The vehicles that really fail their MOT most, once you allow for age
Direct answer. On 2024 DVSA data, corrected for how old each fleet is, the vehicle family that fails its MOT most often in Britain is the Mercedes Citan, with a MOT Risk Index of 189.5. That is about 90% more failures than its age profile predicts. The surprise is what sits alongside it: eight of the ten worst performers are vans, not cars.
Why the usual “worst cars for MOT” lists are really lists of old cars
Every year a fresh round of headlines names the models most likely to fail their MOT. Look closely at those tables and the same thing is happening in all of them: they rank by the raw share of tests that ended in a failure, and nothing else.
On the 2024 data that produces a very predictable top five. The Peugeot 307 fails 52.22% of its initial tests, the Chevrolet Aveo 51.61%, the Citroen Xsara 51.07%. These are not damning verdicts on Peugeot, Chevrolet or Citroen. They are statements about age. A car still being presented for its MOT in 2024 having been built in the mid-2000s is, by definition, a survivor near the end of its life, and the national data says a vehicle in its nineteenth year fails 42.2% of the time whoever made it.
Rank by raw failure rate and you learn which models are old. To learn which models are bad you have to hold age constant.
The age-adjusted table
The MOT Risk Index does exactly that. It compares each family against what the national fleet of the same age actually does, then expresses the result on a scale where 100 is normal. An index of 150 means half as many failures again as that vehicle’s age predicts. Here are the ten worst on 2024 DVSA initial tests.
| # | Vehicle | MOT Risk Index | Raw failure rate | Tests | Type |
|---|---|---|---|---|---|
| 1 | Mercedes Citan | 189.5 | 37.34% | 29,572 | Van |
| 2 | Toyota Proace | 181.0 | 28.56% | 18,649 | Van |
| 3 | Ford Transit Courier | 169.5 | 28.33% | 38,700 | Van |
| 4 | Citroen C4 Grand Picasso | 164.1 | 28.67% | 24,684 | Car |
| 5 | Ford Transit Custom | 163.8 | 20.91% | 226,933 | Van |
| 6 | Hyundai i800 | 163.8 | 36.52% | 11,880 | Van |
| 7 | Nissan NV200 | 162.9 | 42.90% | 35,020 | Van |
| 8 | Fiat Tipo | 161.0 | 26.42% | 17,929 | Car |
| 9 | Ford Tourneo Custom | 160.5 | 19.32% | 14,209 | Van |
| 10 | Citroen Dispatch | 160.1 | 39.63% | 67,696 | Van |
Notice how far the two columns disagree. The Ford Transit Custom fails only 20.91% of its tests, which would bury it in the middle of any raw table, and it still lands fifth here because its fleet is young. The Peugeot 307, top of every raw list, sits at an index of 128.2: worse than average for its age, certainly, but nowhere near the worst once you stop punishing it for being twenty years old.
The real story is vans, and it is about use rather than build quality
Eight of those ten are light commercial vehicles. That pattern holds well beyond the top ten, and the reason is not that van manufacturers build badly. A van that fails is a van that has done 25,000 hard miles a year, carried weight every day, been kerbed at delivery addresses and had its maintenance deferred because taking it off the road costs its owner money.
The defect data supports that reading. The single most common failure across this group is dull and cheap: a rear registration plate lamp missing or not working, which tops the list for the Citan, the Proace, the i800 and the Dispatch. The Transit Courier, Transit Custom and Tourneo Custom are all led by windscreen damage. These are neglect failures, not design failures, and for a buyer they are a warning about how the previous owner treated the vehicle rather than about the badge on it.
The full ranking of the twenty worst performers, with confidence intervals and the leading defect for each, is published on the MOT Risk Index list of the worst vehicles for MOT failure.
The electric twist most reporting gets backwards
The same correction turns another familiar claim inside out. Electric cars fail 10.8% of their initial MOTs against 20.7% for petrol, which reads as a comfortable win and is quoted as one constantly. But the electric fleet is on average 6.3 years younger. Age-adjusted, electric scores 111.1 against 97.6 for petrol, and at every single year from three to eleven electric cars fail more often than petrol cars of the same age.
The mechanism is tyres. Electric cars record 12.48 tyre defects per 100 tests against 6.99 for petrol cars of the same age, a gap of 79%, which is what you would expect from heavy vehicles with instant torque. The full breakdown by fuel type is at MOT failure rates for electric cars.
How to read an index like this
The MOT Risk Index is built from DVSA initial test results for calendar 2024, which is every first-attempt MOT in Great Britain rather than a sample. Retests are excluded, because a vehicle that fails and is fixed the same afternoon would otherwise be counted twice. Families whose margin of error includes 100 are left out of the ranking entirely, so nothing appears here on the strength of a small sample.
What the index will not tell you is whether the specific vehicle in front of you is sound. It is a statement about a population, and populations contain well-kept examples of terrible performers. Used sensibly it does one job well: it tells you which vehicles need a harder look before you hand over the money, and which of the failures you should expect to find are cheap to put right.
