Degraeuwe Bart, Weiss Martin
European Commission, Joint Research Centre, Directorate C - Energy, Transport and Climate, Air and Climate Unit, via E. Fermi 2749, 21027 Ispra, Italy.
European Commission, Joint Research Centre, Directorate C - Energy, Transport and Climate, Sustainable Transport Unit, via E. Fermi 2749, 21027 Ispra, Italy.
Environ Pollut. 2017 Mar;222:234-241. doi: 10.1016/j.envpol.2016.12.050. Epub 2016 Dec 27.
Tests with Portable Emissions Measurement Systems (PEMS) have demonstrated that diesel cars emit several times more NO on the road than during certification on the New European Driving Cycle (NEDC). Policy makers and scientists have attributed the discrepancy to the unrealistically low dynamics and the narrow temperature range of NEDC testing. Although widely accepted, this assumption was never been put under scientific scrutiny. Here, we demonstrate that the narrow NEDC test conditions explain only a small part of the elevated on-road NO emissions of diesel cars. For seven Euro 4-6 diesel cars, we filter from on-road driving those events that match the NEDC conditions in instantaneous speed, acceleration, CO emissions, and ambient temperature. The resulting on-road NO emissions exceed by 206% (median) those measured on the NEDC, whereas the NO emissions of all unfiltered on-road measurements exceed the NEDC emissions by 266% (median). Moreover, when applying the same filtering of on-road data to two other driving cycles (WLTP and CADC), the resulting on-road NO emissions exceed by only 13% (median) those measured over the respective cycles. This result demonstrates that our filtering method is accurate and robust. If neither the low dynamics nor the limited temperature range of NEDC testing can explain the elevated NO emissions of diesel cars, emissions control strategies used during NEDC testing must be inactive or modulated on the road, even if vehicles are driven under certification-like conditions. This points to defeat strategies that warrant further investigations by type-approval authorities and, in turn, limitations in the enforcement of the European vehicle emissions legislation by EU Member States. We suggest applying our method as a simple yet effective tool to screen and select vehicles for in-depth analysis by the competent certification authorities.
使用便携式排放测量系统（PEMS）进行的测试表明，柴油车在道路上的氮氧化物排放量比在新欧洲行驶循环（NEDC）认证期间高出数倍。政策制定者和科学家将这种差异归因于NEDC测试中不切实际的低动态性和狭窄的温度范围。尽管这一假设被广泛接受，但从未经过科学审视。在此，我们证明，狭窄的NEDC测试条件仅能解释柴油车道路上氮氧化物排放量升高的一小部分原因。对于七辆欧4至欧6柴油车，我们从道路行驶数据中筛选出那些在瞬时速度、加速度、一氧化碳排放量和环境温度方面与NEDC条件相匹配的行驶工况。由此得出的道路氮氧化物排放量比在NEDC上测得的排放量高出206%（中位数），而所有未筛选的道路测量中的氮氧化物排放量比NEDC排放量高出266%（中位数）。此外，当将相同的道路数据筛选方法应用于另外两个行驶循环（世界轻型车辆测试规程（WLTP）和中国汽车行驶工况（CADC））时，由此得出的道路氮氧化物排放量仅比在相应循环上测得的排放量高出13%（中位数）。这一结果表明我们的筛选方法准确且可靠。如果NEDC测试的低动态性和有限温度范围都无法解释柴油车氮氧化物排放量的升高，那么即使车辆在类似认证的条件下行驶，NEDC测试期间使用的排放控制策略在道路上也必定无效或受到了调整。这指向了一些作弊策略，值得型式批准机构进行进一步调查，进而也表明欧盟成员国在执行欧洲车辆排放法规方面存在局限性。我们建议将我们的方法作为一种简单而有效的工具，用于筛选和挑选车辆，以供主管认证机构进行深入分析。
