According to the TÜV association, measuring the particle concentration (PN measurement) is worthwhile during the exhaust emission test (AU) for vehicles. The new measurement method, which detects the particle concentration directly at the exhaust tailpipe, replaced the previous opacity measurement method and has been applied to passenger cars and trucks with diesel engines from the Euro 6/VI emissions class since July 2023.
This should allow health and environmentally harmful fine dust concentrations in the exhaust gases to be determined even more precisely. In 2024 alone, almost 4.5 million diesel vehicles in Germany in the Euro 6/VI emissions class were tested using this method. According to test organizations, 3.0 percent did not pass the exhaust emission test on the first attempt. In absolute numbers, this corresponds to around 132,600 vehicles. For the evaluation, the testing organizations TÜV, DEKRA, GTÜ, KÜS, and the recognized AU workshops collaborated. Robin Zalwert, consultant for sustainable mobility at the TÜV association, says:
“With the particle measurement, vehicles with defective or manipulated exhaust cleaning systems are reliably identified and taken out of traffic. The PN measurement contributes to the improvement of air quality and thus makes an important contribution to health, the environment, and the climate."
Zalwert considers the identification of
so-called "Gross Polluters" with this measurement method to be particularly important: because only five percent of such vehicles in the vehicle inventory could alone be responsible for around 25 percent of all traffic-related pollutant emissions, as studies have shown.
Age-dependent
There is also a clear connection with the age of the vehicles: the older, the more likely they were to fail the test. The defect rate for vehicles under 5 years old is 2.0 percent, for vehicles 5 to 10 years old it is 4.0 percent, and for vehicles older than 10 years, it is 6.1 percent. Zalwert comments: “In the coming years, the currently still low proportion of older Euro-6 vehicles will steadily increase.”
According to the Federal Motor Transport Authority (KBA), the average age of cars in Germany is expected to rise steadily: currently, cars in this country are on average about 10.6 years old. “Owners of older cars are urged to invest in the maintenance of their vehicles and to keep an eye on the exhaust systems,” says Zalwert. “Otherwise, there is a risk that the vehicle will fail the HU and AU.”
Trucks fare better
However, there are also opposing developments: the expert assesses it positively that commercial vehicles with
a permissible total weight of more than 3.5 tons have a comparatively low defect rate of 2.2 percent and thus are below the average. “This speaks for the overall good condition of the truck fleet in Germany, which results from a combination of regular maintenance and independent inspections,” says Zalwert.
Consider other emissions classes
The analysis of the exhaust emission tests also revealed that only about one-third of the defects detected during the tailpipe measurement would have been discovered with the electronic vehicle diagnosis system. And a full two-thirds of the defects would have even escaped pure On-Board Diagnostics (OBD). Before the introduction of the new measurement method, the TÜV association reported, there was an intense discussion about the meaning of tailpipe measurement. Critics believed that OBD was sufficient.
Zalwert now concludes from the results that the PN measurement at the tailpipe has clearly proven its effectiveness and represents a successful model that is worth extending to other emissions classes. Diesel vehicles of emissions class Euro-5b are particularly suitable for this. Zalwert believes that a number of high-emitting diesel vehicles are to be expected in this vehicle group: “The introduction of PN measurement here as well would be a consistent and effective step towards
further improving air quality.”
After just about half a year, the TÜV association described the introduction of the new particle measurement method in an interim report at the beginning of 2024 based on the evaluation of nearly a million vehicles as a "clearly" better exhaust assessment method. In a period of three months from August 1 to October 30, 2023, even 3.4 percent of the tested vehicles failed, i.e., 32,285 out of a total of 950,809. And even then, it was suggested that the method be extended to other emissions classes as well as gasoline vehicles with direct injection from class 6. The new particle measurement method was initially supposed to be introduced on January 1, 2023, but this date was postponed by half a year due to the lack of market coverage with measuring devices.
If there are defects in the AU such as defective diesel particulate filters or faulty sensors, the vehicles must be taken to a workshop immediately and the defect corrected within four weeks. Afterward, a re-inspection takes place. If the deadline is missed, the complete main inspection (HU) must be repeated, as the AU is normally part of the HU, and both inspections must not be more than a
