You can't ride a horse on the motorway in the UK(speed limit 70mph) but you can happily ride one on a dual carriageway - which also has a normal speed limit of 70mph.

And cities autonomous only? So what about bicycles? Or tricycles? Or hand drawn carriages(rickshaws etc)? Would those roads have high walls around them ,stopping pedestrians from entering?

And finally - where would the money for that come from? Even very rich countries(I live in the UK) struggle to maintain their roads to a high standard, something simple like adding new pedestrian crossings can take years in planning and approvals, but somehow, we would modify all our roads to suit one specific type of vehicle?

I'm really sorry if I'm being cynical, but I really do have a feeling that this self-driving-car utopia is not going to happen.

I think bicycles and other lightweight vehicles are fine. My main problem is that myself, as a pedestrian and a cyclist I am sharing the road with several-ton metal beasts which are driven by annoyed, angry and tired people. I would feel much safer knowing that the pilot of a car next to me is concentrated on the one thing which it is supposed to do.

I think however that at least for several years (decades) the autonomous vehicles must be able to work on the roads we currently have.

As a disclaimer, I would say that I am actually pro-ban of personal vehicles in city centers today. I really do not see a point of anything that is not an ambulance, fire truck, bus, a taxi or a delivery truck on a road. Why people wake up soon in the morning only to then be stuck in an over than one hour commute when a subway ride would take 20 minutes tops is really beyond me.

Banning all cars first and then progressively let autonomous vehicles (as part of a fleet) in would be a win situation in my opinion.

Will pedestrians ever need to cross those autonomous-only roads?

If you are talking about elevated distribution roads that people will pass under, then maybe. But I don't see it working on a city like the ones we have now. Maybe there's a major urban restructuring to happen soon...

I think they should be able to. Just like now, except the autonomous cars will not run the red lights.