I'm glad you raised that point, because that's kind of where I was headed. I think the overlap could impact the calculus on whether to electrify north of Boston Switch. Hopefully this will make more sense if I frame it in terms of why you'd be looking to run service to Woonsocket in the first place.
If your goal is simply to offer rail service to people in the Blackstone Valley, then yes, a conventional Woonsocket-Providence service could get by with hourly headways and diesel power, especially if stop spacing is kept as wide as the Providence Foundation study proposed (just three intermediates at Manville, Cumberland, and Pawtucket). But what if you view running service to Woonsocket as incidental to the goal of doubling frequencies in the Providence metro?
Say you’re already running a Westerly-Pawtucket service with EMUs, and your main priority is to add another service layer that has both layers overlapping between Warwick and Pawtucket. This cuts headways in half, so you now have trains going through every 30 mins, or maybe even 15 mins. You want to take advantage of the frequencies by adding dense infill stops in that overlap area, and for performance as well as uniformity of fleet/maintenance considerations, EMUs are the rolling stock for the job.
Although most of the ridership and demand is going to come from the segment between Warwick and Pawtucket, you recognize this second service layer could also serve the Blackstone Valley if you extend northwards beyond Pawtucket up to Woonsocket — but electrification currently ends at Boston Switch.
If you don’t want to take on BEMUs for maintenance or performance reasons, could there be a world in which the lower-frequency, wider-stop-spacing, Pawtucket-Woonsocket segment of the overall Woonsocket-Warwick corridor gets catenary not because it warrants it on its own, but because the higher-frequency, denser-stop-spacing, Pawtucket-Warwick segment needs it?
If the Providence Line is running :30 service via Pawtucket and gets its permanent terminus extended to T.F. Green, you'd only need a matching pair of hourlies to give Pawtucket-Warwick :15 service with the triple-overlap. South County definitely isn't dense enough for :30 service, and it's arguable that the Blackstone Valley isn't either. So I don't think you're electrifying the P&W up-front, and at the very least not until an electrified Franklin Line extension pokes itself into Woonsocket Union Station with an accompanying electrified downtown layover yard and enough slack substation capacity to split the P&W spanning miles with the Warwick sub on the NEC. You'd just put up with 1 out of every 4 trains being a diesel in the interim, since RIDOT really can't afford to pay in for BEMU's either. Rhode Island's a very financially constrained state. It's not like South Coast Rail Phase II where the electrification cost for hourly branch-of-a-branch service is a rounding error on a completist's electrified system, and thus the 'waste' of a substation funneling only 2 TPH can be swallowed. RIDOT has to very carefully parse whether it's worth the time and energy to pay for electrifying the P&W with autorack and double-stack freight clearance considerations. I don't think they find it worth their while unless/until the Franklin extension potentially allows them to chain off the nearest NEC and Franklin substations to split the 11.3 spanning miles between Boston Switch and Woonsocket Union.
Hi all, first post here, and it's a crazy idea, sorry. I've been thinking a lot about the barriers to truly frequent Regional Rail. They obviously include NSRL and electrification, but also on several corridors, subway lines have eaten up a lot of the ROW, making for single or double-tracking where 2-6 would be far more efficient, especially on the trunks.
Has any thought been given to converting the Orange Line tracks (including the tunnel) to serve Regional Rail as a pseudo NSRL? There would be several barriers, political and physical, but it kills a couple of birds with one stone...
The idea is basically to run rapid or semi-rapid service through the OL tunnel from say Islington, Needham, Auburndale, Brandeis, Wakefield and Salem (or Lynn). Turning the OL into RR helps minimize bottlenecks on a couple of CR lines, in additionl to providing the tunnel. Obviously most of these lines would continue to run less frequent deisel service from their full end-points to N/S Stations.
The biggest barriers / challenges seem to be:
procuring trainsets that can run both on CR tracks (electrified) AND within the existing OL tunnel, whether that's third rail or converted to catenary
scheduling all this within the CR framework, because there would still be overlapping use of some track
connection from Fitchburg line to OL ROW
these new RR trains would skip South Station entirely, and you might need/want to combine some existing OL stations (Tufts/Chinatown, DTX/State, Hawmarket/NS)
Might replace GL stop at Union with RR stop (political challenge)
The future would still want a real NSRL for Amtrak, Old Colony and Fairmount Lines. Which might also portend a RL/B conversion to RR at some point, and even an elimination of GLX if the ROW is needed to serve RR. It's possible however that this phase 1 use of the OL tunnel would allow the eventual full NSRL to be only 2 new tracks with a single center station at State, slightly reducing costs.
Hi all, first post here, and it's a crazy idea, sorry. I've been thinking a lot about the barriers to truly frequent Regional Rail. They obviously include NSRL and electrification, but also on several corridors, subway lines have eaten up a lot of the ROW, making for single or double-tracking where 2-6 would be far more efficient, especially on the trunks.
Has any thought been given to converting the Orange Line tracks (including the tunnel) to serve Regional Rail as a pseudo NSRL? There would be several barriers, political and physical, but it kills a couple of birds with one stone...
The idea is basically to run rapid or semi-rapid service through the OL tunnel from say Islington, Needham, Auburndale, Brandeis, Wakefield and Salem (or Lynn). Turning the OL into RR helps minimize bottlenecks on a couple of CR lines, in additionl to providing the tunnel. Obviously most of these lines would continue to run less frequent deisel service from their full end-points to N/S Stations.
The biggest barriers / challenges seem to be:
procuring trainsets that can run both on CR tracks (electrified) AND within the existing OL tunnel, whether that's third rail or converted to catenary
scheduling all this within the CR framework, because there would still be overlapping use of some track
connection from Fitchburg line to OL ROW
these new RR trains would skip South Station entirely, and you might need/want to combine some existing OL stations (Tufts/Chinatown, DTX/State, Hawmarket/NS)
Might replace GL stop at Union with RR stop (political challenge)
The future would still want a real NSRL for Amtrak, Old Colony and Fairmount Lines. Which might also portend a RL/B conversion to RR at some point, and even an elimination of GLX if the ROW is needed to serve RR. It's possible however that this phase 1 use of the OL tunnel would allow the eventual full NSRL to be only 2 new tracks with a single center station at State, slightly reducing costs.
Hi all, first post here, and it's a crazy idea, sorry. I've been thinking a lot about the barriers to truly frequent Regional Rail. They obviously include NSRL and electrification, but also on several corridors, subway lines have eaten up a lot of the ROW, making for single or double-tracking where 2-6 would be far more efficient, especially on the trunks.
Has any thought been given to converting the Orange Line tracks (including the tunnel) to serve Regional Rail as a pseudo NSRL? There would be several barriers, political and physical, but it kills a couple of birds with one stone...
The idea is basically to run rapid or semi-rapid service through the OL tunnel from say Islington, Needham, Auburndale, Brandeis, Wakefield and Salem (or Lynn). Turning the OL into RR helps minimize bottlenecks on a couple of CR lines, in additionl to providing the tunnel. Obviously most of these lines would continue to run less frequent deisel service from their full end-points to N/S Stations.
The biggest barriers / challenges seem to be:
procuring trainsets that can run both on CR tracks (electrified) AND within the existing OL tunnel, whether that's third rail or converted to catenary
scheduling all this within the CR framework, because there would still be overlapping use of some track
connection from Fitchburg line to OL ROW
these new RR trains would skip South Station entirely, and you might need/want to combine some existing OL stations (Tufts/Chinatown, DTX/State, Hawmarket/NS)
Might replace GL stop at Union with RR stop (political challenge)
The future would still want a real NSRL for Amtrak, Old Colony and Fairmount Lines. Which might also portend a RL/B conversion to RR at some point, and even an elimination of GLX if the ROW is needed to serve RR. It's possible however that this phase 1 use of the OL tunnel would allow the eventual full NSRL to be only 2 new tracks with a single center station at State, slightly reducing costs.
This is an interesting proposal, and would basically amount to turning the OL into a Japanese-style subway/regional rail combo line, but it would definitely come with some catches that could (probably would) end up making it cost more than just doing NSRL:
Longer trains, and therefore platforms, would be highly desirable. For the SW Corridor and NW extension this isn't a big problem, but downtown this would be a problem. To mitigate this somewhat I would say Chinatown and either Haymarket or North Station should be closed with platforms at the other 3 stations lengthened, but this could overload the GL.
Because running CR trains through the Washington St Subway would mean converting it to a commuter railroad, which would have some major regulatory challenges, it may be easier to convert the CR lines to OL spec instead. The alternative would be electrifying the subway with overhead lines (Which may not be possible due to height restrictions), sacrificing Providence/Stoughton throughrunning, or using dual voltage rolling stock.
Should OL conversion be chosen, because the tracks on the Lowell, outer Haverhill, Providence/Stoughton, and Framingham/Worcester lines need to be shared with Amtrak trains, these lines would not be able to be converted and would continue to run into North/South Stations.
Again if OL conversion is chosen, all grade crossings on lines that run into the subway would need to be eliminated.
This would mean effectively nuking frequencies to Malden, some other solution would be required. One possibility would be converting the Green Line between Pleasant St and Medford/Tufts to heavy rail, transferring Union Sq to the Fitchburg Line and running OL trains between Reading and Community College through Lechmere, Science Park, and then into the subway. This would have severe negative implications for service south of Riverway, and would require a new subway line to Nubian to run the trains onto as Boylston cannot serve as a terminus.
Signal upgrades for trains every 3 minutes in the subway would be absolutely necessary for any of this.
What about frequency? The Orange Line currently runs 10 tph regularly and has about the same ridership as the entire Commuter Rail system. Wouldn’t it be infeasible to retain that level of frequency under such a proposal, amounting to a major transit loss for a very high ridership corridor?
What about frequency? The Orange Line currently runs 10 tph regularly and has about the same ridership as the entire Commuter Rail system. Wouldn’t it be infeasible to retain that level of frequency under such a proposal, amounting to a major transit loss for a very high ridership corridor?
If we're operating this like a Japanese subway line, short-turns would fill in any gaps in regional service to provide consistent headways on the central sections all day. That would probably be to/from:
Readville
West Roxbury
Auburndale/Riverside
Weston/128 or Brandeis/Roberts
Salem or Beverly (This one might be better as a BL extension though), cutting off a branch would obviously help frequency
Very interesting proposal. As far as the grade crossing problem mentioned above instead of converting everything to orange line rollling stock would it be possible to instead put everything on silverliner/metro north/crossrail style trains but just a lot shorter that are pretty much bigger subway cars anyways but can run on main line tracks? I guess if need be you could also do 3rd rail and catenary outside downtown. Would a silverliner size trainset fit in ol tunnels?
If we're operating this like a Japanese subway line, short-turns would fill in any gaps in regional service to provide consistent headways on the central sections all day. That would probably be to/from:
Readville
West Roxbury
Auburndale/Riverside
Weston/128 or Brandeis/Roberts
Salem or Beverly (This one might be better as a BL extension though), cutting off a branch would obviously help frequency
If I’m understanding this correctly, this proposal is essentially to extend the Orange Line in both directions with three branches in each direction, with each branch receiving up to 3-4 tph?
Just want to say I really appreciate the thoughtful responses so far.
Can I ask what regulatory challenges there are with running "Commuter Trains" as opposed to rapid transit? What is the definition / difference between the two?
Also, why do RR trains need to be longer? If running more frequently, and importantly, not including most trains from beyond 128 beltway, wouldn't short trains do the trick?
Ideally you have up to three types of trains that could co-exist on the same tracks in some places, Amtrak, Current CR, new RR EMU's.
You'd need the new RR EMU's to conform to the following:
fit in the tunnel
ideally use the same platforms at least at most stations, including length, boarding height and distance to rails.
lots of doors for quick on/off
ideally still have option for 3rd rail (unless catenary is feasible on entire corridor)
also have batteries or catenary connections to reach destinations as far as 128 (which also need to be electrified obv)
Note that the more you can rely on these as opposed to third rail, the more you are able to expand the system and marry it into the larger CR system, possibly even having all CR trains able to access this tunnel.
example, There are three total tracks from Malden to Oak Grove. If CR and RR can share these tracks, we can maintain service here (and possibly increase it further out), but if CR continues to use only one track because of third rail, the value is minimal.
Also, why do RR trains need to be longer? If running more frequently, and importantly, not including most trains from beyond 128 beltway, wouldn't short trains do the trick?
CR Platforms, and more importantly Amtrak platforms, are 3 inches higher than OL platforms. So either you convert the OL stations, or just omit any lines that run with Amtrak trains. Loading gauge is also a couple inches wider on the Commuter Rail, so again either you convert the OL stations or give up on the lines with Amtrak service.
The NE corridor is electrified at 25kV AC, which is not possible with a third rail. So either you string 25kV AC on the whole line, including in the tunnels, get trains that can use both 25kV AC or 750V DC, or give up on Providence/Stoughton service entirely.
Can I ask what regulatory challenges there are with running "Commuter Trains" as opposed to rapid transit? What is the definition / difference between the two?
Commuter railroads are overseen by the FRA (Federal Railroad Administration), while rapid transit systems are overseen by the FTA (Federal Transit Administration). FRA regulations are generally more stringent, with lower acceptable gradients and higher standards for operator training, just to name a couple. I'm not aware of any place in the United States where rapid transit shares tracks with mainline rail.
Hi all, first post here, and it's a crazy idea, sorry. I've been thinking a lot about the barriers to truly frequent Regional Rail. They obviously include NSRL and electrification, but also on several corridors, subway lines have eaten up a lot of the ROW, making for single or double-tracking where 2-6 would be far more efficient, especially on the trunks.
Has any thought been given to converting the Orange Line tracks (including the tunnel) to serve Regional Rail as a pseudo NSRL? There would be several barriers, political and physical, but it kills a couple of birds with one stone...
The idea is basically to run rapid or semi-rapid service through the OL tunnel from say Islington, Needham, Auburndale, Brandeis, Wakefield and Salem (or Lynn). Turning the OL into RR helps minimize bottlenecks on a couple of CR lines, in additionl to providing the tunnel. Obviously most of these lines would continue to run less frequent deisel service from their full end-points to N/S Stations.
The biggest barriers / challenges seem to be:
procuring trainsets that can run both on CR tracks (electrified) AND within the existing OL tunnel, whether that's third rail or converted to catenary
scheduling all this within the CR framework, because there would still be overlapping use of some track
connection from Fitchburg line to OL ROW
these new RR trains would skip South Station entirely, and you might need/want to combine some existing OL stations (Tufts/Chinatown, DTX/State, Hawmarket/NS)
Might replace GL stop at Union with RR stop (political challenge)
The future would still want a real NSRL for Amtrak, Old Colony and Fairmount Lines. Which might also portend a RL/B conversion to RR at some point, and even an elimination of GLX if the ROW is needed to serve RR. It's possible however that this phase 1 use of the OL tunnel would allow the eventual full NSRL to be only 2 new tracks with a single center station at State, slightly reducing costs.
Because running CR trains through the Washington St Subway would mean converting it to a commuter railroad, which would have some major regulatory challenges, it may be easier to convert the CR lines to OL spec instead. The alternative would be electrifying the subway with overhead lines (Which may not be possible due to height restrictions), sacrificing Providence/Stoughton throughrunning, or using dual voltage rolling stock.
Should OL conversion be chosen, because the tracks on the Lowell, outer Haverhill, Providence/Stoughton, and Framingham/Worcester lines need to be shared with Amtrak trains, these lines would not be able to be converted and would continue to run into North/South Stations.
Again if OL conversion is chosen, all grade crossings on lines that run into the subway would need to be eliminated.
The terms "light rail" and "heavy rail" (and "mainline rail", like the Commuter Rail) are sometimes used with fuzzy definitions, but there is one dimension where their differences are very clear cut: collisions.
Light rail describes trains that are designed to have some exposure to an "open" environment, where they may encounter cars, pedestrians, and unexpected behavior from both. This means they both need to be light enough to stop reasonably quickly (remember that a mainline train can take over a mile to stop from full speed), and light enough that when they do cause a collision, the damage isn't automatically catastophic. (A pedestrian hit by a light rail vehicle is still in very serious trouble, but a collision with an automobile won't be automatically fatal.)
Heavy rail (a term that occasionally includes what I'm distinguishing as "mainline rail") describes trains that are relieved of the burden of coexisting in an open environment, and are able to prioritize moving lots and lots of people very very quickly. These trains are longer, heavier, and aren't really designed with collisions of any kind in mind, since they almost exclusively run in "closed" environments. This is why heavy rail lines are grade separated -- their ROWs need to be "closed".
Mainline rail describes trains that need to be able to carry lots and lots of people very very quickly, but need to do so in a partially "open" environment. One of the big differences in the US is that mainline passenger trains need to be able to withstand (to some extent) collisions with freight trains -- which can be extremely big and extremely heavy. This is where the "FRA compliance" question comes in: the Federal Railroad Administration requires passenger coaches to be "beefy" enough (or whatever adjective you want to use) to "match" freight trains. This means that if a passenger train runs on the same tracks as freight trains and therefore -- hypothetically, if many things went wrong -- might end up in a collision, the requirement kicks in.
Now, in Europe, the regulations are different, and passenger trains are lighter. This is part of why mainline EMUs are harder to buy in the US; there are lots of them in Europe, but not designed to that FRA requirement. There are still distinctions to be made between heavy rail and mainline rail there, but it is certainly blurrier.
Mainline rail and heavy rail systems differ in their trains, but those have all sorts of knock-on effects as well. Mainline trains usually have more staff, which means they can accommodate a wider array of station layouts (e.g. short platforms, mini-highs, etc). Mainline trains historically have run at lower frequencies than heavy rail (in part because otherwise the gates at grade crossings would just remain down at all times), which in turn means that mainline systems can get away with fewer flying junctions -- lower frequencies mean the penalty from flat junctions isn't so painful. Mainline systems also have longer stop spacing, both reflecting differing densities in the suburbs, but also reflecting the benefits that can be accrued from rolling stock that can and does hit 80 mph, if given the time and space to accelerate.
So, back to your question: whether we "convert the Orange Line to commuter rail" or "convert the commuter rail to the Orange Line", you will need to convert large corridors from one model to another. Either you'll need to convert the existing Orange Line into a system that can handle not being fully "closed", or you'll need to convert large parts of the commuter rail into a fully "closed" system.
(And that FRA compliance just becomes a huge pain in the butt here, because if you do the latter -- basically extend the Orange Line as-is to Reading/Woburn/Waltham/Auburndale/Needham/Route 128 -- then you'll need some sort of parallel route still in place for the longer distance services.)
Like I laid out in my blog post, there is some alternate history where things worked out like you're proposing, and it would indeed probably have been a pretty good system. But getting there from today's conditions would be onerous and arguably create more problems than it solves.
deep breath
Now.... that all being said:
There is a version of what you describe that is very feasible and worthwhile: extending the Orange Line to Reading and West Roxbury/Needham. While more limited in scope, it achieves a number of the goals you lay out, including reducing bottlenecks on the commuter rail.
Reading and West Roxbury/Needham are notable because they are the only* corridors that terminate roughly within 128, but don't have any longer distance corridors feeding into them. Contrast that with Beverly/Salem, which anchors a strong within-128 corridor, but also serves as the conduit for the Newburyport and Rockport branches. The Orange Line Extensions let you pull the "pseudo-NSRL" maneuver without needing to maintain parallel mainline infrastructure, but it's only feasible for those two corridors.
Historically, of course, both Needham and Reading were conduits for longer distance routes, to Millis and Lynnfield, etc. But those longer corridors are long gone. Now, arguably, the Lexington Branch also fits the criteria I'm ascribing to Needham and Reading... which is exactly why no one calls for restoration of commuter rail service to Arlington/Lexington, but you do sometimes see advocacy for a Red Line extension. There's nowhere new beyond 128 for a Lexington commuter rail rail to go, making rapid transit the better fit.
There are two oddities that sorta fit this bill. First, the NJT River Line uses diesel light rail vehicles (which do street-running in Trenton -- which is why they need to be "light" rail) on mainline track that it uses on an unusual "timeshare" basis, where freight is only allowed to run at night (I think with some additional oversight/safeguards in place).
Second, IIRC the FRA considers PATH to be a "commuter rail" system, which I think has a waiver for the FRA weight compliance thingy. Idk whether they actually consider it to be "mainline rail" vs "heavy rail", but I get the sense it's not really a relevant distinction for them.
Second, IIRC the FRA considers PATH to be a "commuter rail" system, which I think has a waiver for the FRA weight compliance thingy. Idk whether they actually consider it to be "mainline rail" vs "heavy rail", but I get the sense it's not really a relevant distinction for them.
I'm aware PATH is classified as a Commuter Railroad, but I'm pretty sure it never shares any track with any mainline rail. So apart from being a fun little oddity/trivia answer, it's not really significant in any way.
Like I laid out in my blog post, there is some alternate history where things worked out like you're proposing, and it would indeed probably have been a pretty good system. But getting there from today's conditions would be onerous and arguably create more problems than it solves.
There is a version of what you describe that is very feasible and worthwhile: extending the Orange Line to Reading and West Roxbury/Needham. While more limited in scope, it achieves a number of the goals you lay out, including reducing bottlenecks on the commuter rail.
You could conceivably do Kingston, Greenbush, and Newburyport/Rockport as extensions of the Red/Blue lines respectively. There's a lot of grade crossings that need to be sorted out and any freight operations would need to end, but it's a lot more feasible than the rest of the network.
There are two oddities that sorta fit this bill. First, the NJT River Line uses diesel light rail vehicles (which do street-running in Trenton -- which is why they need to be "light" rail) on mainline track that it uses on an unusual "timeshare" basis, where freight is only allowed to run at night (I think with some additional oversight/safeguards in place).
There's also a signal system overlay for only the DLRV vehicles that does inductive stops (basically a variation on our Orange/Red ATO system) with tightish signal blocks, whereas the freights just follow regular NORAC wayside signals and Positive Train Control on longer blocks since there's never more than one freight train out on the line at night. The signaling differences are another reason why the line must be timeshared. Even if their next generation of DLRV's complies with the FRA's next-gen buff strength regs, the fact that they need to follow the passenger-not-freight signals means that they are forever blocked off from traffic interlining.
Second, IIRC the FRA considers PATH to be a "commuter rail" system, which I think has a waiver for the FRA weight compliance thingy. Idk whether they actually consider it to be "mainline rail" vs "heavy rail", but I get the sense it's not really a relevant distinction for them.
PATH is completely waivered. Their rolling stock is scantly different from the Orange Line's in both dimensions and crashworthiness (our Hawker-Siddeley cars were heavily derived from Hawker's few-years-earlier PA3 make for PATH), and they are a completely closed system. The only reason they are FRA-governed is because they share Amtrak-owned ROW on the NEC and Dock lift bridge with the tracks in close proximity (but never connecting). PATH has actually tried and failed multiple times to sever their affiliation with the FRA and re-register with the FTA. It costs them 3x as much per hour to operate under FRA regs than the NYC Subway under FTA regs, so they dearly want to become an FTA subway for the cost savings it would bring. But the FRA would have to consent to that switch and they have multiple times refused to do so, citing ROW access purview over PATH. Why PATH has to be an FRA road because of track proximity but GLX next to the Lowell Line and umpteen other such identical examples don't is something to ask the FRA administrators. They ain't explaining their rationale. It's just turf warrage.
As a result of the FRA status, PATH had to install railroad Positive Train Control as an extra overlay on their CBTC subway signaling, even though CBTC natively does almost all of the things PTC does. They have to staff trains with certified locomotive engineers, do more rigorous safety checks between runs, comply with FRA regs about staff working hours, and follow some cosmetic access and evacuation rules about things like grab irons on the sides of the cars. But that's it. Functionally they are an HRT system through and through, and because their small dimensions, electrification scheme (600V DC third rail), and operating specs are so similar to the Orange Line they face the same steep/impossible hurdles to any possible conversion into a 'real' interlining FRA railroad.
You could conceivably do Kingston, Greenbush, and Newburyport/Rockport as extensions of the Red/Blue lines respectively. There's a lot of grade crossings that need to be sorted out and any freight operations would need to end, but it's a lot more feasible than the rest of the network.
@F-Line to Dudley can comment further, but I believe that freight service into the Fore River port remains very active. Just to go briefly waaaay down the rabbit hole here, let's say you could triple track from Fore River to Braintree, and leaving the Middleboro Line as mainline for freight access, and then convert the full Greenbush and Kingston lines. But the Greenbush and Kingston lines are the lower ridership lines on the Old Colony. (Plus, giving the affluent communities of the South Shore a Red Line extension while leaving New England's only majority-Black city without... seems unideal.)
Rockburyport as Blue is interesting to consider, but, for example, Rowley and Newburyport are about 5 miles apart... i.e. just about the current length of the Blue Line. The current commuter rail schedule suggests an average speed just a little bit above 40 mph between Newburyport and Beverly, which is a bit more than twice what the subway lines currently average (I assume in part by being able to run at speeds above 50 mph). At a certain point, the needs of regional rail infrastructure do diverge from rapid transit.
@F-Line to Dudley can comment further, but I believe that freight service into the Fore River port remains very active. Just to go briefly waaaay down the rabbit hole here, let's say you could triple track from Fore River to Braintree, and leaving the Middleboro Line as mainline for freight access, and then convert the full Greenbush and Kingston lines. But the Greenbush and Kingston lines are the lower ridership lines on the Old Colony. (Plus, giving the affluent communities of the South Shore a Red Line extension while leaving New England's only majority-Black city without... seems unideal.)
Fore River Transportation's Quincy Shipyard-Braintree Yard freight runs on the innermost Greenbush Line and southernmost Old Colony mainline on the midday off-peak 6 days a week, while CSX's pickup at Braintree via Middleboro runs on the contrasting overnight. The Middleboro Line has that same CSX overnight freight. CSX has unused rights on the mainline north of Braintree if it ever has to switch its Braintree pickup to a Readville-originating job instead of a Middleboro-originating job. And Mass Coastal currently holds Bay Colony's 27-years-unused Braintree-Plymouth freight rights (with rumors that they're rummaging around for a new customer).
So it's practically impossible to timeshare freight from transit on the South Shore.
Rockburyport as Blue is interesting to consider, but, for example, Rowley and Newburyport are about 5 miles apart... i.e. just about the current length of the Blue Line. The current commuter rail schedule suggests an average speed just a little bit above 40 mph between Newburyport and Beverly, which is a bit more than twice what the subway lines currently average (I assume in part by being able to run at speeds above 50 mph). At a certain point, the needs of regional rail infrastructure do diverge from rapid transit.
There's no freight rights north of Beverly Jct. Guilford/Pan Am "abandoned" rights to Newburyport and Rockport in 1984 to force discontinuance of service to the remaining customers on the branches as a typically skinflint cost-cutting move. But the rights are still active to Salem (and indeed CSX has done some spot bridge work on the Peabody Branch this summer, leading to a lot of rumors that they are marketing the rail spur at the closed Rousselot plant to potential new sign-ons), and when Peabody was still active daytime job BO-1 would sometimes proceed all the way to Beverly to run around its train for the return trip. So bridging the gap between Downtown Salem (where the ROW could/would feasibly be side-by-sided 2 x 2 Blue + CR) through the constrained tunnel and over the swing bridge to Beverly is a legal nonstarter right now because of those still-active rights, which are completely free of charge to CSX and thus give them no incentive to voluntarily give them up even if there ends up being no future prospects north of Everett.
You're absolutely right that the speed differential starts to really punish rapid transit north of Salem. The Ipswich-Rowley and Rowley-Newburyport stretches are where Commuter Rail today exceeds 60 MPH, and would with any Rowley-skipping express flavor top out at real 79 MPH. The ROW itself would be good for 90+ if you ever had a far-future Downeaster re-route to Portsmouth making stops only in Salem, Newburyport, and Portsmouth. With EMU's you probably could achieve 70-79 for short stretches on purely local schedules. So there's no way conversion to a closed rapid transit system--even if the freight rights ever did go away--is going to serve those areas of the North Shore better than Regional Rail. We're simply not buying 80 MPH-design HRT trainsets; the edge cases where that would actually help are just too edge for the added cost. So there's a pretty firm feasibility threshold drawn at Downtown Salem (or Beverly if you spent yourself stupid widening the tunnel) for anything-BLX. The Rockburyport branches will forever be better-served by purpose-fit Regional Rail.
Very interesting proposal. As far as the grade crossing problem mentioned above instead of converting everything to orange line rollling stock would it be possible to instead put everything on silverliner/metro north/crossrail style trains but just a lot shorter that are pretty much bigger subway cars anyways but can run on main line tracks? I guess if need be you could also do 3rd rail and catenary outside downtown. Would a silverliner size trainset fit in ol tunnels?
Not even close. An Orange Line car is 11'11-3/4" tall. A Silverliner V is 14'3" tall, nearly 2-1/4 feet taller. LIRR M9's are the smallest EMU's in the Western Hemisphere, but at 13'3" they're still more 1-1/4 feet taller. Crossrail's Class 345 cars are 12'4". It's a very big difference.
Those EMU's aren't "much bigger subway cars". They're full 77-85 ft. length Commuter Rail cars with mostly 3 x 2 seating (M9 and Silverliner), overhead luggage racks, and 90 MPH top speeds that require a beefier power source than the 600V DC subway feed we have.
