# Digital automatic coupling > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Digital_automatic_coupling > Markdown URL: https://mediated.wiki/source/Digital_automatic_coupling.md > Source: https://en.wikipedia.org/wiki/Digital_automatic_coupling > Source revision: 1320777616 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) Automatic railway coupling Voith's DAK product 2024 **Digital automatic coupling** (**DAC**) is a type of [railway coupling](/source/Railway_coupling) developed in the 2020s to replace [buffers and chain couplers](/source/Buffers_and_chain_coupler), initially in Europe. It resembles the [Scharfenberg coupler](/source/Scharfenberg_coupler) with extra contacts to join electrical circuits (power, detection and control) and air hoses.[1] The DAC project is backed by Europe's Rail, a body of the [European Union](/source/European_Union).[2] The system is among several innovations being developed within European working groups to harmonize the rail network and aims to boost freight traffic by 2030.[3] Although not a member of the European Union, Switzerland is associated with the project and wants to subsidize the transition to digital automatic coupling on its territory.[4] ## Advantages - Longer trains up to 750 m. - Brakes remotely controlled like [electronically controlled pneumatic brakes](/source/Electronically_controlled_pneumatic_brakes). - Monitoring of train and wagon performance. - Safety. No need for [shunter](/source/Shunter) to climb between buffers. ## Function levels DAK e-coupler (placed atop) Automatic couplers are categorized into five different levels in general. - no automation - Level 1: automated mechanic coupling (air pipes manual coupling) - Level 2: Level 1 plus automatic coupling of air pipes (partial uncoupling with a lever) - Level 3: Level 2 plus automatic coupling of power cables (allows uncoupling with switch) - Level 4: Level 3 plus automatic coupling of data cables (allows uncoupling at a signal) - Level 5: Level 4 plus remote automatic uncoupling For the DAC the function levels are narrowed down to specific functions. The function level DAK-3 must connect the [electronically controlled pneumatic brakes](/source/Electronically_controlled_pneumatic_brakes). The function level DAK-4 must connect the e-coupler including electric supply (400 V) and digital sockets. The function level DAK-5 must allow for [remote uncoupling](#Uncoupling) using an electric motor (the DAK does not use uncoupling air pipes as defined in EN 16019 for high-speed trains). Rollout plans may use function level DAK-4 when prepared for an update to DAK-5.[5] ## Safe remote uncoupling In addition to uncoupling from the driver's cab, the DAC must also enable uncoupling while moving on the [shunting hump](/source/Classification_yard#hump). In addition to a mechanical device using a cable pull/uncoupling lever, the demonstrator also had an electrical device with switches on a control panel attached to the side of the car. Further development should enable electrical uncoupling both from the train and from a tablet or hump computer. This is essentially software development with high safety requirements.[6] ## Other systems Couplings based on [AAR](/source/AAR_coupler) and [SA3](/source/SA3_coupler) already have automated mechanical couplings, so some of the advantageous features of DAC are lessened. These have a maximum draw gear load well in excess of that possible with the DAC, say 1800 m instead of 750 m. ## Makers - [Dellner](/source/Dellner)[7] - [Knorr Bremse](/source/Knorr-Bremse)[8] ## See also - [Railway coupling](/source/Railway_coupling) - [Railway coupling by country](/source/Railway_coupling_by_country) ## References 1. **[^](#cite_ref-1)** [DAC](https://rail-research.europa.eu/news/digital-automatic-coupling-dac-the-backbone-for-full-digital-rail-freight-train-operations-in-europe/) DAC 1. **[^](#cite_ref-aa_2-0)** ["Digital Automatic Coupling (DAC) – the backbone for full digital rail freight train operations in Europe"](https://rail-research.europa.eu/news/digital-automatic-coupling-dac-the-backbone-for-full-digital-rail-freight-train-operations-in-europe/). *Europe's Rail*. February 28, 2022. Retrieved April 11, 2023. 1. **[^](#cite_ref-3)** ["L'attelage automatique digital de fret (DAC)"](https://www.sncf.com/fr/innovation-developpement/innovation-recherche/espace-ferroviaire-europeen/dac). *SNCF* (in French). March 30, 2023. Retrieved April 12, 2023. 1. **[^](#cite_ref-Cormon_2_4-0)** [Pierre Cormon](/source/Pierre_Cormon) (April 25, 2024). ["Des centaines de millions pour le fret ferroviaire suisse"](https://entrepriseromande.ch/web/er/w/des-centaines-de-millions-pour-le-fret-ferroviaire-suisse) (in French). Entreprise romande. Retrieved November 5, 2025. 1. **[^](#cite_ref-5)** ["Part I: What is Digital Automatic Coupling and what are its levels?"](https://blog.railcargo.com/en/artikel/dak-faq1). *DAC Question & Answer*. Rail Cargo Group. 2021-01-20. 1. **[^](#cite_ref-6)** Wolf-Dieter Deuschle (2022-10-24). ["Konzeptbericht - Automatisierung im Schienengüterverkehr der Schweiz, beginnend mit der Migration zur digitalen automatischen Kupplung"](https://www.bav.admin.ch/dam/bav/de/dokumente/verkehrstraeger/eisenbahn/gueterverkehr/konzeptbericht-dak.pdf.download.pdf/Konzeptbericht%20DAK.pdf) (PDF). Bundesamt für Verkehr BAV (Schweiz). 1. **[^](#cite_ref-7)** [Dellner](https://www.youtube.com/watch?v=AW-9wHoBab0) 1. **[^](#cite_ref-8)** [Knorr-Bremse](https://www.railwaysafrica.com/news/automated-rail-freight-knorr-bremse-tests-digital-automatic-coupler-on-real-freight-train) ## External links - ["Digital Automatic Coupling"](https://www.youtube.com/watch?v=TQ7HlmPljyA). *[YouTube](/source/YouTube)*. 6 September 2021. - DAC4EU Digital Automatic Coupling for Europe (2022-01-13). [*DAC4EU - Operational Tests*](https://www.youtube.com/watch?v=5y1ESfnkXac). 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