Secondly and more importantly for me (and I know unpopular) - kick off the drunk / other rule-breakers and anyone who threatens people even if its just a result of mental illness. No one wants to start their day next to someone yelling - "I'll f* you up... etc" on a crowded bus. At least where I am the bus drivers don't do anything from small - blasting music -> to larger - nonstop threats of violence.
I have only small anecdotes but other places seem to empower the drivers etc more. And the jitney cabs in the Caribbean would flat out leave people on the side of the road if they were sloppy drunk.