Speed Cameras

[happy_face]

The dual carriage way on my way home has a speed camera and last night made me think of how they actually work. If I'm driving in the inside lane and a car speeds in the outside lane but I'm still further ahead than him, how will the police know that it wasn't me that triggered the camera?

Also this particular camera also gets triggered if someone on the other side of the road is driving too fast although they're moving in the direction of the camera. How does the police know that it wasn't the people driving near the camera that were speeding?

[Loosehead]

The cammera takes 2 pictures half a second apart. If there are 2 cars in the picture they can use the white markings to determine the distance both cars travelled in that time and hence the speed. Interestingly though if you where doing 32 and the other car 52, you would not normally set off the camera but he would, but now you are both doing over 30 would they prosecute the slower driver as well? Probably but it would be very unlucky.

[CT]

They shouldn't prosecute for doing 32mph, usually there is a 10% margin of error given. ie 30mph +10% = 33mph

[DrRobBarton]

Actually, in Cambridgeshire at least, the current policy is that police won't prosecute unless you are travelling faster than 10% plus 2 mph above the speed limit - effectively 35 mph for a build up area. More information is available here: http://www.cambssafetycameras.co.uk/

[gary baldy]

A car travelling in the opposite direction can set off a camera but as loosehead says with a Gatso you need two pictures to gauge the distance travelled/speed and these obviously have to clock you travelling in the right direction!
Beware of the front facing/ infra red cameras though that dont flash and can clock you over a distance of inches as apposed to the large area Gatsos need.