[
  {
    "feature": "population",
    "source_variables": "ACS B01003_001E/M/EA/MA",
    "period": "2020-2024",
    "grain": "place/tract",
    "universe": "All residents",
    "unit": "people",
    "role": "Residential context",
    "uncertainty_and_limit": "Matching 90% MOE and annotations; no crash-participant residence inference."
  },
  {
    "feature": "population_per_land_km2",
    "source_variables": "B01003_001 / 2024 TIGER ALAND",
    "period": "2020-2024 estimates; 2024 land",
    "grain": "place/tract",
    "universe": "Residents / land km2",
    "unit": "people/km2",
    "role": "Residential density",
    "uncertainty_and_limit": "Divide matching population MOE by fixed land area; whole-tract values, no partial-area allocation."
  },
  {
    "feature": "commute_minutes",
    "source_variables": "ACS S0801_C01_046E/M/EA/MA",
    "period": "2020-2024",
    "grain": "place/tract",
    "universe": "Resident workers 16+ who did not work from home",
    "unit": "minutes",
    "role": "Resident commuting context",
    "uncertainty_and_limit": "Published mean and 90% MOE; not a trip count, delay measure, or workplace population."
  },
  {
    "feature": "drive_alone_pct",
    "source_variables": "B08301_003 / B08301_001",
    "period": "2020-2024",
    "grain": "place/tract",
    "universe": "Resident workers 16+",
    "unit": "percent",
    "role": "Resident commute mode",
    "uncertainty_and_limit": "Derived subset-proportion MOE, ratio fallback if negative radicand; no assignment to crash participants."
  },
  {
    "feature": "transit_pct",
    "source_variables": "B08301_010 / B08301_001",
    "period": "2020-2024",
    "grain": "place/tract",
    "universe": "Resident workers 16+",
    "unit": "percent",
    "role": "Resident commute mode",
    "uncertainty_and_limit": "Derived 90% MOE; usual journey-to-work measure, not all travel."
  },
  {
    "feature": "walk_pct",
    "source_variables": "B08301_019 / B08301_001",
    "period": "2020-2024",
    "grain": "place/tract",
    "universe": "Resident workers 16+",
    "unit": "percent",
    "role": "Resident commute mode",
    "uncertainty_and_limit": "Derived 90% MOE; no all-day walking exposure estimate."
  },
  {
    "feature": "work_from_home_pct",
    "source_variables": "B08301_021 / B08301_001",
    "period": "2020-2024",
    "grain": "place/tract",
    "universe": "Resident workers 16+",
    "unit": "percent",
    "role": "Resident activity context",
    "uncertainty_and_limit": "Derived 90% MOE; five-year period spans pandemic behavior, not a 2023 daily attendance estimate."
  },
  {
    "feature": "no_vehicle_households_pct",
    "source_variables": "B08201_002 / B08201_001",
    "period": "2020-2024",
    "grain": "place/tract",
    "universe": "Households",
    "unit": "percent",
    "role": "Household mobility context",
    "uncertainty_and_limit": "Derived 90% MOE; keep household universe separate from workers and people."
  },
  {
    "feature": "workplace_primary_jobs",
    "source_variables": "LODES WAC JT01 C000",
    "period": "2023; TIGER 2024 parents",
    "grain": "2020 block -> 2024 place/tract",
    "universe": "Covered primary jobs at workplaces",
    "unit": "jobs",
    "role": "Workplace activity context",
    "uncertainty_and_limit": "Official crosswalk parents; disclosure avoidance and coverage, no ACS MOE; no actual daytime headcount."
  },
  {
    "feature": "resident_primary_jobs",
    "source_variables": "LODES RAC JT01 C000",
    "period": "2023; TIGER 2024 parents",
    "grain": "2020 block -> 2024 place/tract",
    "universe": "Covered primary jobs by worker residence",
    "unit": "jobs",
    "role": "Residence-side job context",
    "uncertainty_and_limit": "Same job type as WAC; distinct universe from ACS resident workers 16+."
  },
  {
    "feature": "incoming_job_share_pct",
    "source_variables": "LODES OD JT01 S000; WAC C000",
    "period": "2023; TIGER 2024 parents",
    "grain": "block-pair -> destination place",
    "universe": "Workplace primary jobs linked to homes outside the place",
    "unit": "percent",
    "role": "Home/work relationships",
    "uncertainty_and_limit": "OD main + aux reconcile to WAC. Relationships are not observed trips; remote work and through traffic unmeasured."
  },
  {
    "feature": "AADT_vehicles_day",
    "source_variables": "WSDOT annual TrafficSections AADT",
    "period": "2020,2021,2022,2023,2024",
    "grain": "state-highway section/year",
    "universe": "Vehicles in directions represented by the section",
    "unit": "vehicles/day",
    "role": "Dated road activity",
    "uncertainty_and_limit": "No summing sections into visitors; mainline exact-key geometry-checked repeats are a section sample, not all-road growth."
  },
  {
    "feature": "municipal_traffic_volume",
    "source_variables": "Seattle AWDT / Bellevue AAWT",
    "period": "Actual study date retained",
    "grain": "local study location/direction/year",
    "universe": "Published local metric and coverage",
    "unit": "vehicles/weekday per source",
    "role": "Local road activity",
    "uncertainty_and_limit": "126 Seattle 2021-2023 pairs; 3 Bellevue 2023-2024 cases. Period and metric differences stay explicit."
  },
  {
    "feature": "severe_events",
    "source_variables": "Frozen WSDOT maximum injury classification",
    "period": "2020-2024; 2021-2023 focus",
    "grain": "reported crash event -> area/time aggregate",
    "universe": "Fatal or suspected serious maximum injury per crash",
    "unit": "crash events",
    "role": "Outcome",
    "uncertainty_and_limit": "Frozen severity and source-city/road category retained; counts are not injured people or exposure-adjusted risk."
  },
  {
    "feature": "solar_phase",
    "source_variables": "NOAA approximate solar equations + event coordinates/local clock",
    "period": "Event date/time; America/Los_Angeles",
    "grain": "event -> city/road/month/hour",
    "universe": "Events with valid coordinates and unambiguous local time",
    "unit": "modeled category",
    "role": "Astronomical environment",
    "uncertainty_and_limit": "Daylight >= -0.833deg; civil twilight >= -6deg; unknowns retained; +/-0.5deg sensitivity. No street-light/weather/terrain observation."
  },
  {
    "feature": "observed_light/weather/road_condition/junction",
    "source_variables": "SDOT LIGHTCOND / WEATHER / ROADCOND / JUNCTIONTYPE",
    "period": "2020-2024 events, 2026 attribute snapshot",
    "grain": "unique report key + exact date",
    "universe": "Matched Seattle City Street records",
    "unit": "source categories",
    "role": "Observed local environment",
    "uncertainty_and_limit": "Seattle only; observed categories remain separate from modeled solar phase. Unmatched and revised-source attributes are audited."
  },
  {
    "feature": "patrol_context",
    "source_variables": "Seattle/Bellevue public boundaries, activity and schedule documents",
    "period": "Historical framework / current reference vintages retained",
    "grain": "area / clock window / annual activity",
    "universe": "Published local reference and activity",
    "unit": "source-specific",
    "role": "Open follow-up source gap",
    "uncertainty_and_limit": "Actual historical duty hours unavailable; no deployment or patrol-causation claim."
  }
]