It is dangerous - trucks struggling to do 40-45 and boneheads overtaking them at 90+.Not sure what is in place south of Newbury currently, but there isn't one between Newbury and Oxford. They ran it on the infamous Ilsley section for a few months. Not sure if it was judged successful or not, I'm guessing not. Unusually, I would actually commend the highways agency if the speed limit was lowered for that section of road as it's incredibly dangerous.
