Transport Canberra and City Services


Traffic signals

The ACT has 340 signalised intersections under the central control of the Sydney Coordinated Adaptive Traffic System (SCATS). SCATS is used around the world and was developed by the Road Traffic Authority of NSW. Some of the functions performed by SCATS include:

  • coordination of traffic signals;
  • fault reporting (for example blown traffic signal lamps); and
  • data recording (traffic volumes at intersections).

Coordinated traffic signals

Coordinated traffic signals provide a progression for traffic as they travel long a particular route. The benefit is that they allow a large volume of vehicles to pass through multiple signals with minimum delay. For information on coordinated traffic signals visit Drakeford Drive - an example of coordinated traffic signals. The alternative to coordinated traffic signals is isolated traffic signals, which rely on vehicle detectors to change the traffic signals. This works well for traffic signals that are located far apart and have low traffic volumes.

Filter turns

Some drivers in the ACT dislike the use of red arrows to prevent drivers turning right, even when there are considerable gaps in the flow of oncoming traffic. The ACT uses the same national standards to determine the use of arrow signals as other states in Australia.

The reason we have so many red arrows is because of safety, and basically stems from the high quality road system in the ACT. Many of our arterial roads are multi-lane with a speed limit of 80kph. Research clearly shows that the higher the speed of the oncoming traffic and the wider the road that has to be crossed, the more difficult it is for a right turning driver to choose a safe gap in oncoming traffic. To try and reduce the frustration that this can cause for some drivers when traffic volumes are light, we are endeavouring to make the lights change more quickly under these circumstances.

Roundabouts vs traffic signals

Traffic signals are relatively expensive to install and operate. They are normally only considered for intersections with particularly high levels of traffic. Roundabouts, by comparison are cost effective to install and maintain, and work well in low levels of traffic. Traffic engineers use the Australian Standard AS1742 and Austroads Design Guidelines manuals to assess whether traffic flow will be improved at particular intersections with the installation of signals or whether the construction of a roundabout would be more useful.

Some people argue that roundabouts are preferable to traffic signals. It is important to note that traffic signals do have some advantages over roundabouts. Traffic lights generally require less land than roundabouts and can have specific facilities for pedestrians. Additionally, roundabouts have an in-built priority rule, which means that in heavy traffic, movements in one direction can tend to dominate and cause excessive delays to vehicle movements in other directions. Alternatively, traffic signals can be programmed to give priority to one direction over another direction. A report published in the UK also suggests that roundabouts are 2-3 times more dangerous for cyclists than traffic lights.

In light to medium traffic conditions, roundabouts can cause less delay to traffic movement than traffic lights. In these instances the relatively low maintenance costs of roundabouts will mean that their installation is preferred.

The installation of signals or the construction of a roundabout at a particular intersection is ultimately based on a thorough assessment of traffic flow, available land, intersection accident history and the intersections overall place in the transport network.

Reporting problems and concerns

To report faults or concerns contact 13 22 81 or submit feedback via the Access Canberra website. When reporting a fault or concern it helps if you can provide the location of the traffic signals, the details of the fault or concern, when it occurred and any other information that may be relevant.

The ACT Government is committed to improving the accessibility of web content. To provide feedback or request an accessible version of a document please contact us or phone 13 22 81.

We acknowledge the Traditional Custodians of the ACT, the Ngunnawal people. We acknowledge and respect their continuing culture and the contribution they make to the life of this city and this region.

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