Extension of subway line U4 in Germany‘s second largest city Hamburg. When completed by the end of 2026, 13,000 Hamburg residents will be able to reach the city center by public transport with almost half the travel time. In order for the line to be extended by two additional stops (Stoltenstraße and Horner Geest), the U4 must be branched off north. The extension of the line will take place in the immediate vicinity of the populated city center. The underground network is operated by Hamburger Hochbahn AG, one of the biggest transport companies in Germany with over a 100 years of experience.