the real use of the north south rail link

Buried in this article is a bombshell of a lede: there is a regulatory limit on how fast a locomotive can switch "ends" from inbound to outbound and this is by far the limiting factor on operations at Boston's two terminal stations. Through running trains are not subject to this timing constraint and can make several times more efficient use of available station tracks. Four through tracks at South Station, even if they were conversions of existing tracks, would do much more to improve capacity there than the currently-planned expansion from 13 dead-end tracks to 20.

Our current state Governor has a strongly suburban base that would greatly benefit from improved operational efficiency at South Station. I can only imagine he doesn't know -- as I didn't -- how much more impact the North South Rail Link would have; it's really the only explanation for his advocacy of the South Station expansion.