(1) Yes, VA plans to add Suffolk. The main issue is that the tracks in use
now are not the tracks they ultimately plan to use, so they don't want to build a station just to have it become redundant in a few years.
(2) In VA, other infill stations that come to mind include Orange, VA (there have been on-again/off-again efforts on this front), Carmel Church, VA (about halfway between Richmond and Fredericksburg), Norge/Toano (on the north/west side of Williamsburg; the target here is folks taking the train from that side of town, since parking at WBG stinks and expecting folks to go to NPN is a joke...does anyone know where the Lightfoot stop was?), and possibly something between CVS and LYH. I'd also add Busch Gardens (since the overflow parking lot for them is literally within spitting distance of the tracks).
@west point:
Going down your list:
-Richmond (south): I agree, insofar as most of the trains don't hit Main Street. Snarkily, one could say this is "Petersburg". The bigger problem here is the "Suffolk problem"...the long-term plan is to move traffic to the S-line, which would make any stop on the A-line redundant.
-Raleigh (already has Cary): Raleigh/Cary is probably sufficient pending SEHSR.
-Charlotte: Gastonia probably qualifies on the southern side of town. Kannapolis or Concord might work on the north side (bearing in mind that Salisbury is "only" 42 rail miles away)
-ATL (both east and west): Actually, I think "Atlanta,
anywhere" would be a good idea due to the parking problems. The fact that the NS tracks parallel MARTA for several miles (and several stops) makes this all the more inexcusable. Lenox, Brookhaven, or Chamblee seem like decent candidates (Lindbergh Pocket, the next stop east/north, has a bad layout for co-location while Doraville is, unfortunately, right next to a yard that NS probably doesn't want messed with, even if that might also make it ideal for "not blocking the line"). There's probably a case for moving to one of these stops (on the "east" side), adding a stop on the west side, and then dumping the current station as being redundant, poorly accessible, and badly located. Note that the current Atlanta station's lack of MARTA access is a killer here: If MARTA served it, this wouldn't be as strong a situation.
-Birmingham (Bessemer): Probably not a big enough city/stop to quite justify.
-Memphis: You may have a case for both sides of town at a higher service level.
-Houston
-Dallas: Going west, I'd argue that Fort Worth should "cut it" and that TRE should take care of the rest of the needs in between. Going east? There might be a case for something out by I-635...if you can get more trains.
-Kansas City: Three sides to look at. Independence covers the River Runner. There's no good location towards Chicago on the Chief, and towards Topeka the pickings are a little slim as well (maybe out by I-435?).
-Chicago: On the east side, Amtrak has experimented with Hammond-Whiting on the LD trains. It wasn't a big success. Most of the other routes have a stop (Joliet, Galesburg, and Glenview). Something co-located with the SSL (at 75th Street) might have more success, but there might just not be the demand here.
-Minneapolis-St. Paul: There's probably a case to add a Minneapolis station as much as anything.
-Denver: Agreed on both sides of town. In particular, westbound should help with the Ski Train as well. Eastbound, is there anywhere you could co-locate with their mass transit system?
-LAX: All of the Amtrak routes have a stop elsewhere within the Metrolink network, but there might be a case to move the Chief over to the San Bernadino line and add one infill station at an existing Metrolink stop. The case for the Sunset Limited is more of a mess because of track configurations...ideally you'd give them both the same stopping pattern going out that way, but stopping the Sunset at San Bernadino would involve a
bad backup move likely to give you a peeved host railroad...while moving the Chief to the Sunset's tracks is just going to add a host to the operation and make things worse for everyone.
-Washington, DC: You already have Alexandria and Capitol Beltway...I mean, New Carrollton. Already covered. While we're at it, Baltimore has BWI (to the south). Martin Airport might be an option to the north...but as usual, I'm not sure of the economics of adding the stop vs adding travel time.
-Philadelphia: Adding some trains to North Philadelphia only seems justified if you start gentrifying the area as well. Note that both routes have high-frequency commuter service, so you could arguably add any of those stops...but those time arguments show up again.
-New Rochelle: Already stopped at by some trains, already suburban to New York.
-Pittsburgh: Three one-a-day routings out of here, two are in the middle of the night. Dubious value.
-St. Louis: Alton to the east, Kirkwood to the west. Covered.
-Cleveland: Already has Elyra.
On all of the NEC discussions, I'd say that if you got to 2-3x hourly service for a given level of train (e.g. Acela vs Regional), mixing stopping patterns (with a consistent number of stops) might be a winning move.