There are a lot of things that contribute to motorway accidents D9, the time I was on the things I used to TRY & drive to the road conditions / traffic, but there was one thing in the HGV favour in many things? HEIGHT, what we could see & what the motorist could see was a hell of a difference, at that time I was driving a Scania with a forward vision on Miles depending on the private car, the HGVs was in vision if a Bump occurred 2>>3 miles ahead but the car driver ( With some, the end of his / her bonnet that's how a lot drive, another example, a slip road coming off a Motorway normally has a slip road coming onto a motorway, If a driver was aware of this HE / SHE/ would not get "trapped" causing them to ease up causing braking behind them, drivers if they forward planned such as what I have just stated accidents would not happen, a lot of these bumps are caused by people that have either just passed their test, have never used a motorway before, or have not got a bloody clue what to do. You are right in what you say regards the 45mph f only persons realised the implications that they cause by doing this, they would think differently.