As shown in the above crudely-drawn diagram, I experienced total auto park FAIL yesterday. I was trying to park in the second -- and only open -- spot in a row of perpendicular stalls. Being unable to sense the car just past the first (occupied) stall, the car backed up until I applied the brake. I then let it continue to see what it would do and it continued backward until the tires hit the curb, I think just grazing the underside of the back bumper on the top of the curb. The car seemed totally flummoxed by its then inability to continue backward and it "gave up in frustration". It doesn't even say anything explicit like "auto park failed" -- it just quietly gives up. It is becoming increasingly apparent that Tesla must add front and rear sensors that can detect curbs to prevent an ever-growing number of auto park and summon-related encounters with curbs and other low obstacles (I've also encountered someone marking the edge of pavement with a row of rocks ).