I decided to ride along in an AI train to just go along Sand Patch, and I found that, to my surprise, AI trains obey the passenger speed limits set on Sand Patch. This is odd because it involves getting trains up to speeds they can't actually make any power at; like a GP40-2 at 79 mph, and because when the player is in control, they are told about the freight speed limits. So it's not a case of the game treating freight trains like passenger trains. The AI probably just does not know how speed limits work. Which can be dangerous if there is something like a 120 passenger limit but 60 on freight. The AI would not only disobey the freight limit, it would probably break any sense of the laws of physics and get the freight train up to 120 mph. AI should at least be coded not go above the rated max speed for any locomotive... This cheeky guy thinks he can go 75 mph here!