On a freight train like that, the 'conductor' is what they called the 'second man' in the UK... the engineer/driver drove the train, the conductor kept an eye on the train itself and also the signals and any other issues that might arise. Pilot and co-pilot in other words.
A game like
World Of Subways 3 - Circle Line (by the same folks who did Bus & Cable Car Simulator) would let you do just that, as you're able to get out of the cab and walk around. Done right, it would make a fairly entertaining game as the driver would have to drive and wait for the guard to do the station duties, and while in motion the guard would have to try and collect as many fares as possible for a high score. Mini-events like fare dodgers, passengers falling ill, etc would liven things up a bit. Plus, as in real life, the guard would likely get carried away trying to sell someone a ticket and then have to push their way back down the carriage in a hurry to operate the door controls.