? Once a year? Bi-annually?
A: The City manages more than 1,100 traffic signals. Engineers perform assessments and review the signal timing designs when parts of the network change. For example, with the Yellowhead Freeway Conversion project, you will see many of the traffic signals redesigned to accommodate the new traffic patterns. When new signals are installed on a corridor, an analysis is done to see the impact to other intersections. The goal is to make sure there are minimal disruptions. If adjustments to the timings are required, they will be made at that time.
Q: What determines the height of traffic signals?
A: The City of Edmonton follows national guidelines when designing traffic signals. The driver’s vision and view of the traffic signals are a large consideration.
Q: Why are some yellow lights slow, but on red light camera intersections they are very quick?
A: The yellow lights at all traffic signals are based on the posted speed limit. They are not adjusted or timed differently at red light camera intersections. The focus is on the speed limit to ensure the safest timing.
Q: In other areas of the world, some traffic signals have the yellow light come on before the signal turns green to tell waiting traffic that they are about to start moving. I thought it was a useful feature, especially when so many are busy on their phones when they should be paying attention to signals. Why don’t we have this yellow light feature here?
A: There are many variations of traffic signals all around the world. The operation described is not used in North America, and there are ongoing studies on the effectiveness. Distracted driving is a problem that is not addressed by adjusting traffic signals.
Late night signals
Q: I would like to know why we need a “no left on double red light” at 2:00 AM on a weekday when there’s absolutely no traffic anywhere?
A: This is a good question. These left-turn signal restrictions are there, above all, for safety. They exist at intersections with double left-turn lanes, high rates of left-turning collisions or where turning vehicles cross LRT tracks. Even when there are low traffic volumes overnight, like at 2:00 AM, the possibility of vehicles in both turning lanes exists. At those moments it might appear like you are made to stop for absolutely no reason, but your safety is still the reason.
Q: Why does Edmonton not use blinking yellow/red lights during off-hours in low-traffic intersections?
A: The majority of traffic signals in the city are not put on flash at night. A flashing traffic signal provides no pedestrian protection. Signal timings are adjusted during low-volume times to reduce delays.
Cameras and intersection safety devices
Q: Why is Edmonton so far behind in real-time traffic monitoring for traffic signal timing? We can have speed/red light cameras at every intersection, but no cameras for traffic timing/flow?
A: A number of detection systems are used in the City of Edmonton. The City aims to ensure that the type of detection chosen will perform consistently and be cost effective to install, operate and maintain. Inductive loops installed under the pavement are not always visible to drivers. Other types of detection used in the City include video camera detection, thermal detection, microwave and radar systems.
In this context, detection cameras are used for timing and flow of traffic signals. Red light and speed violations are monitored by our colleagues in Safe Mobility using different systems called Intersection Safety Devices.
Q: I think more traffic lights should have cameras on them. Is the City replacing all of the old poles with the new ones?
A: Great question. The City of Edmonton will gradually replace the older poles as part of the ongoing replacement program, and contemporary technologies are a part of that upgrade.
People walking, biking, rolling
Q: Why does one have to press the walk button to get the walk signal? In a city that promotes walking, shouldn’t the walk signals come on automatically when the light turns green?
A: Very good question. Some intersections have pedestrian buttons where pedestrian volumes are low. This helps the signalized intersections to operate efficiently for all road users (pedestrians and vehicle traffic). For example, when there are vehicles on the less-busy intersecting roadway without pedestrians, the main street traffic is stopped for a shorter time. If there are pedestrians crossing, then a longer time is given for the crossing and the main street traffic is stopped longer in order to provide a safe crossing time for pedestrians.
In general, the pedestrian walk signals in areas with high pedestrian volumes, such as Whyte Avenue and downtown Edmonton, operate automatically without a push button. As a response to the pandemic, the City also automated the push-button operation at 56 intersections. Controlled crosswalks in high pedestrian areas and around hospitals were automated to help reduce the potential for transmission of COVID-19.
Q: Can anything be done about pedestrian countdown timers that change to “walk” instead of “don’t walk/red light” when they hit zero? As a car driver approaching one of these in their last seconds, I slow down anticipating the light to change, but this is not safe if the light is staying green.
A: Pedestrian countdown timers are programmed and provided for pedestrians, not vehicles. Drivers should use the traffic signals, where the amber signal indicates the impending signal change to red.
Q: Why do we have so few advance turning phases at dangerous intersections on major Edmonton roadways? Example: turning east onto 111 Avenue off 97 Street southbound and turning west onto 107 Avenue from 95 Street northbound.
A: Intersections are assessed and left-turn signals are prioritized city-wide and installed based on safety and operational review and available budget.
Q: Why is there a flashing red hand that then changes to a walk sign at multiple intersections?
A: The “walk” light and “flashing red hand” are indications designed and provided for pedestrians. Traffic signals operate this way to provide efficiency for vehicles travelling on the main roadway when there are no pedestrians or vehicles present on the cross street.
Q: From having to bolt across the street to make it before the light changes, to determining what speed people are actually travelling, regardless of what is posted, as a visually impaired person, I often wonder if the City does any traffic studies. The Valley Line South LRT has dramatically affected traffic flow.
A: Pedestrian safety will always be a priority, especially as the city changes and grows. That’s why pedestrian signal timings are calculated and designed using a standard national walking speed. The timings are designed specifically for each intersection and account for walk time to safely cross each roadway.
Smart traffic signals
Q: Since smart traffic light technology has been around since 1973, when are we going to be installing some of them?
A: We have learned there is potential and lots to learn about this technology. This work will be considered as part of the City’s Smart Transportation Action Plan.
Over the last several decades, the City of Edmonton has used various smart traffic signal technologies. This includes technology that detects pedestrians and vehicles and determines signal timings based on the demand.
The majority of traffic signals in the City currently use detection technology such as video cameras or inductive loops under the pavement to adjust signal timings.
Q: Smart streetlight controls were supposed to be tested back in July 2017. Back then, they were using low carbon as a reason to install them. Then, they were supposed to be tested in October 2019. St. Albert was testing them out in December 2018. According to another source, Edmonton was supposed to be testing them out in June 2018. Is there a plan to do this?
A: The adaptive traffic signal system was trialed from October 2019 to January 2020 on 101 Street between 103A Avenue to 111 Avenue. Here’s a story from the CBC about the pilot project. While the pilot study did not produce improvements to traffic, the City continues to look at emerging technologies and how their application can be used to improve traffic flow on Edmonton’s road network.
Some specific intersections you asked about
Q: What’s with the lights on the Whitemud off-ramp to 91 Street?
A: Recently, the City of Edmonton implemented dual westbound-right turn lanes in order to accommodate the volume of vehicles making this turn. The traffic signals were revised for the dual right turn lanes as a way to increase safety and minimize potential collisions.
Q: Why is the left turn light on 95 Avenue and 87 Avenue so quick on 170 Street?
A: The intersection traffic signal timings at 95 Avenue and 170 Street as well as 87 Avenue to 170 Street are optimized to provide balanced opportunity for all traffic movements to move through the intersection. This means that the length of the green light is based on the number of vehicles in each direction and any delays are equally distributed to all movements, including the left turns.
Q: Why is the light at the Cross Cancer Institute and 82 Avenue/Groat Road not on a sensor?
A: We appreciate you asking this question. The traffic signal at University Avenue and 115 Street is designed to operate with sensors to detect traffic and pedestrians crossing University Avenue. However, as part of the response to the COVID-19 pandemic, the City adjusted a number of signals to serve pedestrian movements without requiring pedestrians to press a push button. This intersection was included in this initiative.
Q: I used to go all the way up and down (north and south) 111 Street and 109 Street for work. I had to stop at most of the lights, regardless of speed. Does the City try to coordinate the lights?
A: We hear this question a lot. Throughout the City, traffic signals are generally coordinated in order to minimize delays or the number of stops through adjacent intersections.
Along 111 Street, the signals are not coordinated due to the frequent interruptions and priority given to the LRT. However, most intersections have sensors to detect vehicles and will service traffic movements only when there are vehicles present.
Q: How are the traffic signals at the intersection of St. Albert Trail and Yellowhead Trail going to improve traffic flow after the intersections at 149 Street and 142 Streets are scrapped?
A: The timings at Yellowhead Trail-St. Albert Trail will be designed based on the proposed roadway changes and projected volumes entering the intersection. Once the roadway changes are completed, the traffic signals will be monitored on an ongoing basis until the new traffic patterns are established.
Q: Why are traffic signals not adjusted when construction closes down roads? A five-month closure of a road in both directions on 109 Street left vehicles idling at red lights for no reason (and much longer than pedestrians require).
A: The City reviews each closure and traffic disruption to determine whether signal timing adjustments are needed. A number of factors are considered, including duration of the disruption, displaced traffic volumes, pedestrian accommodation, turn restrictions and overall impact of the disruption. Pedestrian crossings accommodate the minimum time required for a pedestrian to safely complete the crossing and cannot be reduced.
Thanks for reading and thanks for moving safely in the city, keeping in mind that the City balances the safety and the efficiency of all road users, no matter how they move.
For more information on traffic signals, visit edmonton.ca.