Background Transport infrastructure is essential for economic and social development, as well as being an important sector in its own right. Among the various transport infrastructure options, rail is considered as one of the most sustainable, especially with regard to the fight against climate change. Rail is therefore an essential element of European transport and environment policies and it is expected that its importance will increase further in the coming years. However, more needs to be done to improve the environmental performance of the rail sector. Currently, it is estimated that 28% of the total emissions associated with rail transport come from infrastructure. Almost half of these emissions occur during the construction phase, mainly during the production and transportation of materials. It is estimated that constructing one kilometre of railway produces a total of 1 040 tonnes of CO2. Rail infrastructure is subject to various legal instruments for environmental prevention. However, there are currently no tools to optimise the development of the intermediate stage - between the infrastructure design and its functioning. Such tools could help to support decision-making during the construction of rail infrastructure and to reduce carbon and water footprints during this phase of the life cycle. Objectives LIFE HUELLAS aims to reduce the carbon and water footprint of rail infrastructure by developing tools and methodologies to optimise decision-making during the construction process. It plans to provide railway construction companies with a tool that combines environmental, economic and social analysis to enable them to be, and to be seen to be, more sustainable. The project will work to identify the most appropriate methodologies for environmental impact assessment for the sector, based on footprint calculation, life-cycle assessment (LCA) and intelligent techniques. It will conduct an initial environmental analysis of rail infrastructure, identifying and quantifying all the input and output flows of the construction phase. The beneficiary will research and develop indicators, environmental criteria and assessment tools for each construction operation. The project will establish an overall methodology for evaluating the sustainability of any planned railway infrastructure. It will then develop a software prototype to enable railway construction companies to analyse the economic, social and environmental impacts of their activity. It will also explore methods for validating compliance with applicable legal and voluntary requirements and create a new manual of best practice. Finally, the project will test the new software in the construction of two railway infrastructures with different topologies. In doing so, it will attempt to verify the validity of the tool for assessing the environmental impact of a real-life project. It also hopes to demonstrate the successful minimisation of environmental impacts through the identification and implementation of environmental improvement measures. The pilot phase will enable the project to find an optimum balance between the science and usability of the tool. Expected results: A life-cycle assessment methodology adapted to the specificities of the railway infrastructure industry and based on thorough research; A software tool to enable railway infrastructure companies to conduct environmental, economic and social sustainability analyses of their activities; Demonstrated benefits of the tool for improving the sustainability of two infrastructure construction projects – including a 10% reduction in the carbon footprint and a 5% reduction in the water footprint; Demonstrate economic and marketing benefits of the tool for construction companies; A new manual of best practices in sustainable rail construction.