If some loss of totally free access to stock can be accepted, although not nearly as severe as in block, drive-in or push-back storage, space utilization can be improved using double-deep racking. This supports pallets on pairs of beams as in APR, but improves space utilization by eliminating alternate access aisles, and using a double-reach' fork-lift truck, which can access not just one but two pallets deep into the racking.
Pallet position utilization in double-deep racking is typically of the order of 85 per cent, depending on the precise application. A practical requirement is that the bottom level of pallets in the racking normally has to be supported on a raised beam to allow the legs of a double-reach truck to fit under the racking structure when accessing the pallet furthest in from the aisle. In single-deep APR, the bottom pallet can sit directly on the floor.