Stop

[Bazile]

Red traffic lights means stop - amber also means stop .

So why have an amber light ?

[EvianBaby]

prepare.

[rojash]

"AMBER means ‘Stop’ at the stop line. You may go on only if the AMBER appears after you have crossed the stop line or are so close to it that to pull up might cause an accident"

From: http://www.direct.gov.uk/prod_consum_dg/groups/dg_digitalassets/@dg/@en/documents/digitalasset/dg_070561.pdf

[joko]

amber is to warn you that the light is about to turn red and to prepare to stop.
you can still go through an amber if you are more or less on top of the line.

otherwise people would be getting points and fines all the time, as if the light went red the instant they are crossing the line, the camera would flash.

[Bazile]

A lot of traffic light signals , change very rapidly from Amber to Red .

Take this scenario - you are approaching a set of lights - at the junction there is also a traffic light camera .

You are so close to the stop line it that to pull up might cause an accident ; so by the time you cross the line the lights are on red .

Would you then run the risk of being flashed by the traffic light signal camera ?

[EvianBaby]

If the lights are amber as you approach them then you should have sufficient time (assuming you are not speeding) to stop before they go red.

[Bazile]

I regularily pass a set of lights that change from amber to red in the space of a second .

[EvianBaby]

But there being no amber light would only make that situation worse. You'd have no idea at all they were about to change to red.

[mccfluff]

amber means speed up and run the red light and nearly knock over the pedestrian innocently crossing on her way to work

[Bazile]

//But there being no amber light would only make that situation worse. You'd have no idea at all they were about to change to red. //

Yes - but i have moved on from ' why have an amber light '

I'm now thinking about being flashed by the traffic light camera

[EvianBaby]

ok. Then I think I've lost you.

[Bazile]

I'm here - look .

What I meant was that i had the question answered as to why we have an amber light .
The explanation included , when you can proceed over the stop line ; which has prompted me to ask about traffic light cameras and the possibility of being flashed , when you are so close top the stop line that it is safer to proceed over it - but you then run the risk of being flashed ; at some lights , where the time between the amber and red light is just about less than instantaneous ( if you see what i mean ) .

Dony worry too much about answering further - it's not critical to nail this down before the messiah puts in an appearance again

[New Judge]

Traffic light cameras do not flash cars which cross the line immediately the red light shows. They allow a second or so after red appears before flashing. Their aim is to detect drivers who blatantly run red lights.

Traffic lights on roads with speed limits higher than 30mph have their amber display set to a longer period. Looking at those in 30mph limits, travelling at 30mph a car is covering 44 feet a second. The normal stopping distance at that speed is 75 feet. This means you should be able to stop in well under two seconds. It is most unlikely that you will find a camera set to operate at less that two seconds after amber appears. So provided you stick to the speed limit (which you should) and provided you are prepared to stop when approaching any set of traffic lights (which you should be) you will not be flashed by a traffic light camera.

[Bazile]

ok - that's clarified that