mschwett 

interestingly though, with most decent transit systems, as ridership goes up, speed actually increases as headways are improved to match the ridership... up to the point where they can't be any more, and then crowding begins. still, crowding doesn't usually result in slower trips unless it's so severe (which happens, but not often) that you can't get onto the first vehicle which comes.

contrast this to roads, where just about ANY other people using them in their cars slows you down.

i think this fundamentally accounts for the difference in outlook between users and supporters of mass transit vs private cars in roads. for the former, more users is a virtue. for the latter, the optimum situation is someone else building them a ton of expensive public infrastructure but then nobody else using it.