New variable spped limits on M25, J5 to J7

[robinessex]

A variable speed limit system is proposed for the M25, J5 to J7. I've driven through these variable speed limits since first on the Heathrow section of the M25. Unless I'm blind, they're complete rubbish. I've never yet seem any evidence that they actually work. Usually, I'm sitting under a sign saying 40/50/60 stationary. The speed of the traffic flow is just to variable for them to work, unless they were auto controlled by camera monitoring systems, and then I reckon they'd go into yoyo mode, constantly varying

[SS2.]

I remember the M3-M40 stretch of the M25 before it had an active management system - it was truly awful, especially during peak times. The introduction of the variable limits back then resulted in vehicles travelling at reduced spacings, making smoother progress (less panic braking) and, overall, a higher throughput of vehicles seemed to be achieved.

Can't speak for the motorway these days as I don't travel that section too often, but perhaps the volume of traffic at certain times is now just too great for any management system to have an effect.

[John145]

Good idea, poorly executed imo. Especially annoying when it's 10pm at night and for no known reason they force the speed down to forty then immediately back to NS...

[timbob]

John145 said:

Good idea, poorly executed imo. Especially annoying when it's 10pm at night and for no known reason they force the speed down to forty then immediately back to NS...

Or 20mph, as I experienced on a very lightly trafficked M42 at 3am on Saturday night last year. I was training as a driving instructor at the time, so didn't want to take a chance on the cameras being switched on - so I (foolishly??) obeyed the limit for 2 miles leading up to a single lane closure for what looked like a street light bulb changing guy in a cherry picker.

It felt mighty dangerous seeing traffic shoot up behind me in the rear view mirror (half asleep no doubt) then suddenly swerve around me when they realised I was doing 20mph... But what other options were there?