A complementary emissions test for light-duty vehicles : assessing the technical feasibility of candidate procedures

Light-duty diesel vehicles emit on the road substantially more nitrogen oxides than permitted by regulatory emissions standards. The European Commission addresses this problem by developing a complementary emissions test procedure for the type approval and in-service conformity testing of light-duty vehicles. To facilitate the technical development of this procedure, the Real-Driving Emissions - Light-Duty Vehicles (RDE-LDV) working group was established in January 2012. The working group is open to Member States, NGOs, and industry stakeholders. This scientific and policy report presents the results of the first year of the RDE-LDV working group that focused on the technical assessment of two candidate procedures: (i) emissions testing with random driving cycles in the laboratory and (ii) on-road emissions testing with Portable Emissions Measurement Systems (PEMS). Both procedures are found to be technically feasible. However, PEMS on-road testing appears to be more effective than random-cycle testing in limiting the pollutant emissions of light-duty vehicles because it (i) allows covering a wider range of driving conditions and (ii) might be more effective in preventing the detection of emissions tests by vehicles and the use of defeat strategies. Nonetheless, PEMS on-road testing faces practical challenges, including open safety issues, the currently limited availability of PEMS equipment, and potential climatic, geographical, and seasonal constraints for the execution of onroad tests. Random-cycle testing presents further advantages over PEMS on-road testing in that already established laboratory equipment and know-how to be used. The present assessment is subject to uncertainty because the implementation and running costs as well as the overall effectiveness of the two candidate procedures depend on the definition of concrete boundary conditions (e.g., permitted test temperatures, severity of driving patterns). These definitions are not yet agreed. Accounting for the resulting uncertainty, it has been decided that the JRC will develop a PEMS-based test procedure while vehicle manufacturers are given the opportunity to develop a random cycle-based test procedure. A decision will be made regarding the implementation of these procedures for type approval and in-service conformity testing based on a comparison of the two final and fully developed test procedures by the end of 2013.