Norfolk Southern’s crossing of the Allegheny Mountains west of Altoona requires a lot of helper sets. And on this line, those helpers are paired SD40Es (rebuilt SD50s). One of those helpers pops out of the tunnel in Gallitzin, Pennsylvania, on June 26, 2017. NS 6308 is the former SD50 6519, and it is coupled to SD40E 6325, which was NS SD50 5049, originally Conrail 6715.