Sustainable railways: trade-offs between operational and embedded energy

When considering the energy consumption and associated greenhouse gas emissions of a railway, it is important to account for both operational aspects (primarily running of the trains) and non-operational aspects, including energy and emissions embedded in infrastructure. The latter are heavily dependent on civil engineering structures such as tunnels, bridges and viaducts, as well as earthworks needed to provide route alignment. In some cases this can lead to a conflict between infrastructure design that has operational benefits and that which reduces embedded impact. This paper introduces the idea that there might be trade-offs between embedded and operational energy and emissions. A mixture of empirical and simulation data is used, and tunnels are used as a specific case study. The results are discussed in the context of wider sustainability issues.