There are two economic principles that we need to discuss regarding the economic principles of transportation. They are economy of scale and economy of distance.
Economy of scale is regarding the fixed cost of the truck or ship. It costs the same to ship a truck with 100 lbs of product or 1000lbs. The more goods you can but on board incrementally decreases the per unit cost of transportation. This is until you fill the transportation unit… then it starts again.
Additionally, there is also an economy of distance. The longer the distance the more the fixed costs are spread out. This is often called the tapering principle. If you transport one shipment 1000 miles and then 2 shipments each 500 miles… you spend more time loading and unloading the truck, increasing your costs.
When you are planning your shipments, you want to maximize both elements.