Who decided that the 172 should be the bus that goes from the middle bit to the south-east corner? And why do some have letters in their official designations? Why is there a 474 and a 476 but not a 475? And is it really OK to eat a burger on a packed one during rush hour?
A quite fantastic and detailed response to a question posed to a Transport for London staff member explained some of the thinking behind the seemingly random numbering system, revealing that planners often revert back to historical routes from the very earliest days of the invention of the horse-drawn network -- and that the number 24 route has barely changed its course since.
The questioner asked why two of his local buses -- the 55 and the C2 -- didn't appear to have very much in common when it came to their numbers. The anonymised TfL man explained that the 55 was "...first introduced between Central London and Leyton during a major service re-organisation around forty years ago. Its number was a deliberate echo of a trolleybus route 555 that had run along Old Street to Hackney and beyond some years previously, and also of the tram route 55 that the trolleybus had replaced."
As for the C2, the C stands for Central, as it was granted that number during a London Transport reorganisation in the 1960s that introduced the first letter of a place to some new routes -- P for Peckham, E for Ealing and so on -- to help differentiate them from others.
The first mass reorganisation of the modern system came in the 1930s, when numbers 1--200 were saved for central London, with higher number bands taking routes further out. The current system and the constant expansion of routes now reserves numbers 1 -- 599 for the normal daytime routes, but the numbers within still have some significance, as men with an interest in transport try to preserve at least a little history amid London's constant growth and rebuilding.
As for why there's a 414 but no 402, the TfL source explains: "When we introduce a new route - or make alterations to an existing route by splitting it - the last digit or digits of the historic 'parent' route are used wherever possible, so that passengers might associate the incoming route with its predecessor. This was the case in 2003, for instance, when route 414 was chosen as the number for the new route between Maida Hill and Putney Bridge, which was intended to augment route historic route 14 south of Hyde Park Corner."
Image: Gobbiner via Flickr