Some fixed road safety cameras enforce red light offences only, while others detect both red light and speed.
In-road sensors are used at intersections to detect if a vehicle crosses over the stop line against a red traffic light. This triggers the camera to take an image.
The camera is designed to take 2 images of an offending vehicle that combine to prove that it:
- entered the intersection after the light turned red, and
- continued through the intersection against the red.
The camera also captures the time elapsed between a traffic light turning red and the vehicle entering the intersection.
If a light changes to red while you are already in the intersection, you will not be issued a fine (the camera is only activated by a vehicle driving over the stop line after the light has turned red).
In-road sensors may utilise:
- piezos (when a vehicle travels over the sensor, kinetic energy from the tyres is converted into electrical energy and the electrical impulses indicate the vehicle's presence), or
- inductive loops (a series of electrified wire loops generate a magnetic field that detects the metal of a vehicle as it passes over).
The sensors are installed in individual lanes on roadways, allowing the system to differentiate between vehicles in different lanes.
Wet-film based camera technology is no longer used for the enforcement of red light offences.
A select number of red light only camera locations that utilised this wet-film technology are in the process of being updated to more appropriate fixed digital technology.
For those wet-film sites that were previously enforcing for red light, weekly tests by trained officers while installing and removing the film magazines determined that camera test certificates were no longer required per the Road Safety (General) Regulations 2019.