Traffic Signals

Traffic Signals

When traffic volumes increase beyond the capacity of an all-way stop sign, it may be necessary to install a traffic signal. The criteria for installing traffic signals are based on:

  • vehicle and pedestrian volume,
  • delays to side street motorists and pedestrians, and
  • collision history at the intersection.

A properly timed traffic signal can significantly increase the traffic through an intersection and improve safety for pedestrians and vehicles.

Traffic signals don't always prevent collisions and don't always help traffic control. Where traffic signals are installed without justification, motorists see them as unnecessary, resulting in non-compliance to traffic laws. The decision to install signals must be carefully considered.

For more information on traffic signals visit the Ministry of Transportation’s website.

Common traffic signal questions

Left Turn Phasing (Green left turn arrow)

It is sometimes necessary to install left turn phasing at certain locations. The requirements for adding left turn phasing depend on:

  • vehicle volume
  • number of left turns
  • excessive delays
  • history of collisions at the intersection
  • intersection geometry

Sometimes introducing left turn phasing reduces the amount of green time available for all other traffic and can interrupt traffic flow so it must be carefully considered.

Pedestrian signals and crossing times

Traffic light timing

Some traffic signals operate with fixed timing; however, vehicle detectors are used at many intersections to assign the right-of-way, so timing will vary, based on changing traffic demands.  Most vehicle detectors are loops of wire imbedded in the pavement that sense metal and signal the presence of vehicles.  The City also uses video and thermal cameras to detect the presence of vehicles.

Traffic light pre-emption

Trains and some fire trucks are given priority at traffic signals.  When they approach an intersection, the signals transfer control to a special signal operation called pre-emption.  In pre-emption, the traffic controller provides a green signal for the emergency vehicle, or prevents vehicles from crossing the railway tracks.

Traffic lights on side streets

Many traffic signals assign green light time to side streets based on the traffic volume.  If all vehicles on the side street get through the green light before the time is reached, the signal will change to give more time to the main street to improve traffic flow.

At actuated traffic signals, side streets only get a green light if a vehicle is detected or someone pushes a pedestrian button. 

In a coordinated system, the green light for the side street might be delayed to keep the main street traffic flowing.