As cities extend and renew, neighbourhood projects need environmental assessment methods in order to limit the pressures of urban areas on the environment. Significant research has been conducted on building modelling and Life Cycle Assessment (LCA). Transportation is a major source of impacts and therefore also requires in-depth investigation, especially in regard of interactions that occur between mobility and the built environment. This presentation aims to develop an environmental assessment methodology that considers life cycle effects related to mobility and the transportation system in the case of an urban neighbourhood. In addition to analysing urban transport technologies through a LCA, our methodology puts emphasis on the representation of mobility using microsimulation in order to better consider neighbourhood characteristics. Based on a literature survey that reviews the various methods to represent and evaluate mobility at the local level, our methodology builds on a disaggregated or agent-based approach, as proposed by Anderson et al. 2015 or Saner et al. 2013, while keeping LCA completeness and transparency. A case study on a future neighbourhood close to Paris will illustrate our methodology and reveals the leverage of both urban planning and location choices. To represent daily mobility associated to future neighbourhoods, we develop a stochastic modelling chain, starting from neighbourhood characteristics, with dwellings and jobs, then sequentially the description of potential population, daily mobility and transport system usage. The environmental impacts of transport modes are then assessed through a LCA, including exhaust emissions, fuel production, vehicle production, maintenance and end-of-life, and finally infrastructure, both for private cars and public transit. Using our assessment framework, we estimate daily mobility patterns and related environmental impacts for an actual neighbourhood project. Results highlight various policy instruments that influence the environmental burden. In addition to sensitivity related to transport technological choice and efficiency, we point out effects related to neighbourhood definition, in the hand of building promoters and urban planners. Besides location and urban form, dwelling size, car park availability and public transport pass incentive measures also have significant impacts on the environmental footprint of daily mobility. To conclude, a parallel study is carried out for the same neighbourhood on buildings. It emphasizes the significant role of transportation regarding the environmental impacts of urban projects, with global warming impacts almost equivalent between buildings and transportation.