Traffic signals

Traffic signals manage the flow of traffic.

We control more than 100 sets of traffic signals at intersections across the city. The Department of Transport and Main Roads (DTMR) controls traffic signals on state-controlled declared roads.

How do traffic signals work?

Traffic signals respond to road sensors and are controlled by computers.

Road sensors called loop detectors are buried in the road in each traffic lane. The loop detectors pick up any large metallic objects that drive over them, like cars. When the loop detector senses a car, it will either change the light to green or extend the time of the green light.

Loop detectors can be adjusted to sense smaller vehicles like motorbikes and bicycles. However, they may not detect bicycles made of carbon-fibre, fibreglass, plastic or aluminium.

Each intersection has a local computer that controls the traffic signals. Our traffic engineering team can access the computers remotely if needed.

Lights can be coordinated with other intersections to help traffic flow smoothly on busy roads. The busiest road is usually given priority when two major roads intersect.

Reporting traffic signal faults

Traffic signal faults include:

  • broken lights
  • loop detector and timing issues
  • requesting a new traffic signal
  • requesting changes to an existing traffic signal.

To report a traffic signal fault, please call us on 07 3412 3412 or email us at

To report traffic signal faults on state-controlled declared roads, please call the Department of Transport and Main Roads on 131 940 any time.

For information about road rules at traffic lights, please visit DTMR Road rules.