Abstract: A method of implementing a computer based interlocking system for automatic train protection includes providing a data base of prestored rule sets for a plurality of guideway objects, the guideway objects being represented as one or more virtual gates of a plurality of virtual gate types, the rule sets defining conditions for a respective guideway object which must be met before entry through a virtual gate of the object is permitted. A high-level description of a guideway layout including all of the guideway objects that form interlocking zones is input and processed using the pre-stored rule sets to form an overall interlocking system definition by locating, retrieving and linking appropriate rule sets corresponding to the respective input guideway objects.