Some fixed road safety cameras enforce red light offences only, while others detect both red light and speed.
In-road and radar-based 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 the vehicle:
- 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).
Vehicle detection technology
The specific devices and technology used to detect and record red light offences varies depending on the camera system and location.
In-road sensors
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.
Radar technology
Some fixed road safety cameras send radar signals that bounce off the vehicle and back to the device.
Updated