Complex sentence: The ATO system performed all functions of the driver except for the opening and closing of the doors: the driver pressed two buttons to start the train and, if the way was clear, the train automatically proceeded to the next station.
Split into simpler sentences: The ATO system performs all functions of the driver except for the opening and closing of the doors. The driver needs only to press two buttons to start the train and, if the way is clear, then the train will automatically proceed to the next station.