1. Introduction

Environmental impact (EI) reduction is one of the major focal points of the scientific and political communities; this target passes through correct assessment of several impact types.

In recent years there has been growing attention in the transport sector, no longer only concerning emissions from different means of transport vehicles, but also the EI caused by the construction of new infrastructures and the maintenance processes of existing ones.

In the last twenty years, several studies have been developed for evaluating the environmental impact of the railway sector. In these studies, there is great heterogeneity in the methodological approach, analysis period, railway type, software and data set used. Moreover, different railway systems are considered, including high-speed rail (HSR), ordinary rail, tramways and light rail transit. It is not easy to make a rigorous comparison of these studies as they present different methodologies and limitations. Nevertheless, the most relevant results related to Life Cycle Assessment (LCA) are briefly analysed in this article. A comprehensive approach should consider both the construction activities and the maintenance works of the railway and the use phase. Focusing only on the railway infrastructure, the elements to consider are different from the railway track to the signal and telecommunication systems.

This clarifies why it is not possible to determine a standard impact value of a railway infrastructure section of a given length, because the presence or absence of railway facilities and structural elements depends on a huge number of factors, such as land topography, energy sources, urbanisation, etc. Therefore, it is clear how important the examination of the railway infrastructure during the construction and maintenance phases is for the assessment of the EI.