{"schemaVersion":"1.0","id":"what-london-cars-fail-on","dataset":"mot-failure-systems","title":"What London cars fail on","description":"Brakes, suspension, tyres, lamps and every other recorded reason class 4 vehicles fail an initial MOT.","methodology":"DVSA's separate failure-item archive joined by test ID to class 4 initial tests for vehicles kept in the eight London postal areas. Retests and the twelve boundary-straddling postcode areas are excluded. Counts are REASON-FOR-REJECTION RECORDS, not vehicles: one test can contain several defects, minor items and advisories, so records cannot be added and described as the number of cars failing. The main ranking includes failed items only; the severity view separately retains advisory, minor, major and dangerous inspection records. Current DVSA item-detail and hierarchy lookups assign each record to its published inspection system. Changes to the MOT regime in 2018 limit long-run comparison.","category":"transport","categoryLabel":"Transport","cadence":"annual","placeholder":false,"landingPage":"https://londongraph.com/g/what-london-cars-fail-on","markdown":"https://londongraph.com/g/what-london-cars-fail-on/index.html.md","source":{"name":"DVSA","url":"https://open.data.dvsa.gov.uk/mot-anonymised/index.html","licence":"Open Government Licence v3.0","licenceUrl":"https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/"},"observations":null,"areaStatistics":null,"visualizations":[{"id":"systems","label":"Failure systems","description":"Rank published inspection systems by recorded failure items in each annual extract.","url":"https://londongraph.com/g/what-london-cars-fail-on","renderer":"primary","default":true,"timeControl":"inherit","datasets":[],"transform":null,"controls":null,"metrics":[],"caveat":null},{"id":"severity","label":"Severity","description":"Keep advisory, minor, major and dangerous inspection-item records visibly separate.","url":"https://londongraph.com/g/what-london-cars-fail-on?view=severity","renderer":"composition-bars","default":false,"timeControl":"inherit","datasets":["mot-failure-severity"],"transform":null,"controls":null,"metrics":[],"caveat":null},{"id":"system-severity","label":"System × severity","description":"Cross each inspection system with severity in the latest joined release.","url":"https://londongraph.com/g/what-london-cars-fail-on?view=system-severity","renderer":"matrix","default":false,"timeControl":"inherit","datasets":["mot-failure-system-severity"],"transform":null,"controls":null,"metrics":[],"caveat":"Cells count inspection-item records, not unique vehicles."},{"id":"details","label":"Detailed reasons","description":"Use a treemap for the forty most frequently recorded detailed failure reasons.","url":"https://londongraph.com/g/what-london-cars-fail-on?view=details","renderer":"treemap","default":false,"timeControl":"inherit","datasets":["mot-failure-details"],"transform":null,"controls":null,"metrics":[],"caveat":"A vehicle can contribute several failure reasons during one test."}],"availability":"metadata-only","note":"No observation series is available from this deployment. The source and methodology metadata remain authoritative."}