Signs appeared early Monday at bus stops clustered around a notorious Little Saigon intersection that, in short, read: It isn’t safe here, find another stop. It was the first indication for many passengers that beginning at 3:30 a.m., buses would no longer let them board or alight on South Jackson Street and 12th Avenue South because of “safety concerns.” The routes — 1, 7, 9, 14, 36, 60 and 106 — bring passengers to downtown Seattle from Renton, Othello Station, the Mount Baker neighborhood and elsewhere, all coursing through the busy intersection that sits just west of Rainier Avenue South.