Knowledge base
Railway glossary: DAS, SFERA, signalling, and control terms
Railway work is full of abbreviations. Some come from signalling. Some come from traffic management. Some come from DAS and SFERA. This glossary keeps the main terms short and practical.
Published: January 24, 2026
TopicsGlossaryDASSFERAETCSERTMSSignallingInterlocking
How to use this glossary
- Some terms are standard terms. Others are market shorthand.
- The same acronym can mean slightly different things in different countries or projects.
- When a term is safety-critical, always check the local rule book or system specification as well.
- The definitions below are written to be short, plain, and useful for a first pass.
DAS and SFERA basics
- DAS: Driver Advisory System. A system that gives driving advice such as traction, cruise, coast, or brake.
- S-DAS: Standalone DAS. The advisory works mainly from data loaded before the trip.
- C-DAS: Connected DAS. The advisory gets live updates during the trip.
- DAS-C: Ground advice calculation. The ground side calculates the advice and sends it to the cab.
- DAS-O: Onboard advice calculation. The ground side sends context and the train calculates the advice onboard.
- SFERA: UIC 90940. A standard for exchanging DAS data between ground and onboard systems.
SFERA data terms
- JP: Journey Profile. A real-time package with timing points, references to Segment Profiles and Train Characteristics, and temporary changes such as TSRs. It is sent from ground to board for advice calculation.
- SP: Segment Profile. Static data for a section of route, such as gradients, curves, signals, and positioning references.
- TC: Train Characteristics. Train-specific parameters such as length, weight, maximum speed, braking, and acceleration.
- TPE: Train Path Envelope. A set of time windows and optional speed bounds along the route. It is set by the traffic management side and used as the basis for the Journey Profile.
- DI: Device Identifier. In SFERA message routing, this identifies the sending or receiving device. If a local project uses DI differently, check that local definition as well.
Signalling and train control terms
- Signalling: The railway system that controls and protects train movements.
- Interlocking: The safety logic that prevents conflicting routes and unsafe combinations of points and signals.
- ETCS: European Train Control System. A European train protection and supervision system.
- ERTMS: European Rail Traffic Management System. The wider European framework around train control and traffic management, with ETCS as a core part.
- MA: Movement Authority. The permission for a train to move up to a defined limit under ETCS or another train control system.
- EoA: End of Authority. The point where the current movement authority ends and the train must be able to stop.
- LoA: Often used informally for Limit of Authority, but this acronym was not confirmed as a clean glossary term in the source set checked for this article. Use it carefully and confirm it locally.
- ATP: Automatic Train Protection. A system that prevents unsafe movement, for example by enforcing speed limits or stop commands.
- ATC: Automatic Train Control. A broader control term. In some railways it includes protection plus automatic control functions, so the exact scope can vary.
- CBTC: Communications-Based Train Control. A communication-heavy train control system used mainly in metros and urban rail.
Operational and onboard systems
- TCMS: Train Control and Management System. The onboard system that links train subsystems and exposes train data to other onboard functions.
- TMS: Traffic Management System. A ground-side system that manages train paths, regulation, and conflicts. In SFERA thinking, it can help define the TPE.
- DMI: Driver Machine Interface. The cab display that shows ETCS information such as speed, supervision status, and where relevant the movement authority.
- RBC: Radio Block Centre. In ETCS Level 2 or 3, the ground-side system that sends movement authority by radio.
- ATO: Automatic Train Operation. Automatic control of parts of the driving task, usually layered on top of a protection system.
- GoA: Grade of Automation. The level of train automation, from driver-controlled to unattended operation.
Restrictions and everyday operations terms
- TSR: Temporary Speed Restriction. A temporary lower speed on part of the route.
- ESR: Emergency Speed Restriction. A temporary lower speed introduced urgently, often at short notice.
- Timing point: A location where planned or measured passing or stopping time matters.
- IM: Infrastructure Manager. The organisation responsible for the infrastructure.
- RU: Railway Undertaking. The operator that runs the train service.
- Rule of thumb: first ask whether a term is about signalling, traffic management, onboard train systems, or DAS. That usually clears up half the confusion straight away.
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