I had known there have been limited areas where vessels’ speed has been restricted and had heard about speed limits to protect right whales, but this was the first time I have heard that anyone was considering restrictions on merchant shipping that might be applied globally.

The Clean Shipping Coalition (CSC) has proposed speed limits in the shipping sector as ‘the key to the fast and efficient reduction of greenhouse gas emissions from ships’ (MEPC 61/5/10). It has proposed to the International Maritime Organization’s Marine Environment Protection Committee (IMO MEPC) to discuss mandatory speed controls.

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As a rule of thumb, engine power output is a third power function of speed. Hence, when a ship reduces its speed by 10%, its engine power is reduced by 27%. Because it takes longer to sail a given distance at a lower speed, the energy required for a voyage is reduced by 19% (a quadratic function).

And the assumption is that emissions are in proportion to fuel usage. The study considered global regulation, regulation of shipping in the Arctic, and regulation of those ships that may trade with the EU. The particular consideration for the Arctic is that expanded ship operation in the Arctic will result in the deposit of black carbon that will accelerate global warming and threaten the eco-system.

The full report is available here: Slow Steaming CE Delft final.pdf

In considering this sort of regulation, undoubtedly the CG would be involve. And if it were enacted the CG would most likely be the agency to enforce it for the US.

A number of questions come to mind.

Since they advocate regulation based on speed over ground (because it is easier to enforce) instead of speed through the water, you could get in trouble taking advantage of favorable currents, might not ships be certified as being in compliance with the maximum speed limits and then be allowed to use both use full power and favorable currents without penalty?

Aren’t there other approaches that could reward innovation and investment in minimizing pollution without limiting speed? Would you get to go faster if you used atomic power or wind to augment or replace the fossil fuel power? Or if you used cleaner fuel like LNG?

Is it likely? Soon? National Law or International Treaty? (See pdf beginning page 72) It would depend on how extensive and comprehensive it would be. Local systems, or restrictions specific to those vessels that trade with a particular market could happen relatively quickly. Comprehensive Treaties might take decades, before implementation.

The study also includes an interesting chart (p. 105) listing the average transit speeds of various types and sizes of merchant ships observed in 2007 (before the onset of elevated fuel prices which have resulted in a general slowing of transit speeds as a way to reduce cost.)