That loop is on old maps as the "Doran Scenic Loop." It used to be paved all the way around. I don't think that the current AAA County map lists it, but earlier versions did. That is why there is the pavement 'shelf' in the slot obstacle near the top of Odessa Canyon and fragments of it elsewhere. My dad drove it in a Studebaker in the 50's during a photography field trip. He told me that the pavement was failing then and that he'd had to cut a pinched section of rear brake line loose, fold it over on itself several times, and smash it flat with a rock to have brakes again after a particularly nasty bump that pinched the line against the frame and cracked it.