Here in much of Canada major highways have a "rumblestrips" on the shoulders of our provincial highways.  The goal of rumblestrips is to create a subtle but noticeable noise and vibration through a vehicle if they've coasted onto the shoulder of the highway out of their lane.  They are quite helpful in curbing sleeping at the wheel or as non-damaging, physical queues to remind drivers to slow down (like when approaching a sharp turn or interchange).

Why couldn't the streets and laneways be equipped with rumblestrips (or slightly elevated, flourescent "pods" like on US Interstates) to clearly demarcate the bicycle priority lanes and to actually create a "soft barrier" that reinforces that automobiles are not permitted to drive in this space - yet, they are still allowed to use this laneway for turning or emergencies (or I guess, high volume times like rush hour).

I agree with a commenter that bicycles and motor vehicles need to co-exist on the roads - and some cities do this better than others depending on how automobile designed they are - or how strong the bicycle culture is - so the notion of restricted roads or routes doesn't really treat both modes of transport as worthwhile.  Yet, having soft barriers will not only reinforce proper laneways and space while not forcing a preference of one mode of transportation over the other.  The rumblestrips themselves wouldn't even have a significant cost associated with it as it is just a recyclable and effective as current road construction.