asked Her Majesty's Government:
Whether they have assessed the validity of evidence from Gatso speed cameras bearing in mind that such evidence is based on the second of three photographs taken by the camera when the speed of the vehicle cannot be known, as opposed to the third, taken at the end of the speed check, when it can be known. [HL4631]
The Gatso speed camera in fact takes two images only. The second is used in a secondary check of the speed indicated in the first, by enabling a time-over-distance calculation using the vehicle’s position in relation to lines painted on the road. The device’s initial measurement of speed is carried out by radar.
The Gatso red light camera can generate three images. A third is taken only when a second red-light offence is detected during the time interval between the two photographs of the first offence. The speed shown on the images is for indicative purposes only; it is not used to prosecute for a speeding offence.
Both the Gatso speed camera and the Gatso red-light camera have been type approved, so that their evidence is admissible in court. Type approval is granted only after rigorous evaluation of a device’s practicality, reliability, accuracy and compliance with prescribed standards.