It probably has more traffic on it now?
That said, for it to work, like the variable speed limits introduced on M25 years ago, people have to play by the rules - stick in lane, and stick at the highlighted limit. But we have too many mongrels who either constant speed up and brake (which causes a concertina effect a dozen cars behind), constantly lane change to get ahead (causing cut up cars to brake) or simply drive too bloody slow.
Plus the fact that the system on the M25 was initially delivered with an algorithm developed by some very clever people to maximise throughput and minimise bunching, but, of course the DOT knew better and decided they could keep a couple of civil servants in a job messing about with the limits manually. Hence, that system worked really well for the first 6 months, before they found out how to meddle with it manually. Not sure if that same is true of the other systems being rolled out.
My view is that this is all about installing network infrastructure at the roadside in preparation for road charging.

I wonder how much they spent on all those signs that constantly remind you that letting go of the steering wheel is dangerous, or listening to the stereo too loud? Their only use is to warn of traffic problems, whereby you get "Delay after A<random number>" and you have to fumble with your map to find the road for it to make any sense whatsoever.

Oh, and "Fumbling with your map causes accidents" probably.
