In order to pass EU emissions targets, vehicles are tested in the New European Driving Cycle test (NEDC). This driving cycle benchmark, created in 1997, has been heavily criticized for its failure to conform to any real-world scenario. The test is conducted with all ancillary loads turned off, including air conditioning, heat, lights, defrosters. It’s not clear if headlights are disabled (and this would be significant, since European countries frequently mandate daytime running lights and/or full headlights at all times).
Regardless, the NEDC has been heavily criticized for its reliance on low acceleration, frequent idling, and constant-speed cruising. The original version of the test dates to the 1970s. Results do not include sustained motorway driving, allow the manufacturer to reduce speed by 1.2mph (thereby saving fuel), allow for the removal of both roof rails and passenger door mirrors (changing the aerodynamic profile of the car and saving weight), allows for overinflated tire pressures to reduce rolling resistance, allows companies to self-test with no oversight committee in place to check results, and finally allows car companies to reduce their results by 4% — just because.
Make no mistake, this isn’t a new problem, whatever politicians might find it expedient to say. A report from back in 2006 pointed out that while the NEDC standard had been steadily getting more strict, actual reductions in NOx emissions measured in real-world tests showed virtually no improvement. When this report was written, it showed that the then-new Euro-4 standard was only very slightly better than measured diesel emissions under the Euro-1 standard — which had been enacted a full 13 years earlier.
