What was the offence?

[chief-0369]

not all traffic signals use MVDs (microwave vehicle detectors). Many use inductive loops buried in the roads. MVDs can detect stationary traffic (if they couldnt they wouldnt be any use). **edit** So can inductive loops

Inductive loops and MVDs can normally "see" about 20-30m from the stopline back so unless you are really taking the pee they wont gap change.

Also, if as with many signals, there are two opposing stages running together, the controller will need to see a gap on both approached before It will change.



I think it all boils down to judgement. If you have a 50m gap infront of your car then you are going too slow and should stop numpting about. If you are leaving a few car lengths gap and some twat is getting irate, let them. Its their blood pressure thats at risk



>> Edited by chief-0369 on Thursday 23 September 13:18

[jap-car]

chief-0369 said:

not all traffic signals use MVDs (microwave vehicle detectors). Many use inductive loops buried in the roads. MVDs can detect stationary traffic (if they couldnt they wouldnt be any use). **edit** So can inductive loops Inductive loops and MVDs can normally "see" about 20-30m from the stopline back so unless you are really taking the pee they wont gap change. Also, if as with many signals, there are two opposing stages running together, the controller will need to see a gap on both approached before It will change. I think it all boils down to judgement. If you have a 50m gap infront of your car then you are going too slow and should stop numpting about. If you are leaving a few car lengths gap and some twat is getting irate, let them. Its their blood pressure thats at risk >> Edited by chief-0369 on Thursday 23 September 13:18

Thanks Chief - that clarifies. I think the majority (at least local to me) must use MVDs as (1) my Snooper pickes them up and (2) as JohnL says, you can see the boxes on top of the lights.

Your 20-30m estimate also ties in with my rough estimate of four car lengths (allowing a few feet between cars).

Cheers.

[Pigeon]

jap-car said:

Am I correct in assuming that PIR is P...? Infra Red and therefore that my detector would not detect? (Although at very close range, my TV remote will be detected and this is Infra Red).

PIR is Passive Infra Red, ie. it doesn't transmit anything, unlike the TV remote. It detects moving sources of long-wavelength infra-red, such as homeothermic animals and hot bonnets. The burglar alarm ones don't detect a person wearing motorcycle gear who has just been riding in cold/icy conditions, and I would hazard a guess that the traffic light ones would have similar difficulties detecting a Beetle in the cold.