Another week-plus shutdown looms for a core section of the MBTA.
The agency plans to upgrade its century-old signals in the Green Line’s central tunnel, requiring the closure of much of the line through Downtown Boston from Sept. 19-20 and Sept. 26-Oct. 4.
The nine-day shutdown will extend as far west as Allston on the Green Line’s B branch, to Kenmore Square on the C and D branches and to the end of the E branch at Heath Street…