Difficult to police, no one will think they will get caught, so little additional deterrence. Zero tolerance is no way to treat other human beings, no reasonable person wishes to live in a totalitarian state. Since motorway speeds are obviously believed to be too low by the majority, given the percentage who drive above them, is this just a ruse to get more money from the public and justify it be trotting out the old, 'you didn't have to disobey us so we're pretending its voluntary', mantra ?