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Comment by bee_rider | Hacker News Reader

I wonder if unloading is in some sense greedy, in a way that loading isn’t. I have no justification for thinking so, just a gut feel.

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That's a pretty reasonable mental model. The only real requirement during unloading is ship stability, other than that just use max concurrency with all the cranes and equipment to max throughput. Even just on the crane level, you can just keep unloading stuff to shore, and wait until vehicles pick them up. If they are slow, just keep on unloading until they catch up. Chance of stalling ops is close to zero.

Loading operations are much more variable, especially if your yard is not stacked well and you need to 'dig out' specific containers. If you run out of containers underneath your crane, your operations are stalled until the terminal vehicles catch up and bring you new boxes to load.

> Even just on the crane level, you can just keep unloading stuff to shore, and wait until vehicles pick them up. If they are slow, just keep on unloading until they catch up. Chance of stalling ops is close to zero.

It's not done that way, much. When a container is taken off a ship, it's usually placed on something that moves - a truck chassis, a railroad car, or an AGV. If you clutter up the dock with containers, unloading will stall.

Using human-driven trucks on the dock side: [1]

Full automation with AGVs: [2]

[1] https://www.youtube.com/watch?v=youKZCUZGlw

[2] https://www.youtube.com/watch?v=zm_rlLyelQo

Fair enough, I was thinking of terminals one step smaller where reachstackers or straddle carriers directly drive to and from the quay. On bigger terminals it’s a much more interlinked process indeed.

See https://youtu.be/in2Q1KgqVIQ?si=7kzBKQGtrXyAbZEi

Several steps smaller: Royal Portbury Dock.[1]

This is a small container port with a two lane access road. Not much traffic. No automation. Container stacks are only two high, three high at most. Driver is led through stacks of containers until they find the one they want to pick up. After some yelling, someone driving a stacker removes the container from the top of the one they want, then loads the desired container onto the truck chassis.

Although there's one container ship at quayside, no loading or unloading seems to be happening.

There's a very British feel to all this.

[1] https://www.youtube.com/watch?v=eDXzIACg3j0

Yep, that's more my class of customers. The height limitation is probably because of the gantry crane. In my experience having the truck driver follow the reachstacker is kind of uncommon, you'd ideally either tell the truck driver where to go from the gate, or just have the stacker drive across the terminal. This seems like the worst of both worlds. Perhaps a union or regulation thing about minimizing driving around with a reachstacker holding a box?

Fascinating business nonetheless, this is definitely something different than I'm used to over in NL/BE. Thanks for sharing!

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