| name | btc-trailhead-affordance-check |
| description | Verify access assumptions for Boise Trails Challenge routes. Use when a route starts, ends, parks, shuttles, re-parks, or transitions at a mapped trailhead, pullout, road crossing, residential road, OSM parking feature, private Strava-derived anchor, or informal access point. |
BTC Trailhead Affordance Check
Core heuristic:
A trailhead is not a start until access is real.
Procedure
- Load
docs/BTC_LOCAL_REALITY.md before accepting or rejecting an access point.
- Identify every proposed start, finish, re-park, shuttle, and access node.
- Classify each access point as a known parking area, mapped trailhead, road shoulder, pullout, residential road start, Strava-derived prior anchor, user-reviewed anchor, or unknown access point.
- Search outward for the nearest certifiable parking surface, not only the nearest mapped road. Check parks, official trailhead lots, amenity parking, event meeting points, public community lots, and source-described route starts within a reasonable connector budget.
- Check legal and practical access: parking, road passability, gate risk, signage, seasonal closure, private-property ambiguity, special-management entry/exit direction constraints, mud/condition constraints, and whether imagery is stale.
- Separate official evidence, Ridge to Rivers or land-manager evidence, OSM/map evidence, imagery evidence, field-photo evidence, private Strava-derived evidence, and user-provided evidence.
- State unsupported assumptions explicitly.
- If access is uncertain, keep the route parking-gated or propose a known-access fallback and account for added connector, road, repeat, distance, and time.
Do Not Infer
- Legal parking from a trailhead label.
- Current access from old imagery.
- Road passability from map geometry alone.
- The nearest road touchpoint is the best parking anchor.
- A slightly farther park or official lot is worse than a closer residential road before p75/p90 and connector mileage are recomputed.
- Public use from a service road, cat track, or shoulder without evidence.
- Publication readiness from private exact-coordinate evidence.
- A need to re-block an anchor already reviewed as
yes unless access changed or uncertainty is specific.
- A trailhead is valid for any direction on an adjacent special-management trail just because parking is legal.
Output
- Access status:
known, accepted_user_reviewed, parking_gated, blocked, or unknown.
- Evidence used, grouped by source type.
- Unsupported assumptions.
- Fallback access option, when needed.
- Nearest-road option versus nearest-certifiable-parking option, when those differ.
- Added distance, duplicated official mileage, connector mileage, road mileage, and time impact.
- Human-validity note for whether the route can be recommended now.
