Okay, true, I've not yet watched the video, at the moment the only even potentially conceivable way I can see to get a 2 deck passenger car in the UK loading gauge is with TARDIS technology.
Excepting the Blackpool, or was it Blackburn, trams.
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"There are a thousand things that can happen when you go light a rocket engine, and only one of them is good."
Tom Mueller of SpaceX, in Air and Space, Jan. 2011