PROJECT | SUSTAINABILITY - HAMBURG METRO LINE U5


Right, figure 6:


Reduction targets already achieved and set in various industries


By the end of January 2025, 32,000 tonnes of ‘green’ reinforcing steel and 180,000 m3


Lead markets for the decarbonisation of the cement, of clinker-


reduced concrete had already been ordered and partially installed. The successes are the result of an intensive exchange and close cooperation with the steel and concrete industry. The U5 strategy is having an impact and sending a strong signal to the industry. By saving on materials, a reduction in GHG potential


of around 30% was achieved in the design planning for the emergency exits in the City Nord to Jarrestraße construction section (see Figure 5). At the same time, the width and/or depth of the platforms at the stations have been reduced in some cases, which should also result in less material being used. These initial optimisations will also be applied to the other planning sections of the U5. In addition to these successes, which have already


been achieved in the planning phase, Hochbahn U5 Projekt GmbH is initiating the first individual approval in Germany for SFRC segments to be used in construction. Thanks to their material composition, these contain around a third less steel and therefore have a significantly better CO2


balance.


The first pilot tests for the electrification of construction site logistics took place in 2025.


3 OUTLOOK FOR PLANNING, CONSTRUCTION AND SUSTAINABILITY While construction of the first U5 section is underway, the design planning for the remaining 17km-long section is continuing. In addition to the structural planning of tunnels and stations, the planning also involves construction methods and processes, logistics, traffic concepts and scheduling, as well as the identification and implementation of measures to reduce CO2 emissions. Along with the optimisation potential that has been identified already, further measures are being identified and implemented to bring about an additional reduction in CO2


. Joint reduction targets were discussed with the


industry. In the course of the project, the first interim targets have already been achieved earlier thanks to the partnership-based cooperation between industry, construction companies and clients (see Figure 6).


14 | September 2025


concrete and steel industries are being called for by industry partners and politicians. For U5, the requirement for sustainable products is being stipulated for the first time in tenders and implemented during construction. In future, electrified trucks, excavators and


wheel loaders will be used in test operation on the construction sites of the U5 project, thus gaining initial experience for their practical use. Hochbahn U5 Projekt GmbH assumes that there is great potential for savings here, too. It is expected that even more potential can be


leveraged at material level, which will become apparent in the further course of the project and would have a positive impact on achieving the target of 70%. This finding is based above all on the ongoing exchange with industry representatives and the contractors of the first construction phase. The savings in construction and planning are


documented in the annual balance sheet in the sustainability report and have now also been included in the risk management for the U5. This makes it possible to transparently measure the CO2


reduction measures


for the remainder of the project. The target scenario drawn up two years ago is consistently compared with the annual balancing of the CO2


emissions actually


occurring during construction and the expected CO2 emissions for the further planning stages. This ensures


ongoing quality assurance and the achievement of the reduction target. This means that all the parameters for reducing CO2


emissions during the construction of the U5 are set: sustainability has been integrated into the planning as an equally important criterion and is always taken into account. Thus, the maximum technically possible reduction measures can be considered at an early stage and ultimately implemented during construction. In addition, solutions are still being developed


together with the industry to consistently drive forward the development of sustainable building materials. It can be assumed that the level of CO2


emissions saved during


the construction of the U5 can be further increased by the progress made in the coming years.


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