The ACT has around 400 traffic signals, located at intersections, pedestrian crossings and roundabouts. All of them are controlled by a central control system called the Sydney Coordinated Adaptive Traffic System (SCATS). Some of the functions of SCATS include:
- automatic adjustment of green times to optimise the movement of traffic in response to the traffic demands at the time
- coordination of traffic signals along a corridor
- fault reporting (e.g. blown traffic signal lamps)
- data recording (e.g. traffic volumes at intersections).
Coordinated traffic signals
Coordinated traffic signals help move traffic along a particular route. They ensure that a large volume of vehicles can pass through multiple signals with minimum delay. However, this coordination can mean delays for pedestrians and vehicles entering or leaving the main road. Some traffic signals are coordinated only when traffic volumes are high and warrant increased delays for pedestrians and side road traffic.
Coordination is not always appropriate. For example, it has limited use where traffic volumes are moderate or signals are far apart. Instead, detectors installed in the road are more effective at adjusting signal timings.
Right-turn arrows
Right-turn crashes are a leading cause of fatal and serious injuries. To reduce the severity and likelihood of these crashes, right-turn arrows, or red arrows, are at many traffic signals in the ACT. Their use is determined by Australian standards.
Right-turn arrows are important in the ACT due to the nature of our road network. Many of our arterial roads are multi-lane with a speed limit of 80 km/h. Research shows that it’s harder for a right-turning driver to choose a safe gap in oncoming traffic when:
- the speed of the oncoming traffic is higher
- the road that’s being crossed is wider.
These arrows mean that drivers don’t need to make a judgement, which means safer intersections.
Right-turn arrows can be frustrating as drivers must wait even if there are large gaps in the traffic coming the other way. The traffic signal team regularly reviews the signals and tries to minimise the cycle time so the lights change more quickly.
Roundabouts versus traffic signals
Traffic signals have some advantages over roundabouts. They:
- generally need less land than roundabouts
- provide a safer way to cross the road for pedestrians
- can be programmed to give priority to one direction over another.
However, they are relatively expensive to install and operate. They are normally only considered for intersections with particularly high levels of traffic.
Roundabouts are cost-effective to install and maintain. They work well with low or medium levels of traffic, causing less delay to traffic movement than traffic lights.
One issue with roundabouts is that they have an in-built priority rule. In heavy traffic, movements in one direction can dominate. This causes delays to movements in other directions. A report published in the UK also suggests that roundabouts are 2 to 3 times more dangerous for cyclists than traffic lights.
Traffic engineers use the Australian standard AS1742 and Austroads design guidelines to assess whether traffic flow at an intersection will be improved with the installation of signals or a roundabout.
This decision is ultimately based on:
- a thorough assessment of traffic flow
- available land
- intersection accident history
- the intersection’s overall place in the transport network.
Upgrades
Traffic signals must work continuously and require a routine program of maintenance and upgrades. In recent years, the ACT:
- has converted all traffic signals to higher efficiency LED lighting
- introduced safer lower voltage traffic signals
- began upgrading signals to include Uninterrupted Power Supply (UPS).
UPS enables a continuous power supply to traffic signals, even during a power outage. It ensures that the road network continues to operate safely and efficiently. As a result, ACT Police don’t have to regularly manually direct traffic during a power failure.
Reporting problems and concerns
To report faults or concerns:
Please provide the location of the traffic signals, the details of the fault or concern, when it occurred and any other relevant information.
