Whats a speed sensitive traffic light?
Discussion
omitchell said:
it think it's a red light camera that also acts as a speed camera when the lights are green
No such thing AFAIK
BliarOut said:
I think it checks your speed against the limit. If you're going quick, it goes red to slow you down. If your speed is inside the limit it stays green. Effectively, you travel quicker by going more slowly.
No such thing AFAIK
dilbert said:
Another revenue generator, that's what.
Em, nope...
They date back to well before speed cameras, red light cameras or anything like that. In fact, I think the section on speed detection at traffic signals is one of the oldest sections in the Design Manual for Roads and Bridges, since it was produced in the mid 1970s and hasn't been updated since, while just about everything else has.
What it does is simple. At high-speed signals (defined as "where traffic approaches faster than 35 mph") it adds two safety features, using loops in the road well before the normal 3 X, Y and Z loops in the road. It doesn't use microwave detection or cameras at all.
If the signals are at green, and a car crosses the speed loops at a fair clip, it extends the green for a second or two to let that car reach the normal detectors, so that the lights don't change in front of it and leave the driver either unable to stop or forced to go through on red.
If the signals have just changed to red, and a car crosses the loop at speed in the next second or two, it automatically extends the all-red intergreen for a couple of seconds in case that driver couldn't stop, to give him time to clear the junction before anybody else gets a green.
Simple 30-year-old safety feature, nothing more, no individual vehice recognition, no mechanism for prosecution - it doesn't even store the speed in a memory for any later accident investigation if a crash does occur.
Don't be paranoid...
markmullen said:
AFAIK some of the newer speed sensitive traffic lights use the sensor on top of the pole above the lights themselves to sense speed for the reasons above. Certainly old radar detectors go crazy approaching the lights.
Those microwave sensors can't differentiate speed - they only provide a doppler effect binary signal - ie there's a vehicle moving there (so change the signals) or there isn't...
tvrgit said:
Those microwave sensors can't differentiate speed - they only provide a doppler effect binary signal - ie there's a vehicle moving there (so change the signals) or there isn't...
Which would explain why detectors are set off by them.
Thanks for clearing that one up tvrgit, always wondered about that.
dilbert said:
I never knew that.
I doubt any new initiatives of that sort will come along again......
[michaelcaine]notalotapeopleknowthat[/michaelcaine]
You'd be surprised at how many "initiatives" are still coming on board, there are still some who want to try to help traffic flow rather than hinder it. Computer control and variable plans help, for a start, and are still developing. Of course it all depends on the designer and also on the "political" (small p) will to improve traffic flow and safety...
The 'speed sensitive traffic lights' (SSTL) I am referring to when I mention them, are an alternative to speed cameras.
They are used on the continent, I've had the experience of going through them with and without triggering them.
There is a mechanism to detect you speed. Just like a gatso or truvelo. It does not do anything nasty however like take your picture or details, what it does is instruct a traffic light further up the road to turn red. So:
Driving slowly through a SSTL:
The light stays green
Driving too fast through a SSTL:
The traffic light ahead turns red
You stop and wait a bit
The light turns green
You go
What this actually means is that the speed limit is ALWAYS enforced (unless you fancy jumping a red light), and nobody gets upset, no fines, no NIPs.
This is very different to a British speed camera which works this way:
Driving slowly through a Gatso/truvelo:
No action
Driving too fast through a Gatso/truvelo:
You continue too fast (unsafe)
Blinding flashes, 3 points, £60, complications
So the British system fails and then punishes you, the continental system just slows you down.
The difference? Safety and money.
They are used on the continent, I've had the experience of going through them with and without triggering them.
There is a mechanism to detect you speed. Just like a gatso or truvelo. It does not do anything nasty however like take your picture or details, what it does is instruct a traffic light further up the road to turn red. So:
Driving slowly through a SSTL:
The light stays green
Driving too fast through a SSTL:
The traffic light ahead turns red
You stop and wait a bit
The light turns green
You go
What this actually means is that the speed limit is ALWAYS enforced (unless you fancy jumping a red light), and nobody gets upset, no fines, no NIPs.
This is very different to a British speed camera which works this way:
Driving slowly through a Gatso/truvelo:
No action
Driving too fast through a Gatso/truvelo:
You continue too fast (unsafe)
Blinding flashes, 3 points, £60, complications
So the British system fails and then punishes you, the continental system just slows you down.
The difference? Safety and money.
Globulators said:
The 'speed sensitive traffic lights' (SSTL) I am referring to when I mention them, are an alternative to speed cameras.
They are used on the continent, I've had the experience of going through them with and without triggering them.
There is a mechanism to detect you speed. Just like a gatso or truvelo. It does not do anything nasty however like take your picture or details, what it does is instruct a traffic light further up the road to turn red. So:
Driving slowly through a SSTL:
The light stays green
Driving too fast through a SSTL:
The traffic light ahead turns red
You stop and wait a bit
The light turns green
You go
What this actually means is that the speed limit is ALWAYS enforced (unless you fancy jumping a red light), and nobody gets upset, no fines, no NIPs.
This is very different to a British speed camera which works this way:
Driving slowly through a Gatso/truvelo:
No action
Driving too fast through a Gatso/truvelo:
You continue too fast (unsafe)
Blinding flashes, 3 points, £60, complications
So the British system fails and then punishes you, the continental system just slows you down.
The difference? Safety and money.
They have these in Spain at the beginning of a village.
The locals simply ignore them.
I adhered to them by driving up to them at the speed limit. They went red anyway. Why? Because the car behind rushed to catch me up at a rate of knots and it went red for *that* car - stopping me in the process. One guy nearly ran into the back of me because he simply couldn't believe I would adhere to the (very low) speed limit...and that I would not run a red light!
They don't work IMO. AND they "teach" people to run red lights - which once the red light is at a junction becomes very dangerous.
>> Edited by Don on Monday 7th February 08:47
Don said:
They have these in Spain at the beginning of a village.
The locals simply ignore them.
I adhered to them by driving up to them at the speed limit. They went red anyway. Why? Because the car behind rushed to catch me up at a rate of knots and it went red for *that* car - stopping me in the process. One guy nearly ran into the back of me because he simply couldn't believe I would adhere to the (very low) speed limit...and that I would not run a red light!
They don't work IMO. AND they "teach" people to run red lights - which once the red light is at a junction becomes very dangerous.
>> Edited by Don on Monday 7th February 08:47
It's interesting they have them in Spain, I see them in the middle of small Portugeues villages too - but people repect the red lights there. Funny as most drivers in Portugal are nuts.
More people in the UK are jumping red lights than before, probably caused by crxp phasing and people in a hurry. Advertised red-light cameras (that JUST do that) might cure that - although they make the stop-or-go decision more complex.
Either way we'll have to choose between the following (in order of getting better):
a) speed bumps (crxp)
b) revenue gathering cameras (cynical)
c) SSTLs (they work if you respect red lights)
d) the speed triggered 30 signs (not teen proof)
e) - nothing is often not a possible option (sadly due to teen racer numpties).
I quite often see a nice village with no signs, and the teen village idiot in his chav nova teararsing through. It's very difficult to blame residents with cats and children for wanting to slow them down!
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