What we have here in Vegas are reflectors. Raised, rounded reflectors that we call turtles. A series of 4 of them takes the place of a single stripe, so the lane marking is a repeating series of 4 turtles, with about the same length and spacing as painted stripes.
In daylight the car flat out refuses to recognize the lanes at all. It wouldn't even go into autosteer on a well-marked freeway!
Tesla, please come do some testing in Vegas! It's not that far to go, and you'll really like it here. For now, AP is not usable on the highways I normally drive (215 and 95).