Midwood, Brooklyn
The LIRR Bay Ridge Line continues to the northwest in a trench running through Midwood.
McDonald Avenue / Avenue I Station: The tracks cross under McDonald Avenue, which at this point hosts the elevated BMT Culver Line (F train). At the time the original Bay Ridge Line was built, McDonald Avenue was called Gravesend Avenue and the Parkville station was located here.
The 2006 Hagstrom street map I have still indicates a spur of some kind extending to the southeast of the Bay Ridge Line and, presumably, into whatever was in this area before it became a ShopRite grocery store. The large, decrepit concrete building to the south of the ShopRite certainly looks like it had an industrial past and whatever the ShopRite was before the facade modifications may have been industrial as well. However, I found no trace of the spur in the pedestrian passage between the dead end of 19th Avenue and the retail area, and whatever cut was there may have been filled in - unless there's a hidden tunnel?)
This intersection presents some challenges for direct transfer between lines as the Bay Ridge Line passes a few hundred feet north of the end of the platform for the Avenue I elevated station. One suggestion from the RPA's 1996 proposal is to construct a tunnel down McDonald Avenue to replace the slow-moving elevated track. The Avenue I station would then, presumably, be integrated with the rail-line station. As much as the businesses and residents of the area would probably like a tunnel (but reject it because of the street disruptions needed for its construction), the costs and complexity of such a modification (whether deep-bore or cut-and-cover) would only add an additional obstacle to getting anything built.

51st Street cut by the rail right-of-way

19th Avenue cut by the rail right-of-way

50th Street bridge over tracks - note unusual separation of sidewalks from the street

50th Street bridge over tracks

Pedestrian passage near the tracks at the end of 19th Avenue

Pedestrian passage near the tracks at the end of 19th Avenue

Rail line near the pedestrian passage (near the old rail spur?)

Truck dock for the ShopRite

ShopRite parking lot (location of old rail spur?)

Decrepit industrial building (south of old rail spur?)

Decrepit industrial building

Decrepit industrial building

Demolition permits

South side of industrial building

Culver Line down McDonald Avenue

ShopRite

Avenue I station

Avenue I station stairway

Culver Line running north on McDonald Avenue over the freight line bridge

Freight line running behind ShopRite

McDonald Avenue bridge supporting some kind of duct or pipeline

Engine 250 Station - 126 Elmwood

Older single-family homes on Avenue I at 2nd Street

East 3rd Street bridge over tracks north of Elmwood Avenue

Large contemporary apartment building on Elmwood Avenue

Contemporary row McMansions in the shadow of the 70s-era Marien-Heim Tower

Marien-Heim Tower

Old apartment building on Elmwood Avenue

Fountains seem like a good idea, until you don't care enough to maintain them

Ocean Parkway

Benches beside Ocean Parkway

Tracks leading up to Ocean Parkway Bridge

Detail of retaining wall near Ocean Parkway Bridge

Ocean Parkway

McMansion on Avenue I east of Ocean Parkway

McMansion under construction

New McMansion beside old McMansion

McMansion

McMansion

Street of McMansions dead-ending into the railroad track

Old Synagogue on Coney Island Avenue

Old Synagogue on Coney Island Avenue

Guess he didn't have the money to finish the renovation