managed motorway conundrum
Discussion
Northbound M1 around J7 northwards. Gantries showing various random speeds. In the distance you can see the final illuminated gantry showing the NSL symbol, as you pass the penultimate gantry it is showing 50 mph.
1. Although legally the limit on the section I'm on is 50, I can't bring myself to do that and accelerate up to 70 in anticipation of the final gantry. Could I be prosecuted for this?
2. Obviously I can't see the gantry behind me, so if the road clears, that could change to NSL. Then drivers could be passing that gantry and legally travelling at 70 mph, while I am restricted to doing 50 (or even 40) until I pass the next gantry. Surely that's dangerous?
3. Reverse the situation, and I passed the gantry at a legal 70, then the signs change to 50, but I can't see the one dictating the road I'm on. Driving on bits of road where you don't know the speed limit in force is the conundrum.
So do cameras only enforce at the sign locations, or could there be intermediate cameras? How would a policeman with a laser gun know the limit in force on the section of road he is watching? Does that mean that these sections are unenforceable by 'normal' monitoring?
1. Although legally the limit on the section I'm on is 50, I can't bring myself to do that and accelerate up to 70 in anticipation of the final gantry. Could I be prosecuted for this?
2. Obviously I can't see the gantry behind me, so if the road clears, that could change to NSL. Then drivers could be passing that gantry and legally travelling at 70 mph, while I am restricted to doing 50 (or even 40) until I pass the next gantry. Surely that's dangerous?
3. Reverse the situation, and I passed the gantry at a legal 70, then the signs change to 50, but I can't see the one dictating the road I'm on. Driving on bits of road where you don't know the speed limit in force is the conundrum.
So do cameras only enforce at the sign locations, or could there be intermediate cameras? How would a policeman with a laser gun know the limit in force on the section of road he is watching? Does that mean that these sections are unenforceable by 'normal' monitoring?
speedking31 said:
The point is that once I've passed the gantry I don't know what the limit is.
The limit is what the last indication told you, and stays that way until you pass another indicator which shows a different speed. In your example the limit stays at 50 until you pass the NSL indicator. If the road has cameras on it between the 50 and NSL indicators you could receive a fine if they are average speed and/or spot speed traps.1) This is no different to any other speed limit on any other road. Until you pass the signpost, you are controlled by the speed limit that applies to the piece of road you are on, and not the speed limit up ahead. It doesn't apply until you have passed it.
2) This will always be the case with variable speed limits, that the limit can change on the section of road you're on. Overhead gantries tend to be quite close together so you'll never be in a position where you're under the wrong limit for long.
3) I presume any speed cameras will wait for traffic to clear that section before they become active, to avoid catching drivers who passed under a higher limit.
2) This will always be the case with variable speed limits, that the limit can change on the section of road you're on. Overhead gantries tend to be quite close together so you'll never be in a position where you're under the wrong limit for long.
3) I presume any speed cameras will wait for traffic to clear that section before they become active, to avoid catching drivers who passed under a higher limit.
If you were driving through a village at 30mph dodging children, puppies and kittens playing in the road would you accelerate because you could see the NSL sign 1/2mile in the distance? It's the same situation here legally.
ETA, d'oh, just saw the poster above wrote the same thing as me.
ETA, d'oh, just saw the poster above wrote the same thing as me.
speedking31 said:
As I said.
So every time the system turns off, drivers in the last controlled section MUST continue at 40 or 50 mph while those coming along behind can be legally doing 70! Seems to be introducing danger to me. Some gantries are a good distance apart.
It is very dangerous.So every time the system turns off, drivers in the last controlled section MUST continue at 40 or 50 mph while those coming along behind can be legally doing 70! Seems to be introducing danger to me. Some gantries are a good distance apart.
Every day lots of people fail to cope and crash.
It's a wonder the motorways even move at all due to the hundreds of crashes caused by these naughty signs.
You seem to be indicating that its dangerous for one person to do 50mph while another does 70mph, therefore justifying speeding up to 70mph in a 50mph limit? Lorries travel at 56mph with cars passing them at 70mph+, generally carnage does not ensue.
The limits 50mph, until you reach a sign telling you otherwise, its quite simple really.
The limits 50mph, until you reach a sign telling you otherwise, its quite simple really.
I had exactly this issue on the M25 the other week, As I approaced the gantry, the speed limit was 50, due to heavy traffic and the need to look where I was going I kept my eyes on the road and exactly as I passed under the gantry, Mrs OC said that the speed limit just changed to 40. So now do we have to keep staring up as we pass under gantrys just in case ?
oldchris said:
I had exactly this issue on the M25 the other week, As I approaced the gantry, the speed limit was 50, due to heavy traffic and the need to look where I was going I kept my eyes on the road and exactly as I passed under the gantry, Mrs OC said that the speed limit just changed to 40. So now do we have to keep staring up as we pass under gantrys just in case ?
Yes that's exactly what you should do. This entire thread needs a large dose of common sense.oldchris said:
I had exactly this issue on the M25 the other week, As I approaced the gantry, the speed limit was 50, due to heavy traffic and the need to look where I was going I kept my eyes on the road and exactly as I passed under the gantry, Mrs OC said that the speed limit just changed to 40. So now do we have to keep staring up as we pass under gantrys just in case ?
There was a thread on this very subject not along ago.Apparently if there is a camera on a gantry it will not start recording speeding over a changed limit for a period of time, I recall a period of 2 minutes, this to allow traffic approaching it to slow to the new speed and those that have just passed it to clear the camera trigger area.
Someone said that was very generous, I agree, 10-30 seconds should be sufficient.
sherbertdip said:
There was a thread on this very subject not along ago.
Apparently if there is a camera on a gantry it will not start recording speeding over a changed limit for a period of time, I recall a period of 2 minutes, this to allow traffic approaching it to slow to the new speed and those that have just passed it to clear the camera trigger area.
Someone said that was very generous, I agree, 10-30 seconds should be sufficient.
I'm not sure that there's any time delay involved. However, AIUI, the first gantry in a change of limit does not measure speed, only the second and subsequent ones.Apparently if there is a camera on a gantry it will not start recording speeding over a changed limit for a period of time, I recall a period of 2 minutes, this to allow traffic approaching it to slow to the new speed and those that have just passed it to clear the camera trigger area.
Someone said that was very generous, I agree, 10-30 seconds should be sufficient.
Cyder said:
They don't just turn them off iirc, they normally leave the last NSL sign on until a while after the the rest of the speed limits have been turned off.
Do they even need to do that? I'm pretty sure they have a fixed sign saying something like 'End of Managed Motorways' with a permanent NSL sign on it.[Edit] Here we go, as the M40 north becomes the M42 westbound: http://goo.gl/maps/guQig 'Variable Speed Limit Ends' and an NSL sign.
Edited by Jobbo on Friday 15th August 10:41
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