GLOSSARY

Two-Bay End-to-End Configuration

A two-bay end-to-end configuration, often called an end-to-end continuous helix, is a parking structure layout with two parking modules side by side in which the floors slope along the length of the structure, so drivers climb one full level in a single loop.

PLAN: TWO-BAY END-TO-END (CONTINUOUS HELIX), ONE LOOP = ONE LEVELBAY 1: SLOPES UP THE LENGTH OF THE STRUCTUREBAY 2: CONTINUES UP, BACK TO THE START ENDENTER+1 LEVELSlope runs longitudinally (end to end), not across the width.
Drivers climb along the full length of one bay, make a 180-degree turn at the far end, and climb back along the second bay, arriving one level up at the starting end. Illustrative.

Traffic enters, drives the entire length of the first bay while sloping upward, makes a 180-degree turn at the far end of the building, and continues sloping upward along the entire length of the second bay to return to the starting end, having climbed exactly one level. “End-to-end” means the slope runs longitudinally, down the length of the structure, not transversely across its width.

How it works

  • Two parking bays. Each bay is a full parking module: a row of stalls, a drive aisle and a second row of stalls. See parking module.
  • Longitudinal slope. Each bay rises half a level along its length, so the aggregate length needed to climb one level is shared between the two bays.
  • Turning bays. Drivers make a 180-degree turn at each end of the structure. See turning bay.
  • Continuous parking. Stalls line the sloped bays, so drivers search for a space as they climb.

Where it fits

  • Long, relatively narrow sites, about two parking modules wide.
  • Structures long enough to keep the slope of each bay gentle, since the length of the building sets the slope.
  • Garages with moderate turnover, where circulating past parked cars is acceptable.

Trade-offs

  • Every parking floor is sloped, which is less comfortable for pedestrians and makes later conversion to other uses harder.
  • Drivers exiting from upper levels pass through all the parking below them unless an express exit is provided.
  • Short structures force steeper slopes or a different configuration.

The Parkonomics view

The two-bay end-to-end helix is one of the most efficient ways to park a long, narrow site: nearly every square foot holds stalls or the aisle that serves them. The cost is sloped floors everywhere. If the building may need to become something else later, compare it with a flat-floor design and a speed ramp before committing.

Related terms: Aggregate Length, Turning Bay, Single Helix, Double Helix, Ramp Slope, Speed Ramp

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