GLOSSARY

Module, or Parking Module (see also single-loaded module and double-loaded module)

A parking module is the basic dimension of a parking layout: the width of one drive aisle plus the depth of the stalls it serves on each side, measured across the aisle.

MODULE Single-loaded one stall row + aisleMODULE (wider) Double-loaded two stall rows share one aisle
A module is one drive aisle plus the stalls it serves. Double-loading, stalls on both sides of the aisle, spreads the aisle’s cost over twice the cars and is the more efficient plate wherever the bay depth fits.

For 90-degree parking with stalls about 18 feet deep and a two-way aisle about 24 feet wide, a double-loaded module is roughly 60 feet (18 + 24 + 18). The exact figure depends on stall width, parking angle, aisle direction and the comfort level the designer is targeting. A module can be measured wall to wall, curb to curb, or, for angled parking, interlock to interlock, where the angled stalls of adjacent modules nest together and the module shrinks. Designers state which basis they are using.

How modules are measured

  • Wall to wall. Stall depth is measured to a wall or barrier at the end of each stall. This is the governing dimension inside a parking structure.
  • Interlock to interlock. For angled parking, where two rows of angled stalls meet back to back, the module is measured to the interlock line. See interlock dimension.
  • Single or double loaded. A double-loaded module has stalls on both sides of the aisle; a single-loaded module has stalls on one side only.

Why it matters

  • Structural bay. In a parking structure the module usually sets the structural span. A clear-span design carries the whole module without interior columns. See clear-span construction.
  • Efficiency. The module, multiplied by stall width, sets the floor area each stall consumes. Small changes in module width multiply across every bay.
  • Comfort. Wider modules make parking and turning easier, especially for today’s larger vehicles. See parking geometry and levels of service.

The Parkonomics view

Every other number in a garage follows the module. Get it right for the vehicles and the users the facility will actually serve, and confirm it before the structure is designed around it. A module tuned to yesterday’s fleet becomes a permanent tax on every driver.

Related terms: Double-Loaded Module, Single-Loaded Module, Parking Geometry, Interlock Dimension, Clear-Span Construction

Further reading: The Evolution of U.S. Parking Structures in 2026