Motor assisted bicycles are great, but they beat the crap out of you. Not really a very good alternative for the elderly.
It does point toward another "reduce auto usage" argument; let's leave the cars and the roads to our mothers, fathers, grandparents, etc. Reduced road congestion will give them more breathing space and ease up on the safety issue.
Now it's obvious that the blind or those with disabilities severe enough to make them unable to operate a car must be prohibited from driving. There's no need to take up space with that.
We're talking about people who are still capable.