Industrial networking for rail
Industrial networking for rail refers to the wired communication infrastructure inside rolling stock and at wayside locations that connects onboard subsystems, supports train control and management, and transmits operational data between trains and ground systems.
The foundation of onboard industrial networking is the Train Communication Network (TCN), standardised under IEC 61375.
The original TCN architecture defined two serial bus layers: the Multifunction Vehicle Bus (MVB), standardised in IEC 61375-3-1, which interconnects electronic equipment within a single vehicle — traction electronics, brakes, doors, HVAC, passenger information, event recorders, and cab displays; and the Wire Train Bus (WTB), standardised in IEC 61375-2-1, which connects vehicles across the train using twisted shielded-wire pairs spanning up to 860 metres.
The TCN was adopted as IEC 61375 in 1999, the same year the IEEE Rail Transit Vehicle Interface Standards Committee adopted it without modification as IEEE Std 1473-1999. It was adopted by manufacturers including Siemens, ABB, and Bombardier (now Alstom) and remains in service on a large portion of the European fleet.
Ethernet-based successors
The shift from serial fieldbuses to Ethernet-based networking inside rolling stock is formalised in IEC 61375-2-5, which defines the Ethernet Train Backbone (ETB) replacing the WTB at the train-wide layer, and IEC 61375-3-4, which defines the Ethernet Consist Network (ECN) replacing the MVB within each vehicle.
These standards specify 100 Mbit/s switched Ethernet with proprietary higher-layer protocols including TRDP and IPTCom for the real-time process data exchange that MVB previously handled.
The transition to Ethernet improves bandwidth and reduces the cost of hardware, but the absence of deterministic real-time guarantees in standard Ethernet has limited adoption for the most safety-critical control functions.
Time-Sensitive Networking (TSN) extensions to Ethernet, defined under IEEE 802.1 standards, provide bounded latency and deterministic delivery, and are entering evaluation for railway applications where they would allow consolidation of safety-critical and non-safety data flows on a single Ethernet fabric.
Safety-critical communication requirements
Communication over onboard networks that carries safety-critical data — train protection commands, door interlock signals, brake commands — must satisfy the requirements of EN 50159, which defines safety integrity levels for data transmitted over open transmission systems.
Where TCN or Ethernet carries such data, the application layer must implement the safety coding and error detection mechanisms specified in EN 50159, independently of the underlying physical transport.
The TCMS (Train Control and Management System) coordinates all onboard subsystems through the TCN or ETB/ECN network.
Modern TCMS implementations also provide the gateway function through which onboard condition monitoring data, event logs, and diagnostic information are transmitted to ground systems via the GSM-R or FRMCS radio link for remote access by maintenance teams.