Given the ever-increasing concern about environmental issues, the automotive industry is focusing on the development of innovative technologies that allow reduction of gas emissions and fuel consumption. Over the last few years, Hybrid Electric Vehicles (HEV) and Fuel Cell Vehicles have been developed as the most promising alternative solutions for many car manufacturers. Although fuel cells are considered as the best technology to have zero emission, the impact on infrastructure for a large-scale deployment is not yet solved. For this reason, HEV represent a valid shorter-term alternative that guarantees drastic emissions reduction and reduced fuel consumption with a much lower infrastructural impact.This paper reports the results obtained by the optimization of the emissions and fuel performances of a hybrid electric city vehicle for urban transportation named XAM (eXtreme Automotive Mobility).In order to optimize these performances, a 1D model of the vehicle has been created. This model predicts the HEV behavior in conditions representative of urban use by modeling the most important vehicle parts: the vehicle dynamics, the track properties, the electric motor, the internal combustion engine, the supercapacitors, the regenerative braking, and also the energy management system. This model has been parameterized and used with a numerical optimization tool in order to identify the set-up of the vehicle that meets the optimization objectives. The parameters considered are related to: energy management, cruise velocity, working time of the internal combustion engine and the properties of the regenerative braking. The optimized configuration yielded a fuel consumption close to 100 km/L of gasoline. This result has been confirmed during experimental tests of the vehicle on a real track.