Brake Emission Testing Process – Assuring Repeatability and
Reproducibility of Emission Measurement Results 2023-01-1876
Non-exhaust emissions are clearly one of the focal points for the upcoming Euro 7
legislation. The new United Nations Global Technical Regulation (UN GTR)
defining the framework for brake emission measurements is about to be officially
published. The first amendment to this text is already on the way through the
United Nations Economic Commission for Europe (UNECE) hierarchy for decision
making. In real life, the final emission factor as the ultimate result of a test
is influenced by inaccuracies of numerous parts of the measurement system as
well as additional contributing factors like the performance of the particulate
filter handling process, which might not be primarily related to equipment
specifications. The regulation’s definitions set the basic requirements for
testing, whilst establishing a robust and efficient testing process requires a
thorough assessment of the influencing factors on the measurement quality, which
in turn can be described using e.g., repeatability and reproducibility. This
study shows these influences of the system’s inherent sources of imperfection on
result quality, based on theoretical relations, simulations, measurement results
and experience gathered during productive brake emission testing. Essential
process performance indicators are derived to allow suitably low uncertainty of
results for homologation and development purposes. Based on this, it might make
sense for testing organizations to tighten their internal technical
specifications for specific topics beyond current regulation’s requirements to
allow efficient testbed operation and deliver superior data quality. Considering
lower absolute emission levels in the future, understanding these influencing
factors will get even more important.