In different locations, outside of the downtown area, the timing of traffic signals can vary. Signal timing allows a driver on a route to get a series of green lights along that route. A cluster of traffic signals that turn green in sequence is called a coordinated corridor.
Coordinated corridors are used along major roadways where the majority of traffic is travelling in the same direction such as on Macleod Trail. Coordination is also used when there are many traffic signals in close proximity to each other.
In the downtown area, the traffic signals are coordinated in a pre-timed manner. This indicates that the signal timings do not vary based on traffic and pedestrians. The traffic signals are programmed with traffic conditions based on regular occurrence at different times throughout the day. This allows for a higher level of pedestrian service and more accuracy of predictable outcomes for corridors.
Outside of the downtown area, pedestrian and vehicle detection allows the coordinated road to benefit from receiving more green time where there is low cross traffic. However, the disadvantage is that there is more variability causing the series of green lights to vary at different intersections.
The majority of traffic signals outside of the downtown area will have the timing of the green signal vary based on the traffic and pedestrian flow at the different intersections.
The traffic signals in Calgary with the exception of the downtown area use either video detection or ground based sensors. Both types of detection systems enable the traffic signal to know when a vehicle has arrived at the intersection.