The picture captures the tablet being passed to the train driver.
While watching this happen it reminded me of locking in databases. Like conflicts on rail lines, in databases we have conflicts in data updates, which need to be avoided. Thus giving rise to different types of lock implementations. Anyway database has some additional levels of complexity and has different types of locks, eg. read lock, write lock, Locking levels, table level, row level, page level etc. Perhaps a bit more complex to solve than the railway problem.
But the interesting thing is when doing algorithm design to solve problems perhaps we can actually find inspiration from past solutions and at times even from nature.
Its an interesting topic read the full detail on wiki http://en.wikipedia.org/wiki/Token_(railway_signalling)