A parcel can appear reachable without a documented right to use the route, and a recorded access right can exist without a route that works for the intended project.
Short answer: Before buying land, verify both legal access and physical access. Legal access asks which deed, plat, easement, road agreement, title record, or public right supports the route and who can interpret it. Physical access asks whether the road, entrance, bridge, grade, width, surface, curves, overhead clearance, drainage, gates, emergency access, utilities, construction traffic, and delivery equipment can support the intended use. One does not prove the other.