The Conductor, who if I understand the order of excellence, is the overall responsible party. But he can only pull the emergency cord ( which is in each car) thus applying the train’s brakes. Not long ago, I took my grandson on an errand in downtown Oakland. While we were there the Amtrak Capitol which similar to the train in question runs from the Bay Area to Sacramento pulled in to the station so we went over and the engineer invited us to come up to where he controlled the train. They don't bother to turn these trains around, so the engineer, in one direction sits in a little cubicle in the upper right hand corner of the first car while the engine pushes the whole train from behind. The space is not unlike that occupied by a motorman on a subway train. so while there may be a second seat in the engine, when the train goes a$$ backwards, there is only place for one engineer.
The other thing here in California is that the primary use for the right of way is for freight, so Amtrak has to make way for those trains as they are higher priority to the railroads who actually own the tracks. The other thing is that in most places, here it's a single track designed to handle the slower moving freight trains, hence the very long time to get anywhere. Amtrak is a comfortable ride from Oakland to LA and since in a lot of places it's closer to the ocean than the highway, you do get some scenery ( and you get to see the missile launch facilities at Vandenberg AFB), but those are really the only reasons ( in addition to cost) for taking the train.
I know nothing about trains but it does not seem rational to rely completely on a single person when the safety of 200+ lives is at stake.