Traffic Signals


Traffic signals provide direction and safety to road users by allocating and reallocating right of way. It is important to remember that traffic signals are community devices that provide a service to all types of road users.

Road users include motorists, cyclists and pedestrians.


SCATSImage: Traffic signal photo.PNG

The Perth metropolitan area now has over 900 sets of traffic signals under the central control of SCATS (Sydney Co-ordinated Adaptive Traffic System).

The goal of the SCATS system is to monitor the status of traffic signals and provide traffic signal coordination where possible, to improve traffic flow through adjacent intersections.

SCATS will typically co-ordinate traffic signals in the direction of the major traffic flow. Coordination is dependent on a number of factors including distance between intersections, traffic speed and the number of movements. 

SCATS works by measuring congestion at strategically located collection points. With this information SCATS can adjust signal times in peak traffic.

The SCATS system can also be altered in real time to manage unexpected conditions and minimise delays caused by events or incidents.



Each intersection is individually assessed prior to the installation of traffic signals.

The review includes:

  • Assessment as to whether or not alternative treatments such as roundabouts are more appropriate.
  • The volumes of vehicle, cycle and pedestrian traffic.
  • Access for side street vehicles and pedestrians.
  • Physical intersection layout.
  • The safety record of the intersection.
  • The proximity of schools and facilities.
  • The volume of turning traffic.
  • Impact on the road network.


Traffic signal installation verses roundabout installation 

The type of traffic management to be used at a specific location takes into consideration a range of factors including availability of land, overall road environment, anticipated demands, environmental impacts, heritage impacts and costs.

​Roundabouts Traffic Signals​
​Require more land Better suited for intersections with conflicting traffic flows​
​Better suited for light local road traffic ​Better suited for heavy traffic volumes
​Best suited for roads with equal traffic volume ​Better opportunities for pedestrian crossing

Advanced warning lights

Advance warning lights, installed at the approaches to some traffic signals provide early warning that the traffic signals are about to change.

Advance warning flashing lights start to flash when the traffic signal lights are about to turn yellow and continue to flash while the traffic signals are red.



What happens at any locations where turning vehicles don’t give way to pedestrians?

Turning vehicles giving way to pedestrians is an enforceable element of the road traffic code. Inappropriate driver behaviour should be reported to the police.


How long is the yellow time at an intersection?

Yellow times at traffic signals are set as follows:
  • 3.5 seconds - For 50 km/h speed zones
  • 4 seconds - For 60 km/h speed zones
  • 4.5 seconds - For 70 km/h speed zones
  • 5.0 seconds - For 80 km/h speed zones

How much vehicle green time is given for me to cross an intersection?

All movements at an intersection have a guaranteed minimum green time which will allow a vehicle to safely start up and enter an intersection. This time is calculated to be sufficient to cater for the width of the intersection.


Why do I have to wait so long for the lights to change when there are no other vehicles around?

The most likely cause is that the traffic signals have been set to coordinate with adjacent signalised intersections. In this case the SCATS computer is controlling the introduction of traffic movements in an effort to remain in sync with the other intersections.

Another possible cause is when the vehicle detection systems at an intersection have been damaged due to roadworks or normal wear in the road surface. When this occurs, cycling of the intersection does not operate normally.

On occasion the detection systems may need adjusting to register light vehicles like mopeds and bicycles.

The public can help by reporting traffic signal faults, including detection faults via our online report a fault form.

Why is there no green turning arrow at the intersection?

The inclusion of green arrow and red arrow displays usually increases complexity and may reduce the efficiency of an intersection.

This is typically the reason why all traffic signals don’t automatically have green arrow movements for all directions.

Traffic Engineers make an assessment in regards to whole of community benefit when considering requests for the addition of arrow controlled movements.


Can you increase the green time at the intersection?

Requests in regards to displayed green time should take into consideration the capacity of an intersection. Capacity is affected by the number of lanes and the complexity at the intersection. 

Increasing the green time for a leg of an intersection will either require taking green time away from other users or increasing other road users red (waiting time).

In most cases increasing green time for all directions will subsequently increase red time for all directions. Therefore, after the capacity of an intersection is reached, little is achieved by increasing green time.


Why are "No Right Turn" signals installed at Perth intersections and where and when do they operate?

There are some intersections in Perth that experience increased congestion at certain times of the day due to heavy right-turn movements.

To improve traffic flows and road safety, illuminated No Right Turn signals have been installed to prohibit these heavy right-turn movements.

Listed below are the NRT signalised intersections in Perth. All NRT signals operate at the following locations and times on weekdays excluding Public Holidays.

​Street Name AM operation PM operation​
​St Georges Terrace - King Street ​8 - 9.30 ​3 - 6
​Hay Street - Milligan Street ​8 - 9.15 ​3 - 6
​Adelaide Terrace - Plain Street ​7.30 - 9.15 ​3.30 - 7
​Wellington Street - Plain Street ​7.30 - 9.15 ​3.30 - 6
​Stirling Highway - Alfred Road ​7 - 9.30
​Vincent Street - Oxford Street ​7.30 - 9 4 - 6​
​Main Street - Royal/Hutton Street ​4 - 6
​Stirling Highway - Dalkeith Road 7.30 - 9.30​ ​3 - 6
​Stirling Highway - Bayview Terrace 7.30 - 9 ​3 - 6
​Nicholson Road - Railway Road ​7 - 9.30 ​4 - 6
​Broun Avenue - Coode Street ​7 - 9 ​4 - 6

​Albany Highway - Kelvin/Olga Road

(Also operates Saturdays 8am to 1.30 pm)

​7.30 - 10

​11am - 1pm

3pm to 6pm

Modified: 21 Nov 2018