I'd recommend Vancouver as a decent example of how segregated lanes can work in a North American city.

That said, can you give specific examples of what you mean by "make car infrastructure worse"? Usually segregation is just a matter of putting a barrier on an existing bike lane and painting lines, which doesn't actually change anything for drivers who stay in the lines. In some cases, a lane may be converted, but this rarely impacts travel times much for the same reasons adding additional lanes doesn't improve travel times. Vancouver did lots of traffic studies on this criticism in particular that you can read if you're interested.

> add a bike lane to an existing road

Are you imagining an alternative in which a bike network is added to a city, but not using "existing roads"? Where would these entirely-new roads be placed? Would you knock down the buildings between two car-infrastructure-roads, to pave it for bicycles? I suppose you could remove the car-infrastructure-road entirely and make it just a bike-road / linear park. Or you could put the bike lane underground? Or build a separated-grade elevated parkway network above the city?

You put a sign at the start of the road. "Bike street". This means cars allowed but at bike speeds. You have different paint on the street too, to make it very different from a normal road. I have seen them popping up here and there and it works very well in the towns I bike in.

[1] https://www.reddit.com/r/bicycling/comments/e0qxxz/we_just_g...

As reasonable as that sounds, I think this would fall into the GP's complained-of category of "making that road significantly slower and worse for cars", and does not meet their ask for "a separated infrastructure grid for pedestrians and bicycles".

I remain very curious to hear their vision!

You don't need to make every street a bike street. It's enough if there is a way of getting safely close to your destination. Both for cars and bikes. The car drivers can drive on the next street unless this is their destination location. Works just fine in other big cities so it's just a question of getting used to a slightly different road to work/home.

To be clear, I definitely agree with you, I just don't think ThunderSizzle would. So it's ThunderSizzle's ideal that I am confused about, and trying to clarify. I think ThunderSizzle has asked for a (to my imagination) impossible-to-reach standard, and you have provided a very practical compromise, but exactly the sort that they would probably reject as infringing too much on existing car infrastructure.

I said roads, not streets. I've seen high-speed highways that have been modified to add a bike lane to the middle of no where for miles on end.

This is beyond useless, and is very dangerous as your combining high speed vehicle travel with bikes and pedestrians. The typical response is to then convert the road to a street (e.g. lower the speed limit, reduce lanes, etc) instead of moving pedestrian traffic away from roads. The traffic is still there, because it's the only route, but now you've added the occasional brave and stupid bicyclist or pedestrian.

Beyond that, it's more inefficient for pedestrians, because road layouts tend to follow inefficient directions that add unnecessary travel time for pedestrians.

Oh that makes sense. Yes, I keep seeing proposals to add bike lanes to highways and I just think, who wants to ride a bike next to all those high speed vehicles with no shade?