They just announced the massive 24 day closure of the Braintree branch in September:
Link
The really interesting thing in the announcement is a stated longer-term goal of raising red line MAS above 40mph which is very intriguing. Does anyone know when the last time the red line ran above 40 (if there ever was a time)?
Bradley H. Clark's 1972 book South Shore Quincy - Boston, celebrating the 1971 opening of the Quincy Red Line extension, does not explicitly list the track speed limits on the extension. The book does state, however, the "South Shore Cars" built by Pullman-Standard (015xx - 016xx series) were designed for a max speed of 70 m.p.h.