Help - Search - Members - Calendar
Full Version: Do variable speed sign cameras work for lower speeds when the sign is unlit?
FightBack Forums > Queries > Technical Discussion of Enforcement Devices
Moon jumper
Hi everyone, I have a question that I can't find the answer to online.

I'm aware that variable speed cameras can work to record drivers going over 70mph when the variable signs are not lit. What I'm trying to find out is whether the cameras can work to record someone doing 50mph when the variable sign isn't lit at all?

I always thought that the speed limit applied until you saw a sign saying otherwise but sometimes I've seen 10+ 50 signs followed by 10+ blank signs in a row and then the motorway ends.

I'm not asking if the speed limit remains at 50 despite the lack of signs (as by law it should) but whether the cameras themselves would ever fine you for doing 60 when the sign itself was off.

Logic suggests that the cameras wouldn't work like that because the sign wasn't lit up and surely there's some link between the sign being on and the speed the camera is set to? The computer would think that OFF=70mph and 50=50mph etc? I know there's leeway given but I'm doing these figures without that.

Gantry cameras can and do enforce NSL and any displayed lower limit. IIRC, there is a 40 second delay following a limit being displayed before the enforcement cameras become active.

If you can show a court that no lower limit was displayed at the same time as being flashed for exceeding that undisplayed limit, then it would seem they would have no evidence to convict.
The Rookie
Depending on the camera type but there are safety systems in place so that a camera at a gantry doesn't work unless the gantry is showing a limit, regardless or not of what the previous gantry showed and what the enforceable limit may be. I don't know the reliability of the checks but know they are there.
Moon jumper
Thanks for the replies.

It was something that happened the other day that got me worried. I was in a car (not driving) when the limit went 50 then 40 followed by 15 blank signs. We stuck to the limits and did 40 passed 5 blank signs before having to speed up because we were going at 40 and everyone else, including people joining from the left, were doing 70. It's just weird because I've never seen this happen before, there's always been a national sign.

There were only 3 lower speed signs around a very busy junction so I think it was just slowing people down to help others join and that's where the confusion came from. The joiners were signed for national and we were being told 40.

The only thing I can think of is that maybe the last sign we passed changed to a national as we went under. We were the slowest vehicle on the road in the left lane with dozens of people overtaking us in the minutes that we stuck to 40 after the last sign.

The vehicle has front and rear dash-cams and after checking to make sure of what we saw there were no variable signs showing for miles (15 signs in a row) and no flashes from the cameras as we or any other vehicle went passed them.

I'm probably worrying over nothing but these signs were either not working correctly or it's as I said and we passed under the 40 as it changed to national.
Moon jumper
Just an update in case anyone comes across this in the future and is in a similar position.

Three weeks have passed and I heard nothing. After contacting Highways England they said that blank signs mean national regardless of what the sign before or after says and there doesn't have to be a national sign shown at the end to return to national speed limit.

Even if the signs show 40,40,blank,40 then the blank should be taken as a national speed limit. This is because you may pass under a sign saying 40 just as it turns to national and that's what happened in my case.

So for future reference, blank signs mean national and the cameras on them only catch people going over the national speed limit whatever the sign before or after says.
Just last week I was in a similar situation after midnight on the M25: temporary road works speed limit, 60, 50 then 40. Then two blank gantries (under which I'm the only one pootling along at 45) followed by the NSL signs on the next one. Why couldn't they have either continued to display the 40 limit or the NSL sign?

QUOTE (Moon jumper @ Sun, 11 Sep 2016 - 19:33) *
Even if the signs show 40,40,blank,40 then the blank should be taken as a national speed limit.

The law would disagree.
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2018 Invision Power Services, Inc.