I'm not sure how this would help in the long term. As it stands, most people ignore those flashing signs that tell you to slow down, or immediately speed back up once they pass the sign. Two ways we can really reduce speeding in the long term are better street design and building cities that don't require the use of a car. Mediumly-dense, mixed-use development means people can live close to where they work and shop and won't require cars. Better street design means a lot of things, but essentially it boils down to more tree-lined streets and narrower lanes. When lanes are wide and there Are no obstacles, drivers feel safer to blow past the speed limit, as opposed to when roads are narrower and there's a constant, looming threat of running into a tree trunk or bollard if they go too fast.