i don't drive, and take the bus almost every day. dd has just started walking. i also have hip problems since her birth, and while i am not disabled, maneuvering a pushchair is tough anyway.
on buses in my area, at least, there is space for three buggies (or two and a wheelchair). apart from that, buggies have to be folded. (luckily, i have only had that come up twice, and both times i waited for the next bus rather than struggle with the pushchair.
if you think that i could manage to fold up our stupid pushchair (not large, but cheap and old), hang on to a toddler, changing bag, and even one small shopping bag, without holding up everyone on the bus and generating an awful lot of hatred, you are sadly mistaken.
i do try to be considerate and watch for people's feet, knees, bags. DD likes to reach into handbags if they come into her range, so i have to keep an eye on that.
YANBU to want people to be careful and considerate, but I can't see how this is a big enough problem that it requires a solution which would make life so incredibly difficult for other people.