These days though i wonder why we don't have [semi-]autonomous control there. At least for emergency stop when the end of rails is 100 feet away and your speed is 20mph - any new car have such features today.
The US does. That's what Positive Train Control does.[1]
For a long time, there was reluctance to apply automatic train stops to freight trains, because long freight trains don't do emergency stops well. Just slamming on the brakes on a heavy freight can cause derailments on some steep curves, and may cause wheels to develop a flat side. What PTC does is to display a graph of speed vs. distance ahead, and the driver must stay below the graph. The system will apply brakes if the current speed exceeds the speed limit line, but only as much brake as is required to get below the speed limit. Classic emergency stops forced a full stop, and then someone had to walk the length of the train and examine all the cars before a restart. With PTC, the speed graph will drop to zero at the end of a line, which prevents overruns. It took years, but PTC is now deployed on all US track.
There were generations of previous systems. Here's the New York Subway's classic control system, from General Railway Signal.[2] This is safe, but drastic - it stops trains by raising a metal arm at each signal, which, if raised, hits a valve lever which directly applies air brakes. There are timers, and if a train is going too fast, the brakes will be tripped by the trackside systems. At the ends of tracks, "too fast" is very slow.
[1] https://railroads.dot.gov/research-development/program-areas...
[2] https://www.nycsubway.org/wiki/Subway_Signals:_A_Complete_Gu...
Depending on the train system, engines to idle, medium level braking is probably a reasonable response if there is no operator detected.
> These days though i wonder why we don't have [semi-]autonomous control there.
This is likely the right question. Closed systems have all sorts of mechanisms to prevent overruns or at least reduce speed. Typically something sticking up from the track that will engage emergency brakes on all the cars when the train passes a certain point; and they can be controlled so that the post goes down if the train is has clearance and is traveling at a safe speed.
I suspect NJ transit does not own all the rails their trains run on. A mandate for positive train control on rail lines keeps getting pushed back, but would likely have reduced the speed of this overrun.
They bring the train to a stop.
This tech has existed for many years in motor vehicles and works reasonably well in far more complex environments than literal rails. It doesn’t seem at all like a challenging technology problem.
The things that come to mind are: failures of politicians to enact requirements, negligent or greedy rail infrastructure and/or train ownership, and unions afraid of lost jobs.