I'm SURE this has been discussed before in either this thread or others (and I'm not going to go searching for it): IF the NS Link was built and many of the lines were through-run would this offset any need for terminal expansion. I suppose the answer is yes but by how much? There are still going to need to be certain lines or rush hour runs terminated at SS but has anyone thought about how much space would be needed?
Oh yes...the terminals aren't going away. Not by a longshot. Consider that SS, Cove Interlocking (i.e. the NEC + Worcester feeders), and Tower 1 (Old Colony + Fairmount + yard feeders) are in large part the limiters of all southside capacity and frequencies. Not the mainlines themselves. And that the NS drawbridges and Tower A interlocking (i.e the merge of all tracks + Boston Engine Terminal into the final North Station approach) is the main limiter of all northside capacity and frequencies. Not the mainlines themselves.
If you want "first-world" service with "first-world" frequencies, as our now-departed guest poster likes to say, you have to be able to supplement Tower A, Cove, and Tower 1 with bypasses that outright skip them, elude the drawbridges, and also have enough space at the surface terminals to optimally spread out and take away the other pressure points on capacity that aren't related to the finite capacity of those Big Three interlockings. It's an all-of-the-above strategy.
The N-S link pools Lowell + Eastern/Western before Tower A mashes everything down on the drawbridge approach AND accepts the main funnel of non-revenue traffic in/out of BET (there would still be a back way into the tunnel from the yard, but with run-thrus there'd be a lot less deadheading to the yard during the service day). And then Fitchburg merges at a new underground interlocking. Lower-traffic than the surface, and also avoids the draws.
On the southside the NEC portal takes in NEC and Worcester at an extra set of crossovers grafted onto Cove Interlocking...but it avoids the main thrust of all of Cove's staggered-out crossovers that do the platform sorting by bailing out early. 1 simple underground interlocking with none of the sorting. The Old Colony and Fairmount portals avoid Southampton (Amtrak) Yard entirely, and are underground before crossing Widett Circle. They currently cross a bazillion busy yard switches and something like 3
other yard-related interlockings, which puts a sharp upper limit on their mainline capacity because the busier everything gets, the busier the yard traffic gets. Likewise...the link is a simple underground 2-track interlocking for just the mainline traffic, then a modest-size interlocking where it merges with the 2-track NEC/Worcester leads deep underground.
So you have the run-thrus underground, nice and clean. But not a whole lot of mainline capacity or platforms to choose from because it's of course in a confined space impossibly deep underground. But what's the upshot? You have now taken 20%? 30%? of the traffic--and the highest-priority traffic at that--out of these limiting interlockings. Which means you can cram way more trains into the terminals...and not only way more, but at more relaxed urgency because stuff is constantly churning underground. So when Alon rants on about how you really don't need >2 tracks on the Providence Line because blah blah blah "first-world dispatching" and passing opportunities, he's partially right. In terms of natural mainline capacity if you had everything moving one after the other under
no schedule stress from the get-go on departure from the terminal. But that's unfortunately only part of the picture because it's not about the mainlines (other than catching up on state-of-repair and running the right equipment)...it's about the terminal district. So we do need those 3-4 tracks and easy Amtrak passing opportunities to account for the speed differential instead of threading the needle with rote precision...because the terminal district is a stressor.
If the highest-traffic lines are going to be the primary users of the Link, then the more 'relaxed' resiliency of the surface terminals after they're supplemented by the Link is where you can pack the headways full like we've never seen before, and start doing dense branchline service the likes of which haven't been seen since the 1930's. You'll still be using most/all of that SSX capacity. You'll still be using all of that drawbridge capacity at NS...probably even when it gets Draw #3 put back and extra platforms on the ex-Spaulding land.
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What I don't think is going to happen, or what isn't the kind of cure-all "replacement" for other modes and other termini are...
1) Central Station, for obvious flaws that are engineering-impossible to solve.
2) Some sort of utopian "everywhere runs thru to everywhere!" setup like the original promo for the study. No...I think NEC-Lowell/Haverhill, Worcester-Eastern Route are going to be the primary run-thru pairings because they are the heaviest-traffic mainlines that best correspond to points on the compass and hit the destinations hardest to reach via car on polar opposite ends of 128. Then some pick 'em of Indigo-bearing routes that likewise *roughly* match up with a compass direction. Some other routes (branchlines in particular) that just don't form any distinct ridership demand...or go west in two inbound like a Greenbush-Rockport...just don't have it and probably are going to be surface-only except for a couple key rush-hour slots where something on every line has to be paired to make optimal use and spreading of total system capacity.
3) SEPTA on the MBTA. SEPTA intentionally crippled its system when it opened Center City by ditching all diesel routes and shortening its branches to point where its system is a whole lot of Fairmounts and Needhams that barely exit the city and way fewer Franklins and Lowells. Center City's senselessly under-capacity, and for all their Indigo-like stop density...compare the schedules with MBTA commuter rail. It's not impressive at all. It's not even an adequate complement to rapid transit despite barely covering any more territory. SEPTA is precisely the
wrong example to follow, and precisely the right example to avoid because of the way they permanently ruined themselves. Just look at how traffic-choked the Philly 'burbs are because they don't give a shit about serving them. The goal here is not to get rid of the surface terminals...it's to do what SEPTA totally and irrevocably fucked up on its system coverage and system frequencies.
4) It does NOT replace the need for rapid transit expansion (I disagree very strongly with Alon there). In fact, with how transformative it is at pumping traffic around 'burb transit density will grow to a point where it's non-optional and the CBD flat-out won't function without enormous amount of radial builds. "Green Line Reimagined" becomes vitally important. The Urban Ring becomes totally non-optional. Heavy rail service enhancements, inner 'burban extensions (some more than others depending on where they diverge on path to the CBD...Blue-Salem being a potentially much more important one than GLX past Medford because of the more divergent places existing Blue serves like Logan), and full-blown rapid transit service to the uber-critical bus nodes (LynnLynnLynn, RozzieRozzieRozzie) all become orders of magnitude more important
because of first-world commuter rail. Not as trade-ins
for commuter rail. You know...those square-to-square local travel patterns that have existed since 18th century cow paths, which can't be replicated by airlifting the U-Bahn onto our commuter rail ROW's.
5) I also think some CR routes that are squeezed for capacity today and have
legit mainline pinch points are going to need to be evaluated for conversion. Definitely Needham...if anything, N-S Link accelerates the urgency to expunge it off the RR and onto Orange and Green. And possibly the Western Route to Reading and that long-deferred Orange extension...since the two interlockings it shares with the Eastern Route in the terminal district after forking off from the Lowell Line aren't going away, the single-tracking to Oak Grove isn't going away, and the Eastern is the one that really needs to gobble the lion's share of slots in the Link era so the Western's going to become more and more the northside's (not nearly as bad) analogue to Needham at just not having a high enough ceiling or traffic priority when we go 'first-world'.
So I think you do in that brave new post-car rail-dependent world need to continue building out the rapid transit system to 128 as a complement and shorten the bench a little bit of purely inside-128, purely passenger with no freight dependencies (sorry, Fairmount), non-long distance (or, in the inner Western's case, redundantly inferior long-distance), inherently capacity-constrained routes by putting them on the mode that does have prodigious capacity...because the N-S Link just isn't going to help them get 'first-world frequencies' like the NH Main + north-of-Wilmington Western, the Eastern, the Fitchburg, the Old Colony, the B&A, the Midland (Fairmount + Franklin), and the supersized 2040 NEC.
It's an all-of-the-above strategy. Use every mode in the toolbox--Yellow-painted, rubber-tire included in large quantity--to transform inside-128 AND inside-495 AND regional intercity into a less car-dependent culture. Total transformation...full-stop. There is no one killshot that solves all our mobility needs for the century. Not even a megaproject like N-S.
