My personal take on this is that cyclists and cars cannot share the road.
To me, it makes no sense to expect 200-pound cyclists to share the road with 4000-pound vehicles.
Many people, myself included, would ride bikes more often if we weren't expected to do so.
I think urban planning departments should make bike paths mandatory.
Cities should buy back or reclaim land from their city core-- from derelict land owners and the like-- and construct bike paths. It would really cost that much to put a slab of asphalt on the ground, and it may even reduce traffic congestion. Incentives could be offered to landowners with neighbouring lots to agree to add a bike path for public use.
And these bike paths would be cyclist-only. If you walk on them, it's at your own risk, and if you get run over, you're out of luck.
My only caution is that cyclists tend to differ in speed and ability. There should probably be a fast lane and a slow one. I find it annoying that cycling seems the "reserve" of those who take it seriously and pedal at top speed. Leisurely cyclists don't seem to fit into the scheme of things at all.