{
  "categories": {
    "stairs": {
      "display_name": "Stairs",
      "geometry_model": "tread_riser_block",
      "primary_users": ["mobility_impairment", "blind_or_low_vision"],
      "surface_role": "level_change_barrier",
      "risk_metrics": ["step_edge_continuity", "riser_height_consistency", "handrail_or_obstacle_clearance"],
      "annotation_priority": ["target_visible", "target_amodal", "hidden", "obstacle", "stair_edges_y"],
      "notes": "Use category-specific tread and riser geometry. Do not treat stairs as one smooth ramp."
    },
    "ramp": {
      "display_name": "Accessible Ramp",
      "geometry_model": "sloped_prism",
      "primary_users": ["wheelchair_user", "walker_user", "mobility_impairment"],
      "surface_role": "accessible_level_change",
      "risk_metrics": ["slope", "cross_slope", "landing_continuity", "side_edge_clearance"],
      "annotation_priority": ["target_visible", "target_amodal", "hidden", "obstacle", "ramp_edges"],
      "notes": "Fit a continuous sloped surface and solidify as a ramp prism with side caps."
    },
    "tactile_paving": {
      "display_name": "Tactile Paving",
      "geometry_model": "surface_attachment_ribs_or_domes",
      "primary_users": ["blind_or_low_vision"],
      "surface_role": "navigation_cue",
      "risk_metrics": ["pattern_direction", "pattern_periodicity", "warning_surface_coverage", "continuity_under_occlusion"],
      "annotation_priority": ["target_visible", "target_amodal", "hidden", "obstacle", "pattern_type"],
      "notes": "Reconstruct as shallow raised dots/ribs attached to a walkway or ramp base surface, not as a standalone thick body."
    },
    "curb_cut": {
      "display_name": "Curb Cut",
      "geometry_model": "curb_ramp_prism",
      "primary_users": ["wheelchair_user", "walker_user", "mobility_impairment"],
      "surface_role": "street_sidewalk_transition",
      "risk_metrics": ["curb_transition_height", "ramp_slope", "gutter_alignment", "truncated_dome_presence"],
      "annotation_priority": ["target_visible", "target_amodal", "hidden", "obstacle", "curb_edges"],
      "notes": "Model as a local ramp transition between sidewalk and roadway, often with tactile warning surface."
    },
    "raised_curb": {
      "display_name": "Raised Curb",
      "geometry_model": "raised_curb_prism",
      "primary_users": ["wheelchair_user", "walker_user", "blind_or_low_vision", "mobility_impairment"],
      "surface_role": "non_walkable_level_change_barrier",
      "risk_metrics": ["curb_height", "top_edge_continuity", "vertical_face_continuity", "route_clearance"],
      "annotation_priority": ["target_visible", "target_amodal", "hidden", "obstacle", "curb_top_edge", "curb_base_edge"],
      "notes": "Model as one continuous raised prism with a top surface and vertical face. Never infer repeated stair treads or a sawtooth profile."
    },
    "walkway": {
      "display_name": "Walkway / Flat Ground",
      "geometry_model": "flat_or_low_slope_slab",
      "primary_users": ["wheelchair_user", "walker_user", "blind_or_low_vision"],
      "surface_role": "travel_path",
      "risk_metrics": ["surface_continuity", "clear_width", "obstacle_clearance", "roughness"],
      "annotation_priority": ["target_visible", "target_amodal", "hidden", "obstacle"],
      "notes": "Use a continuous slab or low-slope plane. Keep tactile paving as a separate overlay category when present."
    }
  },
  "user_groups": {
    "wheelchair_user": {
      "requires": ["ramp", "curb_cut", "walkway"],
      "high_risk_categories": ["stairs", "raised_curb", "curb_cut", "ramp"]
    },
    "walker_user": {
      "requires": ["ramp", "curb_cut", "walkway"],
      "high_risk_categories": ["stairs", "raised_curb", "walkway"]
    },
    "blind_or_low_vision": {
      "requires": ["tactile_paving", "curb_cut", "stairs", "walkway"],
      "high_risk_categories": ["tactile_paving", "stairs", "raised_curb", "curb_cut"]
    },
    "mobility_impairment": {
      "requires": ["ramp", "curb_cut", "walkway", "stairs"],
      "high_risk_categories": ["stairs", "raised_curb", "ramp", "curb_cut"]
    }
  },
  "dataset_policy": {
    "split_by_category": true,
    "split_by_user_group": true,
    "allow_multi_label": true,
    "gold_for_training": false,
    "automatic_category_is_ground_truth": false,
    "automatic_mask_is_ground_truth": false
  }
}