DB Class 420
The DB Class 420 (German: Baureihe 420) is a three-car electric multiple unit (EMU) commuter train developed by the Deutsche Bundesbahn in the late 1960s specifically for alternating current (AC) electrified S-Bahn networks, featuring high acceleration, multiple doors per side, and suitability for tunnel operations in urban environments.[1][2] First introduced into revenue service during the 1972 Summer Olympics in Munich—where it earned the nickname Olympiatriebwagen (Olympic multiple unit) for transporting spectators efficiently across the expanded network—it represented a technical milestone as the first series-production DB train equipped with thyristor phase-angle control for precise power regulation.[3][1] A total of 480 three-car sets, comprising 1,440 individual vehicles, were manufactured between 1969 and 1997 by a consortium including MAN, Orenstein & Koppel (O&K), Linke-Hofmann-Busch (LHB), and Düwag, initially using steel construction before transitioning to lightweight aluminum for later series to reduce weight and improve energy efficiency.[1][4] Technically, each set measures 67.4 meters in length, weighs approximately 138 tons in service, and is powered by 12 commutator traction motors delivering a continuous output of 2,400 kW, enabling a top speed of 120 km/h and rapid acceleration of 1.0 m/s² from standstill to 60 km/h.[1][2] Designed without inter-car gangways or onboard toilets to prioritize high passenger throughput—offering 194 seats and 12 double sliding doors per side for quick boarding in stations—the trains were optimized for short-haul, high-frequency urban services but faced criticism for limited flexibility and comfort.[4][1] The Class 420 entered widespread operation across Germany's major S-Bahn systems, starting with Munich (where 218 sets were allocated), followed by expansions to the Rhein-Ruhr area (Düsseldorf and Dortmund), Rhein-Main (Frankfurt), and Stuttgart, serving as the backbone of these networks until the late 1990s.[4][2] In 2002, a batch of 25 sets was exported to Stockholm's Roslagsbanan as SL Class X420 for temporary use, though they were withdrawn and scrapped by 2005 due to compatibility issues.[4] Upgrades from the mid-1990s onward, including the "420 Plus" modernization program starting in 2006, involved interior refreshes with vandal-resistant materials, improved seating layouts, and accessibility enhancements, extending the lifespan of surviving units.[4][1] As of 2025, a small number of sets (primarily from the 8th production series) remain in service exclusively on the Munich S-Bahn, with phase-out ongoing in favor of newer models such as the Class 1420, while select preserved examples, such as prototype 420 001, operate as heritage trains and cultural monuments.[3][2][5]Overview
Development and manufacture
The DB Class 420 was developed in the late 1960s by the Deutsche Bundesbahn to standardize rolling stock for its expanding electrified S-Bahn networks, particularly in response to the need for high-capacity, tunnel-compatible trains capable of rapid acceleration and efficient passenger handling.[1] This initiative aimed to create a versatile electric multiple unit suitable for urban commuter services, drawing on prior experience with prototype S-Bahn vehicles to achieve higher speeds and greater throughput compared to earlier designs like the ET 427.[6] The design emphasized stepless entry, multiple doors per side, and robust electrical systems to support frequent stops in dense networks.[1] Production of the Class 420 commenced in 1969 and continued until 1997, resulting in 480 three-car trainsets comprising 1,440 individual cars.[7] The first unit, 420 001, was delivered on 30 November 1969, with initial batches prioritized for the Munich S-Bahn to meet the demands of the 1972 Summer Olympics, where enhanced transport capacity was essential for handling increased passenger volumes.[1] Subsequent procurement phases expanded production across eight series to equip other networks, including those in Frankfurt, Stuttgart, and the Rhine-Ruhr region, reflecting a phased rollout to standardize operations nationwide.[2] The primary manufacturers involved were Linke-Hofmann-Busch (LHB), Messerschmitt-Bölkow-Blohm (MBB), Orenstein & Koppel (O&K), Waggonfabrik Uerdingen (later Düwag), and Waggon Union, with additional contributions from MAN and Rathgeber for specific components and assemblies.[1] Electrical systems were collaboratively developed by AEG, BBC, and SSW to integrate thyristor phase-angle control, a novel feature for the era that improved energy efficiency and performance under the tight timelines imposed by Olympic preparations.[1] These partnerships ensured the class's adaptability, with later series incorporating minor refinements for ongoing standardization efforts.[2]Operators and deployment
The primary operator of the DB Class 420 electric multiple units is Deutsche Bahn (DB), with operations managed by its subsidiary DB Regio on S-Bahn networks across Germany. These trains have been integral to suburban rail services, providing high-frequency transport in urban and regional corridors. Deployment has centered on key metropolitan areas, with the Munich S-Bahn serving as the primary and ongoing location, where 36 sets remain active as of 2025 to support lines such as S2, S4, S6, S8, and S20. Historically, units operated in the Stuttgart S-Bahn until their phase-out in 2016, the Frankfurt/Rhine-Main network until the early 2010s, and the Cologne/Rhine-Ruhr area until late 2024. A secondary operator was Storstockholms Lokaltrafik (SL) in Sweden, which leased 15 sets—designated X420—for Stockholm commuter services from 2003 to 2005 as an interim measure during delays in local fleet deliveries. By 2025, the active fleet in Germany has been reduced to approximately 36 sets due to ongoing withdrawals, concentrated solely in Munich with no major new deployments since 2020. Modernization efforts, such as the 420Plus program, have helped extend the operational life of remaining units in this primary deployment area.Design features
Exterior and livery variations
The DB Class 420 employs a lightweight aluminum body construction using extruded profiles for the sidewalls (3 mm thick) and roof (2 mm thick), with early prototype end cars (420 001 and 420 501) featuring steel panels (2 mm thick) instead. The underframe incorporates steel elements for structural integrity, while the overall body width measures 2.9 m, complemented by an aerodynamic cab design to minimize drag in suburban operations.[8][9] Each car is equipped with four double-leaf sliding doors per side—pocket sliding type in early series and swing-sliding in later ones—enabling efficient passenger boarding and alighting in dense S-Bahn networks.[8][1] The three prototype sets introduced in 1971 showcased distinct liveries to test public preference: set 420 001 in orange and white, 420 002 in blue and white, and 420 003 in wine-red and white. Production units from the same year adopted a pebble grey (kieselgrau) base with operator-specific accents for visual identification—green-blue stripe for Munich S-Bahn, orange for Rhein-Ruhr, and carmine-red for Frankfurt and Stuttgart networks.[10][1] Livery standardization progressed in the 1980s and 1990s; Munich units transitioned to full orange/pebble grey in 1984 for fleet cohesion, with some receiving a specialized airport blue scheme in 1991 for Flughafenbahn service. By 1997, all active units shifted to the unified DB traffic red (poppy red) scheme featuring white doors and black window bands, reflecting broader Deutsche Bahn branding. Refurbished examples from the late 1990s onward incorporated enhanced coatings for graffiti resistance, while post-2010 updates added accessibility symbols to the traffic red livery for improved inclusivity.[1]Interior layout
The interior of the DB Class 420 trains features an open-plan layout designed for high-volume commuter traffic, with transverse seating in a 2+2 arrangement across the three-car units to maximize passenger flow and capacity.[1] Each three-car set originally provided approximately 195 seated passengers, supplemented by standing room for up to 275 more, yielding a total capacity of around 470 during peak hours; some configurations optimized for all-second-class service adjusted this to 192 seats with standing capacity reaching up to 450 in denser loading scenarios.[11] Longitudinal folding seats were incorporated near entry areas and multi-purpose zones to accommodate bicycles, luggage, and wheelchairs, enhancing flexibility for diverse passenger needs.[1] Early units included designated smoking sections, typically partitioned areas in the end cars, which were eliminated following the 2007 nationwide ban on smoking in German public transport vehicles. Priority spaces for disabled passengers and bicycles were integrated into the open design, featuring dedicated areas with securement points and foldable elements to prioritize accessibility without compromising overall capacity.[12] Lighting consisted of fluorescent fixtures providing even illumination throughout the cars, while ventilation relied on forced-air systems that repurposed heat from the brake resistors for winter heating, though summer cooling was limited to natural venting without dedicated air conditioning in the original build—later additions addressed this in modernization efforts.[1] Accessibility was supported by step-free entry at a floor height of 1,000 mm, wide doors measuring 1,300 mm, extensive handrails along aisles (minimum 600 mm wide), and audio announcements for station information, facilitating easier movement for all passengers including those with mobility impairments.[12] Interior color schemes, often in neutral tones like beige or gray, were coordinated with exterior liveries to create a cohesive visual experience.[11]Modernization programs
The ET 420 Plus program, implemented between 2005 and 2006 at the DB Regio workshop in Oppum, focused on upgrading select Baureihe 420 units for the S-Bahn Stuttgart network to improve passenger comfort and extend operational viability. Key modifications included the installation of air conditioning systems, a complete interior redesign modeled after the more modern Baureihe 423 with updated seating and lighting, LED front headlights replacing conventional bulbs, and enhanced passenger information displays. Initially, two prototype units (such as 420 416 and 420 916) were refurbished as part of a broader concept to modernize up to 90 sets, though the program ultimately covered a limited number due to the impending introduction of newer Baureihe 430 trains. These upgrades, estimated at around €6 million overall, emphasized cost-effective enhancements without altering core technical specifications like propulsion or dimensions.[13][14] In the Munich S-Bahn network, refurbishment efforts for Baureihe 420 units began in earnest during the 2010s to bolster fleet reliability amid growing demand. Between 2018 and 2020, Deutsche Bahn modernized a total of 22 sets, with nine completed in 2018, two in early 2019, and eleven by mid-2020, including updates to interiors with new seating for improved ergonomics, preparations for Wi-Fi integration, and compatibility enhancements for safety systems like LZB (Linienzugbeeinflussung). An additional project retrofitted units with RIS/FIS passenger information systems and LZB for better real-time announcements and train control, supporting up to 25 sets overall. These efforts, conducted at facilities like Hannover-Leinhausen, addressed aging components and ensured continued deployment on lines such as S2, S4, S6, S8, and S20, where the 36 active ET 420 units provide reserve capacity. By 2023, transferred and upgraded units from other regions, including Hannover, further reinforced the Munich fleet's stability. As of 2025, Class 420 units in Cologne are being phased out in favor of new Class 424 EMUs.[15][16][17][18][5][11] Additional upgrades across the Baureihe 420 fleet in the 2010s included pantograph renewals to maintain overhead line contact efficiency and door control modernizations for enhanced safety compliance. Battery backup systems were also integrated in some units to support emergency operations, particularly in tunnel sections. These targeted interventions, part of broader DB Regio reliability initiatives, have extended service life into the 2030s in key areas like Munich, with reported reductions in failure rates contributing to more consistent operations. Post-upgrade, the trains continue to serve urban and suburban routes, providing flexible deployment options.Technical specifications
Train formation and dimensions
The DB Class 420 consists of a standard three-car formation per unit, comprising two end power cars (ET 420) equipped with driving cabs and one middle power car (ET 421), all with powered bogies for distributed traction.[9] These units are designed for short coupling between cars, forming a rigid three-car set known as a Kurzzug.[1] Up to two such units can be coupled to create a six-car Langzug, enhancing capacity on busier routes while maintaining operational flexibility.[1] Key dimensions of the three-car set include an overall length of 67.4 meters over couplers, with individual car lengths of 22.9 meters for end cars and 20.4 meters for the middle car.[9] The structure has a roof height of 3.84 meters above rail level and a body width of 3.08 meters (first series) or 3.02 meters (second series) over guardrails.[9] The bogie wheelbase measures 2.5 meters, supporting stable running on S-Bahn infrastructure.[9] These parameters ensure compatibility with urban tunnel profiles and platform heights typical of German S-Bahn networks. The empty weight of a three-car set is 129-139 tonnes depending on series (aluminum vs. steel construction for end cars), distributed across powered bogies with a maximum axle load of 16.5 tonnes.[9] This configuration balances load distribution for efficient track usage, with end cars at approximately 49 tonnes each (steel construction) and the middle car at 41 tonnes (aluminum).[9] Coupling employs a fully automatic Scharfenberg center buffer system at unit ends, enabling quick connection of electrical, pneumatic, and mechanical systems between sets or compatible S-Bahn classes like the 423.[1] The trains operate on the standard 1,435 mm track gauge prevalent in the Deutsche Bahn network.[8]| Parameter | Value | Notes/Source |
|---|---|---|
| Overall length | 67.4 m | Over couplers[19] |
| Height | 3.84 m | Roof above rail[9] |
| Bogie wheelbase | 2.5 m | Powered bogies[2] |
| Empty weight (set) | 129-139 t | Depending on series[9] |
| Axle load | 16.5 t | Maximum[9] |