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With warehouse and distribution centre bosses under constant pressure to make maximum use of all available storage space within their facilities, it has become seen to be essential that the width of the aisles along which materials handling equipment and order picking staff travel around the store is kept to an absolute minimum.

But, John Maguire, sales and marketing director of Narrow Aisle Flexi – whose G4 electric VNA counterbalance truck is the most popular articulated forklift in Europe, believes that modern warehouse designers and some forklift truck manufacturers now place too much emphasis on achieving the narrowest aisleways and, as a result, safety and productivity can be compromised.

“In attempting to squeeze the highest number of racking runs into any given storage cube many companies are in danger of adversely affecting the efficiency and productivity of their forklift fleet,” he says.

John Maguire continues: “Quite simply, narrowing the aisleways restricts the speeds at which a forklift can travel between picking locations. When using an articulated forklift truck it might be technically feasible to pick up and turn pallets in aisles as narrow as 1.8 metres, but in applications where high throughputs need to be achieved, faster travel speeds are required. If there is insufficient clearance in the aisleway, then the speed at which the truck can be safely operated will be reduced.

“I recently visited a site where the articulated trucks in operation have no choice but to travel at less than half of their top speed within the aisles because the aisle widths are so narrow that there is very little margin for error on either side of the truck. This is clearly counter productive to any benefits the user may have derived by being able to add extra pallet positions by cutting the aisle dimensions.”

Some years ago the British Industrial Truck Association (Bita) introduced Guidance Note 9 (GN9) – a guide that allows the minimum aisle width to be quickly and easily determined based on the type and combination of fork trucks being used.

In simple terms, GN9 outlines the ideal aisle width where a truck and a pallet can turn safely.

“The most important dimensions when assessing the ideal aisle width for any operation involving articulated trucks to conform to GN9 is the distance diagonally across the pallet, ie, from one corner to another when a pallet is being rotated in the aisle. Safety clearance of 100mm either side (200mm in total) of a typical pallet will need to be added to ensure safe pallet put-away and retrieval. Flexi articulated trucks can operate in aisles as narrow as 1.8 metres, but in applications where a high throughput is required and where 1200mm deep Euro pallets are being stored, I would always say that the optimum aisle width is two metres. It is certainly worth remembering when designing any storage system that the use of Euro pallets is growing in the UK and increasingly companies need to plan for handling them as well as a traditional pallets.”

John Maguire continues: “The regulation width for reach truck aisles is 2.7 metres wide but no-one would design a storage system around 2.7 metre wide aisles because the trucks would be forced to operate too slowly. That’s why the majority of aisles where reach trucks are in operation – including most of the major supermarket RDCs – tend be 3 or 3.1 metres wide.

“Just because it is physically possible for an articulated truck to turn a pallet in a 1.8 metre wide aisle, doesn’t necessarily mean that it makes sense to set the aisles 1.8 metres wide.”

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