Are TSIs mandatory for all railway projects?

TSIs are mandatory for new, renewed, or upgraded subsystems within the European Union rail network. However, exemptions can be granted for limited cases, such as isolated networks or heritage railways.

What is the difference between a TSI and an EN Standard?

A TSI is a European Law (Regulation) that defines 'what' must be achieved for interoperability. An EN Standard (CENELEC/CEN) is a technical norm that describes 'how' to achieve it. TSIs often refer to EN standards as a way to prove compliance.

Who verifies compliance with TSIs?

A Notified Body (NoBo) is the independent third-party organization responsible for assessing and verifying that a subsystem complies with the relevant TSIs.

The Rulebook of Europe: Technical Specifications for Interoperability (TSI) Explained

Standardizing Europe’s railways. Explore how Technical Specifications for Interoperability (TSI) harmonize subsystems for a seamless cross-border network.

December 11, 2025 8:34 am

What are Technical Specifications for Interoperability (TSI)?

Technical Specifications for Interoperability (TSI) are the legal regulations adopted by the European Union to define the technical and operational standards for each subsystem of the railway network. Their primary goal is to ensure that trains can travel safely and seamlessly across all EU Member States, creating a Single European Railway Area (SERA).

Unlike voluntary industry standards (like ISO or CENELEC), TSIs are mandatory laws. Any new railway line, significant upgrade, or new rolling stock introduced within the EU must prove compliance with the relevant TSIs through a verification process led by a Notified Body (NoBo).

The Structure of TSIs: Subsystems

The railway system is too complex to be covered by a single document. Therefore, TSIs are divided into specific “Subsystems.” These are categorized into Structural (hardware) and Functional (operational) areas.

Category	TSI Acronym	Full Name & Scope
Structural Areas	TSI CCS	Control-Command and Signalling: Covers ERTMS, ETCS, GSM-R, and onboard/trackside signaling interfaces.
	TSI LOC&PAS	Locomotives and Passenger Rolling Stock: Defines vehicle structure, braking, and safety systems for trains.
	TSI ENE	Energy: Standards for overhead contact lines (catenary) and pantograph interaction.
	TSI INF	Infrastructure: Track gauge, rail profile, track resistance, and switch requirements.
Functional Areas	TSI OPE	Operation and Traffic Management: Rules for drivers, signalers, and train preparation.
	TSI TAP/TAF	Telematic Applications: Data exchange for Passenger (TAP) and Freight (TAF) services.

Transversal TSIs

In addition to specific subsystems, some TSIs apply across the entire board to address specific safety or social needs:

TSI PRM (Persons with Reduced Mobility): Ensures accessibility for disabled passengers (e.g., ramp slopes, door widths, restroom access).
TSI SRT (Safety in Railway Tunnels): Fire safety and evacuation standards for tunnels longer than 1km.
TSI NOI (Noise): Limits the noise emission levels of rolling stock.

Compliance and “Open Points”

While TSIs aim to cover everything, unique local conditions sometimes exist. Areas not yet fully standardized by a TSI are called “Open Points.” In these cases, National Rules (checked by a Designated Body) apply instead of the European regulation.

The Essential Requirements

Every TSI is designed to satisfy the “Essential Requirements” defined in the Interoperability Directive. These form the foundation of the regulations:

Safety
Reliability and Availability
Health
Environmental Protection
Technical Compatibility