{
  "id": "clock-change-v1", "registeredAt": "2026-10-21", "status": "Frozen before this study's outcome extraction; not an external preregistration",
  "geography": "Great Britain", "developmentYears": [2005,2006,2007,2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019,2022],
  "excludedPandemicYears": [2020,2021], "reservedValidationYears": [2023,2024,2025],
  "holdoutCaveat": "Reserved from this clock-change analysis. These years have appeared in other Data Lab studies; they are not globally unseen data.",
  "primarySeason": "autumn", "secondarySeason": "spring", "timezone": "Europe/London",
  "transition": "Last Sunday in October (autumn) or March (spring)",
  "primaryOutcome": "Reported injury collision count, all hours, days 1–21; adjusted counterfactual estimation deferred to phase 5",
  "descriptiveWindows": {"before": [-21,-1],"after": [1,21],"diagnostic": [-42,42],"sensitivityDays": [7,14,28],"omitDayZero": true},
  "timeBands": {"morning": [7,10],"midday": [12,15],"evening": [16,19]},
  "publishedSeverityComparisonHours": [16,21], "youngCarDriverAges": [17,24], "olderCarDriverMinimumAge": 25,
  "youngDriverDefinition": "At least one car (vehicle_type 9) driver aged 17–24. Older group at least one car driver aged 25+. Groups can overlap; driver age from vehicle table.",
  "solarBands": {"daylight": "solar elevation >= 0 degrees", "twilight": "-6 <= solar elevation < 0 degrees", "darkness": "solar elevation < -6 degrees"},
  "alpha": 0.05, "tests": "Two-sided", "secondaryMultiplicity": "Holm within each prespecified family at modelling stage", "proposedPracticalMarginPercent": 5,
  "interpretation": "Counts and fatal proportions are descriptive. No mileage rates, causal attribution, sleep mechanism or insurance claims inference in phases 1–3.",
  "phase2Dependencies": "Independent weather and regional school-holiday feeds must be linked before adjusted causal work; missing feeds remain explicitly missing, never zero.",
  "amendmentPolicy": "Record and date any scope changes; do not tune definitions to observed effects. Holdout unlock requires a frozen model and phase 7 release."
}