Width of the aisle is determined by the type of forklift truck to be used. This is usually given by the manufacturer assuming a 1200mm x 1000mm pallet is being used. But check, sometimes they assume a 1000mm x 1000mm pallet.
If the pallet is being used by the customer is larger, a bigger aisle is required.
ALWAYS INCREASE THE MANUFACTURERS RECOMMENDED AISLE BY AT LEAST 200MM.
Why?
Warehouse Pallet Racking layouts invariably involve a compromise between the use of the available space and the speed of the materials handling. Working to the manufacturers minimum aisles is like parking in a very tight parking space. It can be done, but it takes time and it can cause considerable wear on the vehicle and driver. It is reasonable to expect between 20 and 30 pallet movements in an hour. The throughput will be halved with restrictive aisles.
When calculating minimum aisle widths, fork truck manufacturers assume that pallets will be located as far back as possible on the fork