The European Commission today published a recommendation to improve the periodical technical inspection of vehicles. With road transport being the largest source of air pollution in cities, accurate testing is key to ensure that vehicles are in line with emission standards throughout their lifetime. Harmonised testing also ensures fair competition amongst manufacturers. As current testing methods are not adapted to more recent vehicles equipped with particle filters, they cannot ensure that vehicles with defective or tampered diesel particulate filters are detected during inspections. Certain Member States have therefore introduced or will soon introduce particle number (PN) measurement as part of their inspections. While those methods are similar, they however differ in certain aspects. (....)