variable speed limits on the M25. whats that all about?

i know they`ve been in place for ages but just started using the M25 J10 to J16 regularly and the variable speed limits are a nightmare. 2 hr traffic jams on a 4 lane motorway and the only visible cause were these variables 40, 50, back to 40. what IS it all about? ok i do admit im in my cage at the time but its bloody infuriating.

imagine being a lorry driver, with a tacho, running out of hours, then getting stuck in them. turns the cab blue it does!!


They’re (allegedly) to slow the traffic to accidents etc, so rather than doing 80 up to the scene of a breakdown/crash you go 80/60/50/40 etc, in theory it means there isn’t a huge bottleneck …in theory.

But as I proved on Friday, you can go 60 through a 40 variable speed camera like everyone in front of you and it doesnt flash :Whistling:

I always heard they’re (the cameras on the M25) only live when they’re showing a limit, I know they don’t go off at 130 when not illuminated…

Or 150 when it`s really foggy.

I’m not even sure if they work. I used to commute to round the M25 in the Volvo and I thought that they were just 70mph cameras so I went through them at that regardless of what they were showing. Not all the gantrys have cameras, the garmin tells you that and you can also look in your rear view mirror to see. I think I set one off once doing 85 when it was showing 60. There are lots of urban legends about these being out of sevice or when they actually operate. I don’t risk it any more though and slow down to the posted limit to pass them.

So basically, the variable speed gantries are just fancy Christmas lights for the coppers to look at

There has been average speed camera’s on the M3 for the last 5 years!!! just as you join the M3 at the M25 heading south. I completely ignore them now especially on the bike as they are not rear facing.

I hate these things, there’s a section of the M1 after the M25 that have them that I pass through everyday. When theyre showing 50 or whatever, some drivers ignore them, some do the limit, I don’t know what the hell, I’m not gonna risk my license for the sake of a few mins but then If i’m the only one paying attention to them then its frikin dangerous cars rushing up behind you etc. Worst is when the HGV’s ignore them and your being overtaken by them. Surely they’re not active you’d think but I really dont fancy finding out. They just add more stress and confusion. Safety cameras my arse.

The Garmin says that the ones on the M1 are not active. But that is not going to stand up in court. I want to get a radar detector really. Or I could just not break the law. Mmmm. Radar detector it is.

At least with the M1 ones you can clearly see beforehand which gantries have them unlike most. Would’nt trust the garmin myself.

Most of the 50/40/50 stuff on the west side of the M25 is due to the need to slow traffic so traffic coming off the M3 and the like can filter in safely. The M3 average speed cameras are for the same reason, they are to stop people who have hammered down the deserted J1-J2 section at 100mph smashing into people accerating from 50 on the bends on the access road as used to happen a lot.

As someone who up until a year ago had spent the previous 15 years using the western side of the M25 & M3 on a daily commuting basis using both 2 & 4 wheels, the introduction of the variable speed cameras on that stretch of the M25 made a huge improvement in traffic flow & overall average speed during the rush hour. Previously it was stop start all the way as people joined & tried to force their way over to the outside lane only to have to bang their brakes on & initiate ‘traffic waves’ -

The M3/M25 junction bit controlled by the average speed cameras was a prime example of this too, as well as the accidents Giuliano mentions above, in anything above light to moderate traffic, the M3 would always grind to a complete halt just after the M25 junction on the stretch heading out of London, I don’t travel that way much anymore, but I don’t think I’ve seen it happen once after they reduced the M3 from 2 to 1 lanes under the M25 & put the average speed cameras on.