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 remaining body length outside the wheelbase is split approximately between front and rear. The turning-circle input is converted into an estimated rear-axle path radius; this is necessarily approximate because public turning-circle specs do not include full steering linkage geometry.

Path search

For forward entry, the solver tests multiple lateral starting positions, turn-start locations and steering fractions, then chooses the collision-free path with the strongest modeled clearance. For reverse entry, it models the time-reverse of a forward exit from the garage and searches the turn-out point and steering fraction.

Collision checks

At short path intervals, the vehicle rectangle 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.

Safety margin

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 for a larger apron depth or opening width that would meet that margin.

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
• 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.