PURPOSE: To prevent passengers from falling down one upon another due to a sudden stop by providing an output means for maintaining the output signal of a digital computer to the same state as it is at the time of failure being detected, upon detecting the failure by a failure detecting means.

CONSTITUTION: In a digital computer, control signals to driving machines remain as they are for a while after the generation of failure. Accordingly, when the failure is detected at a failure detecting means 201, the output of the digital computer is maintained to the same state as at the failure time, before the change of the control signal. A passenger conveyor is in operation before the failure and therefore maintained to the operated state regardless of the failure of the digital computer. Passengers are there by prevented from falling down one upon another, and have no trouble of getting off as they reach the exit automatically by just remaining on a conveyor.