Was in the pub the other night and a friend was saying that traffic signals are quite intelligent, controlled by detectors and computers, and can monitor traffic flows to decide when to change etc. Is this true or was it just the drink speaking!
While on the subject does flashing at lights (as taxi drivers do a lot!) actually cause make them change quicker?!
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Hiya
I believe that the big sets on the junctions (i.e. not the little roads) work on two modes;
1) Static, allow the lanes a set interval each - rush hour mode I think
2) Dynamic - non rush hour times - use camera's, pressure sensors etc to change the cycle dependant on traffic. I.e. if all lanes are clear bar one - let that one go next. I think they still have to cycle all lanes fairly often to ensure that all traffic (i.e. Motorbikes) gets to go (just in case a vehicle wasn't detected..)
>While on the subject does flashing at lights (as taxi drivers do a lot!) actually cause make them change quicker?!
doubt it. I think approaching slowly to the cameras probably helps ensure detection though?!
Just my thoughts - not 100% sure how true.
I expect google knows...!
James
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Thanks for the replies James.
Blimey, guess they are intelligent and I always thought they just went through their sequences to let traffic through at set times!
I guess signals are one of those things that you just take for granted are there and don't really think how they work!
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I think they are quite clever actually. If you read the sefton pages (particularly the Scoot link) they say quite a lot about it - the types of detectors etc.
Interesting stuff really.
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Yes so its all controlled by loops in the road by the looks of it and not by camera. Will have to take a look at these loops next time I am out.
And I guess the flashing lights probably doesn't work then so may argue that with the taci driver next time I am drunk in the back of his cab!
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Round here, temporary roadwork lights have a sensor on top (as they can't easily put loops in the road!). I guess it's a movement sensor, but it could be light. I don't see that flashing it will make you stand out more but it may...
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Most of the temporary ones I come across are very intelligent, but they find brainwork tiring. So most mornings they are still soundly asleep, showing permanent red lights which mean "Do not disturb". The few early morning commuters simply ignore them.
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Most of the temporary ones I come across are very intelligent
The ones that are nearly everywhere in London nearly all the time are quite unbelievably unintelligent. Nor would three quarters of them ever have been needed until recently. One wonders quite why roadworks have to be surrounded by obstructive cages shutting off half the road when the actual hole in the carriageway is small and conveniently placed for traffic to squeeze past. One wonders too why the cages have to be there for six weeks when the actual work doesn't seem to take long. What it all looks like is undeserved profit for idle business spivs and horrible, politically-exploitable inconvenience for London drivers, all paid for by the taxpayer, local and national, and engineered by our elected representatives, with encouragement from their even worse opposite numbers elsewhere in the West.
That's what it looks like. But perhaps I am just getting irritable in my old age.
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Unfortunately, the effectiveness of traffic signalling is more a function of the intelligence of the planning folk than that of the signals themselves :-(
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Some on fast roads look for a gap in the traffic before changing from green to red. There's a name for them, but I forget what it is now.
There's a set near me, and it's a pain if one of the cars in front doesn't keep up with the traffic as the detectors see a gap and change the lights.
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Traffic lights have had sensors for many years-they used to be pneumatic- a little rubber cushion just before the lights;we had lights at the entrance to the factory where I used to work-there were three sets of sensors in the road-so someone would stop over the one furthest from the lights to make them think there was a long queue and give that road priority.The sensors in "temporary" traffic lights are usually "infra-red" and pick up the heat from the car.
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hi..
i work for a company that does this...well used to,.,,,60% redundancies anounced yesterday...
we use a unit that gets mounted into the road, its about 100m diameter and we drill a bore hole drop it in then fill in over it... and it transmitts a signal to the traffic light controler. there are 3 mounted in the road, and it can detect if a car is above each one, thereby keeping the traffic lights on green longer.
paul.
the company also does solar powered cats eys, and mains powered versions, and traffic counting equipment, you can spot the temp ones, by seeing rubber tubes across the road, but the perm ones are copper rectangles cut into the motorways with green cabinets often with solar panels mounted about 20ft above this,,,,
hmm thats enough waffle...
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Leaping up and down on those rubber cushion things was a bit of a pastime when I was a child. This, if performed accurately would get traffic lights to change and irritate drivers. Best practice though was to get a fat kid with a bike to ride back and forth over them. The weight advantage ensured a more reliable result. If one could delegate two fat kids with bikes stationed at two different approaches to a busy junction, traffic chaos could be instigated relatively easily.......Probably a good thing they have Playstations now.
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Ah yes. I recall at the age of seven or eight, when waiting for the bus after school, there would sometimes be one of those pneumatic tubes across the road attached to box with a counter in it.
A wheeled axle across it would move the counter half a click, so a car would increase the counter by one.
Goodness me, my fevered imagination was delightfully fired by stamping on it so it progressed half a unit on the counter. I gleefully imagined a council employee scratching his head at the sudden influx of unicycles.
The reality of course would be them thinking of the words "kids" and "pesky" or similar substitutes, or indeed, putting it down to a three axled vehicle. Hey, I was eight.
Edited by Dipstick on 12/11/2008 at 16:36
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Intelligent??
Yes they must be. How else could the ones on the roundabout at the intersection of A46/A6 just North of Leicester invariably stop me twice on the way round the roundabout into the services to fill up and again on the way out - at 3 or 4 or 5am when there is not another vehicle in sight?
Why don't they switch them off at night?
Grumpy Phil
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