The first thing I'm wondering is who is going to pay for all that road-work? It sounds expensive. I can just hear the howls of protest at the city council meeting. I'm proposing perhaps a hundred miles of bike-roads. Not just a couple of intersections.

The double entry at intersections might work in non-snow areas. But around here the plows have to have access to the full width of the road. The separate lane at intersections could only be done with painted islands, which would get covered by snow and slush. Speed bumps would be hard to plow as well.

Regarding blocking off the road, I think that would really antagonize mv drivers. I know when I get "trapped" I'm NOT at all happy. As a cyclist, I wouldn't want to shoot myself in the foot like that. The point is not to ban mvs from the bike-road, only to discourage them. A stop EVERY block would do that.

The great advantage of using signs to make a bike-road, instead of physically changing it to be unfriendly to cars, is that you do not diminish the road's utility for cyclists. I would hope that bike-roads would eventually become bike-highways with huge bike traffic. You'd want a good road for that, not one full of speed bumps and islands.