Budd Car--This is about FANTASY commuter rail, not about critiquing others' ideas.
(P.S. There is an excellent space for an Easton train station along the former CNJ at 4th and Larry Holmes Dr. Which happens to be in walking distance to downtown.)
Anyway, some of my ideas (keep in mind this is all for commuter/regional rail):
New York
MNRR
East of Hudson
-Restore the Old Putnam Branch. From Brewster, head east at least to Danbury and possibly Newtown or beyond.
-Extend service on the Beacon Line. As a branch from the Hudson Line, to Hopewell Jct.; as a branch from the Harlem Line, to Poughkeepsie.
-Extend the Danbury branch to New Milford.
-Extend a short branch from the Danbury branch to Ridgefield.
-Fold Shore Line East into the New Haven Line.
-Extend a New Haven Line branch to Hartford.
-Restore service along the former New York, White Plains, and Boston interurban to White Plains. This may be treated as a branch of either the Harlem or New Haven Lines.
-Extend passenger service down the West Side Branch to Penn Station.
-Extend New Haven Line service to Penn Station via Hell Gate and Sunnyside.
West of Hudson
-Restore service on the former Northern Branch to Nyack.
-Restore passenger service on the West Shore Line at least as far as Newburgh.
-Restore service on one of the routes in the Walkill Valley (either the NYC one, or the L&HR one; the former better hits town centers.)
LIRR
-Extend the Port Jefferson Branch to Wading River.
-Restore service on the Central Branch through Levittown.
-Possibly restore the former Sag Harbor line(s) and service.
NJ Transit
to Hoboken
-Restore COMMUTER RAIL service on the Northern Branch (to Nyack).
-Utilize the former Erie Piermont Branch to link this route with the West Shore Line (see above).
-Extend service along the NYS&W main line from the Northern Branch to Sparta.
-Restore passenger service along the former New York and Greenwood Lake line, at least to Pompton or Erskine, if not all the way.
-Restore service along the Lackawanna Cutoff to East Stroudsburg.
to Penn Station
-Extend the Raritan Valley Line from High Bridge to either Phillipsburg, Easton, or Allentown. This will likely have to be done via the Lehigh Valley alignment.
-Restore passenger service via the CNJ's Southern Division to Toms River (Tuckerton with effort).
-Restore the former CNJ Highlands Branch.
-Restore the former Camden & Amboy main. For NYP trains, terminate at Burlington.
-Extend service along the former RDG from Bound Brook to West Trenton (SEPTA interchange).
-Extend service along the former CNJ and PRR Flemington Branches to Lambertville via Flemington.
CORE
-Build a new tunnel linking the Hoboken Division to the LIRR via the Bergen Arches to Fulton St. to Atlantic Terminal.
-Build a new tunnel south from Grand Central to Prince George, most likely via Fulton St. and Downtown Brooklyn.
-The Northern Branch of the SIRR becomes the west approach to this tunnel, feeding into the Raritan Valley Line.
-Build a new crossing of the Kill van Kull from the Chemical Coast Line to the Northern Branch via the Travis Branch. This feeds into North Jersey Coast Line at Perth Amboy.
-A branch of the Hudson Bay tunnel ending at Bay Head links the SIRR into the broader New York subway network.
Philadelphia
SEPTA
PRR Side
-Restore service along the West Chester Branch.
-Restore service along the Octoraro Line to Oxford via Kennett Square and Chadds Ford.
-Extend Paoli/Thorndale service to Coatesville or Parkesburg (with new interlocking).
-Convert the former RDG Chester Branch into a HSR bypass allowing Airport access. Extend commuter rail along this too.
-Restore Cynwyd Line service to Ivy Ridge. Extend it to a connection with the Manayunk/Norristown Line.
-Restore the Newtown Square Branch.
-Restore the Bensalem Branch as an access route to NE Phila Airport and associated industrial area (jobs).
-Extend a subway line down the Delaware Extension (25th St. Elevated).
-If crowding occurs on West Chester Branch, reopen Chester Creek Branch to alleviate it.
-Open Swampoodle Connection between Chestnut Hill West and Manayunk/Norristown Lines to cut CC travel time.
RDG Side
-Extend Manayunk/Norristown Line service to Pottstown via Phoenixville.
-Extend Lansdale/Doylestown Line service to Quakertown.
-Restore service on the Stoney Brook Branch from Norristown to Lansdale for Doylestown trains. They will utilize the former Cynwyd Line to enter CC via 30th St.
-Restore service on the Newtown Branch.
-Restore service along the Perkiomen Branch north to Pennsburg/Red Hill via Collegetown and Schwenksville.
-Extend Warminster Line service to New Hope (maybe).
-Convert Chestnut Hill East Line into a subway.
NJ Transit
-Restore service along the Millville Branch. Utilize the CNJ line from Vineland to Bridgeton as a branch line.
-Restore service along the former PRR Atlantic Division to Toms River. A branch to New Egypt via Fort Dix will also serve as a commuter rail line.
-Restore service to Pennsgrove/Carneys Point along the former PRSL Pennsgrove Branch.
-Restore service to Cape May via the PRSL line diverging at Winslow Jct.; branches from it will also serve Wildwood and Ocean City.
-Restore service along the PRSL Clementon Branch to Hammonton (rejoins Atlantic City Line at Winslow Jct.)
-Restore service along the PRSL Salem Branch.
-Restore service as a light rail line along the PRSL Grenloch Branch. This can then continue down NJ-42 to Sicklerville.
-Develop a heavy light rail line (like the one in Honolulu) to Cherry Hill, Mt. Laurel, and Medford via NJ-38-73-70.
CORE
-Focus NJ commuter operations, due to Delair capacity problems, in downtown Camden. Do this with the implementation of the 3rd commuter rail line.
-Once the NJ commuter operation is fully developed, electrify.
-Once electrification is fully developed, build a tunnel under the Delaware River to Market East Station.
-Grenloch/Sicklerville light rail will eventually take over the River Line's downtown Camden circulator network.
-Either extend Grenloch/Sicklerville light rail onto the new Cherry Hill line or build a subway from Center City Philadelphia linking to it (following the same alignment as the commuter rail tunnel, of course).
Baltimore-Washington
MARC
-Extend Penn Line service from Perryville to Wilmington.
-Branch from the Cumberland Line to Hagerstown.
-Restore commuter rail along the B&O line from Camden Station up the Patapsco to Frederick.
-Restore commuter rail along the former WM main line from Baltimore northwest, to Westminster. Interurban rail along this line to Hagerstown?
-Extend a branch of this line to Manchester via Hampstead. Extend further to York and Gettysburg?
-Restore commuter rail along the former line from Annapolis Jct. to Annapolis. Service would diverge and head to both Baltimore and Washington.
VRE
-Extend Potomac Line service to Richmond.
-Extend Manassas Line service to Culpeper. Possibly to Charlottesville.
-Restore commuter rail along line from Manassas to Front Royal.
CORE-Baltimore
-Convert the Howard St. Tunnel into a passenger tunnel. Link services heading north and west via the WM line(s) with those heading south and east via the B&O lines. Do this, of course, under the aegis of the Great Circle Tunnel.
CORE-DC
-Develop the D.C. Union-Alexandria Union corridor into a passenger thru system. Integrate converging MARC and VRE systems.
-Develop a freight bypass of this crucial route.
MISC
-Investigate the viability of a commuter line linking D.C. with Waldorf and/or North Beach. De novo rights-of-way are likely needed.
Boston
-Electrify the existing network.
-Shift stations closer to existing town centers.
-Build North-South Tunnel linking B&M and New Haven commuter systems.
"A train or a train concept with a history of success elsewhere should by default be legal on mainline tracks in the US and so should the established operating and maintenance practice..." --
Alon Levy