But (there is always a but), for visually impaired people it does not work that well. For example no kerb edges. For idiots (think stronger word than that), they will drive at the still high speed - at then the accident are worse (severity of outcomes) so it fails.
Speed bumps just are not good - better with a chicane or shuttle working which allows an emergency vehicle to go straight through the obstacle.
>If you want people to drive 20mph, make it hard to navigate at 30mph. There is a wide range of driving skills - design sometime has to account for the worst. Making driving test harder - is a political problem not a technical problem. Driver assist means road get easier to navigate. Driver assist enforcing the speed limit ... is a political problem not a technical problem.
There is probably an art to this, and it's not as easy in practice as the popular books I've read on it claim. My neighborhood in Brooklyn is part of the "neighborhood slow zones" project. That means they put a speed bump midway down the street, which is a popular way to bypass some traffic lights on the way to the BQE. People drive 90 miles an hour right up until the speed bump, slam on the brakes, and then accelerate back up to maximum cruising speed. It doesn't really serve much purpose. (Meanwhile, if you got rid of the curb, and people's lawn furniture / outdoor dining started impinging on available space, it would be impossible to drive more than 5mph. But, there's no political will to block the street like that -- what if a fire truck got stuck and people died in a fire! So it will never ever happen.)
But, like tolerance, it's something we can work on if we choose to.