4 ms·

That's not true in my experience. Loading outbound cargo is way more complex, since the stowage plan of the ship dictates where each container goes. Theoretical

That's not true in my experience. Loading outbound cargo is way more complex, since the stowage plan of the ship dictates where each container goes. Theoretically a lot of containers can be swapped as long as weight is similar, the container type is identical, and the port of discharge is the same. In practice it's still incredibly complex compared to just unloading stuff. While you may need to do less 'digging' on shore, the nitty gritty of the actual operations are way more complex than throwing some boxes ashore. Import cargo is annoying in that it is mostly random access on pickup. For pickup by train, barge, or feeder ship, a vast minority, you typically don't have cargo manifests until a day or two before pickup at best, so in practice this is also random access-ish. The customs processes are also trickier. My experience is mostly in Rotterdam and Antwerp, and I'd say the problems in the US probably don't have to do much with automation. Rotterdam and Antwerp have very different automation levels at the biggest container terminals, yet productivity is quite similar. There is lots of low hanging fruit in optimizing operations, like more collaborative stowage planning, simultaneous unloading and loading operations, and 'modal shifting' from road to rail and water combined with early preannouncement of manifests for trains and barges. Disclaimer: I'm in the business of consulting and building software for container terminals, so I'll generally be biased towards those solutions.

SoftTalker 2y ago
Unloading can be complex also I would think, in that you have to maintain balance on the ship so it doesn't list or even roll over. You can't just grab the nearest container with your crane.
- superice 2y ago
  Yes, although that's the same for loading. As a general rule, container ships are unloaded tier-by-tier, breadth-first if you will, not shaft-by-shift (depth-first), so this is not much of a problem in practice. That does start to change if you want to do simultaneous loading and unloading operations, then you'd want to clear out a vertical shafts first so you can start loading operations as quickly as possible. Which is one of the many reasons dock workers hate that style of operations.
  - bee_rider 2y ago
    Clearly, should have used a queue instead of a stack!
- bee_rider 2y ago
  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.
  - superice 2y ago
    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.
    - Animats 2y ago
      > 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 https://www.youtube.com/watch?v=youKZCUZGlw [2] https://www.youtube.com/watch?v=zm_rlLyelQo https://www.youtube.com/watch?v=zm_rlLyelQo
      - superice 2y ago
        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 https://youtu.be/in2Q1KgqVIQ?si=7kzBKQGtrXyAbZEi

SoftTalker 2y ago

Unloading can be complex also I would think, in that you have to maintain balance on the ship so it doesn't list or even roll over. You can't just grab the nearest container with your crane.

superice 2y ago
Yes, although that's the same for loading. As a general rule, container ships are unloaded tier-by-tier, breadth-first if you will, not shaft-by-shift (depth-first), so this is not much of a problem in practice. That does start to change if you want to do simultaneous loading and unloading operations, then you'd want to clear out a vertical shafts first so you can start loading operations as quickly as possible. Which is one of the many reasons dock workers hate that style of operations.
- bee_rider 2y ago
  Clearly, should have used a queue instead of a stack!
bee_rider 2y ago
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.
- superice 2y ago
  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.
  - Animats 2y ago
    > 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 https://www.youtube.com/watch?v=youKZCUZGlw [2] https://www.youtube.com/watch?v=zm_rlLyelQo https://www.youtube.com/watch?v=zm_rlLyelQo
    - superice 2y ago
      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 https://youtu.be/in2Q1KgqVIQ?si=7kzBKQGtrXyAbZEi