Comment by codingdave

Trains cause traffic congestion on the train tracks. Trains already stop each other, to take turns on tracks when there are single tracks going through an area with more than one train. Trains have entire dispatch offices to manage where each train is, how long their operators have been working, and have to fit very tight regulations, sometimes even stopping trains to switch people out when their regulated working time is maxxed out.

For the most part, this all works smoothly. But the idea that you can just throw more trains on the tracks without impacting even their own traffic isn't seeing the big picture.