What is the main purpose of the EN 61375-1 standard?

The main purpose of EN 61375-1 is to define the general architecture for the Train Communication Network (TCN). It provides a standardized, hierarchical framework for all on-board electronic communication, ensuring that equipment from different suppliers can work together reliably on a train.

What is the difference between a Train Backbone and a Vehicle Bus?

The Train Backbone is the high-level network that connects different vehicles or consists across the entire train. The Vehicle Bus is a lower-level network that operates within a single vehicle, connecting local subsystems like brakes and doors. A gateway connects the Vehicle Bus to the Train Backbone.

Which is better: Wire Train Bus (WTB) or Ethernet Train Backbone (ETB)?

Neither is inherently 'better'; they serve different needs. WTB is a highly reliable and deterministic bus ideal for critical control functions and is widely used in existing fleets. ETB offers vastly superior bandwidth, making it essential for modern data-heavy applications like CCTV and passenger Wi-Fi. Newer trains predominantly use ETB for its future-proofing capabilities.

What is 'train inauguration' in the TCN context?

Train inauguration is the automatic self-configuration process of the TCN when a train is powered on or its composition changes. The network automatically discovers the number, order, and orientation of all vehicles, assigns addresses, and prepares for operation without manual intervention. This is crucial for operational flexibility.

Does EN 61375-1 cover cybersecurity?

EN 61375-1 primarily focuses on the communication architecture and does not deeply specify cybersecurity measures. However, other parts of the EN 61375 series and separate standards like IEC 62443 address cybersecurity for industrial control systems, which are applied to protect modern IP-based TCNs (like those using ETB and ECN) from cyber threats.

EN 61375-1: The Central Nervous System of Modern European Trains

EN 61375-1 defines the Train Communication Network (TCN) architecture, the central nervous system of modern trains. Discover its hierarchical structure for seamless, reliable data exchange.

December 15, 2024 2:02 am

What is EN 61375-1: The Train Communication Network?

EN 61375-1 is a foundational European standard that specifies the general architecture for the Train Communication Network (TCN). It establishes a standardized framework for data communication on board trains, ensuring interoperability between electronic equipment from different manufacturers and enabling the reliable control and monitoring of all vehicle subsystems. The standard defines a hierarchical communication system designed to meet the demanding requirements of the railway environment.

The primary goal of the TCN architecture defined in EN 61375-1 is to create a robust, scalable, and interoperable communication backbone for modern rolling stock. This allows critical systems such as traction control, braking, door systems, passenger information, and HVAC to communicate seamlessly both within a single vehicle and across the entire train consist.

The Hierarchical Structure of the TCN

The core concept of EN 61375-1 is a two-level hierarchical network architecture. This structure logically separates communication needs, optimizing bandwidth, reliability, and real-time performance. The two main levels are the Train Backbone and the Vehicle Bus.

H3: The Train Backbone: Inter-Vehicle Communication

The Train Backbone is the higher-level network responsible for communication between the different vehicles or consists that make up a complete train. Its primary function is to ensure that train-wide commands and status information are reliably exchanged. EN 61375-1 outlines two primary implementations for the Train Backbone:

Wire Train Bus (WTB): The original, field-proven backbone based on a redundant shielded twisted-pair cable. It is designed for high reliability and deterministic data exchange, making it ideal for safety-critical functions. It operates with a token-passing protocol to manage network access.
Ethernet Train Backbone (ETB): A modern implementation using Ethernet technology. The ETB offers significantly higher bandwidth, making it suitable for data-intensive applications like CCTV video streams, advanced passenger information systems (PIS), and onboard internet access. It provides the foundation for IP-based communication across the train.

H3: The Vehicle Bus: Intra-Vehicle Communication

The Vehicle Bus, also known as the Consist Network, is the lower-level network operating within a single railway vehicle (e.g., a locomotive or a passenger car). It connects the various end devices (sensors, actuators, controllers) within that vehicle and manages their communication. The Vehicle Bus is connected to the Train Backbone via a gateway.

Key implementations for the Vehicle Bus include:

Multifunction Vehicle Bus (MVB): A highly deterministic and reliable fieldbus specifically designed for the railway environment. It supports real-time data exchange (Process Data) and event-driven communication (Message Data), making it perfect for controlling subsystems like brakes, doors, and traction converters.
Ethernet Consist Network (ECN): Similar to the ETB, the ECN uses Ethernet technology for communication within a consist. It provides high bandwidth for modern subsystems and simplifies integration with IP-based devices.
CANopen (CiA 457): Based on the Controller Area Network (CAN), CANopen is another option for the vehicle bus, often used for specific applications or subsystems like HVAC or lighting control due to its cost-effectiveness and widespread adoption in other industries.

H3: Gateways and End Devices

A critical component in the TCN architecture is the Gateway. The gateway acts as a bridge between the Train Backbone and one or more Vehicle Buses. It is responsible for routing and filtering data, translating protocols if necessary, and ensuring that information flows correctly between the vehicle level and the train-wide level. End Devices (EDs) are the final nodes on the network, such as a brake control unit, a door controller, or a passenger display, which produce or consume data.

Key Technical Principles of EN 61375-1

Beyond the physical structure, the standard defines several crucial operational principles that ensure the TCN functions correctly and reliably in a dynamic railway environment.

Train Inauguration

Train inauguration is the automated process by which the TCN configures itself upon train startup or when the train composition changes. During this process, the leading vehicle’s gateway becomes the network master and performs several key tasks:

Topology Discovery: The system automatically detects the number of vehicles, their order, and their orientation (direction).
Address Assignment: Unique addresses are assigned to each vehicle’s gateway on the Train Backbone.
Function Allocation: Train-wide functions are mapped to the physical devices present on the network.

This automated process is vital for operational flexibility, as it allows train consists to be coupled and uncoupled without manual reprogramming of the communication network.

Data Communication Models

The TCN supports two primary types of data traffic to meet different operational needs:

Process Data (Cyclic): Small, fixed-size data packets transmitted at regular, predictable intervals. This real-time, deterministic communication is used for safety-critical functions like traction and braking control, where consistent and timely updates are essential.
Message Data (Acyclic): Larger, event-driven data packets used for non-time-critical information, such as diagnostics, configuration downloads, or passenger information updates. This traffic is handled on a best-effort basis without interfering with Process Data.

Comparison of TCN Communication Buses

The choice between different bus technologies depends on the specific requirements for bandwidth, determinism, and legacy compatibility. The following table provides a technical comparison of the main TCN buses.

Feature	Wire Train Bus (WTB)	Ethernet Train Backbone (ETB)	Multifunction Vehicle Bus (MVB)	Ethernet Consist Network (ECN)
Primary Level	Train Backbone	Train Backbone	Vehicle Bus	Vehicle Bus
Physical Medium	Shielded Twisted Pair (Redundant)	Ethernet Cabling (e.g., Cat 5e/7)	Twisted Pair or Optical Fibre	Ethernet Cabling
Typical Bandwidth	1 Mbps	100 Mbps / 1 Gbps+	1.5 Mbps	100 Mbps / 1 Gbps+
Determinism	High (Token Passing)	Medium (Managed with QoS/TSN)	Very High (Master/Slave)	Medium (Managed with QoS/TSN)
Primary Use Case	Train-wide control, safety functions	High-speed data (CCTV, PIS, Internet)	Real-time control of vehicle subsystems	High-bandwidth intra-vehicle data
Key Advantage	Proven reliability, high robustness	High bandwidth, IP-based, future-proof	Extreme reliability, real-time precision	Flexibility, standard COTS hardware

The Role and Future of EN 61375-1

EN 61375-1 serves as the master document for the entire EN 61375 series, which details the specifics of each sub-protocol (e.g., WTB, MVB, ETB). By establishing a common architectural language, it has been instrumental in enabling the creation of complex, multi-vendor trains. The standard’s evolution to incorporate Ethernet-based backbones and buses (ETB/ECN) reflects the rail industry’s move towards higher data rates, increased connectivity, and the adoption of Internet Protocol (IP) as the universal communication standard. This transition paves the way for advanced applications like predictive maintenance, remote diagnostics, and enhanced passenger experiences, solidifying the TCN’s role as the central nervous system of modern rolling stock.