[squeaky-clean]

They're slowly switching each line to a CBCT based signaling, the lines that do have it are vastly improved. Aside from all the budget and construction corruption issues of the MTA, it's difficult to do because the NYC subway is expected to run 24/7. And so upgrades need to be scheduled around limited times during which lines can be shut down, usually just a few hours overnight. And also keep the old system running while upgrades happen which tend to take years for a full line upgrade.

https://en.m.wikipedia.org/wiki/Communications-based_train_c...

[mike22]

Anecdotally, CBTC is a greeat improvement in many scenarios. On long and straight stretches between express stops, trains now fly along (probably at least 40mph; never got to see inside the TO’s cab). And upon approaching an occupied station, they slow down to a crawl but keep moving until about 25-50 feet before the station, instead of being stuck several fixed blocks back before the station. Thus there is much greater track capacity = more (potential) trains per hour, and generally more reliable trips.