The Massachusetts Department of Transportation will be having a third meeting on this project this evening in the Allston neighborhood of Boston.
They have set up a good web page with a lot of information on it, at http://www.massdot.state.ma.us/highway/HighlightedProjects/AllstonI90InterchangeImprovementProject.aspx.
Additionally, the page includes an excellent map of the area which I am posting.
The Charles River is at the top with Magazine Beach above it to the right. That is probably the BU Bridge crossing the Charles River at the top border to the right. The Mass. Pike viaduct is the thin, pointed part of the study area aimed to the top right. Barely visible stretching under the BU Bridge and to the right toward the Mass. Pike viaduct is the Grand Junction Railroad Bridge.
The map gives the impression that the area that the Department of Transportation is working with goes to the Charles River. My recollection is that they have specifically said it does not include Soldiers Field Road / Storrow Drive, the limited access boulevard which parallels the Charles River on the Boston side.
The boulevard coming from the top right corner is Commonwealth Avenue.
In an earlier report I showed how to create a Green Line A spur connecting the new Harvard Medical School (in planning on top of as much as they can get away with) to the existing Red Line B which runs on Commonwealth Avenue, I commented that all that was needed to connect the new spur to the existing line is old technology, a switch which would allow the connection. That comment said the new switch would duplicate an existing switch at Packard’s Corner.
If you follow Commonwealth Avenue downwards, you will see a much larger boulevard running to the right. That much larger boulevard is Commonwealth Avenue. Straight ahead is a different street, Brighton Avenue. The “square” where they split is Packard’s Corner, named after a long dead car dealership.
The existing switches are (or were) where Green Line B turns with Commonwealth Avenue. The former Green Line A went straight ahead on Brighton Avenue.
Here is my map showing the Green Line A proposal to put things in context.