MOT testers pass 2.9 million unroadworthy cars
Research reveals there could be 2.9 million unroadworthy and potentially dangerous cars being driven on the UK’s roads...
More than one in 10 (10.7%) cars that passed their MOT last year should have failed, because garages failed to uphold Government testing standards, a What Car? investigation has revealed.
With 26.7 million used cars over three years old that need an MOT test every year, that means there could be 2.9 million vehicles being driven on UK roads with potentially dangerous defects.
These figures are based on the findings of an annual Driver and Vehicle Standards Agency (DVSA) report, which we obtained via a Freedom of Information request.
As part of its 2023-2024 MOT Compliance Survey, a team of DVSA expert examiners retested a randomly selected sample of 1487 used vehicles at the sites where the vehicles were originally assessed.
The aim of these annual inspections is to establish if the correct test standards are being applied. But the DVSA examiners disagreed with the MOT test outcomes in 13.7% of instances, saying that 3% of the cars that had failed were actually worthy of a pass certificate, and that 11% of the cars passed by MOT testers should have failed.
These numbers are slightly lower than those from the MOT compliance retesting done in 2022-2023, when the overall discrepancy with MOT tests was 14.4%. However, in the latest set of retesting the number of cars that should have passed the test but failed is higher, rather than too many unroadworthy cars being given an MOT pass.
MOT test error data by year
| Year | % of cars that passed MOT test that should have failed | % of cars that failed MOT test that should have passed |
| 2023-2024 | 10.7% | 3.0% |
| 2022-2023 | 12.2% | 2.2% |
| 2021-2022 | 10.1% | 2.1% |
Worryingly, 55% of the cars where the MOT test result was disputed had three defects that the retesters didn’t think had been classified correctly. Among the other cars where the MOT test result was deemed incorrect, 20% had two faults where opinions disagreed and 25% had one area that was disputed.
The most commonly overlooked MOT test fail items were tyres, suspension and brakes, all of which are safety-critical components. MOT testers didn’t apply the correct test standard relating to tyre condition in 53% of cases; that’s 731 of the cars examined. Defects with suspension were incorrectly diagnosed on 678 vehicles, and 629 MOT tester decisions relating to brakes were deemed incorrect by the testers.
Most common areas where DVSA disagreed with MOT test station
| Defect category | Number of defects disagreed |
| Tyres | 731 |
| Brakes | 678 |
| Suspension | 629 |
| Lights, reflectors and electrics | 392 |
| Non-component advisories | 157 |
| Visibility | 147 |
| Noise, emissions and leaks | 135 |
| Body, chassis and structure | 127 |
| Steering | 59 |
| Vehicle identification | 50 |
| Seatbelts | 40 |
| Wheels | 25 |
The DVSA took action against some of the garages that were found to not be sticking to the correct MOT test standards. It instigated disciplinary actions against 14 garages and wrote 67 advisory warning letters to others. However, not all MOT test errors resulted in disciplinary outcomes, and no action was taken in 123 cases where the examiners believed the errors to be marginal.
About the report author
Claire Evans has been a motoring journalist for more than 30 years, and has focussed on consumer issues for much of that time. She was the advice columnist for Carweek magazine in the 1990s, helping car owners with faulty cars get the right level of reparation from car makers.
She also spent six years working on motoring content for Which?, and it is here she oversaw the running of the charity's annual used car reliability survey.
Claire launched the What Car? Reliability Survey in 2017, and since then has helped thousands of buyers choose the most reliable new cars and SUVs, as well as the most dependable used cars.
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