Are Calgary's Traffic Signals Optimized?

It all started with a simple question, “Why doesn’t the City have more flashing traffic lights late at night when there is little traffic?”

Recently, I had an opportunity to chat with a seasoned traffic engineer (who does not work for the City of Calgary and wishes to remain anonymous) and ask if s/he thought Calgary was doing a good job of optimizing our city’s 1,034 traffic lights.

While sitting in traffic, we all question the wisdom of traffic light management - in our own city and when visiting other cities.

This third party expert’s comment are enlightening.  Read on.

At 9:30 on a Monday evening the traffic at the corner of 19th St. and 5th Ave. NW is sparse, perhaps flashing red and yellow lights would be more environmentally friendly? 

Rush Hour Priority

“The City spends a lot of time and effort developing signal timing plans to optimize traffic flows on major roadways. These efforts are noticed when you catch every green light (I am not sure this ever really happens, but we will pretend it does) as you head down a major road in rush hour.

Creating an optimal traffic light signals program for major roads is a complicated process at the best of time. It gets very complex with variables like winter weather, accidents and construction. The needs for side street traffic, pedestrian and cyclist movement add another level of variables. 

On the whole, the City of Calgary does a very good job at optimizing the major roads during the morning and afternoon rush hours.”

Off-Peak Period Needs Improvement

“Where Calgary’s system is less effective is during off-peak periods and weekends. Often, the signal timing plans and progression models are less precise during those periods due in part to City resources being focused on making the busy rush hour periods work really well. There is only so much money to go around and to acquire all the necessary traffic count data. To utilize the necessary staff time to optimize signals in the off-peak periods more effectively would be a substantial undertaking.”

Everyday Tourist Research: It is true that while everyone focuses on the rush hours (aka peak hour traffic), in fact midday and evening traffic (3.3 million trips) is more than both rush hours combined (2.6 million trips). So it would make sense to optimize lights for off-peak period also. City doesn’t have current figures for weekend traffic. (Source: City of Calgary)
City of Calgary, 2015 Vehicular Trips/Day

City of Calgary, 2015 Vehicular Trips/Day

Benefits of traffic light optimization

“There are two major impacts of improved traffic light management – time and emissions. Time is significant because unnecessary idling at red lights lengthens the period that vehicles are on the road, which creates more congestion, which then could lead to a demand for more or larger roads to accommodate the congestion. Congestion also adds to driver stress levels and perhaps even road rage. Emissions are significant because the longer a car is operating, the more noxious fumes it is emitting into the air.”

Everyday Tourist Research: Using the Natural Resources Canada “Individual Idling Calculator,” if the average Calgary driver sits idling in traffic for 20 minutes a day (say 10 minutes each way for commuters), it costs the driver $150/year in gas alone and each car emits 450kg/year of greenhouse gas (GHG) into the atmosphere.
Given Calgary has 2.6 million trips per day during peak hours or about 1.3 million round trips (includes workers, school buses, transit, commercial vehicles) that adds up to a cost of $195 million/year and 595 million kg/year of GHG.  So even a 10% improvement (2 minutes) in traffic signal optimization would mean a cost savings of $20 million and 60 million kg/year less GHG emitted in rush hour alone.

“The City is spending a considerable amount of time and money on measures like cycle tracks to reduced emissions through reduced vehicle usage. That is excellent and should be continued, but we could also reduce emissions with improved off-peak and weekend traffic signal optimization.”

Red Light Rage

“Every driver stews when stopped at a signal for what appears to be no good reason. It’s late at night when no other traffic is anywhere to be seen, or during the middle of the day when the opposing flows clearly don’t need as much green time as they seem to be given.

The City does have an on-line opportunity for citizens to identify under-performing traffic signals. A driver stuck at the light that seems to be red for no reason should report it at City of Calgary Traffic Signals Link.

The City will then review it in the field to see if the traffic light needs to be tweaked in terms of cycle length, or could become a flash light at certain times of the day or perhaps earlier in the evening than is currently applied.  We need to work together to help the City optimize traffic lights.”

There were lots of times when there was no traffic at 19th St and 5th Ave SW at 9:30 on a Monday evening.  There area probably lots of secondary and tertiary intersections like this that could benefit from flashing lights during the over night period.

Last Word

Obviously, there is a need for resources to be set aside by the City to facilitate this.  Its takes time and horsepower to send staff out to look at hundreds of signals, many of which might have perfectly good reasons for operating the way they do and require no adjustments.

However, relatively small amount of effort could potentially produce a significant positive impact on Calgarians’ quality of life and our environment. It would also be a significant cost savings for businesses; especially given Calgary is a major distribution hub.

There are opportunities in traffic signal optimization to make a difference that could benefit everyone….not just drivers. And we can all play a role in identifying the biggest trouble spots.” 

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