Traffic lights, fast roads and the point of no return!
Discussion
Any tips on approaching traffic lights on fast roads?
Below is a junction on the A54 near Kelsall in Cheshire. I often go through in a van and have nearly been caught out by the traffic light cam on a few occasions.
My usual approach is to use two sets of lamp posts (typically 30m apart) to roughly mark the stopping distance at 60ish to gauge the "go / no-go" point but interested to hear any other views.
Below is a junction on the A54 near Kelsall in Cheshire. I often go through in a van and have nearly been caught out by the traffic light cam on a few occasions.
My usual approach is to use two sets of lamp posts (typically 30m apart) to roughly mark the stopping distance at 60ish to gauge the "go / no-go" point but interested to hear any other views.
If you are observing both the lights and the speed limits, there will be no need to stop quickly if they change to amber when you are close. If the road is a ‘fast road’ (that is, people are up to and beyond the posted limit) then;
Leave a gap from the car in front, in case they are the twitchy, hard-brake on amber type, and
Always know what is behind, and around you.
My other technique, especially on the fast, large, traffic-light roundabouts between A/M roads, is, if the green is on for some time as I approach, observe behind, check for red-light runners going across, lift off as you approach the last 25 metres or so, and cover the brake, but do not touch the pedal. Most modern cars have very little engine braking, so you will more or less maintain speed until you take up the throttle again as you. I hasten to add that I cover the brake for red light runners going across me, NOT for a sharp stop if the lights change. Reason? I have seen too many cars chancing their arm.
ETA. Just found this site, which says similar.
https://www.joanwallacedrivingschool.com/amber-tra...
Leave a gap from the car in front, in case they are the twitchy, hard-brake on amber type, and
Always know what is behind, and around you.
My other technique, especially on the fast, large, traffic-light roundabouts between A/M roads, is, if the green is on for some time as I approach, observe behind, check for red-light runners going across, lift off as you approach the last 25 metres or so, and cover the brake, but do not touch the pedal. Most modern cars have very little engine braking, so you will more or less maintain speed until you take up the throttle again as you. I hasten to add that I cover the brake for red light runners going across me, NOT for a sharp stop if the lights change. Reason? I have seen too many cars chancing their arm.
ETA. Just found this site, which says similar.
https://www.joanwallacedrivingschool.com/amber-tra...
Edited by Pica-Pica on Thursday 13th October 16:07
Pica-Pica said:
If you are observing both the lights and the speed limits, there will be no need to stop quickly if they change to amber when you are close.
Are you sure? UK traffic lights show amber for about 3 seconds regardless of speed limit plus or minus 0.25 seconds (per Department for Transport 2016).Highway Code gives us stopping distance from 70 mph as 96m. So you are just past 96m when lights change to amber and it would take you more than 2.75 seconds to get to and through the lights ...
There are no traffic lights on NSL dual-carriageways near me, so I cannot experiment.
In recent years some junctions like that seem to have grown a short stretch of 40mph or 50mph limit, to encourage people to slow down on approach to the lights even when on green.
Seems like a good idea even if no reduced limit. Of course I mean gentle slowing down, not standing on the brake.
Seems like a good idea even if no reduced limit. Of course I mean gentle slowing down, not standing on the brake.
waremark said:
Pica-Pica said:
If you are observing both the lights and the speed limits, there will be no need to stop quickly if they change to amber when you are close.
Are you sure? UK traffic lights show amber for about 3 seconds regardless of speed limit plus or minus 0.25 seconds (per Department for Transport 2016).Highway Code gives us stopping distance from 70 mph as 96m. So you are just past 96m when lights change to amber and it would take you more than 2.75 seconds to get to and through the lights ...
There are no traffic lights on NSL dual-carriageways near me, so I cannot experiment.
On a side issue, the overall stopping distances are probably about right, although like for like vehicles have an improved braking distance nowadays, it would seem the ‘thinking’ distance is more than originally calculated, hence the importance of covering the brake on a ‘stale’ green (as said we are talking about an almost unnoticeable drop in speed when the foot is off the accelerator, and we are talking about hazardous areas.
We are so used to dibby-dabby brakes that people use 40% of total braking power and think they're on emergency brakes
Remember, if lights are green there's only one way they can change
You know what your stopping distance is, subject to not going full ABS and subject to the numpty behind you. If neither of those are an issue, don't start writing an internal monologue, just get on the brakes, you'll have far more room to play with than you think
Remember, if lights are green there's only one way they can change
You know what your stopping distance is, subject to not going full ABS and subject to the numpty behind you. If neither of those are an issue, don't start writing an internal monologue, just get on the brakes, you'll have far more room to play with than you think
Pica-Pica said:
waremark said:
Pica-Pica said:
If you are observing both the lights and the speed limits, there will be no need to stop quickly if they change to amber when you are close.
Are you sure? UK traffic lights show amber for about 3 seconds regardless of speed limit plus or minus 0.25 seconds (per Department for Transport 2016).Highway Code gives us stopping distance from 70 mph as 96m. So you are just past 96m when lights change to amber and it would take you more than 2.75 seconds to get to and through the lights ...
There are no traffic lights on NSL dual-carriageways near me, so I cannot experiment.
On a side issue, the overall stopping distances are probably about right, although like for like vehicles have an improved braking distance nowadays, it would seem the ‘thinking’ distance is more than originally calculated, hence the importance of covering the brake on a ‘stale’ green (as said we are talking about an almost unnoticeable drop in speed when the foot is off the accelerator, and we are talking about hazardous areas.
Which leaves us with the concept of the "point of no return" - to be specific, the speed/distance combination where it becomes impossible to stop before the line. These are easily determined from stopping distances, as I'm sure we all have committed to memory:
SD
80mph (35.8m/s) = 133m
70mph (31.3m/s) = 96m
60mph (26.8m/s) = 73m
50mph (22.3m/s) = 53m
Also useful is a "distance on amber":
DOA
80mph = 107.4m
70mph = 94m
60mph = 80m
50mph = 67m
Note how the DOA and SD are roughly equal at 70mph, and the SD exceeds the DOA at 80mph. Say you are doing 50mph - you can stop more quickly than you will reach the light if it changes. At 80mph however, it will take you longer to get to the light if you start to brake than if you kept your foot in. This readjustment is fundamental to assessing the safety of progressing through the junction - obviously it's always safer to be able to avoid a marginal red light by stopping rather than piling through.
Where does that leave us? Well, at 50mph you have some leeway - if you are 60m away (3 seconds) and then light changes, you have a choice of proceeding or stopping, depending on your assessment of which is safest. If you are 80m (4 seconds) away you have to stop. If you are 40m away (2 seconds) you have to go.
At 70mph you have no margin for error - closer than 95m (3 seconds) you have to go, further than that, you have to brake.
At 80mph and 120m (3 seconds again), you're stuck - too far away to get through (you need 107m), but too close to stop (you need 133m). Too fast for the junction.
I don't know about anyone else, but I can't assess distances to the metre when travelling at 70mph (30m/s). I conclude that somewhere around 50mph is the maximum safe speed to progress through a junction like that above, because you have about two seconds' thinking time before you have to commit either way.
Edited by modellista on Wednesday 2nd November 11:55
waremark said:
Are you sure? UK traffic lights show amber for about 3 seconds regardless of speed limit plus or minus 0.25 seconds (per Department for Transport 2016).
Highway Code gives us stopping distance from 70 mph as 96m. So you are just past 96m when lights change to amber and it would take you more than 2.75 seconds to get to and through the lights ...
There are no traffic lights on NSL dual-carriageways near me, so I cannot experiment.
Waremark, you are right - at 70mph there is 2m difference between having to keep going or do an emergency stop. Highway Code gives us stopping distance from 70 mph as 96m. So you are just past 96m when lights change to amber and it would take you more than 2.75 seconds to get to and through the lights ...
There are no traffic lights on NSL dual-carriageways near me, so I cannot experiment.
modellista said:
At 70mph you have no margin for error - closer than 95m (3 seconds) you have to go, further than that, you have to brake.
At 80mph and 120m (3 seconds again), you're stuck - too far away to get through (you need 107m), but too close to stop (you need 133m). Too fast for the junction.
Cracking bit of work there and fascinating result.At 80mph and 120m (3 seconds again), you're stuck - too far away to get through (you need 107m), but too close to stop (you need 133m). Too fast for the junction.
Reality is that 70mph is probably too fast to be steaming through a lot of junctions from a safety point of view...but your analysis above does tend towards a "damned if you do, damned if you don't" result when doing a legal speed. At least, the margin for error is so small that the chances of doing something either dangerous or illegal are fairly high.
modellista said:
Waremark, you are right - at 70mph there is 2m difference between having to keep going or do an emergency stop.
And that's if you get the full 3s on amber whereas there is apparently leeway in both directions.Like you, I think you should slow below 70 if approaching traffic lights on green.
Pica-Pica said:
waremark said:
Pica-Pica said:
If you are observing both the lights and the speed limits, there will be no need to stop quickly if they change to amber when you are close.
Are you sure? UK traffic lights show amber for about 3 seconds regardless of speed limit plus or minus 0.25 seconds (per Department for Transport 2016).Highway Code gives us stopping distance from 70 mph as 96m. So you are just past 96m when lights change to amber and it would take you more than 2.75 seconds to get to and through the lights ...
There are no traffic lights on NSL dual-carriageways near me, so I cannot experiment.
On a side issue, the overall stopping distances are probably about right, although like for like vehicles have an improved braking distance nowadays, it would seem the ‘thinking’ distance is more than originally calculated, hence the importance of covering the brake on a ‘stale’ green (as said we are talking about an almost unnoticeable drop in speed when the foot is off the accelerator, and we are talking about hazardous areas.
Know these lights very well, commuted along this road daily for three years.
I still drive through it on occasions, there's also another red light camera further up the road in the opposite direction to this photo which is past the Shell garage getting closer to Northwich.
I don't think I ever noticeably saw someone go through it on red, however I feel nervous every time I go through it, especially if heading to Chester about to go down the hill.
I still drive through it on occasions, there's also another red light camera further up the road in the opposite direction to this photo which is past the Shell garage getting closer to Northwich.
I don't think I ever noticeably saw someone go through it on red, however I feel nervous every time I go through it, especially if heading to Chester about to go down the hill.
Years back I complained about a set of lights locally on an NSL dual carriageway. The Amber timing was 2.1 seconds being the most accurate I could get it. Just to make things worse the eejits had put a combined Speed RL camera on it with a hair trigger and it was just a spot waiting for a giant rear end collision with the combination of locals who had sussed the situation pegging their speed back and ready to jump on the brakes versus strangers barrelling on unabated.
The excuse given was that this was an experimental camera setup, nobody would be prosecuted, yet they were completely oblivious to the increased risk of collisions.
Situation these days is that the camera has been removed and 40 limits imposed.
The excuse given was that this was an experimental camera setup, nobody would be prosecuted, yet they were completely oblivious to the increased risk of collisions.
Situation these days is that the camera has been removed and 40 limits imposed.
It's almost as if they should increase the amber time on fast roads, so that you have a reasonable time to stop when it changes.
The East Lancs coming out of bolton way is another example; you get very little time to make a decision, and if you do decide to stop, you have to stop pretty hard, which in itself can be dangerous.
Time on amber should surely be callibrated to the speed of the road, with a set minimum.
The East Lancs coming out of bolton way is another example; you get very little time to make a decision, and if you do decide to stop, you have to stop pretty hard, which in itself can be dangerous.
Time on amber should surely be callibrated to the speed of the road, with a set minimum.
1993ish, North Circular Rd, Hanger Gyratory System. Travelling southbound from Ace Cafe, Stonebridge, towards Ealing.
Metro Panda car following too closely
Prepped student re car to close, ATL light change possibility, ability to stop safely before stop line
Informed too close to stop and to proceed, lights changed, student panicked and went for brakes cos of police, I put foot under brake, instructed for gas, no response, had to lean over and push gas.
Got through lights fine, but met with vehicles coming from North Circular coming from Ealing on green. Lots leaning on horn etc.
Exited A40 Uxbridge and took first left and parked to debrief.
Metro panda pulled up and the questions started:
Why through red? Explained he was too close and to stop at the line could have caused a collision. I would have had to stop after the line.
Did I see that my actions had stopped the free movement on green? Yes, page 54 (old HC) states "proceed if safe to do so" (sorry, I used to know it verbatim but the wording has now changed). We were clearing the junction so it was not safe for the vehicles to move as it was not clear.
Went through it all a few times until he said "OK, I will let you off this time", at which point I started to raise my voice, asked for his number, station etc. A call later, the desk sergeant was crying and told me he would have a whip round for a Highway Code and bid me good day.
My student was absolutely gobsmacked at the dismantling of what he thought was a sure ticket. I resumed the debrief, which he was familiar with anyway, as the sun roof was open
and continued our lesson (with a little extra time added on for (no) penalties.
Metro Panda car following too closely
Prepped student re car to close, ATL light change possibility, ability to stop safely before stop line
Informed too close to stop and to proceed, lights changed, student panicked and went for brakes cos of police, I put foot under brake, instructed for gas, no response, had to lean over and push gas.
Got through lights fine, but met with vehicles coming from North Circular coming from Ealing on green. Lots leaning on horn etc.
Exited A40 Uxbridge and took first left and parked to debrief.
Metro panda pulled up and the questions started:
Why through red? Explained he was too close and to stop at the line could have caused a collision. I would have had to stop after the line.
Did I see that my actions had stopped the free movement on green? Yes, page 54 (old HC) states "proceed if safe to do so" (sorry, I used to know it verbatim but the wording has now changed). We were clearing the junction so it was not safe for the vehicles to move as it was not clear.
Went through it all a few times until he said "OK, I will let you off this time", at which point I started to raise my voice, asked for his number, station etc. A call later, the desk sergeant was crying and told me he would have a whip round for a Highway Code and bid me good day.
My student was absolutely gobsmacked at the dismantling of what he thought was a sure ticket. I resumed the debrief, which he was familiar with anyway, as the sun roof was open
and continued our lesson (with a little extra time added on for (no) penalties.Edited by PhilAsia on Friday 4th November 16:37
Percy. said:
Know these lights very well, commuted along this road daily for three years.
I still drive through it on occasions, there's also another red light camera further up the road in the opposite direction to this photo which is past the Shell garage getting closer to Northwich.
I don't think I ever noticeably saw someone go through it on red, however I feel nervous every time I go through it, especially if heading to Chester about to go down the hill.
I live near Kelsall and I think they put the camera there as people were ignoring the red light when turning left into the village. It's unusual for traffic to turn right across the road at the point, and you can see it clearly anyway, so the red at that point is a bit of a nonsense.I still drive through it on occasions, there's also another red light camera further up the road in the opposite direction to this photo which is past the Shell garage getting closer to Northwich.
I don't think I ever noticeably saw someone go through it on red, however I feel nervous every time I go through it, especially if heading to Chester about to go down the hill.
My wife freaks out about these cameras - to the extent that she has an SAC coming up after being caught doing 35 by one on the A41 in Chester.
PhilAsia said:
1993ish, North Circular Rd, Hanger Gyratory System. Travelling southbound from Ace Cafe, Stonebridge, towards Ealing.
Metro Panda car following too closely
Prepped student re car to close, ATL light change possibility, ability to stop safely before stop line
Informed too close to stop and to proceed, lights changed, student panicked and went for brakes cos of police, I put foot under brake, instructed for gas, no response, had to lean over and push gas.
Got through lights fine, but met with vehicles coming from North Circular coming from Ealing on green. Lots leaning on horn etc.
Exited A40 Uxbridge and took first left and parked to debrief.
Metro panda pulled up and the questions started:
Why through red? Explained he was too close and to stop at the line could have caused a collision. I would have had to stop after the line.
Did I see that my actions had stopped the free movement on green? Yes, page 54 (old HC) states "proceed if safe to do so" (sorry, I used to know it verbatim but the wording has now changed). We were clearing the junction so it was not safe for the vehicles to move as it was not clear.
Went through it all a few times until he said "OK, I will let you off this time", at which point I started to raise my voice, asked for his number, station etc. A call later, the desk sergeant was crying and told me he would have a whip round for a Highway Code and bid me good day.
My student was absolutely gobsmacked at the dismantling of what he thought was a sure ticket. I resumed the debrief, which he was familiar with anyway, as the sun roof was open and continued our lesson (with a little extra time added on for (no) penalties.
And then everyone in the station started clapping?Metro Panda car following too closely
Prepped student re car to close, ATL light change possibility, ability to stop safely before stop line
Informed too close to stop and to proceed, lights changed, student panicked and went for brakes cos of police, I put foot under brake, instructed for gas, no response, had to lean over and push gas.
Got through lights fine, but met with vehicles coming from North Circular coming from Ealing on green. Lots leaning on horn etc.
Exited A40 Uxbridge and took first left and parked to debrief.
Metro panda pulled up and the questions started:
Why through red? Explained he was too close and to stop at the line could have caused a collision. I would have had to stop after the line.
Did I see that my actions had stopped the free movement on green? Yes, page 54 (old HC) states "proceed if safe to do so" (sorry, I used to know it verbatim but the wording has now changed). We were clearing the junction so it was not safe for the vehicles to move as it was not clear.
Went through it all a few times until he said "OK, I will let you off this time", at which point I started to raise my voice, asked for his number, station etc. A call later, the desk sergeant was crying and told me he would have a whip round for a Highway Code and bid me good day.
My student was absolutely gobsmacked at the dismantling of what he thought was a sure ticket. I resumed the debrief, which he was familiar with anyway, as the sun roof was open
and continued our lesson (with a little extra time added on for (no) penalties.Edited by PhilAsia on Friday 4th November 16:37
fidzer said:
PhilAsia said:
1993ish, North Circular Rd, Hanger Gyratory System. Travelling southbound from Ace Cafe, Stonebridge, towards Ealing.
Metro Panda car following too closely
Prepped student re car to close, ATL light change possibility, ability to stop safely before stop line
Informed too close to stop and to proceed, lights changed, student panicked and went for brakes cos of police, I put foot under brake, instructed for gas, no response, had to lean over and push gas.
Got through lights fine, but met with vehicles coming from North Circular coming from Ealing on green. Lots leaning on horn etc.
Exited A40 Uxbridge and took first left and parked to debrief.
Metro panda pulled up and the questions started:
Why through red? Explained he was too close and to stop at the line could have caused a collision. I would have had to stop after the line.
Did I see that my actions had stopped the free movement on green? Yes, page 54 (old HC) states "proceed if safe to do so" (sorry, I used to know it verbatim but the wording has now changed). We were clearing the junction so it was not safe for the vehicles to move as it was not clear.
Went through it all a few times until he said "OK, I will let you off this time", at which point I started to raise my voice, asked for his number, station etc. A call later, the desk sergeant was crying and told me he would have a whip round for a Highway Code and bid me good day.
My student was absolutely gobsmacked at the dismantling of what he thought was a sure ticket. I resumed the debrief, which he was familiar with anyway, as the sun roof was open and continued our lesson (with a little extra time added on for (no) penalties.
And then everyone in the station started clapping?Metro Panda car following too closely
Prepped student re car to close, ATL light change possibility, ability to stop safely before stop line
Informed too close to stop and to proceed, lights changed, student panicked and went for brakes cos of police, I put foot under brake, instructed for gas, no response, had to lean over and push gas.
Got through lights fine, but met with vehicles coming from North Circular coming from Ealing on green. Lots leaning on horn etc.
Exited A40 Uxbridge and took first left and parked to debrief.
Metro panda pulled up and the questions started:
Why through red? Explained he was too close and to stop at the line could have caused a collision. I would have had to stop after the line.
Did I see that my actions had stopped the free movement on green? Yes, page 54 (old HC) states "proceed if safe to do so" (sorry, I used to know it verbatim but the wording has now changed). We were clearing the junction so it was not safe for the vehicles to move as it was not clear.
Went through it all a few times until he said "OK, I will let you off this time", at which point I started to raise my voice, asked for his number, station etc. A call later, the desk sergeant was crying and told me he would have a whip round for a Highway Code and bid me good day.
My student was absolutely gobsmacked at the dismantling of what he thought was a sure ticket. I resumed the debrief, which he was familiar with anyway, as the sun roof was open
and continued our lesson (with a little extra time added on for (no) penalties.Edited by PhilAsia on Friday 4th November 16:37
... after it's been explained to them. ™ Alfie Moore.
Pica-Pica said:
If you are observing both the lights and the speed limits, there will be no need to stop quickly if they change to amber when you are close. If the road is a ‘fast road’ (that is, people are up to and beyond the posted limit) then;
Leave a gap from the car in front, in case they are the twitchy, hard-brake on amber type, and
Always know what is behind, and around you.
My other technique, especially on the fast, large, traffic-light roundabouts between A/M roads, is, if the green is on for some time as I approach, observe behind, check for red-light runners going across, lift off as you approach the last 25 metres or so, and cover the brake, but do not touch the pedal. Most modern cars have very little engine braking, so you will more or less maintain speed until you take up the throttle again as you. I hasten to add that I cover the brake for red light runners going across me, NOT for a sharp stop if the lights change. Reason? I have seen too many cars chancing their arm.
ETA. Just found this site, which says similar.
https://www.joanwallacedrivingschool.com/amber-tra...
From the link-Leave a gap from the car in front, in case they are the twitchy, hard-brake on amber type, and
Always know what is behind, and around you.
My other technique, especially on the fast, large, traffic-light roundabouts between A/M roads, is, if the green is on for some time as I approach, observe behind, check for red-light runners going across, lift off as you approach the last 25 metres or so, and cover the brake, but do not touch the pedal. Most modern cars have very little engine braking, so you will more or less maintain speed until you take up the throttle again as you. I hasten to add that I cover the brake for red light runners going across me, NOT for a sharp stop if the lights change. Reason? I have seen too many cars chancing their arm.
ETA. Just found this site, which says similar.
https://www.joanwallacedrivingschool.com/amber-tra...
Edited by Pica-Pica on Thursday 13th October 16:07
Most professionally trained drivers will internalize the thought process of approaching intersections.
They are actively thinking about stopping by covering the brake.
Only when past the point of no return will they move their foot from covering the brake back to the accelerator.
Just about covers it, in my humble opinion if you observe the speed limit, anticipate the lights changing you should be able to stop before the red, I don’t think passing an amber is an offence, is it?
I often do online HC quizzes, and this subject comes up.”Wht should you do when approaching traffic lights at green”, choices are usually speed up, slow down or carry out and be ready to slow down and stop, the answer is always carry on and be prepared.
You also mentioned stopping distance from 70, but I may be wrong but I don’t think there are traffic lights on NSL, near me they drop to 40 before the lights and the junction for obvious reasons.
Edited by Vipers on Thursday 5th January 09:07
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