1. An automatic train operation apparatus incorporating a security function, for controlling a train operation, comprising: an automatic train operation and control (ATO/C) system including a plurality of ATO/C units provided redundantly, each ATO/C unit having a fail safe configuration with a reliability ATO including a plurality of execution processors and a supervisory processor for monitoring operations of the execution processors and determining an output of said each ATO/C unit, all of the execution processors in the plurality of ATO/C units simultaneously executing an identical automatic train operation program for obtaining a control command output for controlling the train operation; and majority logic means for selecting an output obtained by a majority of the ATO/C units of the ATO/C system as a control command output of the ATO/C system for controlling the train operation such that a total reliability R of the apparatus is greater than the reliability ATO of each ATO/C unit.