What @EggInDisguise@lemmy.blahaj.zone said, goes. But as for the amount of lanes, I do think I overlooked that one, so I edited my comment just now. I do think it's worth in general to reduce the amount of car lanes (given that induced demand's a thing).

Still, for protected bike lanes that are fully separate from car lanes, by a strong barrier (not just an elevation), I think you could do with 4, maybe 6 lanes. More would be unnecessary or dangerous for all, though.

We also have 'bicycle main pathes' where car drivers are 'guests'. That is, cars must drive behind bicyclists and not overtake them. They generally are in 30 km/hr zones, and the width of 2-3 car lanes (so about 7-10 m). Sidewalks are also present there, of course.

Typically, those are in residential-heavy areas where a lot of people bicycle (often near the city centre where most stores are). They provide that cars can drive around the centre, while bicyclists can easily go in and out of the centre.