Original research
What actually fails an MOT around here
We read DVSA's published MOT records for 210,390 car tests carried out in the Cambridge (CB) postcode area during 2025, plus 124,130 of those cars matched back to their 2024 test, and counted what failed and what testers warned about. Every figure below is ours, computed from the raw files rather than taken from anyone's summary, and every percentage is shown with the count behind it.
Source: SV Autos research, 2026-09-23, from DVSA anonymised MOT test results 2025. The dataset is free and public, so anyone can check this.
James Snow, owner and mechanic, SV Autos
Six years working on cars, based in Soham. Analysis computed 2026-09-23 and last reviewed 2026-09-23. If a figure here is wrong, tell us and we will correct it.
What an advisory actually is
An MOT has three outcomes that matter here. A fail means the car is not legal to drive until it is fixed. An advisory means it passed, but the tester noticed something heading that way and printed it on the certificate. A dangerous defect is a fail the tester judged an immediate risk. Most of what follows is about the middle one, because it is the one people ignore.
The ten commonest reasons a car failed
Counted per car, so a car failing on two things appears in two rows. Shares are of the cars that failed, not of all cars tested.
| Defect | Cars | Share of failures |
|---|---|---|
| A tyre seriously damaged | 8,939 | 15% |
| The aim of a headlamp is not within limits laid down in the requirements | 7,683 | 12.9% |
| A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning | 5,976 | 10% |
| A suspension pin, bush or joint excessively worn | 5,829 | 9.8% |
| Windscreen washers not working or not providing sufficient fluid to clear the windscreen | 4,875 | 8.2% |
| A spring or spring component fractured or seriously weakened | 4,842 | 8.1% |
| Wiper blade missing or obviously not clearing the windscreen | 4,467 | 7.5% |
| A suspension joint dust cover missing or no longer prevents the ingress of dirt etc | 3,681 | 6.2% |
| A tyre cords visible or damaged | 3,420 | 5.7% |
| Tyre tread depth not in accordance with the requirements | 3,341 | 5.6% |
What an advisory one year predicts the next
Cars tested in both 2024 and 2025, comparing those warned about something with those that were not. The right-hand column is what makes the left-hand one mean anything.
| Advised on this in 2024 | Cars advised | Failed on it in 2025 | Cars not advised | Failed on it in 2025 |
|---|---|---|---|---|
| Steering | 1,798 | 306 (17.02%) | 122,332 | 1,942 (1.59%) |
| Lamps and electrics | 3,458 | 965 (27.91%) | 120,672 | 13,603 (11.27%) |
| Suspension | 19,527 | 3,361 (17.21%) | 104,603 | 7,384 (7.06%) |
| Brakes | 26,358 | 2,438 (9.25%) | 97,772 | 3,820 (3.91%) |
| Tyres | 35,595 | 4,164 (11.7%) | 88,535 | 5,699 (6.44%) |
How failure rises with age
Age is taken from the date of first use. Bands with fewer than 500 tests are left out.
| Age | Tests | Failed | Failure rate |
|---|---|---|---|
| 2 to 3 years | 17,715 | 2,356 | 13.3% |
| 4 to 5 years | 22,650 | 3,399 | 15% |
| 6 to 7 years | 28,375 | 5,368 | 18.9% |
| 8 to 9 years | 32,362 | 7,879 | 24.3% |
| 10 to 11 years | 29,263 | 8,895 | 30.4% |
| 12 to 13 years | 22,522 | 8,136 | 36.1% |
| 14 to 15 years | 19,091 | 7,765 | 40.7% |
| 16 to 17 years | 13,733 | 5,927 | 43.2% |
| 18 to 19 years | 9,954 | 4,263 | 42.8% |
| 20 years or older | 14,504 | 5,739 | 39.6% |
Small and medium vans against cars
Vans are identified by model name, so a few passenger versions of the same vehicle are in the van column. Large 3.5 tonne vans are tested in a different class and are not counted here.
| Vans | Cars | |
|---|---|---|
| Failed the MOT | 4,095 of 11,279 (36.3%) | 55,652 of 199,111 (28.0%) |
| Failed on lights or electrics | 2,023 of 4,095 (49.4%) | 21,766 of 55,652 (39.1%) |
| Average age | 10.0 years | 10.7 years |
What this does not show
This is one year in one postcode area, not a census and not a national picture. It is directional, and the smaller the group in a row the less weight it carries.
CB is not Cambridgeshire. The Cambridge postcode area takes in Newmarket and Haverhill in Suffolk and Saffron Walden in Essex, and it leaves out Peterborough, Huntingdon, March and Wisbech, which are all Cambridgeshire. Nothing here may be read as a county figure, and nothing may be attributed to a single town: the data records the postcode area of the test, nothing finer.
An advisory does not cause a failure. Both follow from the condition of the car. And MOT failure is not reliability: a car failing on a bulb says as much about how it was looked after as about how it was built.
Of the cars tested in 2024, about a third did not appear again in 2025. They were sold, scrapped, untested that year or re-registered, and this data cannot tell those apart.
Got an advisory sitting on your certificate?
The table above is the reason it is worth dealing with before next year's test. Send us the certificate and we will tell you which items actually need doing and roughly what each one costs, at your home or work across Soham, Ely, Newmarket and Cambridge.
Related: MOT advisories explained, what is checked in an MOT, our pre-MOT check, van servicing.