A Comparison of Gaseous Emissions from a Hybrid Vehicle and a Non-Hybrid Vehicle under Real Driving Conditions

In this study, two vehicles were tested under real driving conditions with gaseous exhaust emissions measured using a portable emissions measurement system (PEMS). One of the vehicles featured a hybrid powertrain with a spark ignition internal combustion engine, while the other vehicle featured a non-hybrid (conventional) spark ignition internal combustion engine. Aside from differences in the powertrain, the two test vehicles were of very similar size, weight and aerodynamic profile, meaning that the power demand for a given driving trace was very similar for both vehicles. The test route covered urban conditions (but did include driving on a road with speed limit 90 km/h). The approximate test route distance was 12 km and the average speed was very close to 40 km/h. The test route featured multiple stop periods, little driving at constant speed (<10%) and several relatively rapid accelerations from standstill to speeds in the range 50-75 km/h, the latter being conditions under which fuel consumption, regulated exhaust emissions and the corresponding impact on urban air quality are typically high. Multiple significant differences in the emissions profiles of the two vehicles were observed: emissions of CO₂ and CO were much lower in the case of the hybrid vehicle, while HC and NO_x emissions were broadly comparable and very low.