1.Introduction In 2021, urban areas worldwide accounted for 75% of global energy use and produced 70% of the planet's carbon dioxide (CO2) emissions [1]. Cities are therefore on the front line of the energy transition, as the International Energy Agency (IEA) headlined in 2016 [2] in terms of both impact reduction (mitigation) and adaptation issues. Artificialization is particularly noticeable in public spaces, mainly dedicated to cars. In Paris, in 2000, 60% of public space was devoted to cars (traffic and parking) [3]. However, in cities, private car use is reduced or even reversed in favour of other modes of transport (bus, rail, etc.) [4]. This calls for an evolution of roads, which are currently 80% dedicated to cars [5]. At the neighbourhood scale, scientific literature considers the environmental impacts of infrastructures such as roads and sidewalks seem to be underestimated [6]. The objective of this study is to develop a detailed life-cycle model estimating impacts associated with roads construction and maintenance, that can be used for a neighbourhood LCA during early design phases. The developed model is parametric and based on road design best practices in France [7] using the Brightway development framework [8]. Identification of key data for the construction and maintenance of pavements at the neighbourhood scale is carried out. A sensitivity analysis is also conducted. 2.Methods Our model is based on roads best pratices design methodology [7]. It considers a road structure consisting mainly of bitumen, which is a standard case of road implementation, supporting up to 6.5 million lorries during 20 years on one lane and one direction. We have established processes for road construction and maintenance. It includes: refinery, quarry, asphalt plant and associated energy production system, construction and maintenance machinery and transport processes. The model created is based on the EcoInvent 3.9.1 data. Unit foreground processes related to construction machinery come from work carried out by A. Jullien et al.[9]. Methods EF v3.1 EN15804, ReCiPe 2016 v1.03, IPCC 2021 and Cumulative Energy Demand (CED) were used for life cycle impact evaluation. A Monte Carlo analysis followed by a sensitivity analysis (following [10] methodology) is carried out for CED and climate change indicator. Sankey diagrams are also presented to identify key impact-producing processes. The construction phase results are compared with road LCA French expert tools SEVE and ECORCE [12, 13] and with a tool capable of carrying out LCAs at district scale (Pleiades[13]). 3.Results and Discussion The model provides the cumulative energy demand for the construction phase and accounts for 20 TJ for 30,000m². The GWP accounts for 1600 t CO2 eq. for the same area. And the aggregate consumption accounts for 21,000 t (for 30,000m²). For the road maintenance phase, calculation is made with 40% recycled aggregates, and impacts are approximately equivalent to half of those of the construction phase. Very similar results between the specialized tools (SEVE and ECORCE) and therefore the same orders of magnitude are shown. Between these specialized tools and our model, a factor of 2 on cumulative energy demand and climate change is observed. The consumption of aggregates is of the same order of magnitude. As for the building and neighbourhood-oriented tool (Pleiades), a factor of 4 is noted for cumulative energy demand. For climate change and aggregate consumption, the orders of magnitude are the same. These results raise the question of the data used to model road construction and sensitivity to the chosen modelling hypothesis. Bitumen production was identified as the most sensitive parameter of our model, whether for cumulative energy demand or climate change indicator. Finally, road impacts were compared to the overall results at the neighbourhood scale based on a real case study. In this case study, roads account for around 1% of the total for cumulative energy demand and 2% for climate change. 4.Conclusions The development of a road LCA model, based on data from the EcoInvent database and, by processes adaptation thanks to specialized scientific literature has been developed. Although our development only accounts for thick bituminous structures, this remains representative of the French context where this construction technique is widespread. Our results identified bitumen as the main contributor to the CED and GWP impacts. However, the data provided by EcoInvent is very different from those provided by EUROBITUME, which is used in specialized tools. The bitumen data quality provided by EcoInvent and EUROBITUME is therefore questionable since they have significative differences on energy consumption and CO2 emissions. Our results also suggest the low impact of roads within neighbourhoods calling for more attention to what circulates on roads and therefore the daily mobility impact allocation. Finally, roads, through their ability to link places together, could offer support for the creation or improvement of green belts and participate in the formation of a green network in cities, participate to urban heat island reduction. The thermal performance of buildings could also be better studied taking into account the albedo of roads. Those aspects of their design could reduce their impact on biodiversity while improving the urban living environment. 5.References [1]IEA, ‘Empowering Cities for a Net Zero Future – Analysis’, IEA. Accessed: Feb. 09, 2023. [Online]. Available: https://www.iea.org/reports/empowering-cities-for-a-net-zero-future [2]IEA, ‘Cities are at the frontline of the energy transition - News’, IEA. Accessed: Jan. 17, 2023. [Online]. Available: https://www.iea.org/news/cities-are-at-the-frontline-of-the-energy-transition [3]APUR, ‘La proportion de l’espace public dédiée à la circulation motorisée’, 2012. Accessed: Apr. 15, 2024. [Online]. Available: https://www.apur.org/sites/default/files/documents/espace_public_pratiques_usages.pdf [4]OECD, Usage de la voiture particulière: Les tendances à long terme. Paris: Organisation for Economic Co-operation and Development, 2014. Accessed: Nov. 29, 2023. [Online]. Available: https://www.oecd-ilibrary.org/fr/transport/usage-de-la-voiture-particuliere-les-tendances-a-long-terme_9789282105993-fr [5]M. Robert, ‘Pour en finir avec la société de l’automobile’, 2005. [6]C. Lausselet, K. M. Lund, and H. Brattebø, ‘LCA and scenario analysis of a Norwegian net-zero GHG emission neighbourhood: The importance of mobility and surplus energy from PV technologies’, Build. Environ., vol. 189, p. 107528, Feb. 2021, doi: 10.1016/j.buildenv.2020.107528. [7]LCPC and SETRA, Catalogue des structures types de chaussées neuves. Bagneux, Paris: SETRA ; LCPC, 1998. [8]C. Mutel, ‘Brightway: An open source framework for Life Cycle Assessment’, J. Open Source Softw., vol. 2, no. 12, p. 236, Apr. 2017, doi: 10.21105/joss.00236. [9]A. Jullien et al., ‘Chapitre 4: Collecte des données environnementales’, in Analyse de Cycle de Vie appliquée à un chantier d’entretien routier sur la RN 76. Evaluation technique et environnementale d’une couche de liaison d’enrobé bitumineux pour différents taux de recyclage., 2006. Accessed: Mar. 11, 2024. [Online]. Available: https://hal.science/hal-00932819 [10]S. Cucurachi, C. F. Blanco, B. Steubing, and R. Heijungs, ‘Implementation of uncertainty analysis and moment-independent global sensitivity analysis for full-scale life cycle assessment models’, J. Ind. Ecol., vol. 26, no. 2, pp. 374–391, 2022, doi: 10.1111/jiec.13194. [11]IDRRIM, ‘Avis technique N°160 : Système d’Evaluation de Variantes Environnementales V 2’. Sep. 2013. Accessed: Feb. 26, 2024. [Online]. Available: https://www.seve-tp.com/wp-content/uploads/2022/05/1936IDRRIM_AvisTechnique_160_0310V2.pdf [12]IDRRIM, ‘Avis technique n°158 : ecOcomparateur Routes construction entretien v2.0’. Jun. 2013. Accessed: Nov. 29, 2023. [Online]. Available: https://www.idrrim.com/ressources/documents/3/1717,IDRRIM_AvisTechnique_158_2307_V2.pdf [13]‘Base Pleiades - L’écoconception du bâtiment, de l’esquisse à l’ACV’, https://www.izuba.fr/. Accessed: May 13, 2024. [Online]. Available: https://www.izuba.fr/logiciels/outils-logiciels/