It appears to have worked in the Netherlands in the 1950s. (Notice how you don’t see many fat people.)
Don’t think it could happen in this country? Chicago banned cars on Lake Shore Drive to give 18,000 cyclists a crack at it. The video of a major freeway clogged with bikes is inspiring.
How about in Portland, where there are bicycle traffic jams and where it’s projected that more than half the trips in one corridor will be made by bicycles before long.