I can see monotony and distraction affecting train engineers. You don’t have to steer. Why watch out what’s ahead? You can’t stop the train quick enough to avoid hitting whatever you see.
You could say the same for airplane pilots.
Regarding the automatic speed control mechanism that’s being deployed, and referred to as very expensive, I mentioned earlier that my car GPS tells me the speed of the car and the speed limit. A GPS-based speed control mechanism seems like it would be cheap.
There are (and were in this case) speed limit signs.
“A GPS-based speed control mechanism seems like it would be cheap.”
Therein lies the problem. No room for a union slush fund.
A simple GPS-based system wouldn't work because the speed limit on a particular stretch of track might be 30 mph under normal circumstances, but it would be 0 in other conditions (i.e., the train shouldn't even be there if there is already another train on that section of track).
Now take that complexity and multiply it exponentially because the systems have to be interoperable between multiple railroads if they share sections of track. This covers most of the country where AMTRAK operates on private freight railroad rights-of-way.
In my early working career, I had an opportunity to intern with the old N&W railroad. The locomotive engineer operated under a strict set of written "train orders" for the route and specific train. Extreme discipline was required as the trains were monitored by on board recorders, Central Traffic Control and interlocking manned towers. I guess like anything else over the last forty years, professionalism and job performance standards have deteriorated to accommodate social justice.