[dustinmr]

In the US, you already have to report the cargo’s arrival date before it leaves its origin port. So the information is there.

Graduate the port fees based on average speed for arrival.

[sillyquiet]

It's hard to visualize, but a ship's engine speed is only one factor in its overall speed across an ocean, even with powerful engines, wind and especially current will improve or degrade a ship's overall speed as measured by satellite. So a naive port fee based on time of departure will not exactly work.

[gwbas1c]

I thought all ships have some kind of international tracking system now?

You should be able to accurately estimate all ships's speeds, using basic high school physics, from a site like https://www.marinetraffic.com/en/ais/home/centerx:-12.0/cent...

[beerandt]

Not gonna happen. Even if you implemented this, port capacity dictates that a docking time slot is always going to trump a speed incentive.

There are steep contractual penalties for missing your time slot.