It's not just a sensible average speed all round that's needed - they would need data for individual roads, and at different times - some roads (i.e. Piccadilly approaching Piccadilly Circus) are busy at all times and average speed would be *much* lower, whereas other roads on the outskirts would be much higher.
I know the route you're on about, but my route would only use the top end of that, and only heading anticlockwise around the North Circular. Clockwise (grab your A-Z) from Brent Cross I'd go A41, Wayside, Armitage Road, Hoop Lane, Meadway, Kingsley Way, Ossulton Way, East End Road, Church Lane, High Road, Creighton Avenue, and up towards Bounds Green station and cutting through to the Clockhouse Junction - coming back I'd go via Dukes Avenue-Queens Avenue in Muswell Hill, just using the top bit of the Bishops Avenue, and cutting up Winnington Road onto Meadway, and then shortcutting through the various side streets in Golders Green to avoid the queuing traffic on the main road, normally joining the North Circular from Western Avenue (the one that's not the A40).
I've often avoided going via Spaniards Road due to that bloody width restriction and the minor chaos that causes.
Yeah, if someone did do it, and did it *well*, it could be quite a hit, methinks.
-- Coming Soon: The British Apathy Party - though I bet nobody'll vote for them.
