Sometimes it’s difficult to run power from another railroad so you might just run your own engines - from another era. First generation power isn’t always dropped somewhere back in the consist or assigned to work train duty. It might be cut in right up front where it affords the crew a smoother ride. Or maybe it’s just that the heaters are working in that old FPA7.

In this case, steam for the passenger cars is provided by a generator car so wintertime operation has simply demanded more traction than can be offered by the lead engine’s 1700 horse power. What a great way to use some old F units in conduction with your ‘modern’ fleet.