I have done quite a lot of reading on how Holland and Denmark have done it. I am interested in the views of people who view that any segregation is a bad idea.
I have come to the pragmatic conclusion that we don't need special infrastructure everywhere, but on certain road conditions it is necessary to provide fast and convenient links between roads and areas where the roads and streets can be managed to become cycle friendly without the need. The key is that cycle infrastructure needs to work for cyclists, not be something to be added where it doesn't impact motorists and disappear where it does. It also needs to be part of a wider strategy on walking and public transport - ie. you could have the best infrastructure in the world, but if there is nowhere to park the bike for people using the train it really becomes a bit useless. Also, painting cycle lanes on narrow pavements which conflict with pedestrian movement is simply unacceptable.
One of the key features I see in other countries is that they differentiate between streets and roads. In the UK we have had a transport policy for years that hasn't - so we have seen small streets being actively designed to take traffic overflow from roads. For example, I live near major junctions where right turns for traffic have been banned to increase traffic flow through them, and minor residential roads been used to allow traffic wanting to turn right to cut through. I just don't see this in Holland and Denmark, where they actively stop through traffic in residential areas.
I'm mostly
anti segregation. That's not to say that I don't believe that there are some forms of segregation that aren't valuable, far from it. But I am anti-segregationist on the car/daily wail/populist idea that suggests that Cyclists have little place on the roads and should be completely removed from traffic because cars are more important.. Unfortunately when segregation is mentioned in the meedja or bile-induced anti-cycling rants of the Clarkson kind that's what is meant. BUT, I think any form of segregation should be either as a last resort OR, to provide a means of travel as you say to link places effectively where riding on the roads would be a non-starter.
Segregation has subtle forms. I'm quite a fan of the wide shared-use paths around Abingdon that are great for genteel cycling, jogging, walking the dog, pushing a pram etc. They are heavily used by the community of which many use them to cycle from A2B, Schools etc. Those that want to ride fast can use the road.
I'm a fan of the path that runs alongside the A23 from Brighton to Crawley. I'm a BIG fan of Bus Lanes. I like the curtailing of Rat-Runs except peds and cyclist etc. all of which have some means of segregation from cars, but does not remove the choice of being part of the regular traffic either.
Some segregation like that shown by SteveinDenmark along major roads would be great, but it would take a bazillions years for anything significant to happen here and anything like a useful scale.
Other ideas as srw mooted are much simpler, cheaper and quicker to put into practice and would have a far bigger impact.