Flashing At Traffic Lights Turn Them Green?
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emzino said:
Taxi's do this a lot around here, but I think they have moved the sensors from the top of traffic lights to the ground, since they still change when you approach in the daytime.
Craigybaby37_A3quattro
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i heard it was something to do with police cars etc with flashing lights that change them to green so its the same principle with a car flashing its lights.
through saying that some it works on and others it doesnt.
through saying that some it works on and others it doesnt.
Hotscar
Four Wheel Drifting
It does work on some, they are usually temporary lights and have a sensor on the top. It's not always the case as some company's just use a timer and as said above, modern lights (permanent) use inductive loops in the road similar to what are used for 'traffic signal camera's' before and after the white line!
Craigybaby37_A3quattro said:
Without trying to offend anybody, I've never seen so much rubbish in my life! Its an old wives tale...
No traffic lights can detect light... otherwise everybody would be flashing their lights at the things and the whole system would descend into choas! The boxes that are on the top of lights are motion detectors (the same goes for temporary lights). If you look closely you will also see exactly the same boxes pointing down towards the 'waiting' areas of pedestrian crossings... and from one side of the road to the other to check if there are pedestrians still crossing too.
Inductive loops (those lines in the road before traffics lights, basically electro magnets) on old traffic lights were designed to 'pick up' on Iron in vehicles. As the levels of Iron drops (which it has done significantly due to lightweight alloys, plastics, and other advanced maufacturing proccesses etc) the effectiveness of detection of vehicles by iron detecting induction loop is falling. This is why motion detectors are now employed as an alternative method of detection at some lights, as well as to extend the range of the detection (as traffic levels have increased) at others.
If they do change on approach (by any vehicle) it is nothing more than coincidence (many, but not all, fixed traffic lights still operate on a timer if there is no detected traffic) or the motion detector has picked up on your presence (checked all the other 'zones'... finding nothing) and has changed the light to green before you even got to the loop/lights.
auroan
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Shades said:
I beg to differ. There are a couple of sets of lights around where I live which control the flow of traffic over single lane bridges. These have sensor on them to pickup approaching traffic. Why do I know this ? I was talking to a techie who was repairing one after a truck took a light out. I was having the very same discussion with a mate in the car, hence we asked the techie.
And the induction loop argument is tross. Tell me how the induction based parking sensor works when picking up a brick wall ? Its nothing to do with iron content, is all to do with how and object alters/influences the magnetic field of the induction loop.
During the early nineties when I came back from living in the states I brought my Gul radar detector back with me.
The thing was a bit over sensitive & it always went ballistic every time I approached traffic lights, temporary or fixed with a sensor box attached (middle or top), it did not like supermarket automatic door openers either.
Although it was a pile of poo over here (it worked ok in the US) my mates called it a traffic light/supermarket detector but it did actually save me once.
So according to BELTRONICS USA the boxes used on traffic lights contain a radar sensor.
The thing was a bit over sensitive & it always went ballistic every time I approached traffic lights, temporary or fixed with a sensor box attached (middle or top), it did not like supermarket automatic door openers either.
Although it was a pile of poo over here (it worked ok in the US) my mates called it a traffic light/supermarket detector but it did actually save me once.
So according to BELTRONICS USA the boxes used on traffic lights contain a radar sensor.
Lol, the sensors you see on the top of lights are motion sensors, not lux sensors. Light doesn't move, therefore the old myth is a little busted!
Ess_Three
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timps said:<pedant mode> light does move.
I agree..
How else could one, for example, fire a laser beam at the Moon to see how far away it is, if the light beam did not travel to the Moon, reflect off the reflectors left by lunar missions, and be detected back on Earth?
Or how else would laser speed detectors work, if they did not fire a beam of laser light and time how long it takes to return to the unit?
Ess_Three
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Pah! Poor retort...
I thought you were supposed to be an Engineer?
Or is that twice removed on your Mothers side...?
I thought you were supposed to be an Engineer?
Or is that twice removed on your Mothers side...?
Ess_Three said:
It's all down to waveparticle duality and quantum mechanics. (I forgot the rest, its been too long since I did physics at school)
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Ess_Three said:
Ha, that's the point. I'm supposed to be an engineer!
However, light exists as both electromagetic waves and photons and yet it has no mass. And if you follow the theory of relativity, then if there is no mass then there can be no movement! (Actually, its also the Newtonian theory - force = mass x accelleration)
auroan
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Yes well all know wikipedia isn't 100% but... have a good read of all this
http://en.wikipedia.org/wiki/Traffic_light#Control_and_coordination.
You will note that there are a multitude of systems used;
induction, motion sensor, light/strobe sensors, noise sensors, timing, co-ordinated.
http://en.wikipedia.org/wiki/Traffic_light#Control_and_coordination.
You will note that there are a multitude of systems used;
induction, motion sensor, light/strobe sensors, noise sensors, timing, co-ordinated.
A lot of new Traffic Lights installations have sensors in the tarmac, next time your near some newish lights look about 4 metres infront of them before you get to the line and see if theres any cut lines in the road, usually means its had them fitted.
Also some lights change in a pattern, if i pootle to work through town at 40 mph all the lights on my journey to work change in sync and I tend to cruise straight through... (at 5am)
Also some lights change in a pattern, if i pootle to work through town at 40 mph all the lights on my journey to work change in sync and I tend to cruise straight through... (at 5am)
Shades said:
Not so sure about that.
Where I live, you can be sat at the lights for an absolute age, yet when a bus comes along they will immediately change.
Buses hardly ever have to slow down for these lights, never mind stop.
Whether it's just a case of the sensors being heavily angled in favour of the bus lane or not, christ knows.
An ex bus driver here insists the buses are fitted with 'strobes', whatever he means by that.
It's damned annoying though.
So annoying, in fact,that I regularly (at night, when it's quiet) ignore the lights and just treat it like a normal junction.
Those road loops are a nightmare too.
They only work if traffic moves over them.
If the traffic is static, they don't register anything 'new' and you'll sit there for an age.
I see it every night, exiting our industrial estate.
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mitch78 said:I can't believe you actually admit to that, never mind publishing the fact online!
If you were meant to treat it like a normal junction, there would be give way lines and not traffic lights. Doing something like that is asking to cause an accident, no matter how careful you are. At least a car coming up to a junction would consider that you may not have seen them and could possibly pull out in front of them, but most people just assume that if the lights for them are green, then there is no chance of cars coming through from other directions.
You may find this useful.
There's comes a point when common sense provails, when sitting at the said lights for 5 minutes and no traffic around, I'm sure most of us will just 'jump' the light as it were, don't see a problem with that myself, but not telling you to go out and break the law.
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jojo said:There's comes a point when common sense provails, when sitting at the said lights for 5 minutes and no traffic around, I'm sure most of us will just 'jump' the light as it were, don't see a problem with that myself, but not telling you to go out and break the law.
I thought the cameras on top of the traffic lights (small cameras) were there so if you do jump the lights, you get a nasty letter through the door... so there is no way you can jump the lights. Or have I been told wrong
emzino said:
No cameras on many traffic lights up here.
I defy anyone to sit at these lights for ages, at night, when there is sod all coming in either direction.
1/4 a mile straight down to a roundabout on the left.
1/2 a mile straight to the right.
Therefore, zero chance of me causing an accident.
I'm not hugely impatient, but these lights take the ****.
The council has been told about the delays, they deny a problem.
When a bus comes though, you're laughing.
emzino said:
As someone else says, common sense prevails.
If it's two in the morning, I've been sitting there for ages and I can clearly see there's feck all coming, I'm going son.
If you want to sit there, that's up to you.
bowfer said:
Okay, I concede that you may have a point (buses and sometimes emergency vehicles) can be fitted with either radio transmitters or IR strobes that can be picked up by some traffic lights but that is the exception rather than the rule... these methods can be easily replicated and therefore are open to abuse which is why they are not very common.
bowfer said:
As I said, inducution loops work by detecting changes to the magnetic field they produce by the presence of metals which can strongly affect magnetic fields, Iron being one such metal. As iron is being used less and less in the production of vehicles, in favour of lightweight alloys, plastics and other advanced, modern manufacturing processes which do not strongly, or if at all, affect magnetic fields, the effective detection rates of vehicles by induction loop has dropped.
This is why, at traffic lights without additional motion detectors, you can sit at traffic lights for ages without them realising you are even there... Then you have to (or at least should) wait for the lights to change on timer (as most still have timers in place to regularily change the lights should other vehicle detection methods fail or not detect anything over a certain period of time).
AndyMac
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Try reversing back & forth over the induction loop (traffic permitting of course).
The Italians have it absolutely right, after 11pm you can legally jump red lights with no traffic around, you can also turn right (left in the UK) on a red. Obviously the incompetent drivers in the UK could not be trusted with such common sense, which is why we have traffic lights on roundabouts (even at 3am).
The Italians have it absolutely right, after 11pm you can legally jump red lights with no traffic around, you can also turn right (left in the UK) on a red. Obviously the incompetent drivers in the UK could not be trusted with such common sense, which is why we have traffic lights on roundabouts (even at 3am).
treblesykes
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I once came up to some temporary light on a bridge in the middle of nowhere, It was about 10pm the road was straight no other cars in sight, so I went straight thru on red. A cop car immediately appeared from a little tree sheltered lay-by followed me for about 2 miles then pulled and breath tested me. I passed the test but the cops made me wait while they confirmed my details, more cops arrived and they had a long chin wag while I sat in my car waiting waiting, after about half an hour they let me on my way.
I couldnt kick up a fuss because I didnt want a producer ticket as while waiting in the car I remembered the car was overdue its MOT
I couldnt kick up a fuss because I didnt want a producer ticket as while waiting in the car I remembered the car was overdue its MOT
treblesykes said:
Ahh, the other old wives tale: If you can see the road ahead is clear on the other side of temporary traffic lights you may pass through a red light.
This may have been true once, but only on a technicality. Temporary traffic lights didn't have the same legal status as fixed traffic lights up until 1994. While you were still supposed to stop at a red light it wasn't actually punishable by law if you failed to do so. Now the laws covering temporary lights are exactly the same as fixed lights and under no circumstances can you legally pass through a red light, no matter how long you have been waiting, unless there is legal course for you to do so (i.e directed by a police officer, moving out of the way of an emergency vehicle, verifiable traffic light failure, etc).
treblesykes
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ChriS3 said:
if E=mc2 then wherever there is mass there is energy and wherever there is energy there is mass.
Light has momentum it can never be at rest but theoretically if light is trapped in a box with perfect mirrors so the photons are continually reflected back and forth in both directions symmetrically in the box, then the total momentum is zero in the box's frame of reference but the energy is not. Therefore the light adds a small contribution to the mass of the box.
So maybe the boxes on top of traffic lights contain mirrors and trap the light which now has a mass so it can be detected.
You'll probably find that the sensors on top of traffic lights are motion detectors which are linked to a timed unit/controller. In theory, these sensors should change the lights when you approach, subject to a number of variables including traffic flows (won't bore yer wth it).
The motion sensors on top of temporary lights are usually f***ed because they're usually knocked about by contractors and as a result revert to a peak hour fixed time; hence why you can sometimes spend 10 minutes hanging around when it's relatively quiet looking like a complete tit whilst waiting for the red light to turn green..
The motion sensors on top of temporary lights are usually f***ed because they're usually knocked about by contractors and as a result revert to a peak hour fixed time; hence why you can sometimes spend 10 minutes hanging around when it's relatively quiet looking like a complete tit whilst waiting for the red light to turn green..
At the end of the day they're only traffic lights. Does it really matter how they work? You'll still see the occasional dafty flashing their lights at them at nightime.
Oh, and Bowfer, for the lights around here have you tried doing the reversing and pulling forward thing? Seems to be the only way to get out of my office later on and at the weekends.
You'll still see the occasional dafty flashing their lights at them at nightime. Oh, and Bowfer, for the lights around here have you tried doing the reversing and pulling forward thing? Seems to be the only way to get out of my office later on and at the weekends.
auroan
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bowfer said:As someone else says, common sense prevails.
If it's two in the morning, I've been sitting there for ages and I can clearly see there's feck all coming, I'm going son.
If you want to sit there, that's up to you.
What we really need is common sense from the road planners etc.
In Germany at quieter junctions the lights change to flashing amber at light which turns the junction into a stop or give way junction so provided it's clear you can go instead of waiting.
I'm always tempted to drive through pelican crossings (especially the ones right on roundabout exits in Aberdeen
) at red when the person who pressed the button has already crossed but knowing my luck I'd get caught.
