Triples/Doubles are allowed in ATS in Nevada. As clarified by the rules, the only restrictions are in ETS2 where Doubles are only allowed in Scandinavia. I may be mistaken, but it seems to be that Triples are allowed anywhere in ATS, though, as nothing is saying against that in the rules. I am seeing a few status updates of people saying that whenever they get a triple trailer, they are kicked from the game. This may be a bug.