There's this procedure in train companies that an instructor comes and rides along, next to the driver, checking that everything is done according to the rules. While doing that, he or she doesn't provide any additional instructions, doesn't assist the driver in any way, just observing. What is the proper word/phrase for that person and the job/activity?
They are traditionally called Road Foremen.
However, you may very will find the exact Personnel title in a given operator, CSX/BNSF for example, to be different.
Also note, this may be a US specific term.