Comparing real-world off-cycle NOx emissions control in Euro IV, V, and VI
Real world NOx performance of Euro VI-D trucks and recommendations for Euro VII
This study analyzes the real-world emissions of seven Euro VI-D trucks and evaluates the avenues for extending the in-use PEMS test provisions to better capture a wider range of frequently occurring conditions in real operation.
The analysis finds that urban operation is responsible for 50% to 90% of total NOx emissions from the trucks tested. However, the Euro VI ISC methodology to assess compliance, as set by implementation steps D and E, does not capture the real-world NOx performance in cold-start conditions and low-load or low-speed operation typical of urban driving.
For the ISC test evaluation to be representative of the real-world urban emissions, the power threshold would need to be lowered, all cold-start data must be included, and the percentile for evaluation must be increased to 100%. These extensions to the ISC procedure would ensure that the work-specific NOx emissions used for compliance evaluation are comparable to the measured real-world emissions in urban operation.
In the most stringent Euro VII proposal, the NOx emissions of Euro VI-D vehicles tested would have to be reduced, on average, to one-quarter of current values to comply in cold-start and low-load operation. Upcoming standards in California, on the other hand, would require larger relative improvements mandating emissions to be reduced to one-seventh of current values. For the stringency of future Euro VII standards to be aligned with that set by the regulation in California, Euro VII provisions should ensure that low power operation is adequately included and that the limits are set, at a minimum, at the most stringent level in the current proposal.
A previous version of this report contained erroneous calculations under Euro VI-E provisions. These have been corrected in the text and in Figure 2. The original version can be found here.