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I should clearly know this one but..
On the motorway into Edinburgh there are overhead gantrys with variable speed cameras on them. Every time I've ever been on that road, if there was a speed restriction in place it is clearly shown on the gantry. There is usually a national speedlimit sign on the gantry at the point the limit ends, so you know when to speed up..simples
Except today there was a 40 sign that I went under, slowed down, but the next gantry and the ones after that had no limit. Which would normally mean 70, but would also usually have been preceded by the national speed limit sign to indicate end of restrictions
So was I in a 40 or a 70? Everyone seemed to be going at 70 even though there was a camera on one of the gantry. My car dash indicated I was in a 40.
I've had that before. I tend to wait a couple of gantries to check if it is not just one gantry broken, plus by then the herd of other cars is galloping away and I just follow.
If a display is blank or unlit it means that the previous instructions must still be complied with.
https://nationalhighways.co.uk/road-safety/variable-speed-limits/
“When a lower speed limit no longer applies, we convey this using the national speed limit symbol.”
Except today there was a 40 sign that I went under, slowed down, but the next gantry and the ones after that had no limit. Which would normally mean 70, but would also usually have been preceded by the national speed limit sign to indicate end of restrictions
I'd assume what I think you did too: that it was still a 40. My understanding is the limit is whatever the most recent gantry sign you've pass is displaying. Of course, the management of these signs and control of the variable zones is a total shitshow at times IME.
+1 matt_outandabout
It's probably a software/sensor glitch
Technically, it remains a 40, but IME every gantry within the lower limit displays the new speed. The camera adds its gantry speed to the evidential image, as shown here https://wmsafetycameras.co.uk/enforcement-images-explained/
The problem comes when the visible display glitches out but the limit is still 40. NB cameras can default to 70 24/7 on a blank display
Dashcam and common sense are a big help 😉
"Time Since Speed Limit Change" is important because you usually have a grace period to adjust your speed without emergency braking if the limit changes suddenly
I've had this on the M25 and M3...
I'm super cautious, but AFAIK, if there is no limit displayed on a motorway, it defaults to NSL.
It does make driving thru VSLs horrible.
My understanding is It's the same as normal, static signs. The limit is the most recently posted limit. So you were correct to go at 40.
Eg If you drive through a village and there's a sign saying it's a 30, that doesn't change until you see a sign indicating it's changed.
No sign = no change.
When a lower speed limit no longer applies, we convey this using the national speed limit symbol.
Until you pass such a symbol the lower speed limit will continue to apply.
A blank sign does not negate or cancel the lower speed limit displayed on a previous gantry.
On occasion, a faulty signal may prevent the national speed limit symbol from being displayed. However, if this occurs, our signal setting system should automatically move it to the next available signal display, so you should continue to comply with the lowered speed limit until you see the national speed limit symbol.
Well kilos link suggested it was a 40, but as someone mentioned above, I've never seen a gantry not display the lower limit, especially 2 of them in a row
I ended up taking matt's approach...after thr 2nd gantry with no limit I started feeling unsafe driving at 40 whilst every other car was doing 70 so just sped up to match the rest of the traffic
As others have said I believe legally, it's whatever the last signed limit was. But VSL managed motorways are, quite a lot of the time, an absolute mess. I travel around south England too much, and have seen so many 'glitch' and not have the final return to nsl signed. I've had 50 limit on a slipway joining traffic that clearly is not limited. Loads go directly from no limit to 40 and then back to nsl for one gantry - Cambridge A14 junctions are particularly bad for this. And loads I go past at 9 pm or later with no traffic and they've been left on at 40 or 50. The operators seem to want to kill people (since other drivers are still doing 70).
So like others, I try to give it a few gantries to see if it's a glitch on one or a f-up by the operator, but that depends how busy it is and how quickly I start getting buzzed by other drivers especially trucks (keeping left of course).
My understanding is It’s the same as normal, static signs. The limit is the most recently posted limit. So you were correct to go at 40
Which would make sense if it's consistent. But every other time I've driven that road every gantry covering the restricted area displays the restricted limit
It needs to be clear and consistent otherwise you have motorists driving at vastly different speeds.
Loads go directly from no limit to 40 and then back to nsl for one gantry
Yeah, M27 is great for this. Successive numbers are pretty much randomly* jumbled quite often
*(Still in multiples of 10, disappointingly)
I've always understood it as the last bit of speed signage you passed (including matrix jobs) indicates the applied limit until you pass one that indicates a change, a lack of further signage would mean the 40 limit still applied (IMO/IME) unless and/or untill you see an NSL sign...
So was I in a 40 or a 70? Everyone seemed to be going at 70 even though there was a camera on one of the gantry. My car dash indicated I was in a 40.
Herd mentality isn't a viable defence. The Car reads the signs and informs you accordingly, it's really just trying to help you keep your licence.
Application of the rules might not always align with the law though (there's some discretion available), but if you get snapped doing 70 and the last sign you passed said 40, you're basically bang to rights I reckon. Sounds like there might have been a bumper crop of fines in Edinburgh this morning...
Many sections of variable are not lit up. So are you supposed to guess what the previous speed limit was the last time they were used?
I have been on many motorways where the speed has varied between 40-60mph up and down, but come out of countless restrictions where the national speed limit has not been displayed.
The Car reads the signs and informs you accordingly, it’s really just trying to help you keep your licence.
My only experience of cars knowing/reading speed limits/ signs has been woefully inadequate & more likely to help you lose your licence than keep it.
Technically the last posted speed limit would apply, but I would have thought the fact it wasn't displayed for more than a few gantries would be a sound legal defense as IIRC anything other than NSL or 30mph (or 20 in Wales)* requires repeater signs every so many hundred meters. Hence why 20's in England and Scotland have a proliferations of repeaters through villages (ditto any 40/50mph roads should IIRC have repeaters).
*because technically 30mph is the NSL if the lamposts are closer than whatever the rule says. But for clarity there's still a 30 sign to indicate where it starts and ends.
Personally I treat one blank gantry as a glitch, if the 2nd one is blank I just assume I wasn't paying attention and missed the NSL gantry.
Many sections of variable are not lit up. So are you supposed to guess what the previous speed limit was the last time they were used?
No, you're supposed to remember the last sign that you drove past which informed you of the speed limit.
Sounds like there might have been a bumper crop of fines in Edinburgh this morning…
Indeed so. And I'd be a bit pissed off if that's the case as every other time it's had the limit displayed on every gantry. The 3rd gantry I went through had a camera but no 40 sign, and it absolutely usually does..i drive that road alot...I was doing under 50 so itll only be 3 points max but still unfair imo.
Herd mentality isn’t a viable defence.
I Think my defense would be that it was clearly not obvious, and there were no signs for a Mile when clearly there should have been. And whilst herd mentality may not be a defense in law, it's a defense against a truck ploughing into you at 70mph because I'm doing 40.
This was rush hour, So busy. And I was by far the slowest car on the road so if I get caught I imagine every single other car will as well
I can't be the only person who thinks that the gantries should br turned on and display a speed limit at all times (even if it is a NSL)
Loads go directly from no limit to 40 and then back to nsl for one gantry
Yeah, M27 is great for this. Successive numbers are pretty much randomly* jumbled quite often
*(Still in multiples of 10, disappointingly)
Yeah, this for the M27. Also often nothing on the gantries for miles, and then out of the blue, one that says 'END'. End of what? When did what start? etc.
No, you’re supposed to remember the last sign that you drove past which informed you of the speed limit.
Agreed. but this isn't the same situation as a fixed road sign. Usually it will show the restricted limit, and if no limit shows its a 70. That's how that road has been since the Introduction of the variable limit.
So when 3 gantrys in a row show nothing there are 3 possibilities
1- there was a glitch on the 1st gantry and it didn't display the nsl sign
2- there was a glitch on all 3 gantrys that didn't show the 40 sign
3- they've just decided to change how it works without telling anyone..
I think options 2 and 3 are unlikely
If the NSL sign is not shown the speed limit remains at the previously signed limit. I did a motorway speed awareness course last week and brought up this exact topic as I've seen on a number of occasions no NSL displayed. My car picks them up and changes speed accordingly so it's not just me missing them.
Also don't assume that the first gantry with a reduced limit doesn't have a camera, that's how I got caught (and me relying on the car to automatically slow down which it is pretty good at but doesn't start to decelerate until you get to the sign, so my fault).
When I questioned the patronising trainer on the course about what to do when the NSL sign isn't displayed she just said I'm here to tell you the letter of the law and wouldn't engage further.
I use Matt's approach of give it a few gantries and then assume NSL. I'm also assuming if the gantry isn't displaying a lower limit the cameras will either be off or working at 70, they're linked and the speed changes are usually triggered by speed flow and spacing between vehicles not manual intervention which explains how the speed limit changes so much within a single reduced speed section.
Personally I understand how variable speed limits are supposed to work and the theory is sound but as usual the real world implementation is pretty rubbish and really doesn't seem to have made any difference to overall congestion on the M60 and M6 despite years of disruption while they were fitted.
Hypothetically,
Car A is on the motorway and slows to 40 or whatever as instructed by the gantry matrix. The next gantry is blank.
Car B joins the motorway after the first gantry but before the second. Now what happens? We've got two different motorists both correctly believing that two very different limits are in force.
Well there should be a gantry on sliproad approach for car B.
I can’t be the only person who thinks that the gantries should br turned on and display a speed limit at all times (even if it is a NSL)
Common sense seems to lack in many public infrastructure projects....
I can’t be the only person who thinks that the gantries should br turned on and display a speed limit at all times (even if it is a NSL)
I wondered this. I'm guessing it's a power (and therefore money) saving exercise.
My only experience of cars knowing/reading speed limits/ signs has been woefully inadequate & more likely to help you lose your licence than keep it
The VW system in the Work Connect often claims a 100mph limit on the M4 and other motorways or picks up a nearby road limit or a 5mph industrial estate limit.
It also seems to be unaware it’s a van and identifies as a car for speed limits.
As to the Gantry speed signs, I’ll chance my licence and go with the flow of traffic if the road ahead is obviously clear, rather than risk a collision travelling at 40mph with everyone else accelerating up.
Spend most of my working day on the Motorway and it’s stood me well.
^
Exactly...
A 30mph differential is downright dangerous. I only sped up as it felt unsafe going so slow in amongst the rest of the traffic.
They should either have them working in a consistent manner, or switch them off.
I wondered this. I’m guessing it’s a power (and therefore money) saving exercise.
Meh, the cost of a few LEDs lit on a few signs compared the huge environmental and economic cost of building and maintaining a road and attendant infrastructure, the overnight lighting, the multiple CCTV, the police and Highways agency, and then of course all the exponential environmental and economic costs of the private cars and trucks using the damn road.....But point taken that some bright spark suggested that was the reason.
Hypothetically,
Car A is on the motorway and slows to 40 or whatever as instructed by the gantry matrix. The next gantry is blank.
Car B joins the motorway after the first gantry but before the second. Now what happens? We’ve got two different motorists both correctly believing that two very different limits are in force.
Well if we're getting hypothetical, If you're driving 'Car A' follow the last instruction you were given by a sign and drive at 40.
If you're in 'Car B' it's still you're responsibility to merge safely, you will hopefully notice that all the traffic you've just joined is moving slower than you expected (and might even wonder if there's a reason?), technically you are within your rights to pull into a RH lane and pass, if that's not possible though reduce your speed and maintain a safe stopping distance to the car in front. Just remember whatever you might think the number is currently, it's a limit not a target 😉
Do people normally just plough on into slower moving cars on the basis that they thought the prevailing limit was higher?
Do people normally just plough on into slower moving cars on the basis that they thought the prevailing limit was higher?
I’ve seen people join and exit the Motorway as if other vehicles don’t actually exist and hit each other , so yes I’d say so.
I’ve seen people join and exit the Motorway as if other vehicles don’t actually exist and hit each other , so yes I’d say so.
OK and in those cases where would you say the fault sits?
Cougar - in your hypothetical example Car B would pass a VSL gantry on the sliproad. If that happened to be blank/faulty then it cannot be successfully prosecuted as the offence is not complete (the crown have to show the limit on the sign you passed at the time you passed it).
tpbiker - my guess (and it is only a guess) is there is a 4th option which may well be what happened here. As you approached/left the first 70mph sign it changed to a NSL sign or was switched off so the limit not longer applied. Then when you get to sign 2 (and 3 etc) it no longer "thinks" there is a VSL so nothing to display.
The last displayed speed limit you seen is the speed limit, it’s consistent as in that’s exactly how it works.
Car C passes a 40mph gantry. Promptly breaks down. By the time they're moving again, the VSL limit has gone. Still 40?
I'm not arguing, BTW. I know full well that limits are in force until a new one is, most posters here are correct. I'm just thinking out loud really.
According to my fairly recent speed awareness course, the last sign prevails until you see one to undo the instruction, as per the link above.
Unfortunately, no sound legal defence will include repeater signs.
...anything other than NSL or 30mph (or 20 in Wales)
Yep, no repeaters in a 30 which has streetlamps not more than 200 yards (185m in Scotland & NI) apart. This isn't optional, it's no repeaters allowed. The latest guidance (2019) hasn't been updated for the new 20s in Wales
...requires repeater signs every so many hundred meters. Hence why 20’s in England and Scotland have a proliferations of repeaters through villages (ditto any 40/50mph roads should IIRC have repeaters).
"Should" does the heavy lifting here. Repeater signs aren't required anywhere, they're just a recommendation. The recommendation is for the first lamp post after a speed limit change and between 200 and 600m thereafter on alternate sides of the road. Spacing and sign diameter is generally larger on faster roads, 200m in 20 and 600m in 60.
NSL repeaters are specifically not used on a motorway, lit or unlit
According to my fairly recent speed awareness course, the last sign prevails until you see one to undo the instruction, as per the link above.
Which is great if it's clear that's the case. And every single time you drive the signs work in a consistent fashion. Either you have:
One notification at the start of the restriction, a nsl sign at the end of the restrictions, and nothing on any gantrys inbetween.
Or
You have a restriction showing on every gantry until the restricted zone ends, a nsl sign at the end of the restricted zone, and nothing on the gantrys in the unrestricted areas.
Either option works if its consistently applied, however it's surely clear to any reasonable person that alternating randomly between the 2 options above would be a recipe for confusion to drivers. Regardless of what the highway code states.
The cameras on the M90 either side of the Queensferry crossing have been flashing but not issuing tickets for years now. No idea if/when they are due to actually issue fines.
Do people normally just plough on into slower moving cars on the basis that they thought the prevailing limit was higher?
Youtube is awash with DCW videos of driving like this...
Granted, there are millions of journeys a day which are without incident, but now and again you meet a complete....
The cameras on the M90 either side of the Queensferry crossing have been flashing but not issuing tickets for years now. No idea if/when they are due to actually issue fines.
If you can achieve 90+% of the benefit without needing any staff to do the admin, go to court etc then if you don't get paid any extra for the number of offences detected then you seem to be on win-win: the fear that one day the camera might be on is enough to slow the cooperative, whilst the cavalier would be too fast anyway.
Car C passes a 40mph gantry. Promptly breaks down. By the time they’re moving again, the VSL limit has gone. Still 40?
Yes, technically. Equally if it was saying 70, you get stuck in a queue (or break down) and by the time you are able to move off they've woken up in the control room and put a 30 in - your limit (until the next operational sign), by the letter of the law is 70. The link I posted earlier covers the law: a successful conviction will require them to show what the speed limit was when you passed it and for the 10s before you passed it.
According to my fairly recent speed awareness course, the last sign prevails until you see one to undo the instruction, as per the link above.
That's all very well but say I'm driving from London to Edinburgh and there's a 40 limit outside Watford, then I don't see any more signs. At what point can I assume it's legal to drive at more than 40mph, according to the letter of the law?
Can't base it on the speed of other vehicles. Motorways don't normally show speed limit signs unless it's variable. If I'm (un)lucky and there's no gantry signs for the rest of the journey, at what point can I safely assume the system is faulty? Sheffield?
If I get ticketed for driving too slowly, will it be a viable defence to say that the speed limit is technically 40mph because there was a sign 200 miles back down the road?
This is all a bit stupid in practice but how far does "the letter of the law" extend? Use common sense? Impossible to define. 3 blank gantries? 5? 50?
This is all a bit stupid in practice but how far does “the letter of the law” extend? Use common sense? Impossible to define. 3 blank gantries? 5? 50
Exit the Motorway and rejoin, problem solved ?.
ossify - at the end of the variable speed limit section there is usually (or certainly in the case in the OP) at non-digital sign telling you: e.g. https://maps.app.goo.gl/1zJHxN6Yxp7oVZM67 or https://maps.app.goo.gl/F4A77udhuSDK9m9r5 depending which way you go.
You won't get a ticket for driving too slow - but you might get one for day dreaming and not paying attention to the signs.
You won’t get a ticket for driving too slow – but you might get one for day dreaming and not paying attention to the signs.
I think technically you can be as it constitutes careless driving. Regardless, doing 40 in a 70 on a busy motorway is not particularly safe imo.