In a few places, that might have happened ages ago, but it's not within memory. In most of town, we're light years away from being bike friendly, so it's not like we'll hit that problem any time soon.
U of M's campus is where it might have happened long ago. The hill dorms are a better bike distance to central campus than walking distance. Ages ago, when most of the central campus classes were closer to State Street, the bridge by CCRB might have had a lot more bike traffic than foot traffic. I remember when I go there in 86 there were a good number of us who biked to central campus. But even then there were many more people on foot. I'd have to wonder what the mix might have been like when they built Markley in the late 50s, or during the bike boom of the 70s. The other Hill dorms had all been there for a while.
Actually, the historic aerial photos at MapWashtenaw show the bridge not there in 1966, but in place by 1979.
And, of course, the diag itself has always had mixed traffic, but it's a 'bikes are permitted but not really welcomed' area.
Ken