It's not rocket science. It's just called CBTC and is what the MTA has on the L train line because it was in comparison built much more recently and is "simpler". You can't stack the old cars close together until they roll out all the CBTC upgrades, which is a massive engineering project. I don't think they're as efficient as they could be, but we shouldn't underestimate the amount of work.

https://en.wikipedia.org/wiki/Communications-based_train_con...