The aisle length is the distance between the front end and the rear end of one aisle in the warehouse, this does not include the width of the (potential) cross aisle(s).

This is the distance between the centre of one aisle and the centre of the next aisle.

The total width of the warehouse is the number of aisles multiplied by the centre distance between aisles.

The number of aisles is the number of aisles, in which one picker collects items. This means that this picker is allowed to pick anywhere in these aisles.

A cross aisle is an aisle which is perpendicular to the storage aisles in which the items can be picked (the pick aisle). Its main function is to enable aisle changing. A cross aisle crosses the pick aisles.

The width of a cross aisle is the distance of the interruption of the pick aisles, thus the distance between the left side and the right side of the cross aisle.

The additional time to change aisles is the time needed to go from one aisle to another on top of the normal travel time it takes to cover the distance. If the distance between two aisles is 10 metre and the speed outside the aisles is 1 m/s, then it would take about 10 seconds to leave the first aisle and enter the next. If it takes 20 seconds to change aisles actually, then the additional time to change aisles is 10 seconds. Especially in narrow aisle warehouses this additional time may occur due to the truck backing in and out the aisle. It may be as much as half a minute. In the other types of warehouses, the aisles are rather wide and the trucks are easier to manoeuvre, so that the time needed to change aisles will be roughly equal to the normal time (outside the aisles) to cover such a distance. In a narrow aisle pallet warehouse the default additional time is 10 seconds per aisle change.