Now that we have better quality sensors and electronics, is it not possible for car manufacturers to fit accurate speedometers? On a section of road works where the speeds are closely monitored, most drivers keep to the limit, but only as indicated. If true speedometers were fitted, the whole of the traffic line would speed up by up to ten percent, a truly worthwhile amount. I can imagine the auto marketing people protesting, but it could make a significant difference to journey times and traffic throughout, even more so at 70mph.