Specific Problems of Sampling and Measuring Diesel Exhaust Emissions

The results of emission and fuel economy tests on vehicles are still subject to serious errors. Unclear definitions and inadequately specified test procedures and testing equipment together with insufficient methods of calibration are the main reasons for this unpleasant fact.

Improvements to the situation would only be made possible by improving the test procedures. Fundamental proposals for doing this exist. However, all efforts regarding this are useful only if the authorities are willing to accept such improvements, to put them into use themselves and to incorporate them into the pertinent regulations.

Further investigations are necessary to ensure that test procedures will yield credible results as well as being generally applicable and not merely applicable to particular concepts.