Signals designed for slower trains were unsafe with faster trains and bad maintenance unless the separation between trains was massively increased and speed limits were aggressively enforced.

Bureaucracy was slow to recognize this causing accidents. Then in an overreaction to accidents they added slowdowns and increased separation, without doing a whole overhaul of the system. Then maintenance issues on speedometers and speed signals forced trains well below speed limits to prevent accidental triggering of speed signals. Also trigger spreed signals that were known to be defective was blamed harshly on operators.