In general it appears that it's just roads that aren't publicly accessible which one can't go down. It's not just Downing Street, for example, but a bunch of pedestrianised places, presumably for the obvious reason that the Street View car couldn't go down them.
That tells me there aren’t enough such thoroughfares in London, so they’re being funneled from other streets to Oxford St. Also IIRC (it’s been a while since I was last there) the buses don’t yet have right-of-way through the intersections.
Edinburgh council should be ashamed of Princes Street, it's truly awful. During the whole time I lived in Edinburgh and when visiting I avoided it like the plague. I think I only visited Princes Street about four times (once to buy a mobile phone :) and the others for work and an interview). The real gem is George Street, but council seem to be doing there damnedest to make a mess of that as well.
The Royal Mile is a bloody awful tartan covered tourist trap despite having some fantastic buildings.
My favourite part of Edinburgh is Leith and the shore area. I lived just off of the bottom of Leith walk and always loved dawdling across Leith Links to work in Great Michael house.
For those who aren't aware, bus lanes like this are often the only roads passing through city centres in the UK. The surrounding area is often a pedestrian area, with the only traffic being buses, registered taxis and emergency vehicles (delivery and utility vehicles are allowed in the early morning). The alternative route for regular traffic would be a few miles longer - which could mean 30 mins or more at rush hour.
This street has many highrise offices, universities and residential buildings around it so its a destination of a lot of foot traffic from buildings, not so much somewhere you drive to access. There are also multi level parks on the ends, you just can't drive through it.
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