Legible London
Via diamond geezer: Legible London is an attempt to create a standardized pedestrian navigation system for central London, replacing and improving upon the 33! existing systems. It is an interesting read (pdf) and I think would be valuable in places not quite as complicated as London (i.e. almost everywhere except Tokyo, and may be there too).
By making walking easier, the planners hope to reduce reliance on public transport, which is excessively congested, in part due to the schematic tube map which distorts distances.
If they are successful, they may create a system as iconic as the Underground maps and logo.
Of course the trick with any of these things is not just first installation, but keeping the system live, rather than just a decaying artifact from 2007. But it would seem quite valuable, it just has no source of income for support. (advertising or sponsorship would be a natural, but would be potentially be an ugly blight).