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 concept, an approach that involves maximizing the efficiency of physical distribution activities while minimizing their cost. Often, this means that the company will make cost tradeoffs between the various physical distribution activities. For instance, air freight may be much more expensive than rail transport, But a national manufacturer might use air freight to ship everything from a single warehouse and thus avoid the greater expense of maintaining several warehouse.