Looking at the D street hotel map in the other thread, and thinking of the growth here and in Southie, what would be good possible routes for a Southie/Seaport streetcar?
I think like a City Point, down broadway, up D street then into the tunnel would be great. It's a pretty direct connection, would run in loops and hit major residential and business areas. In the seaport you could even take out a lane and make it dedicated ROW.
The biggest hangup I see is Southie. In reading about the bike lane proposals, people yelled about double parking as an excuse to go against bike infrastructure, so this would need a lot of soothing. Maybe it belongs in the crazy transit thread, but is this the best routing in peoples eyes?
The old City Point line that ran into the subway until 1953 is roughly the route of the current 7 bus. Since the 7, 9, and 10 all overlap once they reach Summer/L that's easily the ripest route for a local streetcar spitting out of a dual-mode Transitway.
Now...one improvement to the area that is coming imminently is the Massport construction of Conley Terminal Haul Rd., which will span Summer St. to a Farragut Rd. extension roughly where Power House Rd. meets Summer on the other side of the bridge. As part of that project Massport will be creating a diagonal connecting street
here between Southie Haul and the Summer/Drydock intersection so the trucks have a straighter shot to the bridge and don't tie up Summer traffic @ the Pumphouse Rd. light. That in turn serves up a straighter shot for all transit vehicles heading to Southie out of SL Way. Laying tracks from SL Way over this connecting street and the bridge is pretty because the bridge-proper--all 4 lanes of it--is now the only place on the Seaport side where the trolleys run in full mixed traffic. All the rest is restricted to trucks and transit vehicles.
So if you do street-running in Southie it's a manageable 1-1/4 miles in full unrestricted traffic on the Southie side to Marine Park @ City Point. Easier sell on the neighborhood. With that effectively displacing the 7 then you can fiddle around with the 9 and 10 to recalibrate those routes to be a little more complementary to this setup.
The other option, a little less attractive, is to lay rail on the Conley Haul Rd. itself. That more or less follows SL3's old route a block north of the old E. 1st St. routing. Misses much of the neighborhood density, but has the big attraction in a street-running phobic state and neighborhood of keeping the tracks entirely on the truck- + transit-restricted roads and only intermixing with cars on the 4-lane bridge. Light volumes, no parallel parkers, no double parkers, minimum possible traffic signals...and no amateur drivers period.
To make this work they would need to hit a home run on the TOD potential of that barren north side of E. 1st that the haul road will subdivide into a new block that can be fully redeveloped into a transitional mixed-use block buffering the dense residential from the waterfront industry. As an economic stimulator it makes sense to have a complete TOD solution here for the biggest swath of all-new density the neighborhood has ever seen. If the street grid gets extended so Farragut on one end meets the haul road and a pick 'em best-2-out-of-3 of M, O, or P get extended then you have a couple intermediate stops. And they can get to E. Broadway/Marine Park or Columbia Rd. by putting a trolley reservation on the park grass.
That traces the outline of the neighborhood and serves up the most rapid transit-like stop spacing for a fast trip. But because it misses the gut of the neighborhood the redevelopment anchor along E. 1st has to be very strong, the trolley frequencies have to be very good and worthy of the extra precautions taken to avoid general street-running, and the buses have to be recalibrated to complement it with a thick, effortless transfer net. Possibly even with an Urban Ring bus flank going Transitway --> E. Broadway --> Red Line Broadway or Andrew --> Dudley to balance the rest of the neighborhood's rapid transit-ish coverage.
Food for thought. In a perfect world a "7" Green Line branch is most logical, since it used to be a real thing. But the other option is worth considering politically if traffic separation and TOD coattails are needed to move the resources. Either way is transformative to the neighborhood...one just requires a lot more multimodal TLC on the Yellow Line side to make sure everyone has equitable access to those benefits.