ERA Railway Terminology visual v0 featured

ERA Railway Terminology Collection

Last updated: 5 December 2025.

The ERA Railway Terminology Collection gathers terms and abbreviations that are contained in the EU legal framework for railway, technical documents produced by bodies which are engaged in the development of important evolution in the railway system and other relevant glossaries.

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Starting with "O" (211)

Disclaimer
ERA Railway Terminology Collection is a consultation tool, developed to support the sharing of information through the actors involved in running the Single European Railway Area (SERA). The responsibility for the correctness, completeness, accuracy, or reliability of the information in ERA RTC lays upon the authors of the definitions, as they derive from reference documents having their own preparation and approval flow. Users cannot call ERA liable for the use they make of the content. Please consider that when the collection is exported (.csv) and then printed or converted, it becomes uncontrolled.
Term	Context	Document Type	Origin document
Occupied	ERTMS	Technical Document	ERTMS/ETCS - Glossary of Terms and Abbreviations - version : 4.0.0 - date 05/07/2023
Occurrence	Freight	Glossary	Transport of dangerous goods. Risks Management Framework. Framework glossary v. 1.0/2018
OCG	International Standard	EU Technical Document	CEN CENELEC ABBRAVIATION ACRONYM 2025	Latest release
OCL	Energy	TSI	Commission Regulation (EU) No 1301/2014 of 18 November 2014 on the technical specifications for interoperability relating to the energy subsystem of the rail system in the Union
OCL	Interoperability	Application Guide	Application_guide GUI/TSI/2023 Version 1.0 20/12/2023Guide for the application of the Technical Specifications for Interoperability (TSIs)
OCL	Infrastructure	Application Guide	Guide on the application of the common specifications of the register of Infrastructure - v. 3.1.0 on 31.03.2025	Latest release
OCTs	EU Policy	EU Technical Document	Technical document from the Publications Office of the European Union - ‘Style guide’ Coordination Interinstitutional Style Guide - version on 19.04.2022
OD	EU Policy	EU Technical Document	Technical document from the Publications Office of the European Union - ‘Style guide’ Coordination Interinstitutional Style Guide - version on 19.04.2022
Odometer accuracy	ERTMS	Technical Document	ERTMS/ETCS - Glossary of Terms and Abbreviations - version : 4.0.0 - date 05/07/2023
Odometry	ERTMS	Technical Document	ERTMS/ETCS - Glossary of Terms and Abbreviations - version : 4.0.0 - date 05/07/2023
Odometry reference location	ERTMS	Technical Document	ERTMS/ETCS - Glossary of Terms and Abbreviations - version : 4.0.0 - date 05/07/2023
ODP	International Standard	EU Technical Document	CEN CENELEC ABBRAVIATION ACRONYM 2025	Latest release
OECD	EU Policy	EU Technical Document	Technical document from the Publications Office of the European Union - ‘Style guide’ Coordination Interinstitutional Style Guide - version on 19.04.2022
Off-Line KMS	ERTMS	Technical Document	ERTMS/ETCS - Glossary of Terms and Abbreviations - version : 4.0.0 - date 05/07/2023
Offer	Telematics Applications for Passenger	TSI	Commission Regulation (EU) No 454/2011 of 5 May 2011 on the technical specification for interoperability relating to the subsystem ‘telematics applications for passenger services’ of the trans-European rail system
Official of the Union	EU Policy	Regulation	Regulation No 31 (EEC), 11 (EAEC), laying down the Staff Regulations of Officials and the Conditions of Employment of Other Servants of the European Economic Community and the European Atomic Energy Community
Official repository of records	EU Policy	Decision	Commission Decision (EU) 2021/2121 of 6 July 2020 on records management and archives
Official website	Telematics Applications for Passenger	TSI	Commission Regulation (EU) No 454/2011 of 5 May 2011 on the technical specification for interoperability relating to the subsystem ‘telematics applications for passenger services’ of the trans-European rail system
Officials of the Commission (Eurostat)	EU Policy	Regulation	Regulation (EC) No 223/2009 of the European Parliament and of the Council of 11 March 2009 on European statistics and repealing Regulation (EC, Euratom) No 1101/2008 of the European Parliament and of the Council on the transmission of data subject to statistical confidentiality to the Statistical Office of the European Communities, Council Regulation (EC) No 322/97 on Community Statistics, and Council Decision 89/382/EEC, Euratom establishing a Committee on the Statistical Programmes of the European Communities
Offshore bulk container	International Relations	Convention	Convention concerning International Carriage by Rail (COTIF) Appendix C – Regulations concerning the International Carriage of Dangerous Goods by Rail (RID)

Common Safety Method
Conformity Assessment
Control-Command and Signalling
Data Protection
Energy
Entity in Charge of Maintenance
ERTMS
EU Policy
Freight
Human and Organisational Factor
Infrastructure
International Relations
International Standard
Interoperability
Noise
Operation
Persons with Reduced Mobility
Railway Tunnels
Registers
Regulation
RNE Glossary
Safety / SSC-SA
Security
SERA_EU Transport
Single Market Mutual Recognition Conformity Assessment
Telematics Applications for Freight
Telematics Applications for Passenger
Vehicles / VA
Withdrawn

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