SUBSET-126 — ATO-OB / ATO-TS FFFIS Application Layer

Scope

Specifies the application-layer Form Fit Functional Interface between the ATO-Onboard and ATO-Trackside subsystems, defining the message set and procedures for automatic train operation commands and status exchange. It complements SUBSET-125 as the interoperable communication protocol for ERTMS/ATO and is referenced in CCS TSI Appendix A for ATO baseline 1.

SUBSET-126 specifies the application-layer Form Fit Functional Interface between the ATO-Onboard and ATO-Trackside subsystems, defining the message set and procedures used to exchange automatic train operation commands -- such as target speed profiles, stopping point instructions and door control triggers -- and status information between the two subsystems. It complements SUBSET-125's system-level functional and performance requirements by defining precisely how ATO-Onboard and ATO-Trackside equipment from different suppliers must communicate to interoperate correctly, in the same way the core ETCS balise and radio interface specifications define interoperability for those functions. It is referenced in Appendix A of the CCS TSI as the interoperable communication protocol specification for ATO baseline 1. Suppliers of ATO onboard and trackside equipment implement the specification directly to ensure their products can interoperate with ATO equipment from other suppliers on the same line. The current edition is version 1.1.0, dated 10 December 2024, developed by UNISIG, ERA and the EEIG ERTMS Users Group.