Take a good look at this LIRR M-7 MU. A 6" wide stainless panel about 3' tall running up the side at each end and up the middle of the car to function as bumper guards in the East River tunnels when rocking and striking the benchwall. The C-3 bi-level cars also have them. The Metro North M-7A did not get built with them, nor are the brand new Kawaski M-9's.