That was my impression as well. You have to babysit the AI the whole time and if you fail to do that it's basically your life (and others' of course) on the line.
Run on premade, static tracks with clearly divided "roads" from the rest of road participants.
Their role is to stop the train in an emergency and adjust to speed etc. to track/driving conditions.
Automating their job probably wouldn't even need the complex ML used for self-driving because the context is significantly simpler and relatively well defined. Maybe a team in city might need such a model but it would still be a significantly simpler task than driving a car.
Trains are really unpredictable. Even in the middle of a forest two rails can appear out of nowhere, and a 1.5-mile fully loaded coal drag, heading east out of the low-sulfur mines of the PRB, will be right on your ass the next moment.
I was doing laundry in my basement, and I tripped over a metal bar that wasn't there the moment before. I looked down: "Rail? WTF?" and then I saw concrete sleepers underneath and heard the rumbling. Deafening railroad horn. I dumped my wife's pants, unfolded, and dove behind the water heater. It was a double-stacked Z train, headed east towards the fast single track of the BNSF Emporia Sub (Flint Hills). Majestic as hell: 75 mph, 6 units, distributed power: 4 ES44DC's pulling, and 2 Dash-9's pushing, all in run 8. Whole house smelled like diesel for a couple of hours!
Fact is, there is no way to discern which path a train will take, so you really have to be watchful. If only there were some way of knowing the routes trains travel; maybe some sort of marks on the ground, like twin iron bars running along the paths trains take. You could look for trains when you encounter the iron bars on the ground, and avoid these sorts of collisions. But such a measure would be extremely expensive. And how would one enforce a rule keeping the trains on those paths?
A big hole in homeland security is railway engineer screening and hijacking prevention. There is nothing to stop a rogue engineer, or an ISIS terrorist, from driving a train into the Pentagon, the White House or the Statue of Liberty, and our government has done fuck-all to prevent it.