If AWS is enabled, after driving for a few seconds, the emergency brakes go on and an alarm sounds. There doesn't seem to be any other indication apart from the HUD. The "Brake demand" light doesn't blink. It also doesn't seem to be caused by either KVB or TVM, seeing as it happens even when those are disabled. This happened in the 14:30 service (1F43), both when started directly from the main menu and when started through free roam. The 14:58 (1F45) scenario seems to work fine. (I could drive past the station without any brakes coming on, even with all safety systems enabled)