Smart Motorway limits start/end points
Discussion
Evening all, just a bit of a pondering relating to motorway smart limits. I suspect i know the answer but as I cant find confirmation anywhere just wanted to double check.
Hypothetical situation, Ive just gone under a smart gantry sign on the motorway indicating the limit is 50mph. I am travelling at 50mph. I can see a few hundred yards ahead the next gantry is posting the national limit sign.
So can I legally start accelerating to 70mph once I see the sign or do I have to wait until I pass the demarcation point of the gantry with the national limit signs and then accelerate to 70mph. I.e. the limit is from the signs onwards per every other speed limit sign posting.
I currently play it safe and wait until I pass the national limit signs before accelerating.
Hypothetical situation, Ive just gone under a smart gantry sign on the motorway indicating the limit is 50mph. I am travelling at 50mph. I can see a few hundred yards ahead the next gantry is posting the national limit sign.
So can I legally start accelerating to 70mph once I see the sign or do I have to wait until I pass the demarcation point of the gantry with the national limit signs and then accelerate to 70mph. I.e. the limit is from the signs onwards per every other speed limit sign posting.
I currently play it safe and wait until I pass the national limit signs before accelerating.
I would think the speed limit would legally change only once you have passed the sign.
However, for the drivers who are actually paying attention to signage, spotting the nsl coming in the distance is usually the cue to resume cruising speed (traffic conditions allowing etc).
Average speed cameras through roadworks tended to have one last camera for this very reason I suspect.
However, for the drivers who are actually paying attention to signage, spotting the nsl coming in the distance is usually the cue to resume cruising speed (traffic conditions allowing etc).
Average speed cameras through roadworks tended to have one last camera for this very reason I suspect.
ridds said:
What do you do when you see a 40 limit sign when in a 30?
And what "should" you do...
Per my op. Im with you. I wait to pass the sign. And what "should" you do...
Im just surprised I don't think Ive ever seen anyone else wait to pass the sign before accelerating which is why im questioning the correct procedure.
Mike 820 said:
Per my op. Im with you. I wait to pass the sign.
Im just surprised I don't think Ive ever seen anyone else wait to pass the sign before accelerating which is why im questioning the correct procedure.
You are correct.Im just surprised I don't think Ive ever seen anyone else wait to pass the sign before accelerating which is why im questioning the correct procedure.
The likelihood of getting nabbed for accelerating once you see the new limit is very, very slim though. Providing you are paying attention to what's around you.
Once I see the new limit, I'm off.
ridds said:
What do you do when you see a 40 limit sign when in a 30?
And what "should" you do...
What tends to happen in 30 limit zones near me is that drivers speed up before they get to the 40 sign. And what "should" you do...
The same happens in roadworks where the end of roadworks NSL sign is visble and they speed up well before passing it.
I do wonder if this question is one of those situations when something than sounds simple is actually a little more complex.
I totally agree that changes to speed limits usually take effect as you pass the signage showing the new limit.
But ….
Motorways have a default speed limit of 70mph (for cars). On other roads where the national limit would otherwise apply maintaining a lower speed limit would require repeater signs to be placed at regular intervals. On smart motorways we have signage gantries instead of repeater signs.
At some point, without a repeater sign the temporary limit falls away. If the last sign was set to 50 mph for some reason that would not be the limit for the next 100 miles. You don’t actually need a national speed limit sign, just the absence of signage for the temporary limit.
I imagine that the argument in most cases would be that the spacing of the gantries is equivalent to the required spacing for repeater signs. However, I’m not sure that is always the case.
So does that mean there are situations where the national speed limit applies again before you pass the gantry?
I totally agree that changes to speed limits usually take effect as you pass the signage showing the new limit.
But ….
Motorways have a default speed limit of 70mph (for cars). On other roads where the national limit would otherwise apply maintaining a lower speed limit would require repeater signs to be placed at regular intervals. On smart motorways we have signage gantries instead of repeater signs.
At some point, without a repeater sign the temporary limit falls away. If the last sign was set to 50 mph for some reason that would not be the limit for the next 100 miles. You don’t actually need a national speed limit sign, just the absence of signage for the temporary limit.
I imagine that the argument in most cases would be that the spacing of the gantries is equivalent to the required spacing for repeater signs. However, I’m not sure that is always the case.
So does that mean there are situations where the national speed limit applies again before you pass the gantry?
Elysium said:
So does that mean there are situations where the national speed limit applies again before you pass the gantry?
No not at all it's about as basic as it gets. Repeaters are completely irrelevant in the case described.You are describing a case of where one or more or loads of blank gantries go by after the last posted lower limit. This is an imponderable (albeit we do know that the vsl lower limit can't go on for ever). It matters not though as the cameras can't enforce a lower limit if it's not displayed.
BertBert said:
Elysium said:
So does that mean there are situations where the national speed limit applies again before you pass the gantry?
No not at all it's about as basic as it gets. Repeaters are completely irrelevant in the case described.You are describing a case of where one or more or loads of blank gantries go by after the last posted lower limit. This is an imponderable (albeit we do know that the vsl lower limit can't go on for ever). It matters not though as the cameras can't enforce a lower limit if it's not displayed.
Totally agree that the simple answer is that the limit shown on the gantry applies from the moment you pass it.
But .. on a long boring journey I have found myself wondering about the ‘imponderable’ situations that occasionally arise
If after a reduced limit, the next gantry has no posted speed (and also fails to show a NSL sign, which is what it should do), then the camera will only trigger at NSL speed. Highways have confirmed this in the past by an email to me, and this question comes up regularly on here.
So:
Reduced speed limit applies until next posted limit.
Camera is set to the posted limit (plus a tolerance) - but will only be able to cover a certain distance past the gantry.
If there is no posted limit, or if NSL sign is displayed, camera will default to NSL (+ tolerance).
If, by some fault, there is no displayed limit on a gantry, despite a reduced limit on the gantries before and after, then the camera will have defaulted to NSL (+ tolerance); and the next gantry that shows a reduced limit will have its camera react at the reduced limit (+tolerance).
Average speed cameras are another matter.
So:
Reduced speed limit applies until next posted limit.
Camera is set to the posted limit (plus a tolerance) - but will only be able to cover a certain distance past the gantry.
If there is no posted limit, or if NSL sign is displayed, camera will default to NSL (+ tolerance).
If, by some fault, there is no displayed limit on a gantry, despite a reduced limit on the gantries before and after, then the camera will have defaulted to NSL (+ tolerance); and the next gantry that shows a reduced limit will have its camera react at the reduced limit (+tolerance).
Average speed cameras are another matter.
Once one has passed a gantry showing a reduced speed limit there is no way of knowing what the limit for that section is for anyone who passed that gantry afterwards.
I was approaching a motorway gantry showing 60mph only last week, a few hundred yards
behind a marked Police car.
I was so hoping the limit would change to NSL just before I got to it, so I could then accelerate and sweep past the Police vehicle at 70mph!
(Yes, childish, I know! But still fun!)
However:
I was approaching a motorway gantry showing 60mph only last week, a few hundred yards
behind a marked Police car.
I was so hoping the limit would change to NSL just before I got to it, so I could then accelerate and sweep past the Police vehicle at 70mph!
(Yes, childish, I know! But still fun!)
However:
- it didn't change
- the Police car turned out to be an Ambulance
Yes, but the question is about the legal limit not the camera protocols.
I’ve driven on smart motorways at the exact moment the reduced limits are switched off when the gantry ahead goes blank. In that situation I think most people would speed up immediately rather than wait until they pass that now blank gantry.
A gantry showing a national speed limit sign has the exact same impact as a gantry showing no sign.
So it’s actually a little odd that we would assume we need to pass that one before speeding up.
Interesting issue that only arises with dynamic limits.
I’ve driven on smart motorways at the exact moment the reduced limits are switched off when the gantry ahead goes blank. In that situation I think most people would speed up immediately rather than wait until they pass that now blank gantry.
A gantry showing a national speed limit sign has the exact same impact as a gantry showing no sign.
So it’s actually a little odd that we would assume we need to pass that one before speeding up.
Interesting issue that only arises with dynamic limits.
the first point is silly, its obvious the speed limit applies only once you pass the sign.
the interesting point for me is the blank gantry in an otherwise smart section showing reduced limits.
often i have seen reduced limits on one then nothing on the next and then reduced on the next, my assumption as ever the last sign you passed id the limit, so if its 60/blank/60 then even in the blank section its 60. The above info suggests any cameras would actually be calibrated to 70 on the blank gantry section.
this is not an issue as the following gantry has the limit (or NSL sign) posted, but the issue i see increasingly is smart motorway, reduced limit then nothing, just blank gantries and no NSL signs due to the incredible incompetence of those responsible for highways management (hello those of you on here!)
I have always been weary, as everyone else guns it, especially on the m25 given the proliferation of cameras, as to what the limit is as officially the last limit posted is reduced, however after a while and further blank gantries i speed up to the NSL.
thus the official rule is if the gantry shows no sign at all after preceding ones show reduced (and even if following show reduced, once passed under a 'no showing sign' gantry its NSL again?
the interesting point for me is the blank gantry in an otherwise smart section showing reduced limits.
often i have seen reduced limits on one then nothing on the next and then reduced on the next, my assumption as ever the last sign you passed id the limit, so if its 60/blank/60 then even in the blank section its 60. The above info suggests any cameras would actually be calibrated to 70 on the blank gantry section.
this is not an issue as the following gantry has the limit (or NSL sign) posted, but the issue i see increasingly is smart motorway, reduced limit then nothing, just blank gantries and no NSL signs due to the incredible incompetence of those responsible for highways management (hello those of you on here!)
I have always been weary, as everyone else guns it, especially on the m25 given the proliferation of cameras, as to what the limit is as officially the last limit posted is reduced, however after a while and further blank gantries i speed up to the NSL.
thus the official rule is if the gantry shows no sign at all after preceding ones show reduced (and even if following show reduced, once passed under a 'no showing sign' gantry its NSL again?
Mike 820 said:
ridds said:
What do you do when you see a 40 limit sign when in a 30?
And what "should" you do...
Per my op. Im with you. I wait to pass the sign. And what "should" you do...
Im just surprised I don't think Ive ever seen anyone else wait to pass the sign before accelerating which is why im questioning the correct procedure.
While its not the 'legal' answer, its what most people think and do.
Cliftonite said:
Once one has passed a gantry showing a reduced speed limit there is no way of knowing what the limit for that section is for anyone who passed that gantry afterwards.
I was approaching a motorway gantry showing 60mph only last week, a few hundred yards
behind a marked Police car.
I was so hoping the limit would change to NSL just before I got to it, so I could then accelerate and sweep past the Police vehicle at 70mph!
(Yes, childish, I know! But still fun!)
However:
I would worry more about not knowing it was an ambulance.I was approaching a motorway gantry showing 60mph only last week, a few hundred yards
behind a marked Police car.
I was so hoping the limit would change to NSL just before I got to it, so I could then accelerate and sweep past the Police vehicle at 70mph!
(Yes, childish, I know! But still fun!)
However:
- it didn't change
- the Police car turned out to be an Ambulance
The service type is written on the rear, the side chequers are different colours.
Gary C said:
Elysium said:
At some point, without a repeater sign the temporary limit falls away.
Eh ?That reduced limit will require repeater signage to be valid as with any other road. If there are no repeater signs the limit goes back to 70mph.
Same thing would happen on a rural road without street lighting, but obviously the limit would go to 60mph
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