Railway safety critical systems with task redundancy and asymmetric communications capability

Control system for a critical railway safety application system, comprising: at least one controller, comprising a computer processor and configured to execute first and second tasks; the first task being able to be in bilateral communication with the second task and being able to send and receive a message from critical safety systems within a critical railway safety application system, the message including a safety code and critical safety data; the second task being able to be in bilateral communication with the first task and being able to receive a message from critical safety systems, but not being able to send the message from critical safety systems to the critical railway safety application system, the second task having a generator of security code; the control system further comprising a communications path between tasks that couples the first and second tasks; wherein the first and second tasks are each configured to receive a common input security critical systems message including input security critical systems data and an inbound security code, independently verify message integrity input and independently generate data from critical safety systems output, the second task is configured to generate an outbound security code and send it to the first task, and the first task is configured to assemble and send an outbound security critical systems message that includes the security critical systems data from exit and exit security code from the second task for use within the critical rail security application system, characterized in that said computer processor is configured to execute said first task and said second task simultaneously, virtually and in real time on said computer processor.