Admittedly I haven't spent much time on a motorway recently but my experience of them has been resoundingly negative. My understanding of the advantage is that if there is congestion up ahead they will reduce the speed of traffic coming towards it giving the congestion more time to clear preventing slow moving tailbacks becoming longer, which makes sense if it actually implemented to do that. That being said, I used the one on the M40/M42 to come back from Manchester airport last year and it didn't seem to have any idea what it wanted you to do. Changing from 50 to 60 then back to 50 at nearly every opportunity, usually increasing to 60 when the traffic was heaviest at one point it actually changed to national when we were crawling along. We were listing to traffic announcements and checking online to see if there was an accident up ahead, neither mentioned anything and as soon as the smart motorway ended traffic freed up and everyone went along at 70. So I could only conclude the crawling speeds were caused by the smart motor. I also feel like the speed camera painted bars on the road under every gantry give drivers a negative impression of them, are they speed cameras or not, if people are going for mile after mile on them, constantly looking at their speedo for fear of getting a fine they aren't watching the road as much. For speeding fines, I once got caught coming into a village in Northampton. I was towing a caravan and the speed change sign was round a bend, I couldn't slow fast enough safely to get down to the speed and was zapped. I think I was doing about 35 or 36 in a 30, having come down from 50. I have no idea why but a couple of weeks later I got another letter saying there had been an issue and they were no longer pursuing it. I am glad I had taken my time and not replied agreeing to it or I suspect I might still have been given the points since I had admitted it but I do wish I knew what had actually gone wrong for them not to pursue it further.