Subtract edging, plants, wheel-drop hazards and required boundary clearance from the physical opening.
Measure the turn into the gap, too.
Minimum corridor figures can hide boundary offsets, approach angle, wall clearance and the room needed to turn. A mower that fits the narrowest width may still fail the route.
Record the entry angle, turn radius and whether the corridor narrows on a bend rather than a straight line.
Account for plant growth, fallen leaves, parked objects and soft edges that reduce a nominal gap.
Evidence to collect
- A dimensioned photo or sketch of each zone transition.
- The current manual’s corridor and boundary-clearance requirements.
- Documented multi-zone behavior and a full route trial.
- A recovery plan if the mower stops where normal access is restricted.
Unknown clearance is kept visible in the comparison rather than treated as a pass.