The Massachusetts Executive Office of Transportation has published some animated 3D renderings of the proposed stations on the Green Line extension, which is scheduled to begin service in 2015. Pictured above is the Union Square station, which the Commonwealth is proposing be located along the existing Fitchburg Line railroad right-of-way… that means you’d have to walk up the hill by the Dunkin’ Donuts to get to the station, something Union Square transit advocates object to (it’s harder for elderly and disabled folks to reach it). The advocates’ alternative, though, is to run the Green Line as a streetcar directly into Union Square from about where the Target store is located at the end of Somerville Ave. That’s not likely to fly.

There’s a bunch more information on the web from the Commonwealth, from the City of Somerville, as well as from Union Square Main Streets, a great neighborhood advocacy organization.