Fixed cameras – all fixed safety cameras are designed to measure the speed of oncoming vehicles, departing vehicles, or both, depending on the type of camera.

Gatso cameras use a radar beam to detect the speed of passing vehicles and take two photographs from the rear, five seconds apart.

Truvelo cameras are front facing and use sensors embedded in the road to calculate the speed of oncoming vehicles. It uses front photography in order to better identify the driver. The magenta coloured filter on the lenses is to ensure that the flash does not distract the driver, which has given rise to the misconception that infra-red illumination is used.

All fixed cameras are calibrated so that vehicles travelling within the speed limit are invisible. Only vehicles travelling above the limit are seen and photographed by the camera.

White line markings on the road surface five feet apart provide a secondary back-up check of the distance travelled, to allow for the speed to be verified by an operator.

Every camera is checked to ensure it is working properly every single time it is placed inside its housing. The cameras are returned to the manufacturer every year for a full calibration. When the camera and film are removed, the camera is checked again to ensure that it has been working properly.

The calibration and checking regime is rigorous to ensure that no law-abiding motorists are accidentally caught on camera.

Mobile cameras – a mobile Gatso camera can be set up in a mobile enforcement van or at the side of the road. It uses exactly the same technology as the fixed camera version but it is also capable of taking single frontal images of oncoming vehicles

Lastec 20/20 cameras employ sophisticated and accurate laser video technology. When the camera trigger is squeezed, it emits a rapid stream of tiny and completely harmless laser beams that bounce off passing vehicles and record their speed in 2/5 of a second—less than the blink of an eye.

The equipment is so accurate it can take a reading from just the wing mirror of a targeted moving vehicle, meaning that law-abiding motorists need not fear triggering the beam by mistake. By the same token, speeding motorists will not be able to claim that the beam was affected by another vehicle just in front, behind or at the side of their vehicle.

The cameras operate effectively in poor light conditions, including at night, and also operates in rain without the beam being refracted by water drops.

The equipment is calibrated daily, before and after each time it is switched on and is used by experienced, trained police officers.

Red traffic light cameras monitor traffic light junctions 24hrs a day. Vehicles that cross the stop line on red break a magnetic field, which causes a photograph to be taken. As the camera is triggered one second after the red light appears, this will often be at speeds well below the limit for that road. They are designed to capture drivers ignoring the red light, not those breaking the speed limit.

These cameras are installed at junctions with the worst collision history.