I recently had the chance to watch Pixar’s Cars 2. Although the story is located in a pure imaginative universe, there is an issue that goes beyond any (even imaginative) logic.
When the story is set in London, we can see a lot of cabs and double-deckers buses moving around the city streets.
So I was wondering: What the purpose of these vehicles? Obviously they're too small to carry other vehicles... And if they aren't able to carry vehicles, then precisely what is the aim of their “uniform” and why are they in the city at all?