That ignores the economic factors. Much like trains, cargo ships haul a huge amount of cargo while being manned by a small crew. Thus the labor cost as a perc

That ignores the economic factors. Much like trains, cargo ships haul a huge amount of cargo while being manned by a small crew. Thus the labor cost as a percentage of total cargo haul cost is quite low. A truck, though, requires a human driver to move a single cargo container any distance, so there's a much bigger economic incentive to replace the driver with a computer.