Traffic Lights.

Originally Posted by SnoopZ

The ones in my village have sensors ontop that will change them to green when i approach and there are no other cars waiting anywhere. It took me ages to work out why it used to go from green to red to green again in about 2 seconds until i spotted the sensors.

As already said, the sensors work inductively. They are embedded in the road. The lights changing coincides with you passing over the inductive loop.
The sensors ontop of the lights are indeed light sensitive, but they are there to reduce the amount of electrickery the lights need to use. When its dark, the lights are more visible and therefore the supply current can be reduced.

[Anonymouse]

Originally Posted by Felinix_Devotion

I wonder though with this myth.

When you approach a pelican crossing, if you push the button and rotate your finger 90* to the right the lights change quicker.?

What, you mean the pelican crossings in your area actually work? That is, do they change the lights when you as a pedestrian press the button?

I ask because there are several in Bolton, especially at junctions in or near the town centre, which seem to be no more than a sop to the pedestrian. One early evening when there was virtually no-one about (and therefore the pelicans hadn't been used in a while), I watched the sequence of lights for several minutes...and discovered by experimenting that it doesn't make a blind bit of difference whether you press the bloody button or not - the pelican crossing is included in the sequence.

Years ago, if you came to a crossing that'd just been used, it'd take a few minutes to work, whereas if it hadn't been used for several minutes it'd respond immediately. But not any more, it seems - certainly not in Bolton. The crossings near Trinity Street train station and Sainsbury's don't work as pelican crossings are supposed to. Granted, if they did traffic would be stopped from several different directions, but I find it annoying that they're misrepresented as pedestrian crossings when they're really nothing of the kind. The crossings at St. George's Road/Knowsley Street are the same - the sequence is: red lights one way for about 20 seconds; red the other way for 20; red both ways for 20. Your pressing the button has no effect whatsoever on this sequence.

They also give a false sense of security to people who don't realise this - I've seen people pressing the button and expecting the crossings to react more or less straight away. It's a wonder people aren't being killed every day. The buttons should be removed; IMO they're actually a danger to the public.

Has anyone else noticed this phenomenon in their area?

[MovedGoalPosts]

A few of our traditional pelican crossings, those with the flashing amber (go if the crossing is clear) lights have been modernised. No falshing amber anymore. All that means is traffic now sits there for an eternity granny has crossed and is halfway up the street before cars can move. And they wonder why at peak hours we have traffic jams stretching back to the next town. So much for progress

[Chrysalis]

if the traffic lights are normal ones for junctions that have the pedestrian crossings then the pedestrian part is sometimes part of the timer but not always. Where I live now there is some down the road which I think are fixed timers, they include the pedestrian crossing which adds to the queues since there isnt always pedestrians. However nearer where I used to live there is another junction which primarily uses sensors for its traffic since its a quieter junction, and the pedestrian crossing only goes green when the button is used. It could be that at night time the timer versions become intelligent and use sensors plus the buttons but in the day its fully timed.

[ZrByte]

Originally Posted by Rob C

Many traffic lights do react to traffic to adjust the timings. Look at the road surface, the thin black tarmac boxes, diagonals are electronic field sensors that can detect if a car is over them. Great for vehicles to trigger a light change, but useless if your on a pushbike

And with some light motorcycles. I remember myself and a friend about 3 years ago having to back up over one of the pressure sensors and jump up and down on our bikes for a second before we could get the light to change.

Originally Posted by ZrByte

And with some light motorcycles. I remember myself and a friend about 3 years ago having to back up over one of the pressure sensors and jump up and down on our bikes for a second before we could get the light to change.

They aren't pressure sensitive. Its an inductive loop, your metal vehicle disturbs the magnetic field within the loop. Hence why bikes are less effective than a large metalic car.

[Chrysalis]

Every roadwork traffic lights I have seen have some kind of sensors, usually laser thing located above the red light, there was some on the road outside my house today that werent working quite right and one of the workmen ended up directing the traffic after police came informing them the queue was 2 miles long .

Originally Posted by skunk4u

Do they get managed? EG on approach they turn red, no cars coming from the other direction on red for no reason? Do they have sensors on them? They should do. I'm sure a lot of our traffic problems and road rage would end if traffic lights where managed properly. Surely its not that hard?

Another EG, big queue waiting for green, across the road one car goes across and that's it. And were still waiting?

Is it just me??? Just does not seem to make sense to me?

Like whats been said all traffic lights have senors on them but they only work when the traffic has died down like at night times, when I was on the taxis you could hit every green light at 3 in the morning because the sensors picked you up. If you look down at the tarmac when your sat at a set of lights you'll see some markings where the sensors are, when you run over them at a night time the lights change for you.

[MovedGoalPosts]

Originally Posted by Nidge

Like whats been said all traffic lights have senors on them but they only work when the traffic has died down like at night times, when I was on the taxis you could hit every green light at 3 in the morning because the sensors picked you up. If you look down at the tarmac when your sat at a set of lights you'll see some markings where the sensors are, when you run over them at a night time the lights change for you.

You haven't driven round Staines in the wee small hours then. The lights seem to be designed to sense you coming and turn red

[ZrByte]

Originally Posted by Rob C

You haven't driven round Staines in the wee small hours then. The lights seem to be designed to sense you coming and turn red

I found the same thing driving through Liverpool city center in the early hours yesterday morning.
I love driving through my home town as I get the exact opposite and get nothing but green lights but last night was a nightmare, it took about 10mins extra on a 40min trip just because of the amount of time I spent sat at red lights while nothing went by in the opposite direction.

Originally Posted by Rob C

You haven't driven round Staines in the wee small hours then. The lights seem to be designed to sense you coming and turn red

Lol well the lights work ok in Mansfield.

[Gareth]

Originally Posted by Rob C

You haven't driven round Staines in the wee small hours then. The lights seem to be designed to sense you coming and turn red

Rob, that's the Bling Sensor that they had to install in all traffic lights across Staines that is causing this to happen

[MovedGoalPosts]

What you mean if you don't have bling you get stopped

[Stuart]

Just to complicate things a little further, they are currently installing a system in London that changes the prioty of Traffic lights when Buses approach. A similar system is already in place in Croydon (basically, the Croydon tramlink takes priority over any other road traffic).

http://www.buspriority.org/overview.htm

[bob_a_builder]

Great for vehicles to trigger a light change, but useless if your on a pushbike

No one else picked up on the novelty value of a cyclist actually stopping at a red traffic light anyway