But they are, and pretending they aren't, or basing a motoring infrastructure around the buttumption that they're not, isn't a sound idea.
I remember a programme a few years ago where they covered the speedos of a number of motorists and asked them first to drive at a predetermined speed, where their accuracy was measured, and then to accelerate to a speed of their choosing and to guess what speed they thoought the were doing. This was done on a laid out riing training course, designed to simulate a number of different road types including urban and A roads, and some of it may have been done on open roads, IIRC.
I don't recall the exact numbers, but very few if any of them got to within 10% of their correct speed, and a horrible percentage were more than 50% out (travelling at more than 50% over what they thought they were), even where the posted limit was 30. I remember one guy who was asked to accelerate normally to 50 miles and hour and hold his speed there. When he declared himself happy that he was doing 50, he was actually travelling at 84 mph
Brian
