[cjrp]

> Unless there is service disruption I find the bus is at least twice as fast as walking, typically a lot faster.

Anecdata, but I can say the opposite is true in central London (London Bridge to Liverpool Street, for example) during rush hour. The bus takes about 20 mins on a good day, and I can walk it in the same time.

[MagnumOpus]

Agreed, but that is really only true for some very specific sections at very specific times (5pm rush hour around the City fringe and Westminster) -- even in rush hour I would say that the 2x rule of thumb works in general.

[OJFord]

Especially given if you're not on the bus you don't (probably) have to walk bus stop to bus stop, you go straight to wherever you're going. Lots of little alleys around there too, saving 2x road to the junction and a light change.