thought of the day 2009 11 08 - right of way

I was walking down the street yesterday and had to move out of the way on the narrow sidewalk because there was a lady pushing a stroller coming up the street. I had to do it again when I passed a guy in a wheelchair. Now I'm kind of wondering, if there's a guy in a wheelchair and a lady pushing a stroller who happen to cross on a narrow sidewalk, who has the right of way? Does the guy in the wheelchair have to scoot off to the side? Or does the lady with the stroller have to turn around and go the other way?