Pedestrian zones are present in numerous cities around the world, and Hanoi city began to organize one a few years ago. However, closing roads can lead to heavy traffic congestion in surrounding areas and, consequently, more air pollution in these areas. There is, therefore, a need for analyzing and predicting the outcomes in terms of air pollution when certain roads are closed, before actually implementing a plan. In this project, we used the GAMA platform to build an agent-based model that simulates the traffic and air quality in Hoan Kiem district. This model can be used as a decision support tool for local authorities and as an information tool for the general public: thanks to its output on a tangible interface, people can interact with the simulation at public venues and explore various scenarios. Although more accurate data and realistic diffusion models are still lacking and will need further research in the future, the simulation is alreay able to reflect traffic and air pollution peaks during rush hours quite realistically.