Engineer beats traffic lights ...

There was a programme on either channel 4 or 5 last night about london transport. They had a bit about changing traffic lights in it. They can adjust the waiting times, forget what they called it but they can bias a junction from low level to medium to high level.

WE don't know the size of the junctions - which can be huge in the US or the speed limit on those particular roads. As I understand it, you get a ticket if you haven't completely cleared the jubction at the instant that the amber phase ends.

Here we have a short time when all lights care red before the red/amber phase starts in the other direction - which does not mean GO, remember - and in the days of GATSO cameras you could clearly see the one seconds grace between the end of the amber phase and the first flash.

It is important to take the differences in country specific practice into count before reaching a conclusion.

Do you know, for example, the duration of the amber phase in the UK for comparison?

I would have thought that they can vary the green time from each direction (and hence the red in the other), but the amber phases and the time between going red in one direction and red-amber coming on in the other would be calculated for that junction and then never changed. The green phase dictating how much traffic gets through per change, the red phase dictating the wait between greens and the fixed amber and amber/red phases being calculated and set during commissioning to give time for conflicting vehicles to clear the junction - recalculated and adjusted if it turns out to be problematic.

SteveW

That's probbaly why they have settings, rather than someone sitting there keeping a red or green light on until they feel the need to change it.

Not really surprising as they are doppler sensors to detect traffic. You can tell as they don't point the right way and there aren't enough of them. But maybe you can't.

Its supposed to be some international standard,I don't know if the UK is signed up.

As I said its the camera timing that's wrong.

They aren't doppler, they use a form or induction because they detect metal. Doppler

You can't see them because they are implanted/burried in the road.

They are induction loops, those lights you linked too have doppler units on the top. Stop being you usual stupid self and look, digest and think for a change.

New lights seldom have induction loops as they are unreliable and costly. When the lights are replace ti loops remain there and show until resurfacing is done but do nothing.

A friend of mine used to mess with similat sensors on a multi=storey car park (used to keep track of the number of cars inside). He used a large dustbin lid. Cue annoyed motorists with "CAR PARK FULL" - when it wasn't.

Remember the rubber strips in the road. I was telling my wife about when I was a kid and used to go and jump on them.

Get educated

yeah sure.

As a kid in the 70s, I discovered that riding my bike along the exact edge of the induction loop was enough to trigger the rising barrier mounted in the road to lower with an associated change of traffic light colour into the local underground station car park. Hours of fun. It became quite a test of nerves to see how fast you could approach and still make it over the barrier.

You can as you can see the saw cuts made when they are put in. You do know they just cut slots in the road and a push the coils in and then fill the cuts with bitumen/resin?

So what its just a different type of sensor and useless for detecting bikes and stuff like that.

Those lights they show you don't have the doppler sensors.

Glad to see you are starting to understand.

Yes, how else would they do it replace the whole road.

who wants to detect bikes ?

The doppler sensors are used to detect traffic speed. I was on one last week and there was a smilie face traffic sign and as the bus got closer it became a sad face, the bus was going above the 20MPH that doesn;t happen very often.

They don't call them induction loops just detectors that detect metal via magnetic field, which could be a problem when cars and buses get made out of just plastic, but I don't think that is likely to happen just yet.

On 23/10/2019 20:36, Steve Walker wrote: ...

As I have said, that is how it used to work, before it was possible to detect vehicles in as well as approaching the junction. However, when you have very high volumes of traffic and hundreds of linked traffic lights (as TfL has), even a fraction of a second longer than needed on any phase can have a huge knock-on effect.

What I meant is that the the amber, amber/red and time between red in one direction and amber/red in the other are likely set up during commissioning - being safety related. With only the green times adjustable or selectable to suit traffic flow.

SteveW

You can see the diamond/diagonal shaped notches cut into the road and sealed with tar.

I doubt that is true because if you shorten or lenghen the green period then surely the inverse must happen to the red period.

Only if you know and can tell them from a pot hole refile, and then even though you can see them, you can't actually see them any more than you can see coffins in a cemetary. You certainly can't tell whether it's a doppler or magnetic sensor. Have you seen those cameras installed on some grande prix circuits showing the ground level viw as the cars run over them ?

Makes me wonder if some cats eyes could be replaced with cameras in the furture who would know not the average person.