Railway glossary
The vocabulary of rail, defined
46 definitions of the standards, bodies, components and processes RAILMIND must be able to name and connect — from control-command to maintenance, from European regulation to the AI notions applied to rail.
Regulation and standards
The authorities, texts and standards that govern railway safety in Europe and the United States.
- EPSFFrench railway safety authority
- France's national safety authority for rail transport. EPSF issues authorisations and approvals, supervises the actors of the system and publishes reference documentation on operational safety. It is the regulatory entry point for any safety question on the French network.Related sector
- ERAEuropean Union Agency for Railways
- The European agency responsible for railway interoperability and safety. It prepares the technical specifications for interoperability, issues vehicle authorisations valid in several member states and ERTMS approvals, and maintains the European registers of vehicles and infrastructure.Related sector
- TSITechnical specification for interoperability
- European regulation setting the requirements a subsystem must meet to run on the Union network. TSIs cover infrastructure, energy, control-command and signalling, rolling stock, operations and accessibility. Each TSI defines its basic parameters and assessment procedures.Related sector
- CSMCommon safety method
- Harmonised European method for risk evaluation and assessment, applied when a significant change affects the railway system. It requires a structured analysis, the use of risk acceptance principles and, where applicable, an independent assessment body.Related sector
- ECMEntity in charge of maintenance
- Organisation responsible for the maintenance of a railway vehicle and registered as such in the vehicle register. It covers management of maintenance, development of maintenance programmes, fleet maintenance management including return to service, and delivery of the maintenance itself, under certification.Related sector
- EN 50126Reliability, availability, maintainability, safety (RAMS)
- European standard that organises the RAMS demonstration of a railway system across its whole life cycle, from requirement definition to decommissioning. It structures requirements, risk analyses and the evidence to be produced at each phase, and frames the related software and hardware standards.Related sector
- SILSafety integrity level
- Scale that qualifies the integrity requirement assigned to a safety function, from the lowest to the highest level. In rail, the target level drives the design, verification and validation methods to be applied to both hardware and software.Related sector
- UICInternational Union of Railways
- Worldwide association of railway undertakings. UIC publishes leaflets that long served as a common reference before European standards came into force, and remains a major source for operating, maintenance and design practice internationally.Related sector
- FRAFederal Railroad Administration
- United States federal railroad safety authority. Its rules are codified in Title 49 of the Code of Federal Regulations, covering track safety standards, inspections and operating rules among others. It is the applicable reference for North American networks.Related sector
Signalling and control-command
The systems that space trains, supervise speed and transmit movement authorities.
- ERTMSEuropean Rail Traffic Management System
- Unified European control-command and signalling system, designed to replace national systems and make lines interoperable. It combines the ETCS speed supervision part with a ground-to-train radio layer, historically GSM-R and in future FRMCS.Related sector
- ETCSEuropean Train Control System
- The speed supervision part of ERTMS. The on-board computer receives a movement authority, builds a braking curve and intervenes if the driver exceeds it. It comes in levels, from level 1 with balises and lineside signals to level 2 with radio-based cab signalling.Related sector
- GSM-RRailway digital radio
- Digital radio network dedicated to rail, derived from GSM and adapted to operational needs: group calls, priority emergency call, function-based rather than person-based addressing. It carries ground-to-train communication and, in ETCS level 2, movement authorities.Related sector
- FRMCSFuture Railway Mobile Communication System
- Successor to GSM-R, built on broadband mobile technologies. It aims to carry not only voice and movement authorities but also bandwidth-hungry uses: remote diagnostics, video, assisted driving and real-time maintenance data exchange.Related sector
- KVBBalise-based speed control
- French intermittent speed supervision system. Trackside balises transmit to the train the information needed to check compliance with speed limits and stopping at a closed signal, triggering emergency braking if exceeded.Related sector
- TVMTrack-to-train transmission
- Cab signalling system used on French high-speed lines. At high speed lineside signals are no longer readable: speed instructions are transmitted through track circuits and displayed directly on the driver's desk.Related sector
- Block working
- Train spacing principle that divides the line into sections, the blocks, and allows only one train at a time in each. It is the foundation of operational safety: signalling, whatever its technology, expresses the occupancy state of the blocks ahead of the train.Related sector
- Interlocking
- Arrangement that prevents any unsafe combination of signals and points. A route can only be set if the points are correctly positioned and locked, and conflicting routes are refused. It is the core safety function of a signal box.Related sector
Infrastructure and track
Track geometry, its components and the structures that carry it.
- Track gauge
- Distance between the inner faces of the two rails, measured below the running surface at a depth defined by the reference document. The European standard gauge is 1435 mm. Installation and maintenance tolerances are set by the infrastructure TSI and the manager's own references.Related sector
- Cant
- Height difference between the two rails in a curve, intended to offset part of the centrifugal acceleration. Actual cant, theoretical cant and the resulting cant deficiency drive comfort, rail wear and the maximum permitted speed through the curve.Related sector
- Switch and crossing
- Mechanical assembly that lets a train move from one track to another or cross it. It combines switch rails, crossing, check rails and the operating and locking devices. It is the most heavily stressed and most closely monitored track element, with its own tolerances and inspections.Related sector
- CWRContinuous welded rail
- Track whose rails are welded into very long lengths, removing most joints. Comfort and component life improve, but the rail can no longer expand freely: laying requires a reference temperature and monitoring of stresses, particularly in hot weather.Related sector
- Rail corrugation
- Periodic deformation of the rail running surface, appearing as regular waves. It increases noise, dynamic forces and fatigue of both track and vehicles. The usual treatment is grinding, triggered from a depth threshold defined by the applicable reference.Related sector
- Tamping machine
- Track machine that lifts the track and compacts the ballast under the sleepers to restore level and alignment. It works from a geometry survey and leaves a track whose stability must be re-established before returning to nominal speed.Related sector
- Gauge (structure)
- Reference outline separating what rolling stock may occupy from what the infrastructure must keep clear. An exceptional load, a low contact wire or a badly positioned platform are all gauge questions, with profiles defined at European level.Related sector
Rolling stock
The train's components: running gear, braking, current collection, coupling.
- Bogie
- Pivoting frame carrying two or more axles, on which the vehicle body rests. It provides curve guidance, suspension and often braking and traction. Almost every track-holding and ride comfort issue plays out in its dynamic behaviour.Related sector
- Wheel flat
- Flat area created on a wheel tread when it locked and slid along the rail. The resulting repeated impact damages both track and vehicle. Beyond a length defined by the applicable reference, it requires a speed restriction then re-profiling.Related sector
- Pantograph
- Articulated device that collects current from the contact line. Collection quality depends on the force it applies, the condition of its contact strips and the overhead line geometry. A collection fault shows up on both the vehicle and the infrastructure.Related sector
- Automatic air brake
- Pneumatic brake whose brake pipe is kept pressurised to hold the brakes released. Any pressure drop, intentional or accidental, applies the brakes. This design ensures that a coupling failure or a leak stops the train rather than leaving it uncontrolled.Related sector
Energy and electric traction
Contact line supply and the voltage systems used across Europe.
- Overhead contact line
- The set of wires suspended above the track that supply the train with electricity. The contact wire is carried by a messenger wire through droppers, so that it stays at constant height and tension despite the span between masts and temperature variations.Related sector
- Traction voltage systems
- Supply systems used across European networks, mainly 1.5 kV and 3 kV direct current and 15 kV 16.7 Hz and 25 kV 50 Hz alternating current. A train running internationally must be multi-system and able to switch between them while running.Related sector
- Traction substation
- Installation that draws energy from the public grid, converts it to the line's system and feeds it into the overhead line. Its siting determines the length of the supplied sections, the acceptable voltage drop and the line's ability to absorb dense traffic.Related sector
- Neutral section
- Unenergised length of overhead line that separates two electrical sections, for instance between two substations or two voltage systems. The train coasts through it without traction, following a defined procedure: passing under power causes an arc and damages the installation.Related sector
Operations and works
Train running, trackside worksites and the machines that reach them.
- Train path
- Infrastructure capacity allocated to a train to run from one point to another at a given time. The path is the resource the infrastructure manager allocates and charges for, and the basic unit of both timetable construction and possession planning.Related sector
- Road-rail vehicle
- Works machine fitted with both tyres and retractable rail wheels, able to reach the track from a road access and then run on it. Road-rail excavators, platforms and carriers allow work without a works train, under their own safety framework.Related sector
- Overhead line isolation
- Procedure that de-energises a section of overhead line and secures it before work: request, switching off, verification of absence of voltage, earthing. No work near live installations is possible without its complete and recorded execution.Related sector
- Lessons learned
- Process that collects safety events, analyses them and derives corrective measures shared with all actors. It is one of the pillars of the safety management system: an incident that is neither analysed nor shared is an incident that will happen again.Related sector
Maintenance and data
The methods and indicators that drive maintenance, and the data behind them.
- CMMSComputerised maintenance management system
- Information system holding the asset register, maintenance schedules, work orders and intervention history. It is the source of reliability data for a fleet or an asset base, and the natural entry point for AI-assisted analysis.Related sector
- Condition-based maintenance
- Maintenance triggered by the actual condition of the asset rather than a time or mileage counter. It relies on continuous or periodic measurements and justified thresholds, and assumes data that is reliable, timestamped and unambiguously linked to an asset.Related sector
- MTBF and MTTRMean time between failures, mean time to repair
- Two complementary fleet performance indicators. The first measures the average spacing of failures, hence reliability; the second the average restoration time, hence maintainability. Combined, they give the effective availability of the asset.Related sector
- Onboard telemetry
- Remote collection of measurements from sensors installed on a vehicle or an installation: temperature, vibration, pressure, position, consumption. Used together with the maintenance reference, it turns a raw alarm into a documented decision.Related sector
Artificial intelligence applied to rail
The technical notions that describe how an AI can answer from a reference corpus without inventing it.
- RAGRetrieval-augmented generation
- Architecture in which the language model does not answer from memory but from passages retrieved in a document corpus. The answer can then cite its source. It is the only approach compatible with a regulatory traceability requirement.
- Grounding
- Property of an answer whose every claim points back to a specific passage of a corpus document. A grounded answer can be verified; an ungrounded one remains a hypothesis. On a regulatory subject, the distinction between the two must be visible to the reader.
- Hallucination
- Production by a model of a plausible but false statement, often a fabricated figure or reference. In rail, a wrong tolerance stated with confidence is more dangerous than no answer at all: hence the rule of asserting nothing without a source.
- Hybrid search
- Combination of lexical search, which finds exact terms such as a standard reference, and vector search, which finds meaning even when wording differs. On a technical corpus where document codes matter as much as concepts, both are needed.
- Data sovereignty
- Control over where data is hosted and which legal regime applies to it. For a railway operator, it determines whether plans, safety procedures or incident records can be entrusted to an AI at all.
- On-premise and air-gap
- Deployment modes where the software runs on the customer's own servers, up to the extreme case of a network fully isolated from the internet. They address contexts where the corpus cannot leave the information system, common in railway safety and defence.
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