i was talking to a neighbor and he raised some good points about the need always for automobiles
the elderly and infirm are not in shape to use bikes so they will always need cars to get around. also if you have to travel to work and the distance is more than 30 or so miles a bike is not practical assuming you average 15 mph on a bike.
a bike is a five fold increase in speed over walking assuming you travel at 2.5 mph walking and 12 mph riding a bike, so a bike is just a bit better than walking really.
just some food for thought.