TWR....Yes, I agree. We have had horrendous traffic jams, caused by accidents here on the M4 in South Wales, and also over the Bridge on the M5.
I have made this point before. When accidents occur, huge queues build up behind within a few mins. But those cars can be trapped between Motorway exits for hours.
What is needed is places between exits, where cars could be turned around and allowed to escape, and that means removable central reservation barriers.
To address your question directly TWR, from what I can see, most accidents on Motorways are caused by people driving far too fast, and far too close to the vehicle in front. When I am driving on Motorways, which is nearly every day, I try to keep a sensible distance between myself and the vehicle in front, but there is always some twit following behind, far too close.