Agreed - details matter a lot. For example many years ago, Camden in London put in green asphalt cycle paths - one was dangerously hilarious - you ran parallel to the main road, on a painted strip, on the side of a one way street - going against the traffic.

However the new cycle "superhighways" in London are a big improvement but oddly now I find the biggest challenge is to change the attitude of the cyclists - we have effectively been given roads - and so now need to obey the laws of the road - it's a toss up if every cyclist will stop at the traffic lights for these superhighways - frustrating if you are a fellow cyclist and dangerous if you are crossing

At some point however we are going to face the fact that roads are a cheap form of transport because they are shared and so are dangerous - the UK has 4500 deaths a year - and when we look at segregating cycle traffic to make it safer we realise it is effectively asking to build a railway- and we shall face the same as self driving vehicles get close to good enough but plateau out - and I bet the business case for self driving cars rarely has ever been coated with "we build segregated roads everywhere with huge fences to keep out pedestrians and other hard to avoid objects."