New York is upgrading its subway signalling system [1] from pessimistic to optimistic. Sure, denying entry into an occupied block to the next train prevents collisions. But it also wastes time, energy and money. If there is an emergency on the held train, it’s longer to the station. To say nothing of the added wear and tear starting and stopping entails.

[1] https://en.m.wikipedia.org/wiki/Signaling_of_the_New_York_Ci...