Recommendations for the new WLTP cycle based on an analysis of vehicle emission measurements on NEDC and CADC

Past investigations have shown that the current type-approval test cycles are not representative for real-world vehicle usage. Consequently, the emissions and fuel consumption of the vehicles are underestimated. Therefore, a new cycle is being developed in the UNECE framework (World-harmonised Light-duty Test Procedure, WLTP), aiming at a more dynamic and worldwide harmonised test cycle. To provide recommendations for the new cycle, we have analysed the noxious emission results of a test programme of seven vehicles on the test cycles NEDC (New European Driving Cycle) and CADC (Common Artemis Driving Cycles). This paper presents the results of that analysis to show the zones of the cycle that are causing the highest emissions, using two different approaches. Both approaches show that the zones with the highest emissions of modern vehicles differ from vehicle to vehicle. Consequently, a representative test cycle has to contain as many combinations of vehicle speed and acceleration that occur in real-world traffic as possible to prevent that a vehicle does not perform well for certain combinations because they are not included in the test cycle. Furthermore, the paper demonstrates that it is important to include a cold start to ensure rapid warm up of the catalysts.