{
  "version": "mileage-v1",
  "units": "Annual all-motor vehicle miles unless specified",
  "rows": "LSOA2021 x year, 2021-2024",
  "fields": {
    "lsoa": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "name": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "authority": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "authorityName": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "region": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "year": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "population": "Fixed Census 2021 residents.",
    "density": "Residents divided by LSOA land km2.",
    "urbanFraction": "Population share classified Urban in the inherited RUC2021 OA input.",
    "settlement": "urban_resident when urbanFraction>=0.5, otherwise rural_resident.",
    "roadFrostDays": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "roadDecile": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "roadEligible": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "roadCoverage": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "minorNetworkMetres": "Screened physical minor-road length; not traffic mileage.",
    "majorMiles": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "routedMajorMiles": "Subset of majorMiles allocated by routes passing frozen geometry checks.",
    "preferredMinorMiles": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "benchmarkMiles": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "modelMiles": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "preferredMiles": "Total modelled annual motor-vehicle miles = majorMiles + preferredMinorMiles; blank if official authority exposure unavailable.",
    "minus20Miles": "Total after delta=-0.20 minor-decile weight stress and authority renormalisation; major unchanged.",
    "minus10Miles": "As minus20Miles with delta=-0.10.",
    "plus10Miles": "As minus20Miles with delta=+0.10.",
    "plus20Miles": "As minus20Miles with delta=+0.20.",
    "assignedMotorCollisions": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "nearBoundaryMotorCollisions": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "unassignedMotorCollisionsInRecordedAuthority": "Repeated authority context; never sum across LSOAs.",
    "authorityReportingFlags": "See the field reference in assumptions.md and exact derivation in build-frost-mileage.py.",
    "conditionalRatePer100k": "assignedMotorCollisions / preferredMiles * 100000 when exposure positive and inherited rate gate true; conditional and modelled.",
    "majorFallbackShare": "Authority-year fallbackMajorMiles / publishedMajorMiles; repeated at LSOA level, not local fraction.",
    "unsupportedFunctionMinorShare": "Fraction of model minor weight for functions absent from counted training observations.",
    "sparseGroupMinorShare": "Fraction of model minor weight in region x class x function strata with fewer than 30 training sites.",
    "densityExtrapolationMinorShare": "Fraction of model minor weight outside global training log-density range.",
    "denominatorAvailable": "Authority total positive, major allocation complete, nonnegative minor balance. Does not imply positive LSOA exposure.",
    "rateEligible": "Inherited current-year authority rate gate; does not validate local mileage.",
    "balancedModelCohort": "Positive modelled exposure, eligible frost and inherited rate eligibility in every year.",
    "validatedFrequencyEligible": "False for every row. No independent allocation validation.",
    "qualityReasons": "Original authority quality reasons, JSON text.",
    "qualityFlags": "Semicolon-separated warnings."
  }
}