Railway Interlockings – A Review of the Current State of Railway Safety Technology in Europe

Keywords: railway interlocking, railway safety, railway statistics, relay interlocking, electronic interlocking, railway signalling


Interlockings are an essential element of the railway system. They are necessary to command and control devices, such as points and signals in order to route trains within the bounds of railway stations. Their design must ensure the highest level of safety for all involved parties. The European continent has an extensive railway network which has slowly grown over more than 150 years. Interlockings have evolved over the same period from large mechanical devices requiring physical force to operate to computerised systems capable of complex operations. Despite the technological leap, many interlockings using older technologies are still in use in the present. This review aims to paint an accurate picture of the current state of interlockings in Europe by evaluating the share of each interlocking generation (mechanical, relay and electronic). The study covers 15 countries and over 200,000 km of railway tracks, representing over two thirds of the entire EU railway network. A brief presentation is given for each country, while comparisons made between the researched countries highlight certain key findings. The focus is only on station interlockings, not including line signalling. The conclusions of this analysis include recommendations for current and future development of the railway sector.


Bešinović N. Resilience in railway transport systems: A literature review and research agenda. Transport Reviews. 2020;40(4): 457-478. doi: 10.1080/01441647.2020.1728419.

Caruana-Galizia P, Martí-Henneberg J. European regional railways and real income, 1870–1910: A preliminary report. Scandinavian Economic History Review. 2013;61(2): 167-196. doi: 10.1080/03585522.2012.756428.

Grace's guide to British industrial history. https://www.gracesguide.co.uk/Charles_Fox [Accessed 3rd Mar. 2021].

Carstens S. Signale: Die Entwicklung des Signalwesens vom optischen Telegraphen zum Ks-Signal Fürstenfelbruck. MIBA Verlag; 2014.

Theeg G, et al. Railway Signalling & Interlocking: International Compendium. 2nd ed. Hamburg: PMC Media International Publishing; 2018.

Preuß E. Stellwerke deutscher Eisenbahnen seit 1870. Stuttgart: Transpress Verlag; 2012.

Huang L. The past, present and future of railway interlocking system. 2020 IEEE 5th International Conference on Intelligent Transportation Engineering (ICITE); 2020. p. 170-174. doi: 10.1109/ICITE50838.2020.9231438.

Efanov D, Lykov A, Osadchy G. Testing of relay-contact circuits of railway signalling and interlocking. 2017 IEEE East-West Design & Test Symposium (EWDTS); 2017. p. 1-7. doi: 10.1109/EWDTS.2017.8110095.

Pachl J. Railway Signalling Principles - Edition 1.2.; 2021. http://www.joernpachl.de/rsp.htm [Accessed 5th May 2021].

Cavada R, et al. Analysis of Relay Interlocking Systems via SMT-based Model Checking of Switched Multi-Domain Kirchhoff Networks. 2018 Formal Methods in Computer Aided Design (FMCAD). IEEE; 2018. p. 1-9. doi: 10.23919/FMCAD.2018.8603007.

Gašparik J, et al. Railway Traffic Operation. Žilina: University of Žilina; 2016.

Matanić D, Hrvoje H, Sesar V. Safety analysis of the interface between electronic type of automatic level crossing device (LC) and relay based device of automatic block system (AB). Sigurnost: Časopis za sigurnost u radnoj i životnoj okolini. 2019;61(1): 27-37. doi: 10.31306/s.61.1.2.

Pachl J. Railway Operation and Control. 4th ed. Mountlake Terrace: VTD Rail Publishing; 2018.

Bäckman R, Oliver I, Limonta G. Integrity checking of railway interlocking firmware. Computer Safety, Reliability, and Security. SAFECOMP 2020 Workshops; 2020. doi: 10.1007/978-3-030-55583-2_12.

Railway-News. Railway-News 2020. https://railway-news.com/sncf-reseaus-interlocking-partnership-enters-next-phase/ [Accessed 18th Apr. 2021].

Eurostat. Total length of railway lines. 2021. https://ec.europa.eu/eurostat/web/products-datasets/-/ttr00003.

ÖBB. Zahlen, Daten, Fakten. 2019.

NRIC. Network Statement 2020-2021. 2020.

Ministry of Transport. Program for the development and operation of the railway infrastructure 2019 - 2023. 2018.

SŽDC. The Network Statement on nationwide and regional rail networks. 2017.

HŽ Infrastruktura. Statistics of HŽ Infrastruktura. 2020.

VÄYÄ. Rautateiden kunnossapito nyt ja tulevaisuudessa. 2018.

Rautatietekniikka. Suomi 100 vuotta – itsenäistä rautatietekniikkaa 100 vuotta. 2017. p. 30.

SNCF MOBILITÉS. Memento statistiques SNCF Mobilites 2018. 2018.

DB Netze. Infrastrukturzustands- und Entwicklungsbericht 2019. 2020.

Stellwerke. 2021. https://stellwerke.info/ [Accessed 1st Oct. 2021].

VPE. Network Statement on terms and conditions of the use of the open access railway network of MÁV zrt and GYSEV zrt for the timetable period of 2020/2021 – Annex 2020.

PKP. Anual report for 2019. 2020.

CFR. CFR Network Statement 2021 - Annex 12 - Main characteristics of the CFR Network. 2020.

Ministry of Transport. Dodatok č. 3 k Zmluve o prevádzkovaní železničnej infraštruktúry na roky 2017 - 2021. 2017. https://www.mindop.sk/ministerstvo-1/doprava-3/zeleznicna-doprava/zmluvy-o-prevadzkovani-zeleznicnej-infrastruktury/dodatok-c-3-k-zmluve-o-prevadzkovani-zeleznicnej-infrastruktury-na-roky-2017-2021.

SŽ. Signalna varnost. 2015. https://www.slo-zeleznice.si/sl/infrastruktura/javna-zelezniska-infrastruktura/signalna-varnost [Accessed 8th Apr. 2021].

CTCSF. Informe de la Comisión Técnico Cientifica para el studio de mejoras en el Sector Ferroviario. 2014.

Forper. Ställverksregistret. 2021. https://www.forper.se/ [Accessed 8th Apr. 2021].

SBB Infrastruktur. Zusammenfassender Jahresbericht 2016. 2017.

Martí-Henneberg J. European integration and national models for railway networks (1840–2010). Journal of Transport Geography. 2013;26(January): 126-138. doi: 10.1016/j.jtrangeo.2012.09.004.

Eurostat. Real GDP per capita. 2021. https://ec.europa.eu/eurostat/web/products-datasets/-/sdg_08_10.

Eurostat. General government expenditure by function (COFOG). 2021. https://ec.europa.eu/eurostat/web/products-datasets/-/gov_10a_exp.

Railisa UIC Statistics. 3103: Mean annual staff strength – Infrastructure. 2021. https://uic-stats.uic.org/.

European Union Agency for Railways. Report on Railway Safety and Interoperability in the EU. 2020.

European Court of Auditors. Special Report: A single European rail traffic management system: Will the political choice ever become reality? 2017.

Ministerul Transporturilor Infrastructurii și Comunicațiilor, CN CFR SA. Strategia de dezvoltare a infrastructurii feroviare 2021-2025 – Anexa 12. 2020. http://www.cfr.ro/index.php/ct-menu-item-3/ct-menu-item-55/strategia-de-dezvoltare-a-infrastructurii-feroviare.

How to Cite
BĂDĂU F. Railway Interlockings – A Review of the Current State of Railway Safety Technology in Europe. Promet [Internet]. 2022Jun.1 [cited 2022Jul.3];34(3):443-54. Available from: https://traffic.fpz.hr/index.php/PROMTT/article/view/3992