求翻译：Economy of scale in transportation is the cost per unit of weight decrease as the size of a shipment increases. For example, truckload shipments that utilize an entire vehicle's capacity have lower cost per pound than smaller shipments that utilize a limited portion of vehicle capacity. It is also generally true that larger capacity transportation vehicles such as rail and water are less costly per unit of weight than smaller capacity vehicles such as trucks and air. Transportation economies of scale exist because fixed cost associated with moving a load is allocated over the increased weight. Fixed costs include administration related to scheduling, cost of equipment, time to position vehicles for loading or unloading, and invoicing. Such costs are considered fixed be- cause they do not vary with shipment size. In other words, it costs as much to administer a 100pound shipment as one weighing 1000pounds.是什么意思？

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