Let no one tell you that they are too fat or out of shape to surrender their cars. A large proportion of the folks on RAGBRAI were obese - perhaps half - and yet they were riding 50-80 miles a day. Three miles to downtown should not be a problem. A mile to the grocery store? No big deal.
Yet even the folks on RAGBRAI, interested in cycling and presumably with some experience on a bike, would need some help getting started. A fairly large proportion of these riders wouldn't last a week in urban traffic. These folks ARE genuinely unsafe on roads. They don't look before changing road position. In the evenings in town they ride the wrong way, blow through stop signs, and make turns from the wrong lanes.
(As an aside, my kids started measuring the potential for a goofball maneuver based on various criteria. The biggest generic point values? Adjustable stem with aero bars, fat, male, and "wobblers" - those who mash the pedals so hard that the bike wobbles to and fro. They also shied away from those with Upper Iowa University jerseys.)