Why more cars fail their MOT for certain faults in winter
Lamps, reflectors and electrical equipment failures peak in January at 51.0% of failed tests, against a low of 47.7% in March — the overall pass rate barely moves, but what breaks changes with the season.
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“Lamps, reflectors and electrical equipment failures peak in January (51.0% of failed tests) versus a low of 47.7% in March.”
Overall MOT pass rate by month
Note the zoomed y-axis — the overall pass rate moves only a few points across the year.
Lamps, reflectors and electrical equipment: peaks in January
Lamps, reflectors and electrical equipment is behind 51.0% of failed tests in January, against 47.7% in March — a swing of 3.3 percentage points across the year.
Visibility: peaks in April
Visibility is behind 17.3% of failed tests in April, against 14.3% in October — a swing of 3.0 percentage points across the year.
Brakes: peaks in February
Brakes is behind 34.2% of failed tests in February, against 31.2% in December — a swing of 3.0 percentage points across the year.
The data, month by month
| Month | Pass rate | Tests | Top failure category |
|---|---|---|---|
| January | 78.2% | 4,849,011 | Lamps, reflectors and electrical equipment |
| February | 79.2% | 4,594,352 | Lamps, reflectors and electrical equipment |
| March | 80.4% | 5,131,813 | Lamps, reflectors and electrical equipment |
| April | 79.3% | 3,899,296 | Lamps, reflectors and electrical equipment |
| May | 80.2% | 3,841,836 | Lamps, reflectors and electrical equipment |
| June | 80.1% | 3,986,229 | Lamps, reflectors and electrical equipment |
| July | 79.2% | 4,347,186 | Lamps, reflectors and electrical equipment |
| August | 79.4% | 4,207,672 | Lamps, reflectors and electrical equipment |
| September | 79.9% | 4,823,562 | Lamps, reflectors and electrical equipment |
| October | 78.1% | 5,040,265 | Lamps, reflectors and electrical equipment |
| November | 78.0% | 4,360,752 | Lamps, reflectors and electrical equipment |
| December | 79.1% | 3,163,951 | Lamps, reflectors and electrical equipment |
Methodology and data source
- Source: DVSA “Anonymised MOT tests and results”, data.gov.uk, under the Open Government Licence v3.0.
- Coverage: Full year 2024, test class 4 (cars), normal (initial) tests only.
- The overall pass-rate chart isn't age-adjusted month to month — which cars are tested in a given month is mostly about registration-date timing, not a seasonal change in the fleet, so no age confound applies here the way it does across makes or areas.
- A failure category only appears in the seasonal ranking if it had enough tests to clear the sample floor in at least 8 of the 12 months — categories with patchy monthly data are excluded rather than shown with a noisy swing.
- Category shares are of failed tests within that month, not of all tests — this isolates 'what breaks when it breaks', separate from the overall pass rate.
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Frequently asked questions
- Do more cars fail their MOT in winter?
- The overall pass rate moves only a little across the year, but individual failure categories swing much more. Lamps, reflectors and electrical equipment failures are most common in January (51.0% of failed tests) and least common in March (47.7%).