I think it’s an idea that is both good and dangerous in equal parts, firstly it’ll stop the idiots in BMW’s & Audi’s flying up to the back of you at 80/90 mph on motorways & dual carriageways when you’re doing 70 mph, however it’s back to that if you’re driving a van on a national speed limit road, as there is a 10 mph difference between a car & a van,but this is further complicated by the fact that a car derived van has the same speed limits as a car, but a double cab pick up is a commercial so should be driven at the same speed as a large van, however I accept some van/pick up drivers don’t seem aware of this & are regularly seen speeding in large Transit type vans & pick ups, there will be queues of vehicles all stuck trying to overtake, when plainly they won’t be capable of doing so, so if you get stuck in lane 2 or 3 it’s a certainty that no one will let you in when approaching your exit, the other problem is incorrect recording of speed limits on gps systems, so that will need sorting out, it will stop the lunatics who think that the 20 mph limit doesn’t apply to them and overtake because you have the audacity to keep to the limit, I think it’s a flawed idea, it sounds good in principle, but in reality it’s quite unworkable in a real world scenario, just get some motorway patrol police cars back out there on mass and drop on the idiots like a ton of bricks.