I have always wondered, what is the clearance under a modern locomotive?
Federal Law dictates:
§229.71 Clearance above top of rail.No part or appliance of a locomotive except the wheels, flexible nonmetallic sand pipe extension tips, and trip cock arms may be less than 2 1⁄2 inches above the top of rail.
So... 9-1/2 inches... on 115RE rail.