Economies of distance (also known as long-haul economies) are attained when the total transport cost per ton-kilometre decreases as the trip distance increases. Economies of distance arise when there are trip-specific fixed costs that are not affected by the distance of the journey, and also by cost items that increase less than proportionally to an increase of distance. Examples of the former are terminal costs, such as aircraft landing fees and seaport charges; train marshalling (shunting) costs; trip documentation; and loading, stowing and unloading costs. As one has to pay these costs regardless of the distance, doubling the length of a haul does not result in doubling the costs.