> For some reason, Boston never planned for bypass capability, for trains to be able to get around stations, run express or in parallel. NYC did it, and it helps a great deal with construction, disabled trains, express trains, etc... Not all the the T is 100+ years old, and for newer lines/stations such certainly could have been done.

I used/use the D.C. metro system since I was a kid and this has always been an issue with the system. As it gets older, the system gets more unreliable (and constant budget issues from having to span 3 territories continue to defer basic maintenance) it's getting worse and worse. During the summer you're lucky to get 5 continuous days of trouble-free service. Even worse, issues on unrelated lines spill over onto working lines and the entire system grinds to a halt. Even worse, the ride is pretty bad, it's as bumpy as the NYC system, which you wouldn't expect with it being half a century newer. But it's the maintenance that's at fault for all that.

But NYC is unusual in that it has such redundancy built into it, I don't think even other large systems of similar vintage (London, Paris) have such a robust system. Doing so these days is likely so expensive it'll just never happen elsewhere. Even the newest line being built for the D.C. system is single tracked.

That being said, NYC still has issues, probably stemming from it being basically ancient (so does London and Paris). It's a noisy, uncomfortable ride, with stations seemingly randomly closed and a service schedule that's pretty opaque once until you've used it for a long time.

Recently, I was in London, and almost everyday there was some kind of outage on the Tube. It's fortunate that stations are close enough, and the bus system so good, that you can work your way around it without too much fuss (and the TfL did a remarkably good job getting employees out and about to redirect people). It's just part of being an old system, the maintenance becomes pretty heavy.

I worry about the gleaming newer systems in Asia. Huge, complex, mostly built within the last 30-40 years...mostly single tracked like everywhere else. What's going to happen when these systems are more than 100 years old like the MTA or the Tube?