Prompted by a tangentially related discussion in the RUR thread, I got to thinking about what HRT expansions I can
really see happening in the foreseeable future. And on reflection, I realized that there seems to be something more fundamental at play here.
If you look at the ideas we throw around here -- whether in Reasonable, Crazy, or God Transit Pitches -- a lot of them are focused on expansions of LRT, BRT and mainline service (usually under the assumption of those last being pantographed EMUs). With the notable exception of the Red Line X proposal, the expansions of the Blue, Red, and Orange Lines are largely variants of ideas that have been around for almost a century -- Orange to Reading, Blue to Lynn, Red to Arlington and so on. Occasionally we'll bandy about ideas of Blue Line Westward Expansion, but often those are rehashes of the Riverbank proposal.
But this brought me back to a core question --
how many of these could I actually see happening? For example, I can easily see things like Green to Needham, Indigo to Riverside (or even Framingham), or an expansion of the Silver Line into Longwood.
By contrast, Blue to Watertown or Red to Dedham are both potentially good ideas, but I can't see them happening in the foreseeable future, at least not with the same confidence of something like Green to Needham or Porter. So where does that line get crossed?
And I think there actually is a pretty simple heuristic that captures a big 'ol chunk of the variability here: with a small number of exceptions (explained below),
it seems highly unlikely that any expansion of non-mainline HRT will occur in Boston again, ever.
I think HRT suffers from
two key drawbacks in the public eye that serve as "feathers tipping the scales" against the idea.
First, HRT has
higher upfront costs compared to LRT or BRT. (The comparison against mainline expansion is a bit more complicated -- adding HRT alongside mainline tracks will probably be more expansive than retrofitting those mainline tracks to support RUR, but the cost of HRT vs RUR on a brand new rail corridor is less obvious and will likely come down to the specifics of the project.) But, either way, to a public that has been burned by the Big Dig (and to a lesser extent GLX), upfront cost is always going to be top-of-mind.
Second, HRT has the
appearance of being less flexible than the alternatives. If you build an HRT extension, that extension can only ever be used by HRT unless retrofitted. In contrast, an LRT extension can easily be built to accommodate BRT in the future, and vice-versa. Likewise, LRT and BRT remain usable even if a future extension demands an on-street detour; if an HRT line gets built into the town next to yours, the only way to extend it into your town will be costly elevateds or tunnels, or disruptive grade-separated surface tracks. Likewise, RUR infrastructure does not limit that corridor to RUR service -- you can continue to run regional rail over the same tracks and even in the future decide to change the routing of your RUR service.
Now, some of those concerns don't hold up under reasoned scrutiny: for example, capacity is a non-trivial concern that is easy to overlook if you aren't well-versed in these things. RUR service will be capacity limited by the number of through-trains it must compete with, and neither LRT nor BRT can carry as many people in one trainset/bus as HRT can. But, in my opinion, this kind of objection-handling gets pretty esoteric quickly. So, another challenge.
To be clear: I still personally believe HRT is a better option in many cases, especially when cost is amortized over the lifetime of the service, and when the downtown last mile problem is considered. But when faced against the myriad of political challenges, I see most HRT expansion as highly unlikely.
This trend, by the way, is
not limited to Boston. If you look at The Transport Politic's
Transit Explorer, which visualizes transit projects in progress across North America, the vast majority are LRT, BRT or mainline. (In fact, the only HRT expansions I can think of are the Second Avenue Subway in NYC, the Silver Line in DC/NoVA, and the Silicon Valley BART extension. And each of these are unusual in their own way: SAS is a host unto itself, the Silver Line is being built largely in a highway median, and the BART -- especially outside the core -- is more like a commuter rail in many ways and is generally one-of-a-kind in any case.)
There are
three Boston-specific exceptions that I could still see as being reasonable to believe might be built "soon" (in order from most likely to least likely):
First, the
Blue-Red Connector. This is the only seriously proposed HRT expansion in Downtown Boston. It's also the only all-subway one, and moreover its scope would basically be limited to tearing up Cambridge St for a good while. A hassle to be sure, but the major abutters are employers who would benefit greatly from the expansion. Moreover, being limited to Boston, there's only one municipality you'd need to bring on-board. It's also simple and easy to explain: "Connect the only two unconnected T Lines!"
Second,
Orange Line South. This would be some form of expansion beyond Forest Hills along the erstwhile Needham Branch. Whether to Roslindale Village, West Roxbury or even somehow to Needham would be something figured out at the time (and yes, I realize that Needham would be a pretty crazy idea). If Green-to-Needham happens -- and I would wager that it will -- I think that the Commuter Rail branch would likely be eliminated (or shortened into a West Roxbury-Forest Hills dingy, with forced transfer to Orange Line), and that elimination would shift the conversation enough to overcome the usual hurdles. Thus the simple slogan for this project: "Replace the eliminated Commuter Rail service".
Third -- and this I grant will sound unusual --,
HRT to Mattapan. Though more of a long-shot, this still strikes me as feasible, though more of the kind where the stars need to be aligned and if they do, it'll happen surprisingly quickly, à la SL3. As with Orange Line South, this would really only happen when/if the LRT service can no longer be run, thus raising the specter of wholesale loss of service. Likelihood increases if the mandatory bridge replacement can be done separately as a lowkey maintenance project, thus lowering the upfront cost once the project is proposed.
Other than these three, I really have a hard time imagining any other HRT expansion occurring within this generation. BLX is faced with the choice of a residential neighborhood or an environmentally sensitive area. Orange-to-Reading is faced with grade crossings and quiet suburbs. And so on.
To me, this reflects fundamentals about the mode of HRT itself. As I think back over the last few years, I've definitely been working under this unspoken assumption for quite some time, but I had never quite made the connection in explicit terms. From where I'm sitting,
it definitely looks the world of possibilities is much much wider for expanding LRT, BRT and mainline rail.
