Find a way to expose them. Publicize acceptable and unacceptable behavior on the road.
Videos, public shaming, access channels. I don't know, that's a tough one. You have to somehow build consensus in your community that these things are ok and these things are not (norms). Once it becomes the norm everyone pretty much falls in line
How did we get people to stop smoking or not start. How are we combating domestic violence, public littering, racism, and cruelty to animals?
Maybe start with a community group that shares your concerns