Stricter MOT test doubles emissions failure rate

May changes introduced more stringent emissions testing.


Changes to MOT emissions testing has seen the number of cars failing more than double since being introduced earlier this year.

In May 2018, emissions testing within the overall MOT test became more stringent — with smoke of any colour coming from the exhaust resulting in an automatic failure. Automatic failure also applies to any car showing evidence of a diesel particulate filter (DPF) that’s been tampered with.

Six months on, and new Driver & Vehicle Standards Agency (DVSA) figures show 744,592 cars have failed the MOT emissions test — a sharp rise from 350,472 for the same 20th May to 19th November period in 2017.

Diesel cars failing in droves

Of those failed cars, 505,721 were petrol powered — up from 292,468 — while diesel saw a meteoric rise from 58,004 to 238,971 failures.

Meanwhile, the rise in vans failing emissions testing increased from 3,585 in the same time frame to 19,468 — a 448% increase.

Commenting on the figures Gareth Llewellyn, DVSA chief executive, said that the agency’s priority is to protect everyone from unsafe vehicles and drivers. “We are committed to making a real difference to those in society whose lives and health are blighted by poor air quality,” he added.

“Since introducing the new tighter MOT emissions test in May, nearly 750,000 vehicles have been taken off the road or fixed,” Llewellyn said.

Overall MOT failure rates remain steady

Despite the large increase in cars failing on grounds of emissions, the failure rate for the MOT test remains steady since the changes were introduced.

34.7% of petrol cars failed between May 20 and November 19, 2018, a slight drop from 35.7% for the same period in 2017, while diesels saw a marginal decrease from 33.8% to 33.2%.

Andrew Charman
Andrew Charman
Andrew is the News and Road Test Editor for The Car Expert. He is a member of the Guild of Motoring Writers, and has been testing and writing about new cars for more than 20 years. Today he is well known to senior personnel at the major car manufacturers and attends many new model launches each year.

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  1. I bought a car about 5 -6 weeks ago from a large car dealership, when i bought it
    they serviced it (basic) & put on a fresh Mot at their in house Mot station.
    It was due a Gearbox service so I booked it in for the work. When i came to collect it the garage told me i twas missing 2 secondary cats which make up a vital part of the emission equipment on the car & makes the MOT invalid. The Mot rules state it has to have all the catalytic converters in place & untampered with in any way as it left the factory or its an automatic failure regardless of the readings etc. He said tell them its not fit for purpose & get a refund or new cats refitted…

    I contacted the garage ,which is a very large dealership, & after a bit of twoing & froing they asked me to get a quote for the replacing of the cats.
    I did this , in fact I gave them two quotes ,one from a main dealer & another from a Specialist in this brand of car.

    The Manager phoned me & said I could have a full refund of £18500 or a 50% contribution towards the cost of purchasing & fitting the parts.
    Now I would prefer to keep the car but if it did go back I have spent quite a bit on the car ie Insurance ,Tax ,the service that was overdue & really necessary .
    They said they would not pay these extras.
    I queried the offer of a £750 contribution when the two quotes that I sent at their request were £1997 & £1767,apart from the fact that they should never have sold this car as its not legal to be on the road & is against the law to sell a car that has had its emissions tampered with. Also compounded that they ran it through here own MOT station & it a passed 2 days prior to my purchase.

    I have contacted VOSA who gave me this advice.

    What are my rights regarding them paying more than the £750 towards the £1767 ? Also if return the car all the tax,Insurance ,service loss etc on top of the £18500 I paid them cash?
    many thanks


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