Question about smart motorway speed limits

[martin2345uk]

Hi guys,
Please forgive me if this is a very stupid question...
I was driving tonight on the smart motorway section of the M1 southbound between the M6 and M25.

The overhead variable speed limit signs came on saying 50. We all slowed to 50. The next lot of signs said 50, the ones after said 50, then the ones after that were blank.

Now, does blank mean the speed limit remains at the last limit posted ie 50, or does it mean back to NSL? If the former, why would the blank signs not still have said 50, and if the latter, why did they not have the NSL sign, as they did a little further on after a succession of 50-60-50 ones..?

Thank you!
Martin

[Chris5156]

I don't think you should have seen a blank in that situation - if the 50 was still in force, you should have seen 50 displayed, and if not, it should have been cancelled by another symbol.

Sounds like a fault, perhaps with that specific gantry.

[martin2345uk]

Interesting, it definitely wasn't just one gantry, and the whole thing happened in at least three separate stretches (ie limit, limit, blanks)..

[michael769]

Chris is right tge guidlines dont permit blank gantries like that.

Legally a speaking blank gantrie means the reduced limit ends. The enforcement cameras monitor the state of their gantry and are supossedly designed to shut off if this kind of situation develops.

Not that I'd adocate acting on it in such circumstances, yo-yo speeds are a major pain for anyone following.

[Johnathan404]

In my experience on the M25 and M6, it is quite common to see single signs on a gantry not working. Wouldn't that invalidate the whole speed limit?

[AndyB]

Only if none of the AMIs were showing the speed limit.

[Ruperts Trooper]

Was the 50 limit mandatory or advisory, surrounded by red circle or flashing yellow - AFAIK no NSL is need at the end of an advisory section.

[martin2345uk]

Was the 50 limit mandatory or advisory, surrounded by red circle or flashing yellow - AFAIK no NSL is need at the end of an advisory section.

They all had the red circles around them...

IT was a bit annoying, especially when they went 50.. then 60, yay, then the next one 50.. then blank blank blank.. if it's a fault then there sure were a lot of faulty gantries last night!

I tried not to yo-yo my speed but kept up with the general traffic around me.

[Big L]

I had exactly the same thing last night on the M6 heading from 6 up towards 7. Three or four 50 limits then the rest blank.

[AndyB]

I would prefer NSL signs (and "End" in the case of advisory limits) for a period of time on all gantries after a restriction is removed, just to make it explicit that it's not a fault.

[Piatkow]

I use the northern half of the M25 regularly and the display of NSL symbols at the end of a restriction is pretty random although. On at least one occasion where the restriction is for roadworks the nearest gantry to the works has been blank giving the impression that you must slow down to 40 in advance but can go back to 70 just as you are passing the workmen.

[fras]

Let's face it, the equipment that operates these variable speed limits is total CR*P, and has been since it was installed, hardware, software, the whole bloody shebang. But no officials consider nowadays that they are actually there to serve the public so do nothing at all about it.

[Phil]

Let's face it, the equipment that operates these variable speed limits is total CR*P, and has been since it was installed, hardware, software, the whole bloody shebang. But no officials consider nowadays that they are actually there to serve the public so do nothing at all about it.

The equipment is NOT 'crap' as you say. If properly looked after, properly maintained and operated correctly then it will give reliable and accurate service. Any problems are thus down to the following

(1) Poor installation of the kit
(2) Poor maintenance of the kit (not helped by Government decisions to use 'lightweight gantries' and ALR which means a lane closure and Cherry picker are needed to access the signs.
(3) Not enough staff in control rooms to allow a quick response to changing conditions - (particularly given the way so called 'SMART Motorways' are being rapidly rolled out across large sections of the country)
(4) Badly written software - as the saying goes computers are only as good as the programmer who wrote the program plus the data they get. If either are bad then obviously the computer will make bad decisions.

Thus the problem ultimately is the cheapskate approach to UK infrastructure provision and a reliance on technology to produce savings for the Treasury. If the UK Government - and indeed the UK population as a whole was prepared to fund things to a decent standard (rather than obsess about having the lowest taxes and getting the cheepest short term deals) the coutry's road network would be in a far better state.

[nowster]

The hardware can equally be as duff as the software can be. I work with both, and frequently have to "code around" problems in hardware.

[martin2345uk]

Thanks for all the replies guys... I'm glad it didn't turn out to be as daft a question as I'd feared

[Debaser]

Let's face it, the equipment that operates these variable speed limits is total CR*P, and has been since it was installed, hardware, software, the whole bloody shebang. But no officials consider nowadays that they are actually there to serve the public so do nothing at all about it.

The equipment is NOT 'crap' as you say. If properly looked after, properly maintained and operated correctly then it will give reliable and accurate service...

It's a few years ago now, but on the MM scheme I worked on we were told (by those who maintained one of the systems) that the failure rate of the AMIs, for example, would require maintenance personnel to be out replacing them every night.

Thus the problem ultimately is the cheapskate approach to UK infrastructure provision and a reliance on technology to produce savings for the Treasury. If the UK Government - and indeed the UK population as a whole was prepared to fund things to a decent standard (rather than obsess about having the lowest taxes and getting the cheepest short term deals) the coutry's road network would be in a far better state.

The suggestion was, because the money came from different pots, that the scheme promoters/project managers at the HA were only interested in the capital expenditure, the scheme cost, and didn't care as much about the ongoing revenue maintenance costs. Some other countries perhaps having the opposite view.

[avtur]

As dash cams become ever more popular I wonder if their evidence could be used to highlight these problems?

If an individual tries to complain they will no doubt be told the equipment is OK they have mis-read the signs. It doesn't sound beyond the realms of possibility that equipment could malfunction to the point of speeding tickets being wrongly issued. I wonder if evidence from dash cams could be used to defend a wrongful issued ticket?

Police Witness are securing convictions on the evidence of dash cams used by members of the driving public (well, so I understand); on that basis would, should, it be possible to use dash cam evidence to defend and overturn a wrongfully issued ticket.

[Johnathan404]

All the variable signs in the Hindhead Tunnel have cameras watching them, presumably to beat the dashcam point above at their own game.

[WHBM]

The equipment is NOT 'crap' as you say. If properly looked after, properly maintained and operated correctly then it will give reliable and accurate service.

Actually, it is. Any railway signals which gave inconsistent, misleading, inaccurate presentations in the manner of the motorway signals would have been thrown out by all sides of the railway organisation - let alone starting to do prosecutions based on it. If sequential gantries display 50-blank-40 (M25 J25 last Thursday) that can't be something that the procedures permit.

I can remember here, a while ago, commenting on a matrix message for an event which had finished 12 hours previously, and a member who actually was involved with the control centre at the time saying that it must have been a technical fault as they recalled removing it before the end of their shift. That sort of technology certainly deserves the expression.

I still wonder about the abilities and background of those in the control centres. I recall many years ago when an urban motorway monitoring centre (some of you might guess where) was still run by the police. The operators certainly were not the sharpest pencils in the box available to the Traffic Division of the force, in fact the job was seen as something to be given to those who were no longer capable of spending all shift out on patrol. Of course, they complied with all relevant "standards" and "training", yet still just didn't seem to 'click in' to conditions on the monitors in the way that we visitors to the centre could do. As you might guess, I asked a couple of penetrating questions and we were moved on to the next part of the visit ....

[ellandback]

In my experience on the M62 it is not at all uncommon for a reduced mandatory limit not to be cancelled by a single set of gantries showing NSL, as should surely be the case (and indeed does happen most of the time).

I have come across many variations on this theme, including:

1. The "Leave You Guessing":

60 60 60 60
60 60 60 60
60 60 60 60
Blank Blank Blank
Blank Blank Blank
Blank Blank Blank

2. The "Unexpected Gap"

60 60 60 60
60 60 60 60
60 60 60 60
Blank Blank Blank
NSL NSL NSL
Blank Blank Blank

3. The "Got The Message Yet?"

60 60 60 60
60 60 60 60
60 60 60 60
NSL NSL NSL
NSL NSL NSL
NSL NSL NSL

PS: The reason why my examples go from four lanes to three is because the change to NSL more often than not happens at the j26 w/b exit slip, where that is what actually happens.