Almost 1.3m cars failed MOT emissions checks last year as stricter exhaust assessments since 2018 see diesel failure rates surge 240%
- Tougher emissions checks were introduced to the MOT test in May 2018
- Diesel car with particulate filters fails if it has been removed or tampered with
- Vehicles will automatically fail the test if check find smoke coming from exhaust
- Since the new rules were introduced, MOT failure rates for all cars are up 70%
The introduction of new emissions checks as part of the updated MOT test has seen a spike in UK vehicles automatically flunk the assessment due to what is coming out of their exhausts.
Almost 1.3 million vehicles in total failed MOTs for emissions in the previous 12 months, which is 70 per cent higher than before the tougher checks were put in place in May 2018.
And it’s diesel cars that are suffering the most, with over 420,000 being pulled up on emissions in 2019/20 – up 240 per cent on 2017/18, research has revealed.
Tougher emissions assessments as part of the revised MOT test has see failure rates for diesel cars in particular surge in the last two years, new data shows
While emissions-related failure rates had risen most for diesels, there were more cases for unleaded cars last year.
Almost 850,000 petrol vehicles were automatically failed in the their annual check-up because of emissions.
The tougher rules applied almost three years ago include automatic failures for any diesel car with a particulate filter that’s been tampered with or removed and a mechanic can instantly refuse to pass a car if they witness smoke of any colour coming out of an exhaust pipe.
The additional checks and tougher treatment came into force in May 2018 as part of wider efforts to improve air quality following the VW emissions cheating scandal.
It also came in response to many drivers using specialist firms to remove DPFs from the exhaust systems of their cars after many experienced the filters becoming clogged up and blocked by soot and other pollutants – which in turn reduced the performance of their vehicles.
| Financial Year | Diesel failures | Petrol failures | Total failures |
|---|---|---|---|
| 2015-2016 | 118,302 | 748,465 | 868,115 |
| 2016-2017 | 122,838 | 690,247 | 814,684 |
| 2017-2018 | 123,596 | 620,247 | 745,308 |
| 2018-2019* | 397,991 | 910,620 | 1,311,841 |
| 2019-2020 | 420,537 | 849,740 | 1,273,771 |
| Class 4 annual MOT failures due to an emissions related fault *New MOT regulations introduced from 20th May 2018 Source: FOI request to DVSA by BookMyGarage.com |
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The tougher MOT rules applied almost three years ago include automatic failures for any diesel car with a particulate filter (DPF) that’s been tampered with or removed and a mechanic can instantly refuse to pass a car if they witness smoke of any colour coming out of an exhaust pipe
It is now illegal for anyone to remove a DPF from a car that had it fitted from new by the factory.
The increase in failure rates was revealed following a Freedom of Information request by to the DVSA by BookMyGarage.com.
The MOT and service price comparison site found more cars have failed on emissions in the last two years than any other before it.
‘The regulations have mostly impacted diesel cars, causing more than triple the number to fail, compared to petrol car failures which have only increased by a third,’ said Jessica Potts, head of marketing at BookMyGarage.
DPFs became standard on all diesel cars in 2009 to comply with Euro 5 emissions standards, though a few cars older than this may also be equipped with a DPF.
New emissions-related checks were added to the MOT test in 2018 in a bid to reduce the polluting impact of diesel cars in particular
DVSA also introduced new fault categories in 2018, with emissions issues resulting in major or dangerous faults. These lead to an automatic failiure
DVSA also introduced new fault categories in May 2018, with ‘Major’ or ‘Dangerous’ faults resulting in a failed test.
Almost all petrol emissions failures were classed as ‘Major’ last year.
By comparison, around five per cent of all diesel emissions failures were classed as ‘Dangerous’, meaning the car should not be driven until the fault is rectified.
Jessica added: ‘Since the Volkswagen “dieselgate” scandal in 2015, diesel cars have earned a bad reputation for producing harmful exhaust emissions.’
According to the SMMT, the market share of diesel cars accounted for just 16 per cent of new car sales last year. In 2015, around half of all new cars sold were diesels.
Although diesels have seen a much larger failure rate increase in recent years, petrol cars are still more likely to fail, with 4.5 per cent of the total number licenced failing annually due to emissions, compared to 3.3 per cent for diesels.
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