During this research project emission tests were carried out within the national road worthiness test procedure (§29 StVZO). Approximately 2000 registered vehicles from the M1/N1 vehicle categories were examined so that the results of the OBD and tailpipe measurement tests could be compared. Only vehicles which were fitted with an OBD system and which were first registered on or after 1 January 2006 were investigated. All emission tests were carried out in accordance with the specifications of the relevant national Emission Directive of 7 May 2012 (Verkehrsblatt 2012, p. 330) by national bodies for periodical technical inspections (PTI). Even where the national Emission Directive did not require a subsequent tailpipe measurement to be performed after query of the OBD-system, this was nevertheless done as an additional step within the research project. The tests were performed by taking a random selection of vehicles (complete sample per day) and, in principle, there was an even split between petrol and diesel vehicles. The tests were executed between September 2012 and March 2014. FSD examined and analysed the results from 975 tests on petrol engine vehicles and 921 tests on diesel engine vehicles. Tests results with incomplete data, implausible documentation, failed visual inspection, no communication between emission test equipment and vehicle or with incomplete readiness tests were excluded for subsequent analysis, i.e. a comparison of the OBD result and the tailpipe measurement. The subsequent analysis of the measured data was performed separately for diesel and petrol engines with a further subdivision of the results according to the emission standards. Thus a reliable data base was elaborated revealing the extent of differences in emission test results (with regard to "passed" / "failed") between tail pipe measurement and outcome of the on-board diagnostic system. (Author/publisher)
Samenvatting