This brochure summarizes the results of a health impact assessment (HIA) of public transportation projects in the Plaine Commune urban community as part of the future Greater Paris metropolitan area. It was conducted by the Regional Health Agency and the Ile-de-France Regional Health Observatory. Plaine Commune, an intermunicipal community of nine cities (408,000 residents) located north of Paris, is an area with strong growth potential that contrasts with the unemployment rate and the precarious living conditions of a portion of the population. The awareness that transportation difficulties, isolation, and lack of accessibility were affecting the health of its residents, along with the opportunity to anticipate negative effects, improve the project, and involve the population through the HIA process, appealed to the elected officials of the Plaine Commune region. More than ninety recommendations were formulated and presented by health determinants. Some are specific to the selected projects (seventy-five in total); others are common to all three projects (nineteen). They cover seven major areas at the intersection of transportation, urban planning, and health: public transit organization, user information, public space planning, station area planning, land use strategies, access to employment, and coordination of public policies. Five key drivers were identified and ensured the smooth implementation of this HIA: the commitment of the local government, the gradual establishment of a common language with stakeholders, the ad hoc mobilization by certain evaluators of expertise complementary to their own, a participatory approach relying on local actors, and recommendations developed in collaboration with residents and aligned with the operational realities of the projects. The full report is available on the ORS website at http://www.ors-idf.org/index.php/component/content/article/757.