This master thesis in collaboration with FEV Italia s.r.l. concerns the analysis and application of the Real Driving Emissions legislation, along with the simulation and reproduction of the CO2 emissions of a PHEV over the homologation cycles. Due to the increasing gap between homologation and real word driving emissions, the type approval procedures have been updated with the introduction of real driving on-road tests with the goal to reduce the pollutant and CO2 emissions. Those tests rely on a new technology usage, the Portable Emissions Measurement Systems (PEMS), that connected to the vehicle OBD and tailpipe allows the real time measurement of the vehicle’s exhaust gasses.