The interlock dimension is the reduction in depth that occurs where two rows of angled parking stalls meet head to head and their ends nest together. Because angled stalls are drawn as parallelograms, the corners of one row fit into the gaps of the other, so the combined depth is less than twice the depth of a single row.
Designers use the interlock dimension to calculate the true width of a double-loaded module or of adjacent rows of angled parking. Ignoring it overstates the space needed; overestimating it can leave stalls too short for real vehicles.
Where it matters
- Angled layouts. Interlock applies to angled stalls, typically 45 to 75 degrees. Ninety-degree stalls do not interlock.
- Module width. The interlock reduction is subtracted where rows of adjacent modules meet head to head. See parking module.
- Walls and columns. Where rows meet a wall instead of another row, the full stall depth applies.
- Vehicle mix. Large vehicles reduce the real benefit, since their bumpers extend into the space the geometry assumes is free.
The Parkonomics view
Interlock is one of the small geometric savings that add up across a structure. Count it, but check it against the vehicles that will park there.
Related terms: Parking Geometry, Parking Module, Double-Loaded Module, Single-Loaded Module, Compact Stall