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How traffic cameras work

Different safety cameras are used on South Australian roads.

Depending on the camera system it may:

  • photograph a vehicle/s involved in an offence
  • detect the direction of a moving vehicle
  • differentiate between vehicles on a multi-lane road
  • use other traffic data to detect offences such as variable speed limits
  • calculate vehicle speeds
  • use speed verification technology to verify speeding incidents
  • capture the time elapsed after a traffic light has turned red.

Traffic lights

Traffic lights operate on a three phase system.

  1. Green light - drivers can cross the intersection.
  2. Yellow light - warns drivers that the lights are going to change.
  3. Red light - drivers must not cross the intersection.

Warning times for the yellow light are set at:

  • four seconds in a 60km per hour zone
  • five seconds in an 80km per hour zone.

A 10% tolerance for traffic light timings is allowed by the Austroads Guide. The tolerance is applied and an expiation notice may be issued if the reading is below the prescribed time.

See parts six, nine and 10 of the Austroads Guide to Traffic Management to find out how traffic lights work.

View the Guide to Traffic Management on the Austroads' website.

Find out more about the road rules for traffic lights (The Driver's handbook) on the mylicence website.

Fixed safety cameras

Three types of fixed cameras are used in South Australia:

  1. Red light and speed cameras
    Used at traffic light intersections, and pedestrian and railway crossings.
  2. Speed cameras
    Used where there are no traffic lights.
  3. Point to point cameras
    Used to measure the time taken for a vehicle to travel the distance between two locations.

Speed detection

Fixed cameras are connected to induction loop sensors located:

  • under the road surface
  • in each monitored lane
  • just over the painted stop line on the intersection side.

How the camera is triggered

The camera is triggered when the sensors detect vehicles:

  • exceeding the speed limit on a green, yellow or red light
  • entering the intersection on a red light.

Safety cameras do not trigger on a green or yellow light when drivers enter the intersection.

Sometimes the camera flashes when a driver passes through the intersection on a green or yellow light. This could be because a driver in another lane, behind or turning right has triggered the camera.

How traffic offences are photographed

When the fixed safety camera is triggered two photographs are taken, usually of the rear of the vehicle.

The photos are taken a minimum of half a second apart and show for

  • red light offences

Photo 1 that the light has turned red at the point of crossing the stop line
Photo 2 the vehicle further through the intersection while the light is still red.

  • speeding offences

Photo 1 the vehicle travelling over the induction loop
Photo 2 the vehicle's progression after leaving the induction loop.

Vehicles waiting in the intersection while the light changes from yellow to red are not photographed.

Find out more about how fixed safety cameras work: Fixed Safety Camera Operation Practices

Mobile safety cameras

Mobile safety cameras are set up on the side of the road and are either mounted in a vehicle or on a tripod.

These safety cameras use radar to detect speeding vehicles.

Find out more about how mobile safety cameras work (this document is under review and currently unavailable).


Safe-T-Cam is a network of cameras placed on major arterial roads that detect unregistered vehicles.

In South Australia Safe-T-Cam is managed by the Department of Planning, Transport and Infrastructure (DPTI).

Find out more about Safe-T-Cam on DPTI's On Road website.

How safety camera evidence is used

Safety camera photos are checked and verified by trained staff in the South Australia Police (SAPOL) Expiation Notice Branch. Vehicle registration is checked at the same time.

An expiation notice is not issued until the checks have been completed. Notices can be issued for:

  • exceeding the speed limit
  • failing to stop at a red light
  • having an unregistered vehicle
  • not having current third party insurance.

Safety camera testing and maintenance

Technical repair of all safety cameras is carried out in SAPOL’s specialised workshops and laboratories or by the camera manufacturer.

Speed and red light traffic

Speed and red light safety cameras undergo rigorous certification, testing and maintenance.

The cameras are tested regularly to ensure that the:

  • speed measurement device is accurate
  • camera is operating correctly.

Technical repairs are carried out in SAPOL’s specialised workshops and laboratories or by the camera manufacturer.

The maintenance history of each safety camera is documented and monitored.

Fixed safety cameras

Fixed safety cameras are regularly tested and maintained by SAPOL.

  • Daily checks are conducted remotely through the camera network.
  • Monthly run throughs are carried out at each site to check the speed.
  • Once a year the cameras are removed and recalibrated.

Mobile safety cameras

Mobile safety cameras are tested by SAPOL every time they are set up. A vehicle is driven through the radar beam at a set speed and the camera readings are checked to ensure that they are correct.

Mobile safety cameras are recalibrated once a year.

New locations

Before a new safety camera goes live testing is carried to ensure that the infrastructure, technology and processing complies with all the requirements.

A safety camera will only go live after it has been operating in a test environment for four continuous weeks without error.