Most of the flood events have advance warning so you have 24-36hrs to evacuate. If you have a bike, but not a car, it seems a perfectly valid way to get to higher ground, unless you live in Bangladesh and higher ground is 500 miles away.
For more rapid-onset emergencies such as the London terrorist bombings of 7/7 or the Tokyo earthquake, experience shows that bikes are one of the most reliable and useful ways to get around, and bike shops tend to sell out their stock within hours.
I'm not sure if bicycle evac is safe for forest fire or volcano.
Also its not very useful of you have less mobile dependants, old people, children, pets etc.
The idea that there will be armed gangs of ruffians holding you to ransom at gunpoint and you are safer in a car is not really bourne out by experience.
Last edited by MichaelW; 05-31-11 at 02:52 AM.