In 2014, the European Commission has published the “Guidelines for developing and implementing a new look of sustainable urban mobility plans”emphasizing both the direct involvement of citizens and stakeholders, and the coordination among different urban policies (transport, land use, environment, economic, social and energy). The Sustainable Urban Mobility Plan (SUMP) is a strategic transportation plan aiming the sustainability of the urban mobility with respect to the: livability, equity, efficiency and effectiveness of the city. In compliance with the EU guidelines, the aim of the paper was the application of an adaptive rational decision-making process for developing the SUMP related to the city of Naples (Italy), the third largest Italian city and metropolitan area with a very high population density and traffic congestion problems. The specificity of the case study proposed is the application of a theoretical planning decision-making model characterized by an high level of rationality and participation of citizens and stakeholders, besides an intense use of quantitative methods to quantify and “rationally” compare different project scenarios.