Ultimately, the engineer is responsible for the safety of the passengers
Actually a lot of that responsibility is on the conductor and in this case possibly both. Duties of the conductor include,
* Making sure the train stays on schedule
* Ensuring the train follows applicable safety rules and practices
* Jointly coordinate with the engineer and dispatcher the train's movement authority, and verifying this authority is not exceeded
* Be alert to wayside signals, switch position, and other conditions that affect safe train movement
The engineers responsibilities include
* Their duties require that they control acceleration, braking and handling of the train underway.
* They must know the physical characteristics of the railroad, including passenger stations, the incline and decline of the right-of-way and speed limits.
(Above from wiki, https://en.wikipedia.org/wiki/... https://en.wikipedia.org/wiki/... )
So two people in the cab and both responsible with the conductor managing and the engineer operating.