“Knight Bus” is a play on “Night Bus”—Night Buses run through the night in London and, after the Tube and trains stop running (around midnight)* are the only public transport available. They are a very welcome sight when they (eventually) turn up to take you home, and are the traditional red double-deckers, so it can feel as if a knight in shining armour has come to rescue you. The roads being clearer at that time of night, once you are out of the centre, the bus bounces along at a considerable pace, for a bus, tree-branches rattle along the roof and you’re sure the driver’s never going to make that corner (but he always does) so the whole experience is not unlike the Knight Bus – apart from the comfortable beds, panelling and chandeliers, of course! I also love the name Ernie Prang—”prang” is old RAF (based on Malay, I think) slang for “crash”, extended to road traffic, and is associated with a rather insouciant attitude to crashes, as in “pranged the Jag last week—what a bore!”. The Knight Bus is another example of JKR finding the magic in the everyday, or, in this case, every night.
Effective in the Fall of 2015 Transport for London is beginning Night Tube Service on some lines.