A story here of a man having a seizure, falling onto the subway tracks as a train is approaching.  A father of two jumps down and rolls him between the tracks, lies atop him hoping he can hold him down and the train can go over them.  The clearance is 21″.  They made it by 1/2 inch.  Sometimes the one you think is holding you down is saving your life and keeping you from hurting yourself.
Click here to watch this story: http://www.wimp.com/subwayhero/