Call for stricter diesel emissions MOT Tests for illegally tampered diesels

Posted on June 24th, 2021 by Rob Marshall

Call for stricter diesel emissions MOT Tests for illegally tampered diesels

The Westminster Commission for Road Air Quality (WCRAQ) is calling for the MOT to include a diesel particulate filter (DPF) efficiency test, in a bid to rid UK highways of cars that have had their anti-pollution systems tampered with illegally.


DPF trap carbon particulates, which are known carcinogens, hindering them from being expelled into the atmosphere. Engine faults, poor maintenance, or frequent short journeys cause them to block. Instead of fixing the problem, some unscrupulous individuals destroy the DPF’s internal monolith structure, so that it can no longer trap soot. Instead, it simply expels the particulates into the atmosphere. The current MOT Test comprises a visual test only but it can be difficult, if not impossible, to identify a DPF that has had its innards removed by just looking at it fitted to the car.


The WCRAQ estimates that 10% of diesel cars have DPFs that are either damaged, faulty, or boast illegal modifications. It is calling on the government to follow the Dutch example, where an examination of DPF efficiency has been included in the Netherlands’ version of the MOT Test from July 2022.


Using research that was carried out in the Netherlands, implementing a DPF efficiency test at MOT time could prevent 1,000 tones of PM2.5 particulate matter from being expelled into the air.


The Associate Professor at the University of Leeds and WCRAQ Chair of Research, Dr James Tate, explained that:


“We fear a significant amount of the very fine particles from diesel combustion are now coming from damaged or tampered DPFs. They shouldn’t be in the air we all breathe. The testing equipment technology to identify failing DPFs is available for a reasonable cost, and the UK should make it an absolute priority to tighten diesel MOT testing in the shortest possible time.”