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Comment by banana_giraffe | Hacker News Reader

The container in question is SLHU4500470. The first four characters are the owner, the next 6 digits are the unique (per owner) number, and the last digit is a check digit.

Somehow I always assumed there'd be more than 6 digit IDs for these things. I'd guess collisions have happened, but never been caught in the same port before.

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I believe the 4th character of a container ID is always a U, so the container owner is the first 3 characters.

U is code for freight container so yes :)

What happens when somebody has more than a million containers? 6 digits doesn't seem enough to guarantee uniqueness.

You assign a second owner number to the group, probably

There's only about six million active containers in the world. If one owner has more than a sixth of them, an easy fix would be to issue them a second owner code, basically extending the six-digit field by a bit.

> There's only about six million active containers in the world.

Huh, that's a lot less than I expected there to be.

Though that's about 1 per 1000 people, and if you imagine how much stuff you'd end up with using all that a container could carry when constantly in use, I guess about a thousandth of that isn't too weird an amount.

6 million seems like a underestimate. There are meant to be 54k container ships in the world. That would mean an average of 110 containers per ship, and ignores all of the ones in use on land. Some of those ships can carry 24k containers _each_.

There are not at all a vast number of 8,000 TEU+ ships however. Small enough that any one ship owning company might have a few dozen at most. Evergreen says it has something like 150 ships.

Evergreen is still growing, though; They've got several 8,000+ TEU ships set to launch in the next few years. Consolidation is key.

I would guess that the next answer is "Evergreen gets multiple Owner codes", because that's a real simple way to stretch it, but...

Wikipedia says 20.5 million _in 2012_ https://en.wikipedia.org/wiki/Cargo_container

This was their source. Apparently not updated since that 2012 survey: https://www.csiu.co/resources-and-links/world-container-flee...

Well, we'd probably just switch over to UUIDs since those things are practically infinite and we've now got a lot of well established infrastructure in place for handling them.

Nope, that many characters would be impractical in daily use. There’s a lot of copying, pasting, reading, and reciting of numbers via email/web/phone/TMS/WMS/etc.

Ahem, 10 million

The 7th digit is a checksum digit, as previously noted. So only 6 "free" digits so a million is correct.

You can read more about the container numbering standard here: https://en.wikipedia.org/wiki/ISO_6346

Thanks for the info

Like IEEE OUIs, one company can have multiple owner prefixes. Maersk has 41:

* https://www.bic-code.org/bic-company-search/?searchterm=MAER...

* https://en.wikipedia.org/wiki/ISO_6346

> “I have never seen two containers carrying the same number in my 27 years of career in the shipping sector,” pointed out Mohammed Abdullah Jahir, chief operating officer of Saif Maritime Ltd, adding that such an incident cannot be detected unless the boxes arrive at the same port at the same time.

If the port authority conducting the inspection are not diligent, it's easy to miss this.

I always wondered if this was designed to integrate into the existing railway numbering system. In the US, at least, owner identifiers are pretty consistently 4 characters or less, and individual unit numbers are 6 digits or less (i. e. BNSF 123456).

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