## 1 Introduction  
Construction, rehabilitation, and maintenance of highway pavements require obtaining, processing, transporting, manufacturing, and placement of large amounts of construction materials. pavements, in fact, represent one of the most important infrastructural assets and require massive investments. The need to design and provide a sustainable maintenance service is becoming a priority and this comes mutually with the intention to reduce impacts caused by maintenance treatments to the environment. Several tools are available to quantify and compare materials and techniques in terms of environmental sustainability. Unfortunately, articles and manuals describing such tools base the evaluation of the environmental impact on a different set of data. This makes it difficult to adopt a single, universally-recognized method to have a direct comparison of pavement preservation and maintenance treatment options in terms of environmental sustainability [1]. With the recent inclusion of environmental consideration into public procurement, also known as Green Public Procurement (GPP), a comprehensive and official approach to the sustainability analysis of flexible pavements is needed. Starting from that, a third-partiesverified declaration known as Environmental Product Declaration (EPD) certification was introduced. In 2013, the EU founded the EDGAR project, aiming at supporting the National Road Administrations in the sustainability assessment of novel green bituminous mixtures and bridging the gap between innovation and adoption [2]. The methodology developed within the project considered both the environmental aspects which rule the EPD declaration, but also socio-economic factors and a long-term vision of sustainable aspects. In 2013, starting from the Norwegian EFFEKT model [3], the LICCER model was presented with the objective to provide planners with quantitative information to assess life cycle cumulative energy consumption and greenhouse gas emissions of road corridor alternatives [4]. Additional efforts were also made in the characterization of maintenance operations with the HERMES project that developed a methodology enabling the selection of the best available technology and strategy with the lowest cost for the environment and society. The overall objective of this research project was to establish a long-term dynamic inventory of carbon emissions deriving from the analysis of a variety of urban roads, based on best practices in Europe and China [5]. All of the projects mentioned emphasize the complexity of the assessments resulting from the large number of factors to be considered. In some cases, the models developed are based on simplifications that consider a limited set of parameters included in EPD certifications. In each project, however, the need to have a single indicator that is overall representative of the environmental impact is noted. Lastly, it can be pointed out that, none of the mentioned projects took into account parameters related to performance and, in particular, the durability of the materials considered. Starting from these considerations, the present work proposes to develop an innovative index named Environmental Asphalt Rating (EAR) which, still starting from the parameters derivable from EPD certifications, aims to:  
* Unambiguously quantify the potential environmental impact due to different maintenance strategies;
* Provide to Autostrade per l'Italia (ASPI), in its capacity as contracting authority, a reference parameter for the evaluation of technical offers and the assignment of scores in the tender phase in terms of environmental impact;
* Monitor and fully estimate the impacts on the basis of the bids submitted by the awarded contractors. The EAR index proposed here has been designed as a dimensionless value that can collect and summarize all the information that can be extracted from EPD certifications.