For any business, the cost of transportation is normally the largest single item in the overall cost of physical distribution. It doesn't necessarily follow, though, that a manufacturer should simply pick the cheapest available form of transportation. Many companies today use the total physical distribution activities while minimizing their cost. Often, this means that the company will make cost trade offs between the various physical distribution activities. For instance, airfreight may be much more expensive than all transport, but a national manufacturer might use airfreight to ship everything from a single warehouse and thus avoid the greater expence of maintaining several warehouses.