Few days ago I returned from my Agile consulting mission in Delhi, India for one of the local outsourcing vendors. On the way home I found quite an interesting thing...
During the security check process while standing in the line and gradually approaching to the "belt" I noticed these (quite big) number plates, like the one on the picture here. And they apparently use them for two purposes:
first, they have them in pairs with same number, so in the end, when you want to get your baggage that went thru the scanning, you just hand the officer your number plate and get your stuff in return. So it is to make sure that you get your own baggage.
second, they don't use all the pairs, but give away only limited amount to control the "work-in-progress". This way only limited number of passengers are at the belt at any moment of time.
Interesting scenario, isn't it.
It's actually not even Kanban, to be precise. It is CONWIP system, if we consider only the security check as a system. In CONWIP, which is also an example of a pull system alternative to Kanban, there is no WIP limit on each step of the process instead there's one WIP limit for the system as a whole. So CONWIP actually means CONstant WIP. It may look not as "configurable" as Kanban but it is way easier to implement. I am especially big fan of this model as, unlike Kanban, it does not drive you to a kind of isolated phases in processes where phases actually have quite fuzzy boundaries like... in case of software development. From this perspective you can call Scrum as a very precise example of CONWIP in software development.
Good luck with security checks!