I was walking to my car from San Francisco’s 22nd Street Train Station when I first saw the old man. He was on the wrong side of the chain-link fence that separated the sidewalk from the steep rocky slope that led down to the train tracks. The station was an asphalt platform beside the train tracks, set at the bottom of a ravine. Steps from the platform led up to the street, but no steps led where the old man was walking. The only way to reach that particular spot was to climb a six-foot concrete block wall.