MIMOZA is a simulation tool developed by CITEPA at the request of the French Ministry for Ecological and Solidary Transition as part of the implementation of Low Emission Zones (LEZ) to reduce air emissions from vehicles in cities and improve their air quality. It is intended to facilitate the assessments carried out by local authorities responsible for the implementation of LEZ. This innovative tool simulates the impact of different LEZ scenarios on NOx, NO₂, PM₁₀ and CO₂ emissions from the vehicle fleet concerned; i.e. between a scenario without LEZ (baseline scenario) and a scenario with LEZ for a given year (test scenario). This last scenario corresponds to the year of the LEZ implementation. After selecting the year of the test scenario, national default or local emission factors are identified accordingly. The vehicle fleet composition and the associated traffic (i.e. vehicle x kilometers traveled) are also proposed by the tool. As for emission factors, national default or local data can be selected. Emissions from the baseline scenario are then calculated on the basis of the traffic per vehicle fleet category and the corresponding emission factors. Finally, assumptions on traffic restrictions per vehicle categories and renewal rates of vehicles have to be selected. This leads to modified vehicle fleets (and traffic), which combined with emission factors, provides the new emissions for the test scenario.