In lieu of something new and exciting, here's a whole pile of links about the train that shares the name of the avenue, the Franklin Avenue Shuttle:
History: A great piece from Forgotten NY here. Fascinating tidbits include the lost stops at Dean Street and Consumer's Park, the Malbone Street Wreck of 1918 (the worst disaster in the history of the NYC subway), the track's origins as a legitimate line that ran straight on down to Coney Island, and the resurrection of the shuttle in the 1990s. Wikipedia has a bit of info here and here (including the bit about how the extension of the D straight through to Coney robbed the Franklin Avenue Line of transfer passengers).
Celebration: The NYT did a nice piece on the shuttle this summer, which lauded it as a community institution and the most on-time train in New York City.
Service: Leaves on the ones at each endpoint station (1:01, 1:11, etc).
Pipe Dreams: And to close it out, here's a proposal that's not going to happen anytime soon but is a fun idea nonetheless--an extension of the shuttle to connect it to the G train. I've also heard the suggestion of drilling beneath Prospect Park to attach it to the F at Bartlett-Prichard floated, but at over a billion dollars per mile, I don't think that's happening in the near future, either.
Nothing much to conclude here, beyond the fact that once upon a time I could have walked out my door on Dean Street, walked 100 yards, and hopped a direct line to Coney Island. That would have been something. At least today I could take the B49 bus direct, but something tells me it'd take longer.