The Commission has revised the core technical specification governing onboard and trackside train control system, introducing new testing procedures, clearer transitional arrangements, and updated specifications for automated train operation
April 15th, 2026 – Commission Implementing Regulation 2026/693, published today, amends the main technical specification governing train control and signalling interoperability across the EU rail network, the Control-Command and Signalling Technical Specification for Interoperability, or CCS TSI, established under Regulation 2023/1695. The amendment follows a recommendation issued in December 2024 by the European Union Agency for Railways and addresses a set of technical gaps that had emerged since the 2023 version entered into force.
The most substantive changes concern testing. The regulation introduces new testing procedures for ETCS Baseline 4 and Automated Train Operation (ATO) Baseline 1 (the current generation of train protection and automated driving specifications) clarifying how onboard and trackside equipment must be validated before deployment. Alongside this, the regulation completes the description of ETCS system versions 2.1 and 2.2, which had been defined only by reference to the more complete version 3.0 rather than in their own right. This matters operationally because many ongoing projects across Europe are deploying intermediate versions rather than the full 3.0 specification, and the absence of precise definitions had created compliance ambiguity for manufacturers and notified bodies.
The regulation also revises the transitional arrangements in Annex B, which govern how long existing certifications and in-progress design phases remain valid as specifications evolve. The previous provisions had proved open to divergent interpretations and, in some cases, were generating disproportionate costs for the rail sector by requiring unnecessary recertification.
Specifically, the rules have been updated to prevent existing onboard or trackside systems from facing new mandatory authorisation requirements solely because of minor specification maintenance updates, provided the changes do not affect safety or interoperability interfaces. The regulation additionally fills a gap regarding radio system compatibility: while the 2023 TSI included obligations for infrastructure managers to maintain ETCS compatibility specifications, equivalent provisions for radio system compatibility had been omitted and are now introduced.
From a compliance standpoint, the regulation is directly applicable across all EU Member States as of twenty days after publication. The transitional tables in Annex B are detailed and product-specific: manufacturers and railway undertakings with ongoing design phases should note that several new requirements, including those concerning ATO Baseline 1 testing specifications and the updated harmonised marker board standard EN 16494:2025, apply from 1 January 2026 for relevant implementations, while others trigger at the close of specific design phases. Notably, the regulation confirms that previously issued CE certificates based on the 2023 TSI remain valid unless the specific transitional rows in Annex B require revision.
No renewing of existing notified body notifications is required as a consequence of this amendment, and the regulation explicitly states that no new conformity assessment competencies are needed to evaluate it.
