Originally Posted by UniChris

The fully separate bike route is great for little kids in summer, but to be the ultimate answer two conditions are necessary:

1. It needs to be plowed within a few hours of the road after each winter storm
2. Because it's invariably far more dangerous at intersections (where most of the crashes occur) it needs to go a long way - ideally at least a mile - between them

Any time one has to interact with traffic anyway, you're really better off on a safe portion of the road.

And if there isn't a high confidence that the separated bike path is going to be managed as a true year round transit (vs simply "recreational") resource, then it's much better having that width as part of the fungible roadway space, than having it walled off for bikes 8 months of the year and unavailable even to bikes much of the other 4.