Methodology: what GarageTurn calculates

GarageTurn is a browser-based planning estimate. It uses a simplified bicycle-style vehicle model and a rectangular body envelope to compare a 90° side-entry maneuver against two primary constraints: the opposite apron edge and the garage wall/opening.

Vehicle model

The model uses overall length, body width, wheelbase, turning-circle diameter and optional front overhang. If front overhang is omitted, the body length outside the wheelbase is split evenly between front and rear for the estimate. The turning-circle input is converted into an estimated rear-axle path radius; this is necessarily approximate because public turning-circle specifications do not provide the complete steering-linkage and tire geometry needed for an exact manufacturer model.

Path search

For forward entry, the solver tests multiple lateral starting positions, turn-start positions and steering fractions. For reverse entry, it models the time-reverse of a forward exit from the garage and searches multiple turn-out points and steering fractions. Candidate paths use short numerical steps, with the final partial step calculated to finish the 90° arc rather than snapping the vehicle heading after an overshoot.

The modeled maneuver is a single continuous turn plus a straight segment. The solver does not claim that its searched path is the mathematically optimal trajectory, and it does not model three-point turns or repeated steering corrections.

Collision checks

Along each candidate path, the full rectangular body envelope is tested against the opposite apron boundary and the garage wall plane. The opening segment is passable; wall segments outside the opening are not. The reported clearance is the smallest modeled clearance encountered along the selected path. Forward- and reverse-entry paths are carried far enough that the full modeled vehicle body is behind the garage-door plane at the inside end of the maneuver.

Safety margin and target dimensions

A path can be geometrically collision-free but still be classified TIGHT if its minimum clearance is below your chosen safety margin. GarageTurn also searches a bounded range of larger apron depths and opening widths to estimate a dimension that would meet that margin. If no target is found, that means no qualifying result was found within the tool's search range; it is not proof that a solution is impossible.

What the model does not include

• Exact manufacturer steering geometry, tire slip or suspension movement
• Mirrors, tow hitches, open doors or accessories unless included in your dimensions
• Slope, crown, curb height, gate hardware, posts, columns or irregular boundaries
• Garage interior wall geometry beyond the opening plane
• Multi-point turns, steering corrections or driver-specific technique
• Local zoning, fire-access, setback, drainage or building-code requirements

How to use the result

Use FITS as a planning signal only when there is a sensible margin. Use TIGHT as a reason to verify physically or in professional CAD. Use FAIL to explore a larger apron, wider opening, alternate entry direction or different vehicle—not as proof that no skilled maneuver is possible.