induction loops in the road

[asallen]

Why on major roads are there so many induction loops cut into the road? Who monitors them? What are they for? On some roads (A27/M27 junction for example) there are dozens of loops in a one mile stretch, in groups of four in a line, pairs or singular loops. I am now completely paranoid about who is watching my progress down the road! Is it big brother, a speed cop or are they not even connected?

[BillyNoMates]

They are generally used for the Highways Agency to monitor traffic flow and volumes. Some other agencies such as TrafficMaster use the data for the same reason, although they use overhead sensors too. At junctions with traffic lights they are used to help control the light sequencing. Also for triggering cameras if you were to jump a red light.

[Hippy]

Additionally, when a loop breaks it is not possible to repair it effectively, so the authorities just cut in another one.

[hartley]

I understand that the loops are also used to trigger the orange matrix signs that give the speed of traffic ahead. Incidentally you can check traffic flows via www.trafficmap.co.uk , the speeds given on there come from the loops in the road.

[asallen]

All relevent and informative answers. Thanks. No problem if I pass them at 130 mph then! (only jokin')