73 Auto Research · MOT statistics
Dangerous MOT defects: how many cars have them and what they are
7.9% of MOT tests in Great Britain in 2023–24 found at least one dangerous defect — 5,141,819 of 65,477,892 DVSA tests. The commonest was “Tread depth: tread depth below requirements of 1.6mm”, and tyres was the area with the most dangerous-defect tests.
Source: DVSA anonymised MOT data, 2023-01-01 to 2024-12-30 (n = 65,477,892 tests). Download the data (CSV)
Data to 2024-12-30 · Page updated 2026-09-28 · Publisher: 73 Auto
Key findings
- DVSA data5,141,819 MOT tests in 2023–24 found at least one dangerous defect: 7.9% of all tests, about 1 in 13 (DVSA data).
- DVSA dataThe most common dangerous MOT defect was “Tread depth: tread depth below requirements of 1.6mm”, on 1,598,898 tests in 2023–24 (DVSA data).
- DVSA dataTyres accounted for more dangerous-defect tests than any other area: 3,164,027, or 61.5% of tests with a dangerous defect (DVSA data).
- DVSA data4.2% of MOT tests on 3-year-old cars found a dangerous defect, rising to 10.9% at 15 years (DVSA data, 2023–24).
- 73 Auto analysisAllowing for age, mileage and fuel, SsangYong cars had dangerous defects at 1.56 times the rate of comparable cars and Aston Martin at 0.31, the extremes of 45 makes (73 Auto analysis).
At a glance
| Figure | Value | Basis | Type |
|---|---|---|---|
| Tests with a dangerous defect | 5,141,819 | of 65,477,892 tests | DVSA data |
| Share of tests | 7.9% | 2023–24 | DVSA data |
| At 3 years / at 15 years | 4.2% / 10.9% | n = 3,907,416 / 2,510,983 | DVSA data |
Official data
Counts and rates taken directly from DVSA's MOT records: 73 Auto counted them, but applied no model or adjustment.
Dangerous defects by test area
DVSA data
| Area | Tests with a dangerous defect here | Share of all tests | Share of dangerous-defect tests |
|---|---|---|---|
| Tyres | 3,164,027 | 4.83% | 61.5% |
| Brakes | 1,719,912 | 2.63% | 33.4% |
| Suspension | 331,323 | 0.51% | 6.4% |
| Body, chassis and structure | 122,425 | 0.19% | 2.4% |
| Lights, reflectors and electrical | 92,674 | 0.14% | 1.8% |
| Steering | 65,804 | 0.10% | 1.3% |
| Road wheels | 47,626 | 0.07% | 0.9% |
| Seat belts and airbags | 22,069 | 0.03% | 0.4% |
| Noise, emissions and leaks | 21,595 | 0.03% | 0.4% |
| Driver's view of the road | 8,616 | 0.01% | 0.2% |
The most common dangerous defects
DVSA data
Dangerous defects by age
DVSA data
| Age at test | Tests | Dangerous defect |
|---|---|---|
| 3 years | 3,907,416 | 4.2% |
| 4 years | 4,633,623 | 5.0% |
| 5 years | 4,808,669 | 5.8% |
| 6 years | 5,056,332 | 6.4% |
| 7 years | 5,283,534 | 6.8% |
| 8 years | 5,152,384 | 7.4% |
| 9 years | 4,706,087 | 8.1% |
| 10 years | 4,163,623 | 8.8% |
| 11 years | 3,650,413 | 9.4% |
| 12 years | 3,355,332 | 10.0% |
| 13 years | 3,175,830 | 10.4% |
| 14 years | 2,802,860 | 10.6% |
| 15 years | 2,510,983 | 10.9% |
| 16 years | 2,298,708 | 11.0% |
| 17 years | 1,826,895 | 10.9% |
| 18 years | 1,392,716 | 10.8% |
| 19 years | 1,063,140 | 10.5% |
| 20 years | 793,834 | 10.1% |
Dangerous defects by mileage
DVSA data
| Recorded mileage | Tests | Dangerous defect |
|---|---|---|
| under 40k | 14,349,525 | 3.9% |
| 40k-80k | 23,289,005 | 7.4% |
| 80k-120k | 15,109,795 | 10.3% |
| 120k+ | 9,784,104 | 12.0% |
73 Auto analysis
Figures 73 Auto derived from the same records: adjusted ratios, intervals and rankings, explained in the method below.
Dangerous defects by fuel, ages 3–10
73 Auto analysisThe rate is a DVSA count; the ratio (73 Auto analysis) compares it with the national rate for tests of the same age and mileage band.
| Fuel | Tests | Dangerous defect | Vs same age and mileage |
|---|---|---|---|
| Petrol | 19,069,451 | 5.9% | 1.02 |
| Diesel | 16,627,244 | 7.7% | 1.00 |
| Hybrid | 1,473,950 | 4.4% | 0.72 |
| Electric | 330,180 | 6.3% | 1.26 |
Makes with the lowest and highest dangerous-defect ratios
73 Auto analysisFive lowest and five highest of 45 makes with 20,000+ tests, adjusted for age, mileage and fuel.
| Make | Tests | Dangerous defect | Vs similar cars |
|---|---|---|---|
| Aston Martin | 43,571 | 1.5% | 0.31 |
| Bentley | 44,444 | 2.6% | 0.46 |
| Porsche | 346,550 | 3.4% | 0.51 |
| Subaru | 120,127 | 5.7% | 0.64 |
| London Taxis International | 28,414 | 7.9% | 0.71 |
| Kia | 1,822,129 | 8.2% | 1.21 |
| DS | 86,532 | 7.5% | 1.25 |
| Chevrolet | 123,727 | 11.3% | 1.32 |
| Tesla | 129,232 | 10.3% | 1.51 |
| SsangYong | 47,647 | 10.2% | 1.56 |
Method
Source: DVSA's anonymised MOT tests and results for 2023-01-01 to 2024-12-30, published under the Open Government Licence v3.0. 73 Auto counted every record itself; no figure is taken from a secondary report.
Scope: class 4 vehicles (cars and light vans), normal tests only (retests excluded), vehicles at least 2.5 years old at test, whose make matches 73 Auto's vehicle catalogue: 65,477,892 tests in 2023–24.
First-time pass rate: the share of normal tests with the result Pass. A test where a defect was fixed at the station and the car passed the same day (PRS, pass after rectification) counts as an initial fail, as DVSA counts it.
Failure areas and items: a test counts once for an area or item if it had at least one fail-level (Major or Dangerous, or pre-2018 fail) defect in it, however many locations were affected. Advisories and minor defects are not failures.
A dangerous defect is DVSA's highest deficiency category since May 2018: the vehicle is a direct and immediate risk to road safety or the environment and must not be driven until repaired. A test counts once however many dangerous defects it had.
Adjusted ratio (observed ÷ expected, O/E): indirect standardisation. Each test is given the national failure rate for tests of the same age in whole years, mileage band and fuel; summing those gives the failures a group would have had if it failed like the average comparable car. O/E = actual failures ÷ expected failures, so 1.00 is average for comparable cars and 0.80 means 20% fewer failures. It removes most of the effect of an older or higher-mileage fleet, not differences in how cars are looked after.
Publication test: At least 100,000 tests with a dangerous defect; makes with 20,000+ tests. Tests with a dangerous defect: 5,141,819 (minimum 100,000).
Limitations
Pre-May-2018 defect codes had no 'dangerous' grade; a small number of tests recorded against the old codes cannot show one.
An MOT result records a car's condition on test day. Servicing, owners' habits, annual mileage and where the car is driven all affect it, so a low failure rate is not proof of mechanical reliability or build quality.
Citing this study
Cite as: 73 Auto, “Dangerous MOT defects: how many cars have them and what they are”, 2026-09-28, https://73auto.com/research/dangerous-mot-defects-statistics. Based on DVSA anonymised MOT tests and results, Open Government Licence v3.0. The data behind every table is free to reuse with attribution.
More MOT studies
- UK MOT statistics 2023–24 · 28.5% of UK MOT tests in 2023–24 did not pass first time: 18,656,905 of 65,477,892 tests (DVSA data).
- Which car makes fail the MOT most? A ranking adjusted for age and mileage · Of the 21 car makes with over a million MOT tests in 2023–24, BMW cars failed 24% less often than comparable cars of the same age, mileage and fuel (73 Auto analysis of 3,694,719 DVSA tests).
- The cars that fail the MOT least and most, class by class · Of 190 models with 20,000+ MOT tests, the BMW M3 had the lowest failure ratio against cars of the same age, mileage and fuel (0.41, 31,544 tests, 2023–24).
- How MOT pass rates fall with age and mileage · 87.1% of 3-year-old cars passed their first MOT first time in 2023–24, against 67.5% of 10-year-old cars (DVSA data, 3,907,416 and 4,163,623 tests).
- The most common reasons cars fail the MOT · The most common reason for failing an MOT in 2023–24 was “Position lamp: not working”, found on 2.6% of all tests (1,684,901 tests, DVSA data).
- Which MOT failures rise most as cars get older · Steering failures rise the most with age: 0.13% of MOT tests on 3-year-old cars against 3.4% at 15 years, 26 times as often (DVSA data, 2023–24).
- MOT failure rates by test area: brakes, tyres, lights and more compared · Lights, reflectors and electrical is the MOT area cars fail on most: 11.2% of all tests and 39.1% of failed tests (2023–24, DVSA data).
- Petrol vs diesel vs hybrid: MOT pass rates compared · At ages 3–10, 85.6% of hybrid MOT tests passed first time, against 79.6% for petrol and 75.5% for diesel (DVSA data, 2023–24).
- Electric car MOT statistics: how EVs compare with petrol and diesel · 83.5% of MOT tests on electric cars aged 3–10 passed first time in 2023–24, against 79.6% for petrol cars of the same ages (DVSA data, 330,180 EV tests).
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Where these figures come from
- Anonymised MOT tests and results, 2023 and 2024 — Driver and Vehicle Standards Agency (DVSA). Open Government Licence v3.0.
Figures labelled as 73 Auto estimates are our own analysis of these sources, set out in the methodology and data sources. To report a factual error, see corrections.