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Since the introduction on the 1st December 1993 of Emission Testing in its present form, no substantial changes were made to the threshold values in respect of emission limit values. As a supplementary measure, the On Board Diagnosis (OBD) was introduced.

Considering the technological progress of engines and emission reduction technologies in modern vehicles, the current emission testing regulation is no longer sufficient. It needs to be adjusted in line with current vehicle technology, to ensure that vehicles with high levels of exhaust emissions are detected in the future. Only emission testing that reliably measures the efficiency of all emission components, especially in modern diesel-powered vehicles fitted with a diesel particulate filter, will have an impact on the environment and health.

The authors of this article, who have significant expertise in emission testing, strongly belief that current emission testing as practiced in Europe has lost its effectiveness. Despite the progress of engine technology, emission limit values were not adapted. As a result, the measurement devices no longer meet the requirements.

The On Board Diagnosis in new vehicles introduces an electronic system capable of self-diagnosing exhaust emission deviations. However meaningful this feature, it is not able to amend the limit values, nor can it introduce an efficient tangible measuring method to test compliance with limit values.
Especially for modern diesel-powered vehicles equipped with a diesel particulate filter, a conclusive and meaningful assessment is required, that not only tests but that also documents. This would ensure the efficiency of the emission treatment over the entire period the vehicle is used.

In the meantime the required measuring instruments are available. These devices have demonstrated and proven their thoroughness at a field test of Working Group Emission 2010 (VdTÜV, DEKRA, ZDK, ASA Verband) involving more than 1.000 diesel vehicles in garages and recognised control organisations.
Their accuracy compared to lab instruments used during engine development, was proven and confirmed by university laboratory tests.

In order to adapt diesel emission testing to the present and future requirements, two steps are necessary:

1. First and foremost, the mandatory emission limit values for vehicles need to be adapted to current vehicle technology conditions, as from EURO II. The socalled emission tag values on each vehicle identification plate, of dieselpowered vehicles can be used as a guideline. These values were established during vehicle type approval and documented for the purpose of periodic vehicle inspections.

2. Afterwards, there should be a gradual renewal of emission testing devices for diesel emissions, by introducing new instruments with alternative measuring methods capable of measuring the particulate mass concentration of vehicles in a precise and reliable manner. This measuring procedure should be compulsory for modern diesel-powered vehicles, with a transition period of 3 years. To this intent, these new devices could already be certified today as an alternative for current measuring instruments and it would facilitate the eventual compulsory exchange. Prior to being allowed to use the new devices, they should be granted qualification approval (PTB-A) from the relevant German National Metrology Institute.

How are Particles Measured?

Correlation between Opacity and Particle Concentration

Measurement before and after the particulate trap while driving on road conditions. Both measurements done with MPM 4 devices: