What is the main goal of railway interoperability?

The main goal is to create a Single European Railway Area where trains can run freely across borders without technical or operational hurdles, thereby increasing the efficiency and competitiveness of rail transport.

TSIs (Technical Specifications for Interoperability) are the detailed European regulations that set the standards for railway subsystems (like infrastructure, energy, and signaling) to ensure they are compatible across the EU.

How does ERTMS contribute to interoperability?

ERTMS (European Rail Traffic Management System) replaces the incompatible national signaling systems of different countries with a single European standard, allowing trains to travel across borders without needing multiple signaling computers onboard.

Breaking Borders: The Essential Guide to Railway Interoperability

Seamless cross-border rail travel defines Interoperability. Discover how the Single European Railway Area harmonizes technical standards to connect networks.

December 11, 2025 8:33 am

What is Railway Interoperability?

Railway Interoperability is the regulatory, technical, and operational capability that allows trains to travel safely and continuously across different rail networks. Ideally, it enables a train to cross national borders without the need to stop at frontiers to change locomotives, drivers, or signaling equipment.

This concept is the cornerstone of the Single European Railway Area (SERA). By removing technical barriers—such as different track gauges, electrification voltages, and signaling systems—interoperability aims to make rail transport more competitive against road and air travel.

The Three Pillars of Interoperability

Achieving a seamless network requires harmonization in three distinct areas:

Technical Interoperability: Ensuring hardware compatibility (e.g., standardizing track gauge to 1435mm, using compatible pantographs).
Operational Interoperability: Harmonizing rules for driving, signaling, and traffic management so crews can operate in multiple countries.
Regulatory Interoperability: Creating a unified authorization process (via ERA) so a train approved in one country doesn’t need to be re-certified from scratch in another.

The Role of TSIs (Technical Specifications for Interoperability)

To enforce these standards, the European Union issues TSIs. These are legal regulations that define the exact technical requirements for each subsystem.

If a manufacturer builds a train according to the TSI LOC&PAS (Locomotives and Passenger Carriages) and installs signaling according to TSI CCS (Control-Command and Signalling), the vehicle is theoretically capable of running anywhere on the TSI-compliant network.

Comparison: Legacy Networks vs. Interoperable Networks

The history of rail in Europe is one of national fragmentation. The shift to interoperability represents a massive overhaul of infrastructure and mindset.

Feature	Fragmented Legacy Network	Interoperable Network (Target)
Signaling System	Over 20 different national systems (PZB, KVB, AWS, etc.)	Single standard: ERTMS / ETCS
Border Crossings	Trains stop; Loco/Crew change required	Seamless crossing at full speed
Electrification	Requires specific single-voltage locomotives	Multi-system locomotives compliant with TSI Energy
Authorization	National Approval (NSA) per country	Single Safety Certificate issued by ERA

Barriers to Full Interoperability

Despite significant progress, several challenges remain. The “break of gauge” between Central Europe and the Baltic states (or Spain/Portugal) requires physical infrastructure changes. Additionally, the cost of retrofitting older trains with modern ETCS onboard units is a significant financial hurdle for operators.