When making an individual or family emergency plan, I don't think that it's reasonable to trust in the availability of shared transportation assets like public transit, rental cars and car sharing services, ride sharing services, taxis, public bicycles, and so on.

But I also agree that having a bicycle for every member of the family might be the quickest way to escape when traffic is bad. Keep in mind the distance that you need to traverse -- only the very hardiest residents of Miami could have gotten out of Irma's path on a bicycle.