As Neil said, whichever you passed most recently. It really is that simple.
If they are next to each other, the lower, and accept that even gantry-operators (or whatever they’re called) are human and therefore fallible.
basically the 40mph ones are there to protect the road workers. so stick to those.
yes you probably could win it at court but for the sake of an extra few min why bother, just stick to the lower ones, they’ve been put there for a reason.
Idealy the gantry’s should have been covered up, but would you volunteer to climb up there and do it? 
Whether the matrix signs are advisory or not, i just obey them anyway, i’m a proffesional driver after all. 
They’re ‘normally’ put on for a reason, accident, congestion what ever.
Obeying them reduces tail backs at bottle necks and means emergency services can ‘help’ people with less of a chance of being hit by 40 tons.
I always thought that the gantry speed limits were applied by the police…therefore they overrule the road workers signs…
the reason we have more signs and cameras down here in the south…is because we are proper drivers…and we need keeping under control…you`ll be complaining about the snow next…snow…what snow…
How would you get away with it, and how is it stupid? That whole section is variable speed limit so strange as it may seem the speed limit will , what’s the word…oh yeah vary.
Seems straightforward to me. You pass a sign that says 50, you don’t do more than 50, if the next one says 40 you stay below 40. One says 30 you…well you see the pattern here?
Do i detect a bit of sarcasm
The overhead gantry sign’s are advising you of the recommended speed limit for that section of the road,( ignore them at your pearl) but the sign’s entering roadworks are compulsory and can change as you get further into the roadwork’s for SAFETY REASON’S
I always thought that the gantry speed limits were applied by the police…therefore they overrule the road workers signs…
They can also be set by the highways agency guys.
These signs are all for the ‘maximum’ speed, so common sense dictates you go for the lowest one.
Try this simple mantra 
Speed Limits are not a target 
Wheel Nut:
Speed Limits are not a target
you are correct but since im job and done, getting home asap IS a target but i dont want points added to my licence so i would like to know what the limit isat any given timel if there are long term roadworks, the gantry signs should reflect the speed limit according to those roadworks after all, they will catch your eye better than an unlit sign stuck anywhere at the side of the road!
My interpretation would be to observe any temporary limits that are signed, that is I would obey the roadworks signs before the gantry signs.
scanny77:
i refer you all to a recent case down here where the speed limit was not clear so over a thousand fines were thrown out of court. surely this would be similiar? the roadworks signs are saying 40 but the gantry signs (some with scameras) are saying 50 (with red circle) and these 2 limits are within a couple of hundred yards of each other. how is that clear?
personally, i did stick to the lower limit but i still think that this is ridiculous. if the roadworks are a 40 limit, why cant the gantry signs reflect this consistently rather than each one being a different limit than the roadworks signs?
this seems to have brought some very different responses here which points to a bit of confusion so how do you think car drivers are coping with this when they dont seem to understand the basics of driving anyway?
That was a very different situation, assuming you are on about the one on the A303 at Andover. The reason they got off was because the temp signs were there some days but on others they had been removed, so confusion could be argued, I don’t think the same can be said for the ones on the M25 as they have been there for quite some time and are very clearley signed.
Lucy:
Why not just go with whatever the lower limit is and be sure? Problem solved.
exactly
the Overheadsign is just an additional Help to make Road safer.
If Roadworker place a 40mph sign is a 50mph sign wrong as a 70mph sign in a 30mph Zone
FNG:
Are those gantry signs legally binding?
No, the Highways Agency erect them for the sheer fun of it all! They just flick a switch so that there are pretty lights over the carriageway every now and then. What do you think?
FNG:
Rule 36 is drivers to comply with traffic signs.
You made this statement in another post (Was i at fault ?)
Rule 36 RTA:
…a person driving or propelling a vehicle who fails to comply with the indication given by the sign is guilty of an offence.
Does that answer your question?
FNG:
erm yes why? but I haven’t driven south of birmingham in 10 years and things have changed.I’ve never seen compulsary speed signs on overhead gantries on the M60 or M6 and I’m not aware they have them. (M6 doesn’t even have gantries for a lot it towards Scotland) As I said in my post, they do a lot of things different on the roads in the SE and London that are not needed or done in the NW.
If you’ve not driven south of Birmingham in 10 years, how do you know they do a lot of things different in the SE and London?
Are you one of those nutters who sits in a layby on the East Lancs Road, in a Sierra, with a CB?
I still don’t get this one.
These variable limits are supposed to keep the traffic flowing.
They are in a red circle, so the limit is statutory.
The people setting these variable signs will be aware of the temporary signs.
So why are they bothering to set the variable limit higher — perhaps to keep the traffic flowing?
I haven’t seem any road workers wandering around when the gantry signs are set higher than 40 — they’re showing in the places that appear to have been finished ie the multi lane sections where most people ignore the empty inside lanes!
I’ll give you all a wave as a pass you — and let you know if I get a ticket 
according to the highways agency, the roadworks signs are the ones to follow. through roadworks, ignore the gantry signs. this problem has been brought to their attention before and they are looking into resolving it