The problem with some of these old lines is that they might have level crossings in which pedestrians or cars might occupy the tracks - so someone needs to be there to stop the train if that happens. Fully automated systems like the SkyTrain or Japan's Yurikamome line have grade-separated tracks (and in some cases platform gates as well) to ensure that sort of incursion doesn't happen.

The NYC subway system has no level crossings where pedestrians can occupy the tracks.

The only level crossing where another train might occupy the tracks is Queens-bound from the JMZ stop at Myrtle Ave & Broadway in Brooklyn. The M crosses at grade over the J/Z track.

Some less technology minded people would actually be freaked out by automated trains. The airport where I live has automated trains to go between gates and the cars very closely resemble the public trains cars without the seats.

Most likely its not a technical challenge its a bureaucratic problem. Not to mention the unions aren't going to let the transit authority obsolete their jobs.

You know that the 30's gear on the Tube was more reliable than the 1970's stuff?

Another thing about the NYC subway is that it runs 24 hours a day 365 days a year. Not many metros around the world can make that claim.

Living in New York, the amazing thing about the subway system is how they keep it running. It's old and ridiculously complex, and despite what natives say, the MTA by and large does a good job running it. There's no political will to fix it right now. It's going to take trains becoming unsafe or costing so much to keep safe that people eventually notice and start making noise about it, I think.

Yep. They do a pretty darn good job, considering what they have to work with.

And I'm not talking just the technology - they have 31 billion dollars of debt to service, and constantly get the shaft from Albany when it comes to funding. They continue to take on debt because they have mandated projects and lack the funding to complete them.