Stopping too far back at red traffic signals - driver stupidity or lack of education?

sheramber

This morning temporary traffic lights on the main road through the town are stuck on red at both ends. Long queues at both sides when the first in line is waiting for a green light.

AdrianC

unforeseen said:

ontheroad1970 said:

Permanent lights usually have 3 sets of sensors.

And most work on a timed sequence rather than vehicle detection. 

Many are vehicle detection - you can see the small sensor on top of the main light. Usually, there's a tiny red light that comes on when it senses vehicle movement. You can see how far away it detects quite easily.



If there's a vehicle sensing loop buried in the road, you can usually see the marks in the road surface.

In the instance the OP describes, I suspect the key is that it was a learner. I'd suspect that the lights sensed the car, the driver stalled it. By the time they'd restarted it, they'd missed the green - but of course since they didn't move again, the lights didn't sense their presence.

The issue was not the distance from the lights - but the lack of movement since the lights went red. They simply "didn't know" there was anybody there, until the vehicle moved again.

JenB79

These are the lights where it happened, there's clearly a sensor of some sort at the top:

 

And this is the light on the side street (where I live) and only turns green on demand:

Ectophile

The sensor on top of the temporary lights (and some fixed traffic lights too) is most likely a doppler radar.  It's looking for moving lumps of metal.  If you don't move, then you're part of the street furniture, and it ignores you.

JenB79

Ectophile said:

The sensor on top of the temporary lights (and some fixed traffic lights too) is most likely a doppler radar.  It's looking for moving lumps of metal.  If you don't move, then you're part of the street furniture, and it ignores you.

So does that mean when the learner car first stopped nr the lights, it stopped outside the field of view of the radar? 

Manxman_in_exile

JenB79 said:

Ectophile said:

The sensor on top of the temporary lights (and some fixed traffic lights too) is most likely a doppler radar.  It's looking for moving lumps of metal.  If you don't move, then you're part of the street furniture, and it ignores you.

So does that mean when the learner car first stopped nr the lights, it stopped outside the field of view of the radar? 

Not necessarily?

AdrianC said:

unforeseen said:

ontheroad1970 said:

Permanent lights usually have 3 sets of sensors.

And most work on a timed sequence rather than vehicle detection. 

...In the instance the OP describes, I suspect the key is that it was a learner. I'd suspect that the lights sensed the car, the driver stalled it. By the time they'd restarted it, they'd missed the green - but of course since they didn't move again, the lights didn't sense their presence.

The issue was not the distance from the lights - but the lack of movement since the lights went red. They simply "didn't know" there was anybody there, until the vehicle moved again.

mac.d

AdrianC said:

In the instance the OP describes, I suspect the key is that it was a learner. I'd suspect that the lights sensed the car, the driver stalled it. By the time they'd restarted it, they'd missed the green - but of course since they didn't move again, the lights didn't sense their presence.

The issue was not the distance from the lights - but the lack of movement since the lights went red. They simply "didn't know" there was anybody there, until the vehicle moved again.

Good shout, that seems the most likely scenario.

Car_54

sheramber said:

The temporary lights around us have a  sensor on the top angled to the road. If you do not drive close enough to be in the beam it does not register. hence why there is normally a board saying stop here.  I have seen drivers stop too far back and have to edge forward to trigger the sensor.

That's not the reason for the "Stop here" sign. It's a legal requirement, and they were around long before sensors were thought of.

force_ten

the problem is not stopping to far back because a portable light head fitted with microwave detectors will pick up vehicles that are 40mts down the road and detect up to 5mts from the signal head so at 3mts the car had travelled through the full range of the microwave detector

the biggest problem at temporary lights working in vehicle activation mode and using microwave detectors is creeping, this is where the driver sees the lights and slows down in anticipation of the lights changing and slowly creeps up to the light head and stops 

if they travel through the 40mt to 5mt detection zone at speeds lower than 10mph then the microwave detectors will not send a demand signal to the controller and the lights will not change, but the system has a nudge circuit fitted where the control unit sees no demand from the light head and automatically runs a full cycle nudge is normally set between 2.5 minutes and 3 minutes but this time may be extended slightly at a set of three way lights but should never be over 5 minutes between nudges 

Ectophile

JenB79 said:

Ectophile said:

The sensor on top of the temporary lights (and some fixed traffic lights too) is most likely a doppler radar.  It's looking for moving lumps of metal.  If you don't move, then you're part of the street furniture, and it ignores you.

So does that mean when the learner car first stopped nr the lights, it stopped outside the field of view of the radar? 

Maybe they were out of range.  These radars will be very low power, for safety reasons.  Or maybe, as AdrianC suggests, they missed a green and after that they became a stationary object.