Technically two or three of the silver line buses are also considered to be subway, too. I believe SL1, SL2, and SL3. They’re subway fare and they go underground at some point

And free outbound from Logan! Though I must say, the last time I did this it was a bit of a nightmare. The SL1 was very late and we were packed in like sardines.

Boston is a very small, dense city, only about 50 square miles. A quick check of wikipedia shows Tokyo proper is nearly 15x the size.

Not that the adjoining cities of Boston, Cambridge, and Somerville have a public transit system that covers all completely (or indeed that even what falls under Boston is comprehensive to some areas with respect to the subway) but the Boston metro does have some form of transit that covers the area within the metro proper--past which it peters out aside from commuter rail--which is decent but which mostly functions as, well, commuter rail.

Boston is no denser than Tokyo, and compared to European capitals, very underserved by mass transit. The MBTA is a shitshow and it is fairly unusable as a reliable means of transportation.

As someone who has lived in both Boston and San Francisco.... I'd choose Boston's infrastructure any day. We complained about it constantly, and then we came to SF. And desperately miss it.

They have not included the Green Line which is underground in the central city but is more like a tram in physical dimensions. It is considered a part of the network.