Death penalty, immediate execution after 2nd time in the wrong, will educate people very quickly. I know, it is a bit harsh, but think of all the advantages such as fewer people, cars and motorbikes on the road (and in general); hardly any accidents (stupid people die first!); roads in very good condition; a lot less people to feed...
Negative effects: small (most incomplete) families, huge drop in car/motorbike sales, and rise in gun-related fights