Which mode of long distance transportation would cost the least per ton mile?

Water transportation, particularly via ships, is generally the most cost-effective mode of long-distance transportation when measured in cost per ton-mile. Here's why:

Economies of Scale: Ships can carry massive quantities of cargo, which reduces the cost per ton-mile compared to other modes of transport.

Fuel Efficiency: Water transport is more fuel-efficient per ton-mile than air, truck, or rail, translating into lower costs.

Infrastructure Costs: The natural waterways and ports, once established, do not require as much ongoing maintenance as roads or railways, further reducing costs.

Long Distance Capability: Ships can travel long distances without the need for frequent stops or transfers, making them more economical for intercontinental shipments.