Intersection - Signalise

Most crashes happen at intersections. Traffic signals are a way to stop conflicting flows of traffic entering the intersection at the same time and can reduce crash risk.

Signals can be set to change according to fixed times, or they can be activated according to traffic demands. It is also possible to link a network of signalised intersections together to provide control of the road network as a whole.

Some signals are controlled manually but often this results in cycle times being too long for maximum intersection capacity. This can cause long delays and driver frustration, which can lead to unsafe driving.

  • Can increase intersection capacity.
  • Can reduce certain types of crashes (especially right-angle crashes).
  • Can improve pedestrian and cyclist safety.
  • In countries with poor compliance with road rules, signalising an intersection may have no safety benefit and can reduce the capacity of an intersection.
  • Signals used at intersections with low traffic flows and fixed timings are likely to be disobeyed.
  • Well designed traffic signals will usually reduce total crashes but will sometimes increase specific crash types (e.g. rear-end crashes).
  • Traffic signals should not be used in high speed locations.
  • In urban areas it can be difficult to ensure that traffic signals are visible enough.
  • Before installing traffic signals, information on traffic volumes, pedestrian volumes, intersection approach speeds and previous crashes at the site should be carefully considered.
  • The introduction of traffic signals in a region could increase crashes unless all drivers know the meaning of the signals.
  • Traffic signals need continuous power.
  • Both traffic signals and vehicle detection equipment are prone to malfunction so good maintenance is required.

Benefits

  • Can increase intersection capacity.
  • Can reduce certain types of crashes (especially right-angle crashes).
  • Can improve pedestrian and cyclist safety.

Implementation issues

  • In countries with poor compliance with road rules, signalising an intersection may have no safety benefit and can reduce the capacity of an intersection.
  • Signals used at intersections with low traffic flows and fixed timings are likely to be disobeyed.
  • Well designed traffic signals will usually reduce total crashes but will sometimes increase specific crash types (e.g. rear-end crashes).
  • Traffic signals should not be used in high speed locations.
  • In urban areas it can be difficult to ensure that traffic signals are visible enough.
  • Before installing traffic signals, information on traffic volumes, pedestrian volumes, intersection approach speeds and previous crashes at the site should be carefully considered.
  • The introduction of traffic signals in a region could increase crashes unless all drivers know the meaning of the signals.
  • Traffic signals need continuous power.
  • Both traffic signals and vehicle detection equipment are prone to malfunction so good maintenance is required.

Did you know?

Some 72% of recorded pedestrian casualties occurred while pedestrians were crossing the road (Road Casualties Great Britain 2006)

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