We spend a fortune resurfacing the roads to ensure that they are flat and smooth and then the same again putting bumps back in. I'm pretty sure (although admittedly, I can't evidence it) that speeding is just displaced by humps. You so often see van drivers (not sure why it's always van drivers, but anyway), leaving a 'bump zone' and really putting their foot down, which I'm sure is at least in part born out of the frustration bumps invoke.