Information & Resources - Traffic Control
Pedestrian Signals
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Left Turn Signals
The following summarizes a
frequent request: "I would like to suggest a left-turn signal be installed
at an intersection that I use regularly !"
All requests for
left-turn arrows will be (or have been) considered. Many of these
suggested locations have been examined previously. In most cases, if it
was warranted in the past, the left-turn signal was already installed. The
staff at Traffic Signals will be able to tell you very quickly the reasons
why left-turn signals are (or are not) an appropriate
solution.
In general, left-turn signals are provided at intersections where:
- A historically high volume of traffic makes the left-turn movement when the opposing through movement is also high; or
- where more than one lane is allowed to make the left-turn movement; or
- where high-speed traffic travels towards the intersection on two (or more) controlled approaches; or
- where views of approaching traffic are obstructed by poor intersection geometries; or
- where a combination of high-volume and high-speed traffic creates the potential for serious collisions
Recent advances in Traffic
Control technologies have permitted the installation of Part-time
left-turn signal operations. These part-time operations may
occur:
- when traffic is "sensed" in a left-turn storage lane; or
- when traffic in a shared left-turn and through lane queues back past a sensor in the road; or
A
left-turn movement is added
at an intersection when traffic flow analysis reveals that adding a left-turn
display will have a negligible effect on other traffic using the intersection.
Adding a left-turn movement is generally not advised if it
negatively affects traffic flows through (or from) adjacent intersections.
Other factors considered in the analysis include an examination of
alternative routing through other intersections in the
If there is a recognized problem with a left-turn
movement at a signalized intersection, other adjustments can be made to
the signals to try to accommodate the left-turning traffic without
installing a left-turn display. These include:
- modifying (lengthening the GREEN display interval to better accommodate the left-turning traffic); and / or
- adjusting the timing relationship between intersections (the "Offset") to stagger the arrival pattern of the opposing through traffic flow; and / or
- accommodating the left-turning traffic at an intersection "before" the one where the problem exists.
If you still have questions or comments regarding left-turn signals, please call 311.
Last update: 01.11.2011
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