Options for practical in-use compliance testing of HD vehicles

In 1994 TNO Automotive started its HD vehicle In-use Compliance programme on request of the Dutch Ministry of Spatial Planning, Housing and the Environment. Until now, it has been possible to simulate the homologation test procedure with acceptable accuracy on the vehicle (using a chassis dynamometer), rather than testing the engine on an engine dynamomter as prescribed by the type approval procedure. Advantages of this methodology developed by TNO, are the cost-effectiveness and the possibility to use the homologation test results as a reference. With the Euro 3 legislation coming into effect, new testcycles with transient elements are added to the homologation procedure, where previously it was only a stationary testcycle. As a result of this, the test methodology used so far no longer applies to the whole procedure. Because it is anticipated that emissions from HD vehicles in the near future are increasingly related to transient engine behaviour, a transient testcycle is also important for IUC purposes. This paper will identify and assess alternative options for future practical IUC testing on the basis of the aims and demands for the Dutch IUC programme. Apart from this assessment, a brief overview is presented of the results obtained so far by this programme.