Complex sentence: In normal operation, the crew member sits in the driver's position at the front, but just closes the doors at each station; by pressing two "start" buttons the train would then move automatically to the next station.
Split into simpler sentences: In normal operation, a crew member sits in the driver's position at the front, but is only responsible for closing the doors at each station. By pressing two "start" buttons the train would then move automatically to the next station.