TNO has carried out an exploratory study on behalf of the Ministry of Infrastructure and Water management into the effectiveness and applicability of a short emissions test to check the functioning of the SCR catalyst during the Periodic Technical Inspection of diesel cars. The result of the research is that a hot idle NOx test can be used to determine that an SCR catalyst no longer works at all. To sufficiently warm up the catalyst, a few minutes' drive on the road is required prior to the test.