So how would you interpret this, gantries 1 and 2 say 40mph gantries 3 and 4 are blank/off and the 5th gantry says national speed limit, so does the national speed limit kick in on gantry 3 or is it assumed it’s still 40mph until otherwise stated which in this case is when reaching gantry 5 ?
Always assume it’s the lower speed, to be safe.
bald bloke:
So how would you interpret this, gantries 1 and 2 say 40mph gantries 3 and 4 are blank/off and the 5th gantry says national speed limit, so does the national speed limit kick in on gantry 3 or is it assumed it’s still 40mph until otherwise stated which in this case is when reaching gantry 5 ?
Once you reach the blank gantry it’s crack on full sped ahead as confirmed by gantry 5
biggriffin:
Always assume it’s the lower speed, to be safe.
I’d go with that - although I daresay they’d have trouble enforcing it due to the absence of the required repeater signs.
Also bear in mind there are additional cameras at the fixed camera sites, showing the actual display that you’ve just driven under.
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I’d assume a glitch in the matrix ( see what I did there?) and has been said stick to the lower limit.
the maoster:
I’d assume a glitch in the matrix ( see what I did there?) and has been said stick to the lower limit.
Oh well on the 2nd time it happened I sped up to nearly 50 but hopefully I’ll be fine not sure any of them had cameras anyway .
always best to grab your phone off the dash and video the blank sign as you speed underneath it at the original uninhibited speed limit for that section of road.
if you get the nip,show them the vid…blank/unlit means nothing.
Officially you should stick to the last limit displayed since you’ve not been informed about the end of the “hazard”.
But can confirm the cameras will only flash based in the gantry speed displayed beside them. So if gantry is blank, camera is set to normal speed limit.
If you drive at night, you soon find this out as 40 limits before roadworks then empty gantries for miles are ten a penny and I have tested this many times.
As mentioned by Roymondo, if you look about 100 yards behind the camera, there are 3 little grey cameras. Those take a pic of the gantry display and your vehicle to prove what the variable speed limit was. If no display they cant prove it.
Oh and you will know if you get flashed…as will all the drivers coming the other way who are blinded by the light!
Oh and I do prefer DD’s version however. 
I’ve noticed since lockdown the overheads between Nottingham and Sheffield on M1 now flash even when there is nothing illuminated. Get dazzled quite often when I’m trundling along at 56mph, nearly dropped my book! [emoji6]
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bald bloke:
So how would you interpret this, gantries 1 and 2 say 40mph gantries 3 and 4 are blank/off and the 5th gantry says national speed limit, so does the national speed limit kick in on gantry 3 or is it assumed it’s still 40mph until otherwise stated which in this case is when reaching gantry 5 ?
No assumptions allowed on speed limits. National limits apply unless gantry states otherwise.
If this is the first gantry then simply crack on in the blank lane. 
However if a previous gantry said otherwise then TrevHCS and DD have answered better than I could.
The new stretch of the A14 has been a bugger for this. Where they’ve been finishing off bits and pieces (e.g. installing gantry cameras) they’ve often had a lane or two coned off with the gantry signs moving traffic over and slowing down to 40 where the lane closure(s) kick in, then all subsequent gantries are blank until the end of the roadworks where there’s a national speed limit displayed, causing general confusion in between.
Just gives the impression the people operating the signs haven’t actually driven a car before.
Hurryup&wait:
bald bloke:
So how would you interpret this, gantries 1 and 2 say 40mph gantries 3 and 4 are blank/off and the 5th gantry says national speed limit, so does the national speed limit kick in on gantry 3 or is it assumed it’s still 40mph until otherwise stated which in this case is when reaching gantry 5 ?No assumptions allowed on speed limits. National limits apply unless gantry states otherwise.
If this is the first gantry then simply crack on in the blank lane.
However if a previous gantry said otherwise then TrevHCS and DD have answered better than I could.
You may well be correct…but…
If a gantry shows a lowered limit, next are blank, next shows national limit?
I would wonder why some are blank.
If defective gantry you might end up with a letter in the post. Now, maybe you do have a strong defense against any prosecution, but do you want to go through the rigmarole of defending yourself?
Is it worth the time and trouble to risk doing so, when you have gained maybe a couple of minutes on your trip, bit may expend time and effort in defending a speeding charge?
Easy life for me.
Franglais:
Hurryup&wait:
bald bloke:
So how would you interpret this, gantries 1 and 2 say 40mph gantries 3 and 4 are blank/off and the 5th gantry says national speed limit, so does the national speed limit kick in on gantry 3 or is it assumed it’s still 40mph until otherwise stated which in this case is when reaching gantry 5 ?No assumptions allowed on speed limits. National limits apply unless gantry states otherwise.
If this is the first gantry then simply crack on in the blank lane.
However if a previous gantry said otherwise then TrevHCS and DD have answered better than I could.
You may well be correct…but…
If a gantry shows a lowered limit, next are blank, next shows national limit?
I would wonder why some are blank.
If defective gantry you might end up with a letter in the post. Now, maybe you do have a strong defense against any prosecution, but do you want to go through the rigmarole of defending yourself?
Is it worth the time and trouble to risk doing so, when you have gained maybe a couple of minutes on your trip, bit may expend time and effort in defending a speeding charge?
Easy life for me.
If this is the first lit up gantry you meet with various limits displayed as described by OP then unfortunately you have no idea what limit if any applies to the unmarked lane.
If you prefer to drive at the lower limit then perhaps stay in the lanes with the lower limit marked overhead.
But I would suggest it is extremely poor consideration of other road users for any driver to enter the unmarked lane and impose his personal reduced speed limit on all the other users of that lane.
Fair point about the rigmarole that may theoretically occur but surely you cannot be prosecuted if you are obeying the limit. We have cameras in our trucks so must ask the office how far back the data goes out of interest.
Hurryup&wait:
If this is the first lit up gantry you meet with various limits displayed as described by OP then unfortunately you have no idea what limit if any applies to the unmarked lane.If you prefer to drive at the lower limit then perhaps stay in the lanes with the lower limit marked overhead.
But I would suggest it is extremely poor consideration of other road users for any driver to enter the unmarked lane and impose his personal reduced speed limit on all the other users of that lane.
If one gantry has only some lanes marked, then I agree that anything unmarked should be treated as unrestricted.
I meant the case when one gantry shows a restriction, but the next gantry doesn`t, and may be out of order.
And I do agree, no way should anyone drive slowly in any lane further to the right than is necessary.
trevHCS:
Officially you should stick to the last limit displayed since you’ve not been informed about the end of the “hazard”.But can confirm the cameras will only flash based in the gantry speed displayed beside them. So if gantry is blank, camera is set to normal speed limit.
If you drive at night, you soon find this out as 40 limits before roadworks then empty gantries for miles are ten a penny and I have tested this many times.
As mentioned by Roymondo, if you look about 100 yards behind the camera, there are 3 little grey cameras. Those take a pic of the gantry display and your vehicle to prove what the variable speed limit was. If no display they cant prove it.
Oh and you will know if you get flashed…as will all the drivers coming the other way who are blinded by the light!
Oh and I do prefer DD’s version however.
I’m confident I didn’t see a flash and it was dark at the time, just for interest sake these two incidents occurred on the M4 just before M32 junction heading East and M25 near M23 junction again heading East.
This configuration of overhead signals I find very strange. In my days in the Cambs Force control room we couldn’t set different speeds for different lanes. If a lane needed for example 30mph then all lanes showed 30. But that was 20 years ago, maybe times have changed.
Another one to change was the setting up of roadworks. It was done as per Chapter 12 highways manual then signals were not used once the roadworks were up and running. That’s changed, they are on all the time now.
Went through a gantry today on the M6 by Birmingham. 40mph was sign posted. I was doing 38ish as I was already going slow due to traffic. Another wagon and a car went past me and it flashed.
How are they able to tell who is and isnt speeding?
Went through every set after that paranoid!!
sinclair89:
Went through a gantry today on the M6 by Birmingham. 40mph was sign posted. I was doing 38ish as I was already going slow due to traffic. Another wagon and a car went past me and it flashed.How are they able to tell who is and isnt speeding?
Went through every set after that paranoid!!
It takes 2 photos apparently and the speed is determined by the distance you’ve travelled between these 2 photographs, I think anyway, so the faster car would’ve travelled further.
bald bloke:
sinclair89:
Went through a gantry today on the M6 by Birmingham. 40mph was sign posted. I was doing 38ish as I was already going slow due to traffic. Another wagon and a car went past me and it flashed.How are they able to tell who is and isnt speeding?
Went through every set after that paranoid!!
It takes 2 photos apparently and the speed is determined by the distance you’ve travelled between these 2 photographs, I think anyway, so the faster car would’ve travelled further.
Just have to wait an see, but that does put my mind at rest a bit , thanks
spacemanZ10:
I’ve noticed since lockdown the overheads between Nottingham and Sheffield on M1 now flash even when there is nothing illuminated. Get dazzled quite often when I’m trundling along at 56mph, nearly dropped my book! [emoji6]
The one on the M1 northbound on the downhill section just after Tibshelf services is broken. It has even flashed lorries when there’s nothing on the matrix and even fully loaded you’re not getting to 60 by that point.
Given the limit is 70MPH it would come as no surprise that when there’s nothing on the gantry they default to 70MPH and there’s definitely more than a couple of cars who go whizzing down that stretch above that.