STrRedWolf wrote: ↑Mon Mar 06, 2023 8:53 am
Given past traffic patterns for two decades, I think it's overdue. MARC has trouble even with its current service due to freight interference on a regular basis. Expansion to three-track service was in the cards back in 2007.
The thing though is around DC, to keep going south you need to hit Met to Capital (QN/F tower) to Alexandria, which involves blocking track around Riverdale. Put a flyover in that wye so freight can not block two tracks moving onto that wye and you free up capacity there for MARC to get through.
I peeked at some aerial views of the formation in Riverdale and it looks like either a flyover or a diveunder would be feasible to get traffic to and from the diverging track on the south side of the wye. My rough guess is that a flyover or diveunder track would diverge at a brand new interlocking immediately past the DC boundary, to ensure the shallowest possible gradients for trains coming off the Landover Sub.
Because of the Riverdale level crossing’s presence and a total guess that closing it would be unpopular, I think the easiest conceptual plan for a flyover or diveunder to the diverging track on the north side of the wye would be to extend the existing third track through Riverdale station, have it switch sides around Lafayette Avenue and then extend through a rebuilt College Park station to the existing interlocking at Greenbelt station.
It’s not clear to me from the aerial views if there’s enough horizontal distance on either side of the wye for a flyover or a diveunder, so this is all a total guess on how a grade separation could be achieved.
STrRedWolf wrote: ↑Mon Mar 06, 2023 8:53 am
Take that, plus the push to four-track down past BWI and to the GROVE interlock (although I'd go further to BOWIE) as well as the station expansion onto Track 1 at New Carrolton, and you'll free up a lot of track flexibility.
I agree completely with this. However I suspect that the next four-tracking project will likely end just south of the DFW Sullivan MOW yard, because of the expense of reconstruction at Odenton station. There’s already a stub interlocking there for the yard lead so expanding it temporarily to provide an end for Track A seems very plausible.
STrRedWolf wrote: ↑Mon Mar 06, 2023 8:53 am
At the end of the day, if you got passenger traffic, you need at least one track for it. Double tracks let you snake the passenger train around freight. Triple track helps on congested freight lines. Quad track only helps if you got the flexibility built in as well, and marks where you start getting diminishing returns.
The entire Northeast Corridor would benefit hugely from being four tracks from HANSON to BRIDGE. In my opinion, the only part of the Capital Sub that would likely benefit from being four tracks is the segment from Dorsey MARC station to Savage MARC station, to allow through CSX freights and MARC trains to be dispatched around any trains entering or exiting the Jessup Auto Terminal.