White paper

Impact of improved regulation of real-world NOx emissions from diesel passenger cars in the EU, 2015−2030

Vehicle testing

NOx emissions from diesel cars in the EU have remained high, largely due to a growing gap between emission certification limits of Euro 4 and Euro 5 standards (measured in laboratory testing) and “real-world” emissions of diesel cars operating on the roads. Beginning in 2017, the EU’s emissions type-approval procedure for passenger cars will include a new real-driving emissions (RDE) test conducted using on-board portable emissions measurement systems (PEMS). The RDE test is intended to supplement the laboratory certification tests, which are currently the only demonstration of compliance with vehicle emissions standards required of manufacturers. Under the new type-approval system, to obtain a certificate of conformity with Euro 6 standards, manufacturers must demonstrate that new vehicle models pass the RDE test, which measures NOx emissions in on-road operation rather than in the precisely controlled drive cycle and environmental conditions of a test laboratory.

The RDE test protocol is being defined over four increasingly stringent “regulatory packages” (regulations), the first two of which have already been adopted. The ICCT has previously outlined five specific recommendations to strengthen the RDE regulation by building on the current framework. This white paper examines the potential impact of the RDE regulation and ICCT’s proposed modifications on real-world emission factors of new diesel cars and projected passenger car fleet NOx emissions in the EU through 2030. Findings indicate that real-world NOx emissions from new diesel cars in the EU could be reduced from 5–7 times the Euro 6 limit to 4 times that limit with the introduction of the RDE test. Future changes to the RDE test and European type-approval and enforcement practices recommended by the ICCT could further reduce new diesel car NOx emissions to 1.2 times the Euro 6 limit.