Minimum height for a train engineer

Odd question, namely because CFR49 part 240 doesn't say... but what is the minimum height a train engineer need to be to safely operate an engine? I doubt it's too short but I'd rather not guess if I want *some* accuracy in writing this sequel novel (see signature below).

Probably something close to the minimum height required to operate an automobile - you need to be able to reach the controls and see out the window. Looking at a diagram of the front cab wall of a GP40-2, the side window the engineer would look out of starts about 2'10" above the floor. The two windows in the middle start almost 4' off the floor. Based on that, someone in the engineer's position would need to have an eye level of about 3'6" (minimum) to be able to see clearly out the window. That could be seated or standing, depending on anatomy.