Board Thread:General Discussion/@comment-6369172-20130813134322/@comment-3361105-20130814004142

I'm of the opinion that whether an article appears in both the massive main category and its sub categories is trivial.

The sub-categories still allow you to organize by sub-types, whether the top-category is full of articles or not.

Meanwhile, if someone (a bot, probably) were looking for a particular vehicle from the pool of all vehicles... the top-category being populated would be necessary.