How do I get cars to slow down on the road I live on?

I live on a no-exit road, so the cars that pass my house all live in this small community or are visiting the residents. It is a 30km zone, but when the cars get to where my house is, it’s straighter than the rest and they speed up. It is also where there is a cross walk, made with a very weak speed bump, and a school bus stop. My son and his friends play on the patch of grass and trees at the school bus stop often. We have talked to the police and they don’t seem interested. These people are my neighbours and their teen age kids and often have small children of their own who use this bus stop. Today, I saw a car stop at the cross walk, and another car pass on his left, speeding and overtaking, whizzing right past. If caught, this person would have lost their license. Or worse, they could have hit the person that the first car had stopped for. HELP! I want to stop this before someone gets hurt, or worse!