This thesis work, carried out in cooperation with FPT Industrial, focuses on the description of the homologation process of a new diesel engine for heavy-duty on-road applications, in compliance with the EURO VI step E emission regulation. After an overview of the main pollutants that affect human health and the environment, the emission legislative framework of the most important world market regions will be presented, with a focus on EMEA and NAFTA. It follows a detailed description of the EU pollutant emission standards for heavy-duty vehicles, together with the next emissions targets in terms of CO2. The respect of the current norms has been granted by an high technological content provided on the engine project and the calibration effort, without neglecting the innovative strategies and layout developed for the after-treatment system.