I've thought about solutions: what if you only gave drivers three honks per ride? Or fixed horns so you have to be moving? But all these could endanger safety at some point. And they involve complicated electronic tinkering.
I was just going through a Transportation Alternatives email discussion and came across this brilliant idea (I'd be happy to give credit, but don't want to without permission):
Make car horns punishingly loud inside cars as well as outside. That way people will still use them for safety but not for mere aggression.Now why didn't I think of that? So simple. So brilliant. And it would be so effective. If you're willing to listen to your own horn, lay on it. In the meantime, stop thinking about only yourself, you selfish self-obsessed driving schmuck! Now how can we make it happen?