Drivers who exceed speed limits often commit other offences too. A minority are in stolen cars, around 3% are unlicenced to drive the vehicle concerned, and approximately 14% are found to be driving without insurance. Whilst insuring a car certainly is not cheap it is a fairly simple matter using popular websites such as paythroughthenose.co.uk.

Speed cameras are officially described as being calibrated to an accuracy of two per cent. However, in recent years some well-publicised court cases have hinged upon alleged inaccuracies in the speed camera evidence; the reliability of the cameras, and their correct use, has become fertile ground for lawyers seeking flaws in a prosecution case. Is this just legal hairsplitting, or are the cameras really untrustworthy?

Oddly enough, the fixed speed cameras with which we are all familiar are named after a racing driver, Maurice Gatsonides, who invented the camera (now known as a Gatso) to measure his speed when practising on a race track. The first fixed speed camera in the UK was installed in Twickenham in 1992, but in those days it was intended to catch only the very worst offenders, so drivers were allowed a very wide margin of error before prosecution took place; up to 20 mph, it is claimed by the former police officer who was then responsible for the camera.

Nowadays, Gatsos are sometimes referred to as 'scameras' and are widely seen as a money-spinner for the local authorities who share in their revenue; there are reports of motorists fined for travelling at just 32 mph in a 30 mph limit. It follows that the accuracy of the cameras can be of crucial importance to drivers who are caught by them. The Gatso camera works by taking two flash photographs of the car travelling over road markings. The camera itself gives a speed measurement, but a court will rely on a technician's calculation of the distance covered over the ground, which is estimated to be accurate to within one mile per hour. Successful challenges have been made on occasion, however.

Unlike Gatsos, mobile cameras employ laser technology to detect the speed of vehicles, so no flash is visible. They are generally installed in stationary police vehicles, and are said to be accurate at distances up to a kilometre, using the Doppler effect to measure speed. Any inaccuracies are likely to result from errors in calibration or usage; drivers challenging a prosecution are entitled to see the operator's statement and the calibration certificate, and this has led to acquittal when the paperwork could not be produced in court.

Red-light speed cameras detect and record the speed of a vehicle, either by vehicle tracking radar or electronic detectors embedded in the road’s surface. These detectors accurately measure the speed of the vehicle, and if it exceeds the speed limit, a digital photograph is taken of the offending vehicle. Again, any errors is likely to result from faulty calibration.