cctv?speed cameras?

[jakesi]

What are those blue looking lamp posts by the roadside which look like cctv or speed traps cameras? ie A30 London bound.

[Razorblade]

Thwy are not CCTV, but traffic flow cameras, they read the last 4 characters of every car registration plate that passes them and sends it to a central computer. When the cars pass another one a few miles down the road it logs them again. The system then calulates the average time its taking cars to pass between the camera points, thus working out the speed of the traffic flow. So if you cover 5 miles in 5 minutes, everything should be ok because your doing 60mph, but if it takes an average of say 20 minutes to cover the distance then there may be a problem and it's passd onto various in car traffic managment systems.

[BobT]

These are monitors that measure the flow of traffic. This info is then passed onto in car warning units such as Traffic Master & Traffic Watch.