I don't understand this perspective that much. Have you seen how road traffic works internationally, specifically Europe? There are many examples where significant bike traffic can safely share the road with cars. The Netherlands is one of the best examples here.

The issue is that: 1) Road design - many/most cities do not have adequate road engineering to deal with bikes 2) Driver training - Road drivers in the US aren't trained to deal with non-car traffic 3) Weak Bike traffic law enforcement - I don't think that bike negligence is a key cause of accidents but I do agree that police enforcement of traffic laws on cyclists is lax.

So I disagree with the notion that bike traffic needs to have a separate roadway from urban traffic. I think there are plenty of good examples where a sharing system works.