Project Profile: Hamburg S-Bahn Modernization & S4 Expansion

The Hamburg S-Bahn project encompasses the comprehensive modernization of existing infrastructure and the strategic expansion of the network, most notably through the new S4 line. This initiative focuses on increasing network capacity, enhancing operational efficiency through digitalization, and improving passenger experience to meet the growing demands of the Hamburg metropolitan region.

Project Fact Sheet

Technical Specifications

Power Supply and Track Infrastructure

A defining technical characteristic of the Hamburg S-Bahn is its unique power supply system, utilizing a 1200 VDC third rail. This configuration distinguishes it from other German S-Bahn networks, which typically use 15 kV AC overhead lines. The network infrastructure is a hybrid system; approximately 113 km of the route operates on dedicated tracks, independent of mainline rail traffic, ensuring high-frequency service. The remaining 32 km share tracks with regional and freight services, necessitating complex scheduling and signaling. Central urban sections run through approximately 13 km of tunnels, including the primary City-S-Bahn tunnel and the Harburg S-Bahn tunnel.

Rolling Stock Modernization

The operational fleet is transitioning to modern electric multiple units (EMUs) to boost capacity and passenger comfort. While the legacy Class 472 and Class 474 units remain in service, the fleet is being augmented by the newer Class 490 dual-system trains. These units are capable of operating on both the 1200 VDC third rail and the standard 15 kV AC overhead lines, providing critical flexibility for network expansion projects like the S4 line, which will integrate with the mainline railway. The Class 490 features air conditioning, advanced passenger information systems, and open gangways for improved passenger distribution.

Signaling, Control, and Automation

The network is undergoing a significant transition towards centralized digital control. Legacy local signal boxes are being replaced by modern electronic interlockings managed from centralized control centers, such as those in Altona and Ohlsdorf. A key initiative is the digitalization of a 23 km section of the S21 line between Berliner Tor and Aumühle. In partnership with Siemens, this segment is being equipped for highly automated train operation (ATO) over ETCS Level 2, aiming to enable shorter headways, reduce energy consumption, and increase operational reliability. This project serves as a pilot for the broader digitalization of Germany’s rail network.

Key Takeaways

• Digitalization as a Capacity Multiplier: The S21 automation project demonstrates a strategy of increasing line capacity through technology (ATO over ETCS) rather than solely through costly new track construction.
• Hybrid Infrastructure Integration: The S4 expansion and dual-system Class 490 fleet highlight the importance of integrating a dedicated urban rail system with the mainline network to extend regional reach efficiently.
• Phased Modernization: The project exemplifies a long-term, phased approach to upgrading a legacy system, systematically improving rolling stock, stations, and signaling to maintain continuous operation while preparing for future demand.

Frequently Asked Questions (FAQ)

When will the new Hamburg S4 line be completed?

The construction of the S4 line, connecting Hamburg-Altona to Bad Oldesloe, is being executed in multiple phases. The first sections are scheduled to become operational in the late 2020s, with full completion of the entire route expected in the following years. Passengers should monitor official announcements from Deutsche Bahn and S-Bahn Hamburg for specific commissioning dates for each construction phase.

What is unique about the Hamburg S-Bahn’s power system?

The core Hamburg S-Bahn network is powered by a 1200-volt direct current (DC) third rail system. This is unique in Germany, where most S-Bahn and mainline railways use 15,000-volt alternating current (AC) delivered via overhead catenary lines. This technical distinction requires specialized or dual-system rolling stock for seamless operation across the entire network and its extensions.