Check the route in reality
- Walk the route close to the event date.
- Look for closures, construction, accessibility blockers, event crowding, and low-signal dead zones.
- Assume anything you do not verify can bite you in the field.
Design for safer fallback
- Prefer walking-first sequencing for v1.
- Use broader GPS arrival zones instead of requiring precision nonsense.
- Have QR, code-word, or organizer-help fallback when a checkpoint could fail in the real world.