The caption on the photo at RailPictures.net says "An auto train makes it way up Cuesta Grade through the horseshoe curve on UP's Coast Sub"

http://railpictures.net/viewphoto.php?id=272045&nseq=0

Google Maps puts the Cuesta Grade in the area just north of San Luis Obispo, CA. Looks from the map that there are a couple of horseshoe type curves in the region there.

Thanks for posting this picture.