Keep in mind that this looks like it's using a lot of spaces, but there's only one lane for cars each way. Cyclists and pedestrians use way less space than cars, so if a significant part of the population uses those modes of transportation that would otherwise have been in cars, that's a far more efficient use of space.

The flip side of that is that it's pretty feasible to transform existing car infrastructure into much nicer infrastructure - shave off a single lane, and there's a lot that you can do with that.

The Netherlands is more densely populated than the UK, I think, especially in the Randstad.