SUBSET-125 — ERTMS/ATO System Requirements Specification

Scope

Sets out the system-level functional and performance requirements for ERTMS/ATO (Automatic Train Operation) running over ETCS, covering the ATO-Onboard/ATO-Trackside architecture and the grades of automation (GoA1–GoA4) applicable to interoperable rail. It is the top-level normative reference for ATO deployment referenced in CCS TSI Appendix A for ATO baseline 1.

SUBSET-125 sets out the system-level functional and performance requirements for ERTMS/ATO (Automatic Train Operation) running over an ETCS-equipped railway, defining the split of responsibilities between the ATO-Onboard and ATO-Trackside architecture and describing the grades of automation (GoA1 to GoA4, ranging from driver-assisted operation to fully unattended train operation) applicable to interoperable rail. It is the top-level normative reference for ATO deployment, establishing what an ATO system must be capable of doing and to what level of automation, before a more detailed companion interface specification defines how the ATO-Onboard and ATO-Trackside subsystems actually communicate. It is referenced in Appendix A of the CCS TSI as the specification governing ATO baseline 1, the first standardised ATO baseline recognised for interoperable deployment. Suppliers developing ATO onboard and trackside subsystems, and infrastructure managers and railway undertakings planning ATO deployment, use it as the reference for the functional scope and grade-of-automation targets of a given ATO project. The current edition is version 1.1.0, dated 6 December 2024, developed by UNISIG, ERA and the EEIG ERTMS Users Group.