I can tell you stories, but then you may lose any and all appetite for awhile.
After riding the impossibly crowded New York City #7 subway line in the blazing hot summer of 1987 (120 humid degrees in sardine-stuffed, graffiti-strewn cars, no air conditioning, garbage rotting under the seats, giant stinking rats running free on the stairwells) not much would shock or sicken me about train travel. But at least they didn't make us ride up on top. ;-)