Gatsometer

Gatso is the brand that Gatsometer BV use on their speed cameras and red light cameras. The most commonly encountered Gatso speed cameras emit radar beams to measure the speed of a passing vehicle. If it is travelling above the preset trigger speed, one or two photographs are taken (depending on the device's setting, which generally depends on the requirements of the local jurisdiction). These use a powerful flash, to show the rear of the vehicle, its registration plate, and calibration lines on the road (in many jurisdictions). Newer installations used digital cameras which have limited exposure latitude compared to wet film, these installations use an auxiliary flash placed close to the position where a speeding vehicle would exit the radar beam and the first photograph would be taken.

Gatso installations in the UK and in Queensland, Australia are characterised by a measurement strip on the road surface, which is a series of white lines painted on the road, which are used with two photographs taken by the camera. If the camera is set to take two photographs, with a known time interval between them, this time interval will be 0.5 or 0.7 seconds - 0.5 is better for high speed roads and 0.7 better for low speed roads. The vehicle's position, relative to the white road markings in the two photographs, can be used to calculate the vehicle speed. In the UK, the evidence is only admissible in court if the speed measured by the radar and the speed calculated from the distance travelled between the photographs agrees within 10%. The speed indicated by the radar unit is too unreliable to be used as the sole means of evidence as it is prone to error due to multiple reflections etc. Further, it does not distinguish between multiple vehicles in shot.

The first red light cameras were introduced in an initiative in the City of Nottingham in 1988 following a triple fatal road traffic accident at a traffic light controlled road junction.

The Department of Transport took an interest and a trial was sponsored by that Department involving the Home Office and the Metropolitan Police. The operational base was at the West London Traffic Unit. Roger Reynolds, a Police Sergeant (later to become President of the Royal Photographic Society) undertook operational trials of the equipment and, by adjusting the camera controls, managed to use Colour film for the first time replacing black and white film. Reynolds made the first successful use of the Gatso camera on the A316 road at Twickenham Bridge in 1992.

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Wikipedia