M42 Variable speed limits
Discussion
Travelling along the M42 a few times recently I can’t help but think the constantly changing variable speed limits are done deliberately to catch people out. On one short stretch past Birmingham airport saw us go from 60 to 50 to 40 then 50 then back to 40 then 60 then back to 40 and then finally no limit so 70. All the time there was nothing noticeable that needed changing limits, no workmen, no broken down cars etc etc.
Colleague did a course after being snapped at 46 when set to 40 - 6.15AM, light traffic. Half the people on the course had been caught the same way.
He was oddly fine about it - although there was some issue with the paperwork and he nearly got prosecuted so being "allowed" to do the course probably seemed like a let-off.
He was oddly fine about it - although there was some issue with the paperwork and he nearly got prosecuted so being "allowed" to do the course probably seemed like a let-off.
SLK55AMG said:
Travelling along the M42 a few times recently I can’t help but think the constantly changing variable speed limits are done deliberately to catch people out. On one short stretch past Birmingham airport saw us go from 60 to 50 to 40 then 50 then back to 40 then 60 then back to 40 and then finally no limit so 70. All the time there was nothing noticeable that needed changing limits, no workmen, no broken down cars etc etc.
I remember reading about the reasoning behind the variable speed limits when they were first introduced.The theory is that during periods of high weight of traffic, reducing limits helps to smooth the flow and prevents "phantom traffic jams" occurring.
SLK55AMG said:
Travelling along the M42 a few times recently I can’t help but think the constantly changing variable speed limits are done deliberately to catch people out. On one short stretch past Birmingham airport saw us go from 60 to 50 to 40 then 50 then back to 40 then 60 then back to 40 and then finally no limit so 70. All the time there was nothing noticeable that needed changing limits, no workmen, no broken down cars etc etc.
Sometimes it seems the operators are having a laugh at the motorists' expense but suspect this ridiculous charade is just caused by incompetence.I have a theoretical question on these cameras.
Imagine you are 50 yds from the camera doing 50mph - with the camera reading 50 - then with 50 yards to go it changes to 40mph as you go through - would the camera flash ?
Then imagine the other way it’s reading 50 and let’s assume your doing 60 and then it changes to 60 with 50 yds to go as you go through - would the camera flash?
I’m just trying to understand if any camera delay works one way ? Or both ways ?
Imagine you are 50 yds from the camera doing 50mph - with the camera reading 50 - then with 50 yards to go it changes to 40mph as you go through - would the camera flash ?
Then imagine the other way it’s reading 50 and let’s assume your doing 60 and then it changes to 60 with 50 yds to go as you go through - would the camera flash?
I’m just trying to understand if any camera delay works one way ? Or both ways ?
Markp1706 said:
I have a theoretical question on these cameras.
Imagine you are 50 yds from the camera doing 50mph - with the camera reading 50 - then with 50 yards to go it changes to 40mph as you go through - would the camera flash ?
Then imagine the other way it’s reading 50 and let’s assume your doing 60 and then it changes to 60 with 50 yds to go as you go through - would the camera flash?
I’m just trying to understand if any camera delay works one way ? Or both ways ?
The speed change is one sign, the camera will be a different one further on.Imagine you are 50 yds from the camera doing 50mph - with the camera reading 50 - then with 50 yards to go it changes to 40mph as you go through - would the camera flash ?
Then imagine the other way it’s reading 50 and let’s assume your doing 60 and then it changes to 60 with 50 yds to go as you go through - would the camera flash?
I’m just trying to understand if any camera delay works one way ? Or both ways ?
Mandat said:
I remember reading about the reasoning behind the variable speed limits when they were first introduced.
The theory is that during periods of high weight of traffic, reducing limits helps to smooth the flow and prevents "phantom traffic jams" occurring.
But I think we all know that is nonsense! The theory is that during periods of high weight of traffic, reducing limits helps to smooth the flow and prevents "phantom traffic jams" occurring.
I'm a regular user of the M25 and every time I've joined it at J12 from the M3 going anti-clockwise for over 10 years there has been a reduced limit and a queue on the slip-road, that mysteriously disappears after J11 when the limit goes back to the NSL - only exception was Christmas Day a few years ago, and not surprisingly the traffic flowed really well!
Reduced limits just seem to bottle up traffic and create hold-ups.
Mr Tidy said:
But I think we all know that is nonsense!
I'm a regular user of the M25 and every time I've joined it at J12 from the M3 going anti-clockwise for over 10 years there has been a reduced limit and a queue on the slip-road, that mysteriously disappears after J11 when the limit goes back to the NSL - only exception was Christmas Day a few years ago, and not surprisingly the traffic flowed really well!
Reduced limits just seem to bottle up traffic and create hold-ups.
Have you got evidence that it's the variable speed limit that causes the hold up?I'm a regular user of the M25 and every time I've joined it at J12 from the M3 going anti-clockwise for over 10 years there has been a reduced limit and a queue on the slip-road, that mysteriously disappears after J11 when the limit goes back to the NSL - only exception was Christmas Day a few years ago, and not surprisingly the traffic flowed really well!
Reduced limits just seem to bottle up traffic and create hold-ups.
BertBert said:
Mr Tidy said:
But I think we all know that is nonsense!
I'm a regular user of the M25 and every time I've joined it at J12 from the M3 going anti-clockwise for over 10 years there has been a reduced limit and a queue on the slip-road, that mysteriously disappears after J11 when the limit goes back to the NSL - only exception was Christmas Day a few years ago, and not surprisingly the traffic flowed really well!
Reduced limits just seem to bottle up traffic and create hold-ups.
Have you got evidence that it's the variable speed limit that causes the hold up?I'm a regular user of the M25 and every time I've joined it at J12 from the M3 going anti-clockwise for over 10 years there has been a reduced limit and a queue on the slip-road, that mysteriously disappears after J11 when the limit goes back to the NSL - only exception was Christmas Day a few years ago, and not surprisingly the traffic flowed really well!
Reduced limits just seem to bottle up traffic and create hold-ups.
BertBert said:
Mr Tidy said:
But I think we all know that is nonsense!
I'm a regular user of the M25 and every time I've joined it at J12 from the M3 going anti-clockwise for over 10 years there has been a reduced limit and a queue on the slip-road, that mysteriously disappears after J11 when the limit goes back to the NSL - only exception was Christmas Day a few years ago, and not surprisingly the traffic flowed really well!
Reduced limits just seem to bottle up traffic and create hold-ups.
Have you got evidence that it's the variable speed limit that causes the hold up?I'm a regular user of the M25 and every time I've joined it at J12 from the M3 going anti-clockwise for over 10 years there has been a reduced limit and a queue on the slip-road, that mysteriously disappears after J11 when the limit goes back to the NSL - only exception was Christmas Day a few years ago, and not surprisingly the traffic flowed really well!
Reduced limits just seem to bottle up traffic and create hold-ups.
But as someone else has already said do you have evidence that reduced limits don't create bunching? Logic suggests to me that they always will as the volume of traffic a motorway can handle at 70mph is going to be reduced with a 50mph limit.
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