Traffic signal design and operation

FAQs and further reading

Get the answers to our frequently asked questions and learn more about traffic signals with our further reading options.

How does SCATS know I'm waiting at the intersection?

Detectors located at the stop-line sense that your vehicle is there.

How are bicycles detected at intersections?

Detectors used for vehicles can also detect a bicycle (even those with carbon fibre) waiting at an intersection. To improve detection, it is recommended that cyclists ride in the centre of a lane when arriving at the stop-line.

In some cases where there is a bike lane or off-road path, special bicycle detectors are installed.

Why isn't there signal coordination at some intersections?

a) SCATS has determined that signal coordination is not beneficial at that time of day
OR
b) there is signal coordination but it is not working in your favour because there are other traffic movements with higher priority. Sometimes coordination is disrupted by public transport priority or nearby rail level crossings.

Why do I have to wait so long when travelling on a side road?

The more important arterial roads, which carry higher traffic volumes take priority. Once you have turned onto the more major road, you should be able to move more quickly through intersections.

What is the point of signal coordination in congested conditions?

In congested conditions, you may not be able to drive through consecutive signals without stopping. Nevertheless, signal coordination reduces the level of congestion and is valuable in minimising queues blocking upstream intersections, which can often lead to gridlock.

Why do I have to wait at a red right turn arrow when there is no oncoming traffic?

The intersection has a high risk of crashes involving right turners. We want to keep you safe.

Why do I get a green turn arrow at some times of the day and not others?

Right turns are restricted at some intersections during busy periods to give priority to other movements. At some locations, right turns may only run every second cycle or are banned for the peak period. Other intersections may only allow right turns during the ‘through’ phase, whereby they must give way to pedestrians and oncoming traffic before proceeding.

Why is the side road phase running without a vehicle present?

The vehicle detectors or pedestrian push buttons may be damaged. The detectors and buttons have a fault function which will demand their respective phases to ensure movements can be performed. Faults are automatically monitored and are quickly flagged for repair.

Why is the side road phase still green when all vehicles have left the stop line?

In these circumstances, there may have been a demand for the pedestrian movement that runs alongside the vehicle movement, potentially extending the phase.

Why is there not enough green time for my movement?

SCATS adapts traffic signal timing based on traffic flows recorded by the detectors at the stop line, in order to achieve a balanced outcome for competing movements.

Why is there not enough green time for the pedestrian movements to cross the road?

Pedestrian times comprise of a walk time (green walk display), a clearance time (flashing red display) and a solid red display. If the pedestrian commences their walk during the green walk display, the combination of the times will be sufficient for the majority of pedestrians to complete their walk across the carriageway. On divided carriageways, some pedestrian movements are designed to be staged if the median area is of sufficient width.

Wheelchair detectors are used at some locations to provide more time for people with disabilities to cross the road. It is recommended that slow pedestrians only start crossing at the beginning of the green walk display to ensure they can complete their crossing in time.