I don't believe there have been any mentions of London bus routes so far, not that they seem to have been excluded by the OP.
Two or three years ago, dozens of routes all over London would have passed muster, but now half or more of these have gone to 12 or even 15 minute intervals, even at peak times. The ones that remain are by no means confined to Central or Inner London, like the 2,6,24,38 or 73: outer Kingston has two (the 65 and 85) and Romford (the 5 and 86) for instance both at better than 6bph throughout the day. The not-so-well-known 56, meanwhile, operates every 9 minutes all day, but at 8 minutes in the evening, but its two termini are both major hospitals! Being London, with its unique circumstances, in theory the whole route gets the full service, but unscheduled curtailments occur most days on many routes. Evening and Sunday frequencies are though, in the main, comparable to the weekday daytime ones.