Temporary Speed Limits - Why?
I don’t own a car, and so don’t drive often. This means I usually avoid the passionate debates about speed limits, speed cameras, etc. But I think I’ve come up with a speed limit question that’s less contentious (famous last words). I almost missed a plane the other day when the coach I was on to the airport was held up in a traffic jam on the M25. What made it more frustrating, though, was the temporary speed limit signs (the ones that light up with a speed above the motorway). Either:
It’s impossible to go that fast anyway, which is the case 90% of the time, or:
The traffic jam is ending and everyone is so glad to be out of it they don’t honour the speed limit (and arguably the speed limit shouldn’t be there any more anyway).
So what exactly is the intended point of these? To pack more traffic on the same amount of roadway? Possibly, but if it’s impossible to go that speed, what’s the point? Have I missed something obvious? Is there some subtlety of queueing theory that explains this?
I assume these signs must be manually controlled - a person in a control room switches them on or off after observing the amount of traffic on a camera. Would they be more responsive if they were automatic?
Anyway, enough grumbling. I’d love to know how they are supposed to work though.