Seeing as how my morning and evening 2/3 subway commutes will be crowded for the next 6 months or so, forcing more and more people to pack into already-full cars, I suggest a new upgrade: the MTA should install razor blades inside the car doors. If a door can't close after the first try because someone's bag or ass is sticking out and blocking it, that's acceptable. Second try? Stretching it. After that, though, the blades should shoot out of the doors and stab people still trying to wedge inside. It'll speed up the commute and allow passengers to be more comfortable. I'm sick of doors opening and closing 6, 7, 8 times at a single stop and having the conductor yell "Stand clear of the closing doors please!" If words don't work, it's time for action! After a few amputations, people will learn.