Glossary

Every term used in the data, defined in plain English. How the numbers are computed is covered in the methodology; how to read them, in the FAQ.

MOT test: The annual roadworthiness inspection required for most road vehicles in Great Britain over three years old, run under DVSA rules.
Normal test: A bike's scheduled MOT inspection. All statistics here use normal tests only — retests, aborted and abandoned tests are excluded.
First-time pass rate: The share of normal tests passed at the first attempt with nothing to fix. The headline reliability number throughout this site.
Pass after rectification (PRS): A pass where a defect was found but fixed during the same visit. Counted separately from a clean first-time pass.
Outright fail: A test that ended in failure — the bike left needing work and a retest.
Advisory: A wear item the tester flags for future attention. Advisories do not fail a test and are excluded from all failure statistics here.
Defect: A recorded reason for failure, catalogued against a DVSA inspection item. One failed test can record several defects.
Component group: The DVSA inspection section a defect belongs to — lighting and signalling, brakes, steering and suspension, tyres and wheels, and so on. Failure tables group defects this way.
Test class 1 / class 2: The two motorcycle MOT classes: class 1 for machines up to 200cc, class 2 for everything larger, including sidecar outfits.
Engine capacity (cc): Engine displacement in cubic centimetres, as recorded at test. Used here to band bikes: 125s, A2-friendly 250–500cc, litre-plus.
Median mileage: The odometer reading of the middle bike at test — half read more, half less. Preferred to the average, which a few extreme odometers would distort.
Registration-year cohort: All bikes of a model first registered in the same year, tracked as a group. Cohort pass rates reveal a model's best and worst years.
Survivor bias: The tendency of the oldest cohorts to score well simply because the badly-kept examples already left the road. Read very old cohorts with this in mind.
Model family: Tester-entered model names are free text ("MT", "WW"), so this site groups them into canonical families using engine size and naming rules — the MT-07 and MT07 are one family.
First use date: The date a bike first entered service, from which its registration year and age at test are derived.
Test year: The calendar year a test happened. Trend charts plot pass rate by test year.
DVSA: The Driver and Vehicle Standards Agency — the UK body that runs the MOT scheme and publishes the anonymised results dataset this site is built on.

Statistics on this site are licensed CC BY 4.0 — cite bikereliability.co.uk and link the claim. Source data: DVSA anonymised MOT results, OGL v3.0.