State Implementation Plan (SIP)

The SIP – as approved in regulation by the Massachusetts Department of Environmental Protection and the U.S. Environmental Protection Agency – requires that MassDOT and the MBTA complete the transportation improvements listed below.
  • Green Line Extension to Medford Hillside.
  • Green Line Extension to Union Square (Somerville).
  • Upgrade of the MBTA Fairmount Commuter Rail Line, including the construction of four new stations: Four Corners (Dorchester) and one new station each in the Dorchester, Mattapan, and Roxbury neighborhoods.
  • Construct 1,000 new parking spaces serving commuter transit facilities (complete).

Together, these projects are intended to reduce certain air pollutants in eastern Massachusetts. Questions about the SIP projects should be directed to the Office of Transportation Planning.


2022 State Implementation Plan Documents

MassDOT SIP Annual Report 2022

2022 State Implementation Plan Documents


Previous Documents

2021 State Implementation Plan Documents

2020 State Implementation Plan Documents


SIP Public Meeting

The public meetings will be held:

Thursday, September 29, 2022, at 10:00 AM and at 5:00 PM

Register in advance for the 10:00 AM meeting:

Register in advance for the 5:00 PM meeting:

Additional Resources

MassDEP Notice of Pub Meeting


Contact   for State Implementation Plan (SIP)


(857) 368-0639


10 Park Plaza, Suite 4150, Boston, MA 02116

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