Selection of Track Form in Railway Tunnel from a Life Cycle Analysis Perspective

Abstract

Abstract The use of greenhouse gas emissions as a criterion for decision-making within the rail industry is increasing. The demand for the consideration of this criterion affects the type of decision models acceptable by railway infrastructure managers in the planning, construction, and maintenance of railway assets. The total amount of greenhouse gas emitted from a track solution in tunnels during its service life depends on the track form (i.e., ballasted track or the ballastless track), the type of construction, maintenance machines used, the current traffic profile, and the length of the tunnel. However, the development in the design of ballastless track systems during recent decades to make them environmentally friendly is a motivation for infrastructure managers to rethink and consider the use of the system. This paper addresses the effect of applying the optimized ballastless track system Rheda 2000® in a railway tunnel (the Hallsberg-Stenkumla tunnel) as part of a new line project in Sweden. The greenhouse gas emissions, represented by life cycle CO2 equivalent emission is calculated using the climate impact software developed by the Swedish Transport Administration Trafikverket. The result is compared with the estimated emission from the conventional ballasted tracks. The study shows that CO2 equivalent emissions by a ballastless track during its life cycle is 10% lower than that of the ballasted track. The primary total emission driver for both track form solutions is the emissions generated at the manufacturing of rails. The second important emission factor for the ballasted track solution is the emission from the renewal of the track form during its life cycle. The second important emission factor for the ballastless track solution is concrete manufacturing. The model applied in the study is an integral part of an integrated decision support system for effectively selecting track solutions from a lifecycle perspective.