Bear with me for a little bit here.
Once upon a time I was the kind of nerd who would draw fantasy subway maps for s***s and giggles. A part of my brain still does when I look at maps and the other day I did it again for the first time in a long time. Pick apart this idea if you would please.
I visualized a "Red Line", a third heavy rail subway line for Philadelphia that requires very little new construction - obviously a large factor in such matters - and instead mostly repurposes existing infrastructure, namely the R8/Chestnut Hill West Line.
The biggest issue I factored into my little idea was cost. What was the least capital intensive way of expanding the city's subway system while not simply throwing a line on the map for the purpose of seeing it there? It started with a thought that I've had for a long time now - the two Regional Rail lines that operate exclusively within city limits, the Chestnut Hill East and Chestnut Hill West Lines, are good candidates for repurposing. Station distances are shorter than they are on other commuter rail lines, much closer to those found on typical subway routes. They already exist as ROW with operational infrastructure. So I figured which of the two would be a better place to apply this idea. As the CHW Line both seemed a bit more reasonable a setting considering some of the transit active areas that it runs through and near and the fact that its route doesn't require it to travel through an area like Wayne Junction which would have an impact on rolling stock due to FRA regulations made it an easier fit.
The idea is to sever the connection of the CHW Line to the Regional Rail network and convert it into a third rail operating rail route with rolling stock compatible with the under-capacity Broad Street Subway. Commuter rail service would still operate along the line while third rail is installed. The route would operate over the current CHW Line with two new stations - one at Hunting Park Avenue near the former Budd factory and the recent Bakers Centre retail development in Nicetown and another adjacent to the current Allegheny Station on the R6/Norristown Line forming a station complex similar in nature to the 61st Street-Woodside Station in Queens connecting the NYC Subway and LIRR though in an admittedly economically depressed area.
South of here the line would continue along the current ROW until a point somewhere north of the current North Philadelphia CHW Station which is offset from the main line North Philadelphia NEC station used by SEPTA and Amtrak. From here a new tunnel would connect the line to the Broad Street Subway at a point somewhere just north of North Philadelphia BSL Station. The route from there would operate south using the current express/Broad-Ridge Spur tracks until reaching a newly expanded 8th & Market Terminal which would be double tracked.
Double tracking 8th & Market would involve a level of ingenuity as the current terminal is single tracked, underpinned by PATCO and hemmed in on one side by 801 Market Street and the other by a commercial concourse adjacent to the Mellon Independence Center/Lit Brothers Building. Expanding the current terminal would probably involve truncating, reconfiguring, moving or eliminating the current concourse. In addition, the current fare lines would be reconfigured to allow a gateless transfer between the "Red Line" and Market-Frankford El/Blue Line. The recent news about a potential fare sharing agreement between PATCO and SEPTA also spurred my thinking about this. The current concourse that exists on both the north and south sides of Market Street in and outside of fare lines and allows access to SEPTA and PATCO on both sides could either be open to both systems on either side via any potential fare sharing agreement or, failing that, have one side dedicated to either system - the north concourse for SEPTA's Red/Blue Lines only and the south side for PATCO.
The Broad Street Subway was built as a trunk route for a larger network of subway lines expanding throughout the city, only one of which was partially built. The current BSL operates well under its potential capacity even at rush hour so I've always believed that any new heavy rail route should operate over a good portion of the BSL to access Center City from its outward endpoint.
Playing along and supposing that the money and will existed for such a project to occur the next issues are acquiring rolling stock which would have to be compatible with the specs of the Broad Street Subway as well as a storage/maintenance yard which would seemingly require the acquisition of private property somewhere along the industrial areas that exist between Broad Street and Queen Lane Station.
Such a new service could provide some operational flexibility along the BSL. Two potential Center City terminals - 8th & Market and Walnut-Locust - currently exist. Service along the "Red Line" could operate to one or both stations depending on circumstances, such as rush hour. In addition it would provide some form of full time express service on the Broad Street Subway although this certainly isn't anything of tremendous importance. I haven't given any thought to any other extensions/expansions purely because the cost of such a thing makes it a completely improbable idea as opposed to what I've just shared which I think is merely largely improbable.
Lastly, the idea appealed to me because of the SEPTA's recent move to operate the current subway system 24 hours a day on weekends. The upper reaches of the northwestern part of the city can be more difficult to reach via transit than they need to be during off-peak hours. Rail service along the commuter railroad doesn't operate at headways to make it terribly convenient as compared to a subway. Here there is a high speed, regularly timed and convenient means of reaching upper Germantown Avenue at intervals better than commuter rail and all night long during the weekends.
What do you think?