Which London fails its MOT

Methodology

DVSA's anonymised MOT test extract, one row per test, aggregated by the postcode area of the vehicle keeper. Class 4 only — cars and light vans, about 95.6% of all tests; motorbikes, coaches and heavier goods vans are excluded rather than folded into a figure described as being about cars. INITIAL TESTS ONLY: 15.8% of rows are retests, where a car returns after repair and passes far more often, so including them would measure how many owners fix their cars rather than how many cars were roadworthy. A pass counts P and PRS together — PRS is 'Pass with Rectification at Station', where a defect was fixed during the test — and PRS is also published as its own rate because it has to be read separately. PRS is a test-centre decision, and it varies far more between areas than outright failure does: across London areas it ranges from about 4% to about 11% of initial tests. A meaningful part of the spread between the best and worst areas here therefore reflects what garages choose to fix on the spot, not how roadworthy the cars arrived. Compare the failure rate alongside the pass rate before drawing a conclusion about an area's vehicles. Abandoned, aborted and refused tests leave the denominator. THE GEOGRAPHY IS NOT A LONDON BOUNDARY: eight areas (E, EC, N, NW, SE, SW, W, WC) are the London postal district and are London by definition; twelve more (BR, CR, DA, EN, HA, IG, KT, RM, SM, TW, UB, WD) cover outer London suburbs but spill into Surrey, Kent, Essex and Hertfordshire. Those are marked as fringe and are never summed into any London figure. EC and WC are absent rather than empty: almost nobody keeps a vehicle registered in the City or Holborn, so neither area reaches a reportable number of tests. A postcode area records where the vehicle is kept, not where it was tested. Mileage is the total odometer reading at the test, not an annual figure, and readings at or below 100 or at or above 400,000 miles are dropped as unrecorded or mistyped rather than treated as real. Coverage begins in 2024: DVSA's 2022 and 2023 archives use a different compression and an older column layout, and are excluded rather than approximated.