Comparison of the CO2 balance for maintaining and new construction of railroad bridges. As soon as energy is used for a certain activity, emissions are inevitably generated as part of negative CO2 emissions. Alongside many other sectors, the construction industry is one of the biggest drivers of the ongoing negative balance. A rethink towards the continued use of load-bearing structures in structural engineering can be a potential driving force here. Compared to the proportion of existing arch bridges in the Deutsche Bahn network, the existing durability of these structures and the associated residual load-bearing capacity, a successful saving can be demonstrated with regard to ecological and economic goals, as well as the renovation of existing building culture at the current times of use of current reinforced concrete structures. The CO2 balance presented here for the use of building materials, dismantling, the creation of construction site facilities, the movement of earth masses, rail replacement traffic during the construction period and the operation of the facilities over a service life of 120 years illustrates the potential that the preservation of arch bridges offers compared to new construction. With a view to the upcoming construction measures for the arch bridges and Deutsche Bahn's goal of achieving climate neutrality by 2040, this type of construction can be a step in the necessary direction.