This would replace the 3rd Avenue Elevated which ran in the Bronx until 1973. That part of the Bronx has to deal with long bus rides. Either a crosstown bus, or ride the Bx55 all the way down to the . Fordham Plaza has no direct subway service, a 6 block walk, the Bx12, or the Bx12 SBS is needed to get to the nearest subway stations on Fordham Road.
The East Bronx also has long bus rides, the Throgs Neck PJs have a long ride during rush hours (up to 30 minutes, or even a bit more) from the Bx42 to Westchester Square during rush hours.
Other parts of the Bronx (most of Soundview, Clason Point, most of Riverdale, Co Op City, etc) are bus dependent too.