Re: high level commuter rail platforms
Is there space to potentially end up with four tracks, and side platforms on the outer two tracks (similar to the Newark Penn Station to Zoo Interlocking section of the Northeast Corridor, excluding Newark Penn itself (and the extra platform tracks at Trenton)) or is this going to be limited to a single express track?
Physically possible...yes. Boston & Albany built the line to a contiguous 4 tracks between Back Bay and Framingham, contiguous 3 tracks Framingham-Southborough, and mostly 3-track on the 5 miles east and west of both Worcester and Springfield. Nearly every line out of town was originally constructed as 4 tracks until it shed a couple branchlines' worth of traffic. It was all they could do in the 19th century with unidirectional signaling; opposite-direction train meets were cumbersome to stage because of the extra local signal staff it took, and they were generally avoided until you got further out on the branches. Even the branches were nearly all double-track instead of single for similar reason.
It no longer became necessary to overbuild like that once bi-directional centrally controlled signaling got perfected. That's why so many formerly 4-track lines coast-to-coast got busted down to 2, and so many 2-track lines got busted down to single-tracking with passing sidings. It wasn't completely because of loss of traffic; when 2 bi-directional tracks cover the same traffic density 4 unidirectional tracks used to, it'd be stupifyingly expensive for a private RR to keep maintaining all 4 tracks bi-directional unless they're expecting traffic growth of the extremes that would've required 7 or 8 unidirectional tracks.
Ironically, the only place in the country where "traffic growth of the extremes that would've required 7 or 8 unidirectional tracks" happened is exactly those NEC locations you cited. Welp, Pennsylvania RR started installing bi-directional cab signals--the very same type still used there today--on the NEC concurrent with its electrification installation in the 1920's. That was their move to effectively double the track capacity before all manner of electric service saturated the works with traffic.
You will never ever in the next 100 years come up with the traffic levels to require quad-track anywhere on the B&A. They went to bi-directional signaling in 1963 in prep for the Mass Pike claiming 2 of their 4 tracks inbound of Auburndale. The only reason there's a capacity pinch today is because there's only 1 set of crossovers between the west (New Balance) end of Beacon Park and Framingham Jct., so it's not set up to allow for nearly enough meets or overtakes. Add crossovers at about 1 every 2 stations inbound of Riverside, and 1 every 2.5 stations Riverside-Framingham (same spacing as Framingham-Worcester), and you basically get all the pre-1963 track capacity back.
Exceed that pre-1963 track capacity? Well, all-time passenger RR traffic hit its historical highs in the Roaring Twenties when Worcester was the manufacturing anchor of central New England, there were 3 or 4 branchlines to feed out of Boston, and freight traffic was many many times higher than today. If that didn't exceed the B&A's capacity at the time then I don't know what you can possibly throw out there in the 21st century that would exceed it now. The freight's gone inside of Framingham. The only branchline left to exploit is the Fitchburg Secondary out to Northborough or Clinton. Aside from the Indigo infills in Allston and Newton Corner and possibly the Millbury/Route 20 infill that the town passed up 15 years ago, there are no additional mainline infill stations left to construct. The best comeback story City of Worcester can muster still probably isn't enough to reclassify it as its own distinct metro area.
Indigos to Riverside, NSRL, Amtrak, and electrification for all can all pretty much coexist on the 2 Pike-constrained tracks out to Auburndale without gridlock.
-- You'll have the permanent easement for 1 mile along Beacon Park that retains extra running tracks between West and New Balance stations, and plenty of crossovers to weave around the Indigos.
-- Maybe you drop another stretch of 3rd iron from Auburndale across 128 so an Amtrak train can break away from the pack and sort itself from the pack at higher speed.
-- Maybe you do 1 more such high-speed passer further out, like the cut at Natick.
-- You must do passers at Ashland, Southborough, Westborough, and Grafton for freight clearances around full-high platforms, but they need not connect together contiguously. Intercity trains won't even need to use all of these passing tracks to serve their tippy-top service levels; they would only exist as a mundane technicality for level boarding.
But that's it. This isn't going to outright overtake the Providence Line as the system's densest in any universe, commuter or intercity. And the Acela is not running here, so you also don't have to set it up with extra tracks for a 165 MPH HSR train to overtake a commuter rail local averaging half that when starts-and-stops are factored. In MBTA territory it is at best a 90 MPH line with a couple sub-80 curves and a couple straightaways where a nonstop Amtrak could plausibly hit 105-110. You can do that all on 2 tracks, ample crossovers, and a couple strategically placed passers for the intercity trains' benefit. The only thing you can't do is 100 MPH Amtraks inside of 128, because the frequent Indigos will probably be setting the speed limits for all users at not a whole lot higher than what it is today. But the NEC doesn't exactly set speed records up the SW Corridor once all the branchlines start mashing together, so I'm not sure how much there truly is to gain ripping up every Pike overpass and retaining wall to try to squeeze like hell for a 3rd track between New Balance and Auburndale. Not enough of a speed gain for enough trains to make a difference.
The satellite images on Google Maps leave me with the impression that having a total of three tracks at each affected station would probably at least not run into any buildings. Norwood Central / Norwood Depot seems to be the tightest area, and the bridges appear to have been designed to carry four tracks over Guild St. (I suspect consolidating the two stations into a new Norwood Central between Guild St and Nahatan St is likely the way to go there.) And the amount of bridge work required for full tripple tracking is likely excessive, so a freight passing siding at each station is probably the way to go.
Very, incredibly excessive. Franklin will never have 100% full-highs. The costs are too great since this was an ROW that was never historically >2 tracks, the freight traffic too limited to induce any delays from the act of flipping up and down the retractable edge of the mini-highs, and ridership characteristics still a bit too mid/low-density suburban to make stopping at a mini-high a delay inducer for passenger schedules. It is what it is.
There's only 1 guaranteed freight round-trip between Walpole Jct. and Readville Yard that happens every single day over the Franklin no matter what. Second trips can happen some or even most weekdays, but aren't guaranteed. All of them are midday off-peaks. If South Boston starts getting real port freight in a few years, you'll see a late night and/or overnight trip added Walpole-Readville. It's very meager freight traffic. Some of the carloads just happen to be wide-loads, and CSX is protected by interstate commerce law with irrevocable wide-load rights. CSX already voluntarily gave up the wide exemption on the inner Worcester Line in the Beacon Park swap, and it would be unwise to salt over the southside's last clearance route into Boston. So fair is fair as far as Franklin's status.
But there's not much reason to twist selves into a pretzel modding stations here. On the outer Worcester Line those mini-highs actually will in the future start inducing dwell delays and will start fouling passenger slots when the freight up ahead is flipping the platform levers...so there is scheduling motivation out there for raising the platforms after a certain service increase density. Even when the passing tracks aren't needed for
passenger train meets, but simply raising the platforms. On the Franklin? OK...I could maybe see the point at Norwood Central if Foxboro service initiates and outright doubles their frequencies. Downtown Norwood's going to have such above-average walkability that full-high boarding would help even if it's just the conductors flipping the trap doors for the lone high sandwiched by adjacent lows (a la Lawrence). But how about Windsor Gardens? Endicott? Islington? Norwood Depot which is already skipped by most off-peaks in favor of Central? How much is spending too much to get around the exemption in those places? Is that a rabbit hole worth digging down on a system where Ballardvale, Andover, Bradford, Haverhill, Ayer, Shirley, and North Leominster are all much tougher nuts to crack on wide-load freight routes with
crush-load 24/7 freight traffic and passenger schedules routinely stressed by that crush-load freight traffic?
Other than getting all those non-ADA's outfitted with mini-highs, Franklin really doesn't rate as a high concern here. At the very least, the most rigidly dogmatic of level-boarding perfectionists out there have to come up with answers for how to address the outer Haverhill and Fitchburg Lines before getting driven into a froth over the lack of platform height perfectionism here. Clearance exemptions and the freights that use them aren't limiting anyone's current or mid-future schedules or service here. You can likely triple both the freight and the passenger schedules without having those damned imperfect mini-highs become a noticeable constriction. They are a constriction...
today, arguably...at a couple of those Fitchburg and Haverhill stops. And will be a constriction at a certain service threshold in the future on the outer Worcester Line.
Rank that punchlist by need, and at what level of service increase over today it starts becoming a problem. Fitchburg and Haverhill are always going to be near the top of that needs list. Franklin may carry more riders than the other exempteds...but it's the least affected by it and thus will always be a last priority.
