That is indeed sad, of course more investigation has to be done, but I heard something along the lines that the railroad tracks themselves had originally been meant for slower moving freight trains, not high speed trains, not sure if that was the factor in this instance though.
I would think they track all the trains' locations using GPS trackers on the trains, so you would think there would be a way to program things so when the GPS senses that the train will soon be approaching a reduced speed area that it would set off an alarm to remind the conductor they need to slow the train down soon.