The long-lasting impact of the “transit land grab” in Boston

Posted on April 12, 2024April 12, 2024 by Riverside

Let’s look at a map of Boston’s railroads (courtesy of Alexander Rapp, links at end of post).

Let’s add highlighting to show the railroad ROWs that are now used by, or shared with, rapid transit.

Let’s also add dashed marks to indicate common proposals. Aside from the Red-Blue Connector, most of the SLX alignment, and the North-South Rail Link, all common proposals travel along historical ROWs. (The Union Freight RR doesn’t count.)

And now let’s also add (imprecisely drawn) solid lines to indicate the new subways that were built across downtown, which now connect historical ROWs on opposite sides of the city. (This reveals that the subway was in fact “the original North South Rail Link”.)

Now, here’s the kicker: the original underlying map showing Boston’s railroads… shows how they looked in 1890.

Which brings us to our first point: the large majority of the T’s (rapid transit) route miles run on the same paths that were carved out before 1890 (many before 1870, and quite a few as early as 1855).

What’s more: many common proposals to expand the T simply reactivate ROWs that were first carved out in the 19th century (in some cases, as much as 170 years ago).

The core of Greater Boston was the exception to this. Like London’s railroads forbidden from entering the City of London, the late 19th century saw railroad terminals circling downtown, with clusters at the sites of today’s North and South Stations, and one terminal near today’s Back Bay. As a result, when rapid transit was first built around the turn of the century, new routes across downtown had to be built from scratch.

But there are three other corridors, outside of downtown, which also needed to be built for the burgeoning network. These three corridors – and why they were needed – still hold lessons for us today. And it comes down to water, wetlands, and peninsulas.

Wetlands and Peninsulas

While today’s Orange Line runs along the historical Boston & Providence ROW along the Southwest Corridor, its original route ran down Washington St to what is now Nubian Square, and then further south to Forest Hills. The lack of a historical ROW continues to vex transit designs to Nubian to this day.

So, if so much of today’s network did already exist in 1890, why wasn’t there a railroad ROW to Nubian? A map from 1852 sheds some light:

(courtesy of mapjunction.com, this is the 1852 *Boston McIntyre* map from their collection)

For much of the 19th century, Boston northwest of Tremont St in what is now the South End… was wetland. (Technically a mudflat.) When the Boston & Providence went to survey the route between their eponymous cities, they opted to build a nearly-straight route on a trestle over the mudflat – entirely bypassing the long-settled Boston Neck, which centered on Washington St from downtown to Nubian Square.

For an intercity railroad, this made a lot of sense. They weren’t in the business of providing local service, and plowing through a long-standing neighborhood in the city would have been costly and complicated.

What is now the Fairmount Line had a similar story. Built by the Norfolk County Railroad as an alternative to the B&P’s route through Back Bay, they opted for a route that reached downtown Boston by way of the South Bay… which, at the time, like Back Bay, was an actual “bay” but also was basically wetlands. Again, the new ROW bypassed the Boston Neck altogether.

And Boston Neck hardly lacked access to downtown. Horsecars and streetcars ran down Washington and Tremont, and Boston Neck held the only route into downtown that did not require a water crossing by bridge or ferry.

By the turn of the century, Boston’s built-up environment had expanded significantly. No longer a bucolic suburb, Dorchester was now indisputedly part of the city. Streetcars trundled on a long slow journey into the center of the city, where they joined streetcars coming in from all across the region. Congestion was extreme and the city needed a way to get streetcars off its downtown streets.

So, a subway was built to send local streetcars from nearby neighborhoods underground, and an elevated was constructed to reimagine the commutes from more distant neighborhoods and suburbs: instead of a single long streetcar ride, commuters would make a short streetcar trip to a transfer station, and then take an express rapid transit train into downtown.

The El running south of downtown traveled directly down Washington St, the heart of the historic settlements on Boston Neck. Unlike the steam railroads’ avoidance of the neighborhood, the elevated railroad was designed to be woven into the expanding cityscape.

The rest is an ironic history. Arguably because it was among the oldest part of the city, Boston Neck never received the kind of railroad ROW which, by the end of the 20th century, was essentially the only place rail transit was allowed to run.

The wetlands surrounding Boston Neck were easier to go through than the neighborhood itself, which doomed the neighborhood to miss out on the “transit land grab” of the 19th century, which continues to govern the location of rapid transit to this day.

Water – Rivers

Rivers divide and unite cities. They split cities into left banks and right banks, and they simultaneously attract settlement to their shores as urban centers of gravity. The city of Boston-Cambridge is no different.

In their earliest days, the cores of Cambridge and Boston/Charlestown sat about 3 miles apart as the crow flies, with Boston/Charlestown sitting at the mouth of the Charles as it empties into Boston Harbor, and Cambridge (its earliest village located in Harvard Square) located about 4 miles upriver. By road, it was a circuitous journey of 8 miles via Boston Neck, Roxbury, and Brookline (along a route likely similar to today’s Silver Line and 66 buses) to cross between them.

(Map courtesy of mapjunction.com and the Library of Congress; this is from the 1775 *Boston and Environs* map.)

A bit more than 150 years after their founding, the effective distance between Boston and Cambridge was cut in half by the construction of the West Boston Bridge (where the Longfellow Bridge is today) in 1792.

(Map reproduction courtesy of the Norman B. Leventhal Map & Education Center at the Boston Public Library; this is a 1795 map with a lengthy titled which begins *To the select-men of the town of Boston*; the West Boston Bridge is visible in the top left.)

In the ensuing hundred years, Cambridge’s center of gravity drifted closer and closer to Boston, as main thoroughfares stretched from the West Boston Bridge straightaway across to Harvard Square.

Broadway (originally a turnpike), Harvard St, and today’s Main St and Mass Ave ran in parallel between the two poles of Old Cambridge and Boston, forming the backbone of the city that would eventually develop along their roughly east-west axes. Cambridge St connected East Cambridge to the rest of the town, and gradual land reclamation filled in Cambridgeport and expanded East Cambridge, bringing the edge of Cambridge’s shores literally closer to Boston.

(Map reproduction courtesy of the Norman B. Leventhal Map & Education Center at the Boston Public Library; this is an 1814 map, descriptively titled A plan of those parts of Boston, and the towns in its vicinity, with the waters and flats adjacent, which are immediately or remotely connected with the contemplated design of erecting perpetual tide-mills, illustrating the new “backbone” streets mentioned above.)

The Charles River, in its meandering, deposited Old Boston and Old Cambridge a mere three miles apart. The settlements were far enough apart to develop separately, but close enough that they were inevitably drawn toward each other. Boston was anchored by the Harbor and could not move, but Cambridge had plenty of open space to expand into. The opening of the West Boston Bridge created a focal point for Cambridge’s expansion.

(Map reproduction courtesy of the Norman B. Leventhal Map & Education Center at the Boston Public Library; this is James Hayward’s 1838 *A map of Cambridge, Mass*, showing Cambridge’s east-west growth.)

The combination of the new river crossing and the original location of the settlement at Harvard Square effectively ensured Cambridge’s development stretching west from downtown Boston.

Notably absent, once again, were the railroads. A mid-century short-lived branchline to Harvard Square lasted a mere six years. Cambridge’s expansion was instead fueled by its horsecar and streetcar connections to Boston via the bridges. (Indeed, the first horsecars in the region ran across the bridge, from Bowdoin Sq to Harvard Sq.)

Municipal boundaries notwithstanding, Cambridge became indisputably part of the Boston-Cambridge city, just as Dorchester had. And just like Dorchester, its streetcars were choking Downtown. Dorchester got an elevated railway, and while an elevated was also considered for Cambridge, eventually a subway was chosen instead – a fateful stroke of luck that continues to impact transit access inequity to this day.

Just as the geography of the Boston Neck did, the opening of the West Boston Bridge meant that, by the time railroads started being built, the corridor between downtown Boston and Harvard Square was already well-settled. The railroads had incentive to avoid the area, not serve it.

The dual examples of Cambridge and Boston Neck demonstrate that the construction of railroad ROWs has frozen in time the idiosyncratic mid-19th century divisions between “old” and “new” settlements.

A note on South Boston and the South Bay

I exclude the southern half of the Red Line from my set of corridors that needed to be created to tie the emerging rapid transit network together, beyond merely stringing together railroad ROWs.

While it is true that the subway between Andrew and South Station was not itself ever a railroad ROW, it runs parallel to the historical Old Colony ROW (which ran in part along what is now Old Colony Ave), and to the historical ROW of the Midland Route (which ran along what is now Track 61 before curving west to a terminal near South Station, producing a route of similar shape, though different location, to today’s Red Line). The decision to run the subway under Dorchester Avenue was not forced by a lack of other options.

(Map reproduction courtesy of the Norman B. Leventhal Map & Education Center at the Boston Public Library; this is an excerpt from JG Chase’s 1865 railroad map showing how the Old Colony and Norfolk County railroads presaged the path of today’s Red Line.)

The South Bay was, and remains, an odd no-man’s-land separating South Boston from the rest of the city. 150 years ago, water separated the two, and today they are divided by railroad yards and a highway. As such, like Back Bay, it is unsurprising that the Old Colony and Norfolk County Railroads used it as their route in and out of the city.

I argue that the Dorchester Ave subway is essentially a modest relocation and consolidation of these two historical ROWs, and therefore does not represent a “new” taking of land for transit use in the way that the Cambridge Tunnel and the Washington St El did.

(To put it another way, in some alternate history, BERy used either/both of the ROWs in lieu of the Dorchester Ave subway, producing a Red Line very similar to our real one.)

South Boston provides a third example to support the pattern demonstrated by Cambridge and Boston Neck: areas already-settled by the mid-19th century were bypassed by the new railroad ROWs that now serve as our primary space for transit. The Old Colony RR built their ROW along the edge of Southie, just as they built their Dorchester ROW along the edge of the neighborhood hugging the shoreline.

Water – Harbors

The last piece of today’s MBTA rapid transit system that was not built on land set aside in the 19th century (see below) is the East Boston Tunnel, crossing the waters of Boston Harbor.

(In this piece, I don’t discuss the Green Line’s development, as I’ve covered that elsewhere — see links above. I will note, however, that the B and C’s reservations on Beacon and Commonwealth both also date from the 19th century. The vast majority of our dedicated transit land comes from this era.)

There’s an argument to make that the East Boston Tunnel was, in fact, set aside by private railroads in the 19th century. The Boston, Revere Beach and Lynn Railroad ran from the wharves of East Boston to Lynn along what is today the Blue Line. The railroad was enormously successful, running high frequency electric trains with (I believe) near-24 hour service at some points. The “last mile” of the journey was completed by ferry across the Harbor to Rowes Wharf (likely the reason for BERy’s construction of an el station there).

Given the close connection between the rail service and the ferry service, there’s an argument to make that the cross-Harbor corridor was, in fact, “claimed” by a private railroad in the 19th century, just as I argue most of the T’s current network was.

The popularity of the BRB&L, and the 1924 conversion of BERy’s East Boston Tunnel to heavy rail, speaks to the importance of a Boston Harbor Crossing. East Boston itself, originally an island, remained isolated from the mainland by Chelsea Creek. And Revere, though served by the B&M’s Eastern Route (today’s Newburyport/Rockport Line), was much more directly served by the near-direct 4.5 mile corridor via East Boston, compared to the 7 miles via Chelsea.

Crossing Boston Harbor has a similar effect to crossing the Charles River – providing an alternative to the roundabout route (whether via Brookline or Chelsea or via an unreliable ferry) creates a strong focal point at the crossing, drawing the previously remote far shore closer (both metaphorically and sometimes literally).

(Off-topic but I always want to emphasize this: the BRB&L ran rapid-transit-like service to Lynn until 1940; only eight years later, the MTA began construction of a true rapid transit line along that ROW, intended to once again reach Lynn. The first phase opened in 1952, and the second phase, to Wonderland, opened in 1954, truncated short of Lynn for budgetary and political reasons. There was only an eight year gap in service before public plans were made to restore service to Revere and Lynn, and Revere’s service was restored a mere four years after that. We shouldn’t talk about extending the Blue Line to Lynn – we should talk about restoring the Blue Line to Lynn.)

Like the rapid transit lines across Boston Neck and Cambridge, a rapid transit line across Boston Harbor was needed precisely because it had been too expensive and unappealing for a private intercity railroad company to build the ROW.

And that’s where the rubber hits the road on this topic, even today.

Implications

Most of the MBTA is built along corridors where for-profit railroads found it advantageous to build in the mid-19th century, usually through areas that were lightly settled, avoiding the historical cores that had driven the growth of the region until that point.

Setting aside the Green Line, there are four exceptions to this pattern:

Downtown: where the Main Line’s Washington St Subway provided the “original North-South Rail Link”

Boston Neck: where the El ran above one of Boston’s earliest pieces of land, to serve the large streetcar suburbs in Dorchester beyond, in the 1.6 mile gap between the Boston & Providence RR and the Norfolk County RR’s Midland Route – the largest gap between railroad lines in Boston’s immediate suburbs, except for the gap in Cambridge

Cambridge: where the subway ran along an east-west axis that had been rapidly settled starting at the dawn of the century, filling a 2 mile gap between the B&A’s railroad in Allston and the Fitchburg Railroad’s line in Somerville

Boston Harbor: where a tunnel literally was dug under the ocean to clear a 3,000 foot gap, replacing the choice between an unreliable ferry and a detour of 4 miles (or more)

Among other things, this highlights – yet again – how damaging the loss of a radial line to Nubian is. Imagine if the Red Line had been relocated out of its tunnel to a route along the B&A ROW with a Ruggles-like transfer station near Braves Field, or along the Fitchburg ROW, with a transfer station at Union Square.

I believe this demonstrates that a transit approach that limits itself to existing transit ROWs threatens to overlook corridors that could be as vital in the 21st century as the above corridors were in the 20th.

The map at the beginning of this post is from Alexander Rapp’s utterly delightful timeline of transit routes in Greater Boston by mode, modified to show just the steam/diesel train routes.

Transportation Dreams submissions

Posted on January 16, 2024February 10, 2024 by Riverside

In December of last year, I submitted two maps to the Boston Public Library’s Norman B. Leventhal Map & Education Center’s Transportation Dreams contest. The first is entitled “Project Electric Sheep,” and the second is “Project Gold Line.”

I’m a firm believer in dual creative processes — “campaign in poetry, govern in prose,” “write drunk, edit sober” (in the metaphorical sense), creation and refinement. These two maps present a similar duality: one is wider-ranging in its creativity; the other is a refinement into a focused proposal.

I do want to emphasize that, even on the creative map, all proposals are grounded in examinations of feasibility, cost-effectiveness, and efficiency. These are indeed “transportation dreams”, but they absolutely could be realities.

(I am told these and the other submissions will be on display at the BPL through the end of February!)

“Project Electric Sheep” — a feasible yet fun “crayon map”

This is the statement accompanying my submission:

This map has been perhaps a decade or more in the making. Drawing heavily on discussions I’ve participated in on ArchBoston, I have sought to generate a vision for Boston transit that is both inspiring and feasible.

This design adds over 44 miles of rail to the T’s existing network, only about 9 miles of which would require new tunneling. By focusing on existing infrastructure, extant ROWs, and opportunities for low-cost construction (such as wide streets and areas with well-mapped geologies), we can achieve a radical increase in transit access across the region.

My proposals are built on data from a range of sources, including:

ridership data from the Blue Book portal and Better Bus Profiles,
employment and demographic data from the US Census (especially On The Map), Go Boston 2030, and other sources,
a slew of project studies dating back over 100 years,
the TCRP’s Track Design Handbook for Light Rail Transit,
geospatial data from Google Maps, OpenStreetMap, and other sources (particularly old Bromley Atlases),
USGS geological data,
newspaper clippings sourced through Wikipedia (with grateful thanks to the tireless contributors there), and
numerous historical works by Frank Cheney, Anthony Sammarco, Bradley Clarke, O.R. Cummings, George Chiasson, Jr, Jonathan Belcher, Thomas Humphrey and others

I have also drawn on the qualitative experiences of myself and other T riders.

This map would not have been possible without the years of collaborative discussion at ArchBoston. Much of my thought process in developing this map is documented there, and some proposals are also documented on my website (ever a work in progress).

A small number of stations have been renamed on this map, for ease of wayfinding and to celebrate a fuller array of figures from Boston’s rich history.

This diagram includes the “Gold Line,” an articulation of a long-discussed idea on ArchBoston, which is presented in greater detail in my second submission (below) and here on my website.

Additional details on the various proposals in Project Electric Sheep can be found in the appendix to this post.

(The submitted map had the Bronze Line J service terminating at West Station rather than Boston Landing. Further details in the appendix. The submitted map also had the labels for Edgeworth, River’s Edge, and Wellington in incorrect order, which I have fixed here.)

This diagram is, in some ways, meant to be “fun” (in a way that crayon maps are supposed to be). There isn’t a specific date tied to this map, and it neither represents a “preferred build” nor a “full build” nor a “must build”. Rather, it’s a vision of one possible future.

Project Gold Line

This is the statement accompanying my submission:

Like my other submission, this map has also been long in the making.

Over the last decade, an ongoing discussion on ArchBoston has examined ways to remake the Green Line into a better version of itself. These discussions have been wide-ranging, at times ruthless in pragmatism, and equally unbound in imagination.

Only in the last couple of years has a consensus emerged on certain key pieces of this “Green Line Reconfiguration”. I myself have struggled to find a way to articulate the possibilities afforded by these (relatively mundane and unflashy) key pieces.

Which brings us to: the Gold Line. The “Gold Line” concept seeks to pithily capture the key projects needed to unlock the system’s full potential:

Reroute the E Line via Back Bay to utilize the unused Tremont St Subway
Extend the E Line’s subway west down Huntington, at least to Brigham Circle
Construct a short subway to South Station and run trains through the Silver Line tunnel, linking the Seaport, Downtown, Back Bay, and Longwood

There are additional components beyond these, including connecting the D and E Lines to create a full-length rapid transit line, as well as extending the Green Line to Nubian Square, but the three investments listed above would, in tandem, be transformative.

Particular data sources include:

ridership data from the Blue Book portal and Better Bus Profiles,
employment and demographic data from the US Census (especially On The Map), Go Boston 2030, and other sources,
relevant project studies, particularly the never-built Silver Line Phase 3 (such as its DEIS),
the TCRP’s Track Design Handbook for Light Rail Transit,
geospatial data from Google Maps, OpenStreetMap, and other sources (particularly old Bromley Atlases), and
USGS geological data

Beyond ArchBoston, some of these proposals are also documented on my website (ever a work in progress).

Additional details on the Gold Line concept are available here on my website.

~~~

Teban54Transit also submitted a map to Transportation Dreams detailing the Green Line Reconfiguration concept. He and I corresponded while creating our maps and we decided to intentionally pursue different approaches. My Gold Line map focuses on a set of core components, while Project Electric Sheep shows the Gold Line in a systemwide context with other extensions, such as a Bronze Line through Kendall; his map falls in between, showing a larger and more detailed view of the expansions to the existing Green Line that become possible through the Green Line Reconfiguration. Our maps have some differences, which intentionally demonstrates the flexibility of the improvements we propose.

I redesigned my redesign of the MBTA’s system diagram

Posted on December 20, 2023December 20, 2023 by Riverside

I can never stop fiddling with things, and my redesign of the MBTA’s system diagram is no different. In organizing some files as I finished up the BPL’s Transportation Dreams map contest, I found a few revisions of my redesign that I hadn’t posted here yet. They are also far from perfect, but they’re definitely improvements on my last.

Version 10.0.1 looked somewhat promising:

This version adjusted the Red Line branches, which were probably the ugliest part of the last diagram. I also extended out the southern part of the Orange Line to take better advantage of the extra space at the bottom of the diagram.

Definitely still had problems though — lots of crowding at the top, for one.

Version 10.0.3 looked to address that spacing issue at the top:

I do feel this is the strongest version yet. The spacing is gentler, as are the curves. I feel that the subway lines on a map should create an image that is distinctive but simple enough to remember, and I think this version comes closest to that.

Having experimented with designs that are exclusively 45° / 90°, exclusively 30°/ 60°/ 90°, and a mix of the two (like this one), I wish I had designed this diagram with fewer angles. The bend at Brookline Village, for example, is distracting; my goal had been to align it with the straightaway of the E Line, but that didn’t really have the visual effect I was hoping for. I think that this concept could work with 45° / 90°, so I might eventually give that a try.

The other big change with this version was getting rid of the coloring of the bus routes. It certainly makes the diagram “quieter”, which ultimately is a good thing. I had originally been very opposed to the idea of uniformly brown bus routes, because I didn’t want it to look like cobwebs criss-crossing all over the map. But I don’t think that turned out to be the outcome, and in fact if anything it seems like the quieter bus routes provide a stronger “grounding” for the map.

I also added a text inset to call out the key bus routes that are gonna have really high frequencies, as I feel that’s a valuable piece of information.

I still would like to try to bring some color back into the bus routes. But for now, that version 10.0.3 seems like a satisfying enough place to leave things.

Mapping the T’s Summer 2023 Closures

Posted on June 30, 2023July 9, 2023 by Riverside

Everything old is new again. The T is, once again, shuttering significant parts of its network this summer, in order to accommodate maintenance and construction. The Red Line is seeing a string of late evening closures, while the Green Line is seeing much longer shutdowns — including over 40 days of closure on the Union Square branch.

Naturally, I have made some maps.

(I didn’t want to sink too much time into this project, so the maps below are not free from imperfection.)

UPDATE: as of July 5, the Union Square branch closure has been postponed til September.

Phase 1: July 18 – July 28

During this period, the Union Sq shutdown will overlap with a bustitution of the B Line.

The T will apparently not be providing a shuttle for the Union Sq branch, instead directing riders to local bus routes with transfers at Lechmere and East Somerville. I’ve tried to illustrate those here. Alas, it is a bit cramped.

Phase 2: July 29 – August 9

Following the resumption of service on the B Line, a complete shutdown of service between North Station and Government Center will be instituted to accommodate demolition work on the Government Center Garage. It appears that no shuttle will be provided, and the T’s advice is simply to walk from one station to the other.

Phase 3: August 10 – August 28

During these two-and-a-half weeks, the core segment will be restored and the only ongoing long-term disruption will be the unshuttled closure of the Union Sq branch.

I redesigned the MBTA’s system diagram

Posted on April 18, 2023December 20, 2023 by Riverside

As often happens when one returns to something, on review several months later, I strongly dislike this one, and I am mildly dismayed to have been satisfied enough with it to post. Alas.

Please see the new and improved redesigned version here.

To be clear, this is a proof of concept; there are a number of small details that need correcting, and while I think the overall concept works, there are some clear areas for improvement in a subsequent revision. But, I think it does prove out the concept.

Background

The current diagram draws clear lineage to the Cambridge Seven Associates’ original diagram (which captured my imagination as a child with its simplicity and elegance, particularly when it looked more like this). Today’s diagram is much more complicated than the original, due to the need to add additional information, including

Accessibility markers
Explicit markers for all stops on the Riverside Line
Explicit labels for all stops on the B, C, E, and Mattapan Lines
The Silver Line
Commuter rail stops (particularly along the Fairmount Line)
Key bus routes

Plus the editorial decision to include the geographic markers of the shoreline.

That last point reveals a fundamental difference between the original and current diagrams: the original made zero effort to appear geographically accurate, while the current makes some effort to hint at accurate geography… in some places.

The right half of the map – the South Shore, South Boston, the Shawmut Peninsula (a.k.a. Downtown), Charlestown, East Boston, and the communities along the Mystic River – is vaguely accurate, albeit somewhat compressed.

The left half, by contrast, is much more diagrammatic: straightening and simultaneously stretching & compressing the four branches of the Green Line, straightening and simplifying the Red Line and Key Bus Routes, while maintaining some suggestion of a geographically accurate Charles River.

Kenneth Dumas, the designer of the current diagram (and its previous iterations going back to 2000 when the shift was made away from a purely non-geographic diagram), has spoken about the process by which we arrived at today’s diagram; it’s a fascinating watch that I highly recommend if you enjoy transit maps. Suffice it to say, the current diagram represents an effort to harmonize the desires of a wide range of stakeholders.

My goals

I have long wanted to design a diagram for the T that includes the following:

Key bus routes, shown as cleanly as possible and designed into the map from the start
All stops on the Green Line branches
- (I actually have not particularly wanted to list out all of the surface stops on the B/C/E Lines, but my understanding is that there is user research showing clear preference for their inclusion)
Walking transfers, including
- State – Downtown Crossing,
- Copley – Back Bay,
- Symphony – Mass Ave,
- Brookline Village – Riverway, and
- Reservoir – Cleveland Circle
All stops on the Fairmount Line (future-proofed for its eventual conversion to near-rapid transit standards)
All information included on the present map

And achieve all of the above while fitting into a square and complying with relevant ADA visual design requirements (discussed in part in the video linked above). Now, Cameron Booth at transitmap.net has designed a gorgeous diagram that achieves just about all of these… but which could not fit into a square, which was a key requirement.

The design concept: geographically accurate inner zone & diagrammatic outer zone

Achieving my goals, while maintaining the information on the current diagram, posed several challenges. But as I thought about it further, I realized that several of the thornier issues could all be solved by a highly-geographically accurate diagram, including:

Walking transfers,
the Silver Line, and
to a lesser extent, baking the key bus routes harmoniously into the design of the map

The physical paths of the Green and Orange Lines themselves provided a design to show the walking transfers; this was a key revelation for me: use the physical paths as the starting point for the design, rather than abstract ideas such as “I want the Orange Line to be as straight as possible and form a perfect right angle with a Red Line that is also as straight as possible” (see for example Michael Kvrivishvili’s original design).

At the other end of the spectrum, I got to thinking about Harry’s Beck’s use of a “To” box, listing off-map stops on a line. Cameron Booth offers a modern illustration of this in his Tube map redesign. This is probably the most extreme version of a non-geographic diagram: just a straightforward list of stops.

But, I wondered: was the use of the “To” box really that different from the current diagram’s treatment of the B/C/D/E Lines (and to a lesser extent the Blue Line and Braintree Line)?

There’s very little geographic information being conveyed on those outer lines; there are few or no transfers being shown; there are few or no eye-catching bends that might provide implicit visual cues. Especially on the Green Line branches, the current diagram really just uses a list of stations, along a colored line with white dots.

So, I wondered, what would happen if we had a diagram with a geographically accurate inner section and a maximally diagrammatic outer section?

Hence, the map above.

Notes on the map

A few things to draw attention to:

Sizing

This design uses the original map’s labels and other elements at their original size relative to the page. If printed on a piece of paper the same size as the current map, all of the labels (along with the widths of the subway and bus lines) should be the same size. I know there are ADA guidelines around things like sizing and visual contrast; by reusing as much of the original map’s design language as possible, I’m hoping to generally satisfy those requirements, even if I’m unfamiliar with them.

Alignment for bus routes

Stations are aligned so that connecting bus routes (in this design, the highest frequency “all-day-15-min” routes from the Bus Network Redesign) are maximally straight. These include:

T101: Kendall/MIT – Lechmere – Community College

T109: Sullivan – East Somerville – Union Sq – Harvard

Non-geographic diagram in outer zone

Outside of the “inner zone”, the geographic fidelity of the diagram drops so severely that there’s no way it can be interpreted as being anything other than what it is: a list of stations. This is reinforced by the disappearance of the bus routes and the coastline, and the addition of the “transfer labels” at each station. An earlier version of the diagram featured an explicit “box” delineating the inner vs outer zone; this became unwieldy, however, especially when dealing with the Green Line branches, so I opted instead for an implicit transition.

Color-coded bus routes

Instead of using the current diagram’s “light brown” for the Key Bus Routes, or the official brand guidelines’ “Brand Bus Yellow”, the bus routes have been color-coded based on the hub they operate into. This is far from a perfect system, and in some cases I had to make arbitrary choices. (For example, the T7 and many of the routes running through Roxbury Crossing are colored based on running through State St and Roxbury Crossing respectively, e.g. major transfer points the route travels through rather than to.) Still, I think it is a useful way to differentiate the routes, and somewhat inadvertently highlights the new connectivity of the redesigned routes (e.g. the T28 being a Green route, or the T110 connecting Wonderland to the Orange Line).

Fairmount Line

With today’s timetables, the Fairmount Line should not appear on the map using equal visual language to the rapid transit lines. However, increasing frequencies to “turn-up-and-go” levels should be a major priority for the T and the City, and I wanted this diagram to be future-proofed to enable that.

Silver Line, simplified

The Bus Network Redesign has given us would-be transit map designers a godsend: the elimination of the SL4/SL5 reverse branching & loops. Now we have a simple dog-leg that slots nicely alongside the Orange and Red Lines. The only hiccup is (as I interpret the Remix map), Chinatown will receive northbound service only. I have opted to subtly mark this using a directional triangular for the stop, instead of a circle, and excluding a Silver-Orange transfer indicator at Chinatown (compare to Tufts Medical Center). On a “real” version of this map, the Chinatown label would probably get an asterisk with a note in the legend to the effect of, Silver Line stops at Chinatown going northbound only.

Park St, Winter, Summer, and Washington

This probably falls under the heading of “too clever by half”, but I’m still pleased with it. In general, this map does not mark transfers particularly explicitly. I experimented using black circles, or black dots within circles, but the black circles created contrast problems and the black dots were too subtle.

Instead, the indication of transfers is derived from the physical positions of the stops. For example, the Blue-Green transfer at Government Center is indicated by the Blue and Green Lines sharing a stop indicator. As it happens, only two transfers are marked in this manner: Park St and Government Center.

The rest are marked using transfer bars to connect visually distinct stops. In some cases, the visual distance is a design artifact: for example, the Green-Orange transfer at North Station or the SL1/2/3-Red transfer at South Station are in reality basically as proximate as, e.g., the Red-Green transfer at Park St.

But one benefit is that two of the more complicated transfers are visualized accurately: State, and Park/Downtown Crossing.

State

The transfer between the Blue Line and the southbound Orange Line (the platform formerly known as “Milk” after the cross-street above) is, I believe, the longest in-station transfer on the system. From the western end of the Blue Line platforms to the northern end of the Milk Street platform (I believe under the intersection with School St) is about 800 feet, as I estimate. By comparison, the Green-Orange transfer via the Winter Street Concourse is about 550 feet.

All things being equal, I don’t see a particular need to visually indicate this lengthy transfer distance. However, I chose to add it because I wanted to implicitly indicate that the T7 transfer (on Congress St) is more proximate to the Blue Line than to the Orange Line. So I wanted to separate out the Blue Line station from the Orange Line.

Park & Downtown Crossing

At Park St, the Red Line platform is more-or-less directly underneath the Green Line platform. By contrast, at Downtown Crossing, the Red Line platform is about 200 feet away from the Orange Line platform, with its western edge a little bit west of Hawley Street.

The offset Red Line platforms historically haven’t mattered too much from a map-making perspective. However, with the redesigned SL4/5 route, there will be a minor distinction worth making:

In a clever bit of route design, SL4 and SL5 are going to be combined into a single route that serves Tufts Medical Center, Downtown Crossing, and South Station in a linear fashion, with bidirectional service at each stop. However, instead of serving Downtown Crossing at Temple Place, the new Silver Line stop will be flipped over to Chauncy St – directly outside the entrance to Downtown Crossing at the far end of the Red Line platform.

So, I wanted to indicate on the map that Downtown Crossing will provide a good Silver-Red transfer but subtly suggest that Silver-Orange transfers are better taken at Tufts Medical Center. By separating out the Red Line station (nee “Washington”) from the Orange Line stations (“Winter” and “Summer”), the diagram is able to show exactly that. Again, in this case the physical layout of the network in the real-world has provided the needed design specification.

Drawbacks

There are two sets of problems with my diagram: some problems are execution-related and presumably could be remedied by the touch of a professional; others are conceptual and endemic to the idea of the map itself. Of the drawbacks listed below, I’m not sure which are execution-related and therefore “salvageable”, but I’ll make some guesses.

Busy margins and excess inner blank space

This one I think is execution-related and could be ameliorated by some mild tweaking. This diagram is very busy at the margins overall. To a certain extent, this is by design: I always knew that the outer regions of the diagram were going to be busy with station lists. However, I think the “inner map” section could be compressed by maybe 20%, and free up much needed space, especially at the bottom of the diagram. (For example, there really doesn’t need to be that much space between stops on the Southwest Corridor; the SL4/5 stops probably are the limiting factor here, but they too definitely could be closer together.)

Likewise, I think the “inner map” could also be further compressed along the “Red Line axis”, particularly in the northeast corner. Harvard and Central could both be moved in closer to the core, which would free up more space. For example, the T47 does a small bend at Central right now: in a future revision, I would move Central in closer to the core so that the T47 could run in a straight line between BU Bridge and Union Sq, which would “tug” the northern branches of the Green Line and Red Line further in toward the center. (Looking at it now, I think this would also actually place Central in a more geographically correct location, for what it’s worth.)

Ironically, even though I’m talking about freeing up more space in the top left quadrant of the diagram, in all likelihood I would instead use that space to simply relocate the rest of the map upward, in order to free up more space in the bottom half. The centerpoint of the diagram is currently roughly at the Hatch Shell on the edge of the Charles. In a future revision, I would probably shift things so that the centerpoint is at Back Bay Station.

The busyness of Longwood and Dorchester

These are the parts of the diagram where the shape of the bus network is most germane. The criss-crossing lattice of the Dorchester network does not lend itself to simple labels like “to Ashmont” placed just south of Nubian (which would mirror what I did at Harvard and Sullivan). As for Longwood, the Bus Network Redesign will radically increase bus service to LMA, which definitely merits inclusion on the map, but is challenged by:

Fitting in labels for four bus routes on one segment (between Roxbury Crossing and Brigham Circle)
Fitting in a parallel-but-nearby route for the T47
Showing appropriate proximity to the E Line
Showing appropriate proximity to the D Line (farther away from the E Line)
Illustrating connectivity to Kenmore and Ruggles
Fitting in labels for the E Line and D Line
Fitting everything within the obtuse triangle defined by Copley, Kenmore, and Brookline Village/Riverway

I think the busyness can be partially alleviated by adjusting the compression of the inner core and re-centering the inner core a bit higher up in the diagram to open up a bit more space.

That being said, I think this is a conceptual shortcoming of the map: Longwood and Dorchester both represent areas where higher geographic fidelity is needed, in part simply because the topologies are complicated enough that the geographic representation already is pretty close to the maximally simplified representation of the network.

Unfortunately, this diagram is less effective at fitting in geographic accuracy the further away from the core you get. That’s why re-centering the diagram on Back Bay (or even something further south) is necessary – we need to provide more space for Longwood to fit comfortably within the inner zone.

Dorchester, on the other hand, will likely still have to remain within the “diagrammatic outer zone”, although I think it would also benefit from a little more “breathing” room. That being said, this may be where my design concept for this diagram really breaks down: I dislike the current diagram’s treatment of the Dorchester bus network because I think it looks confusing and hard to read, but I’m not sure mine does that much better.

The “starfish” design centered on Franklin Park feels pleasantly clever, but I worry is still too noisy. Likewise, I’m not wild about the physical disconnect: the bus line ends with an arrow, followed by a “To Destination” label, followed by a relatively small amount of blank space, followed by the diagrammatic stop label with the transfer label (e.g. the T16 going toward Forest Hills). Why not just extend the bus lines all the way to their destination?

Look how close the T16’s *to Forest Hills* marker is to the actual *FOREST HILLS* label, alas

(The reason I didn’t do that is because I’m using the absence of the bus and regional rail lines as a visual cue to the shift from geographic fidelity to diagrammatic lists. Now, it is true that the visual distortion would still remain so extreme that the transition would probably still remain visible. But, that corner of the diagram is already so busy that I’d be hesitant to layer on additional visuals.)

I suppose it could be possible to redesign the diagram such that the geographically accurate “inner zone” extends as far south as Forest Hills and Ashmont. Looking at the diagram now, that actually might be more feasible than it sounds, particularly with some compression and reduced scale, so I may need to play around with that!

Branches on the Green Line

The Green Line branches pose a problem: there are way more stops on the B, C, and D branches than there are on any other leg of the network (though Ashmont + Mattapan come close). What’s more, they are the only legs of the network that fan out to the side of the map, rather than the top or bottom, which makes the “diagrammatic list of stations” less obviously different in appearance. And on top of that, I ultimately wanted to make sure all three branches terminated “lower” on the map than Kenmore – meaning I couldn’t, say, turn the B Line upwards to fit it in as a list of stations.

I’m not thrilled with how the Green Line branches turned out, but I do think the concept can be sound, particularly if I can free up a bit more space to let me put the B Line labels on the outside rather than the inside (where they mix confusingly with C Line labels).

(One note: this design is meant to be future-proofed for an addition of a Needham branch: flip the D Line labels past Newton Highlands over to the left side, and use an upside-down tuning fork approach to add the Needham labels on the right, similar to the Red Line branches.)

Conclusion

Does the design concept of a geographic inner zone and a diagrammatic outer zone “work”?

Ultimately, I think the answer is “yes”: I think the fundamentals of this concept are sound, and it’s a question of execution.

As the “15-minute Bus Network” is rolled out over the next few years, it’ll be more and more important for the T to update its map to integrate those routes properly into the design. I hope that an approach similar to what I’ve illustrated here can be helpful in such a redesign.

Siting an Urban Ring LRT station in the Seaport (and the general challenges of using Track 61 for rapid transit to the Seaport)

Posted on January 22, 2023 by Riverside

The following is purely a fun exercise for a highly hypothetical scenario. I’m posting it more as an illustration of thought process, and not really in advocacy of the proposal itself. (There are many things I would prioritize above an Urban Ring LRT station in the Seaport!)

The scenario

Let’s assume a few things are true for this scenario:

The Piers Transitway (currently serving SL1, SL2, and SL3) is converted to light rail and connected to the larger light rail network via a subway running from Huntington Ave to Back Bay to South Station — we’ll call this the “Magenta Line”
- “T-under-D” has been completed, meaning the subway now extends from World Trade Center station under the current grade crossing at D St to a portal near the current Silver Line Way station
Center-running bus lanes on Congress St in downtown and Summer Street in the Seaport have been built, and the T7 upgraded into a full bus rapid transit service, which we’ll call the “Navy Line”
SL1 service has been transferred to the Navy Line, to provide a one-seat ride connecting North Station, the Financial District, South Station, the Seaport, and the Airport
- We’ll loosely assume that a lane in each direction of the Ted Williams Tunnel has been dedicated to mass transit use
An LRT iteration of the Urban Ring has been built on the southside of the network, connecting Longwood, Nubian, and the Seaport, approaching the Seaport via the Track 61/South Boston Haul Road ROW

In short, our starting point looks like this:

The satellite image doesn’t tell us the whole story, however. This is a highly three-dimensional space, where Summer St and World Trade Center Ave sit elevated above the rest of the street grid, and where a slew of highway tunnels sit under the surface.

World Trade Center Ave looking east, as seen from Summer St

World Trade Center Ave from above, looking north, with Haul Road below and to the right

World Trade Center Ave at “elevated street level” looking north, from nearly the same vantage point as above, but lower down

Track 61 and Haul Road passing underneath Summer St, from above World Trade Center Ave, looking west; the Boston Convention and Exhibition Center is visible at the far left

OpenStreetMap showing the tunnels below the surface

Where to place an Urban Ring LRT station?

“The gravel pile”

As visible in the photo above looking west along Summer St, there is a triangular plot of land bounded by Track 61, the embankment of Summer St, and (effectively) the elevated WTC Ave. (There’s actually an access road that cuts off the corner of the plot slightly east of WTC Ave.) That plot currently is occupied by a massive pile of gravel. (Last I checked, the plot is owned by MassPort, though I assume they would sell it off to a developer if/when they could.)

This is probably the most obvious place to plop down an LRT platform. It’s accessible from the current ROW with minimal modification and landtaking required; it provides good access to BCEC and easy transfer to the Navy Line services (including services to the airport); the Magenta Line subway station at World Trade Center is about 400′ away, which isn’t ideal but is certainly manageable, especially if one of the sidewalks can be covered for protection from the elements.

There are some downsides. The plot is a little small; if we leave the access road untouched, it’s just about 230′ along the long edge, which would be barely long enough for a double-set of the 114′ Type 10 “supertrains” that are expected on the Green Line in the next several years. So it’s likely the modifications at the east end, west end, or both would be needed to fit a center platform, two side tracks and a crossover. (Depending on how the Track 61 ROW is converted to double track LRT, some space might already be reclaimed from Haul Road at the western end, which might simplify the design somewhat.)

The other downside is that this location serves the Seaport, but only somewhat so. A lot of the Seaport is located on the other side of the “highway canyon” that Track 61 and Haul Road sit within, so Urban Ring passengers would need to go “up-and-over” for the last segment of their journey. The current World Trade Center station is much more centrally located.

The gravel pile is potentially an adequate location for a station, and would likely be the least expensive option. On the other hand, if we are going to go to the expense of building an LRT Urban Ring, there’s an argument that it should be built for maximum efficacy, rather than just minimal cost.

The underground parking lots

As can be seen in the photos, there are a number of parking lots at the grade level of Track 61, including one parking lot that directly abuts the southern wall of the current World Trade Center station; open that wall up, and you have a strong transfer to the Magenta Line.

The problem here is that you need to cut across Haul Road and the Mass Pike ramps in order to access the lot. And while that’s doable, it’s far from ideal. There actually already is a traffic light directly underneath WTC Ave on Haul Road, so in theory the disruption to traffic flow would not be new. On the other hand, you could only run trains so often if they need to disrupt traffic, probably capping headways at 5 minutes. Again, that is doable, but seems to trigger the same question as above — if we’re gonna build this thing, why not do it properly?

World Trade Center Ave

One thing that bothered me when thinking about mini-project was how to provide good transfers to both Summer St BRT and Transitway LRT. The distance between a stop in front of BCEC and the entrance to WTC station is roughly 650′, which is long for a transfer but not unheard of. (If I recall correctly, it’s roughly the distance of the transfer between Southbound Orange and Blue at State. Of course, State has the benefit of being entirely indoors, while BCEC <> WTC would have significant exposure to the elements, even if the sidewalk were covered.)

Having two Urban Ring stations — one for the Transitway and one for Summer St — seemed excessive. So then I got to thinking more about what the objectives are for stations/connections at each location.

Summer St

Boston Convention and Exhibition Center
Transfer to Summer St BRT toward downtown: South Station, Post Office Square, Haymarket, North Station
Transfer to Summer St BRT toward Logan
Transfer to Summer St BRT toward South Boston

Transitway (World Trade Center)

Seaport core, including Congress St and Seaport Boulevard
Transfer to Magenta Line westbound: western Seaport, South Station, Back Bay, Longwood
Transfer to Magenta Line eastbound: eastern Seaport

On paper, that looks like a lot of reasons for each, and maybe even more in favor of Summer St due to its connectivity, but when you look closer, some are less relevant:

Summer St

Boston Convention and Exhibition Center
~~Transfer to Summer St BRT toward downtown: South Station, Post Office Square, Haymarket, North Station~~
- By definition, the Urban Ring will have multiple connections to downtown, so this is not a vital benefit
- Also, Urban Ring riders will all but certainly be coming from locations that already have direct service to downtown — it’ll be a very uncommon journey to transfer in the Seaport
~~Transfer to Summer St BRT toward Logan~~
- As you’ll see below, this benefit is in fact not going to be unique to Summer St
Transfer to Summer St BRT toward South Boston
- I won’t put strikethrough on this one, but I will point out that most of the previous connection points along the Urban Ring corridor (e.g. Broadway, Mass Ave/BU Medical Center, Nubian) will hopefully have — and will be better served anyway — by direct bus service from South Boston
- Again, the Seaport itself wouldn’t be a common transfer point

Transitway (World Trade Center)

Seaport core, including Congress St and Seaport Boulevard
Transfer to Magenta Line westbound: western Seaport~~, South Station, Back Bay, Longwood~~
- As mentioned above, pretty much all of the Urban Ring stops between Nubian and the Seaport will have better ways to connect to South Station, Back Bay, and Longwood than via the Seaport
Transfer to Magenta Line eastbound: eastern Seaport

So, to me, the goal of an Urban Ring LRT station would be twofold: connect to the Seaport, and connect to Logan. A stop anchored by the Transitway station better serves the Seaport and, as you will shortly see, also serves Logan. So, insofar as we need to choose which connection to prioritize, we should focus on a Magenta Line connection at World Trade Center station.

Getting to Logan

In some alternate timeline, the Ted Williams Tunnel was built with a third tunnel to carry rapid transit rail service to Logan. This would’ve been so much better than today’s system, but alas.

In the scenario I’ve outlined here (and, in my opinion, in any vaguely realistic scenario), service to Logan is provided by BRT. Now, to be clear, BRT can be a lot better than what we have today. For one, a lane in each tunnel could be dedicated to transit and perhaps very-high-occupancy vehicles, with semi-permanent lane protection to ensure speedy and unencumbered journeys.

But our BRT services still need to get in to the tunnel, and the solution to that problem also solves the problem of Summer St vs the Transitway.

Today’s SL1 and SL3 services make a semi-unadvertised stop at street level on Congress St just outside of World Trade Center station; they do this immediately after exiting the off-ramp, which has the benefit of getting travelers from Logan to a stop in the Seaport quickly, without needing to double back from Silver Line Way.

This stop is marked on my diagram from the top of the post (though I am supposing that the simple sidewalk stop has been expanded into something more like a proper BRT platform):

As far as I can tell, absent a major rework of the Mass Pike tunnels, Logan-originating buses will exit from that off-ramp for the foreseeable future. Now, it is true that Logan buses could instead turn left and use Congress St bus lanes to head toward downtown. However, that would duplicate the lanes on Summer St which would still be needed for South Boston service (i.e. the T7), and would be more awkward to connect to South Station. And while Logan -> South Station is mildly more direct via Congress, the journey in the opposite direction is significantly worse, requiring a lengthy diversion down Haul Road in order to reach the on-ramp.

Funneling Downtown <> Logan service through Summer St maximizes frequencies on the shared trunk, minimizes redundant infrastructure, and maintains good Logan -> World Trade Center service. It is somewhat more roundabout, but connects to more places. (And if we are really worried about an express South Station <> Logan connection, using dedicated lanes in the Mass Pike tunnel running direct into the South Station Bus Terminal is probably a stronger solution anyway.)

So we’ve identified a way for our Logan -> South Station service to transfer at WTC station, but what about the other direction? Well, that’s where those parking garages can come in handy.

Running directly parallel to the Transitway is a small side street/alley that runs into the lower level of the parking garage, and which, I think exits on to Haul Road just underneath World Trade Center Ave. Visible in the second Streetview photo are two large metal doors: I am pretty sure that those lead directly into the lobby of the World Trade Center station — meaning that with some modifications, you could put a BRT platform near there, and have buses immediately proceed to the on-ramp.

This would then provide a strong transfer point to Logan-bound services at World Trade Center proper — benefitting Magenta Line riders, but also providing a crucial transfer point enabling an Urban Ring station at World Trade Center.

Placing an Urban Ring LRT station at World Trade Center

So, where to put a new LRT station at World Trade Center?

We can’t put it at grade level without disrupting all the highway ramps, or otherwise settling for a station at Summer St instead.

We can’t put it below grade level because of the highway tunnels.

What about above grade along the World Trade Center viaduct?

Building a short rising viaduct on the gravel pile’s plot and claiming some of World Trade Center Ave (more details on that below) to add a above-grade LRT platform, combined with building an at-grade BRT platform for Downtown -> Logan services by reclaiming some space under the parking garage and adding a BRT platform on Congress St for Logan -> Downtown service, enables all three services to be centralized in a single station for easy transfers between all three.

So how do you reach the World Trade Center Ave viaduct?

Some of this will depend on how Haul Road is reconfigured for double-track LRT, particularly in terms of the horizontal alignment (do you steal a lane, or eat into the gravel pile?), but I think there’s enough open space to feel comfortable that something could fit, even if we don’t work out the details right now.

One area we have less flexibility on is the vertical alignment: there’s approximately 310 feet of horizontal running space between the Summer St underpass and the edge of the World Trade Center Ave viaduct, and we have to fit our rising viaduct in there.

The WTC Ave viaduct is approximately 25 feet high; 25 feet rise over 310 feet run yields a grade of 4.61°, which is well within the comfort zone for LRT grades. Even a rise of 33 feet over that distance would still come in at our 6° threshold. Likewise, rising 25 feet at <6° is doable in as little as 240 feet. Therefore, even with the known limits, it should be possible to rise from the Summer St underpass to the World Trade Center Ave viaduct at a reasonable grade.

Fitting a terminal on the World Trade Center Ave viaduct

The main question facing us here is whether to maintain some level of automobile access through WTC Ave. I believe I’ve come across proposals to fully pedestrianize that street, which, honestly, based on my experience, seems pretty reasonable. Mostly it seems like the street is used to deliver goods to the World Trade Center proper.

If I needed to maintain some level of automobile access, I would use a staggered pair of side platforms to maintain LRT capacity and keep a shared bidirectional lane open for vehicles to pass through on a limited as-needed basis, placing signals/traffic lights at each entry to coordinate passes through the right-of-way.

Obviously, this arrangement is complicated and would create some disruption to the system, depending on the road traffic volume. This option would need to be considered carefully to assess the cost vs benefit.

The key thing to note is that there is horizontal space to fit all the necessary elements:

First 230′ platform (enough to accommodate a doubleset of the 114′ Type 10 supertrains)
90′ to fit a crossover to provide passing access
Second 230′ platform
A 100′ radius curve from the rising viaduct on to WTC Ave
Reasonably short walking distance between platform and current headhouse to streamline transfers
Maintain pedestrian access to the elevated greenspace between Congress St and Seaport Blvd

The second option is more conventional and straightforward: pedestrianize the whole viaduct, and claim part of it for a GLX-style center-platform terminal station.

There are lots of potential variations on this design — adjusting the width, length, and placement of the platform, trying out different methods of pedestrian access — but they all more-or-less look like this.

Keen observers will note that none of these designs feature fare gates or paid-access vs unpaid-access areas. Numerous transit systems, both in the US and around the world, have demonstrated that it is possible to run ticketed transit systems that do not require metal barriers to enforce payment. Eliminating fare gates makes it possible to build transit access more directly into the fabric of a neighborhood. Both station designs, but particularly the staggered platforms alternative, see no clear demarcation of the “edge” of the station, but rather allow the space to be woven together into a seamless whole.

So how do you site an Urban Ring LRT station in the Seaport?

To me, it looks like this:

Add a BRT platform at World Trade Center station for Downtown -> Logan services (under the parking garage just south of the station)
Build a viaduct to connect Track 61 LRT to the WTC Ave viaduct
Add an LRT station at-grade on the elevated World Trade Center Ave viaduct

Should you put an Urban Ring LRT station in the Seaport?

One thing this exercise illustrates is that the Seaport is not very wide. This sounds obvious and trivial, but one result is that there isn’t really space nor need for a “crosstown” service. The Piers Transitway and Summer St already form strong “east-west” transit corridors (whose elevation difference reduces their overlapping walksheds slightly). But they’re still close enough that a perpendicular service between/across them wouldn’t make much sense (particularly since both originate at South Station and come very close to connecting again at World Trade Center).

So a Track 61 LRT service basically needs to choose a particular point along the “linear Seaport corridor” to terminate. That increases the pressure on that station to be located optimally to maximize access to jobs as well as to transfers. World Trade Center does reasonably well on that front, but both the eastern Seaport (e.g. Design Center) and western Seaport (e.g. Courthouse) would require transfers for short last-mile journeys. But this need to choose lies at the heart of why siting an Urban Ring LRT station in the Seaport is difficult in the first place.

A Track 61 LRT service will likely reach the Seaport in part by passing near Broadway station. Regardless of origin point beyond there, a service near Broadway likely could instead be aligned to pass through South Station instead — and then continue to Seaport along one of the east-west corridors. (For reasons I won’t get into here, a Piers Transitway LRT corridor would very likely have excess capacity to absorb Urban Ring LRT in addition to the Magenta Line LRT I’ve described here.)

Sending an “Urban Ring” LRT service down one of the east-west corridors would provide better access to the entire Seaport, and reduce/eliminate the need for transfers. Running LRT service via Track 61 may in fact be unnecessary.

This brings us to a key difference between an LRT Urban Ring and a BRT one: BRT can continue to Logan Airport and on to Chelsea much more easily than LRT. Rapid transit on the Track 61 ROW, with a transfer station roughly at World Trade Center, and continuing service to Logan is able to catch a much broader swath of journeys (in italics below), compared to service terminating in the Seaport:

Longwood <> Seaport
Nubian <> Seaport
Red Line transfer point TBD (e.g. Broadway) <> Seaport
Longwood <> Logan
Nubian <> Logan
Red Line transfer <> Logan
Longwood <> Chelsea
Nubian <> Chelsea
Red Line transfer <> Chelsea
Seaport <> Chelsea
Logan <> Chelsea

The concept of the Urban Ring was to provide circumferential service that bypasses downtown, for speedier journeys and reduced crowding in the core. A route that terminates at Seaport curtails possible destination pairs, and becomes less competitive against transferring downtown via the radial services (especially for long circumferential journeys).

Returning to the point about connecting at Broadway vs South Station: South Station is, to be clear, the bigger fish. Nubian <> South Station journeys surely outnumber Nubian <> Broadway journeys. Urban Ring concepts usually favor a transfer at Broadway or to the south — but can justify skipping South Station because they are providing speedier service to Logan and Chelsea. Track 61 LRT can’t do that.

So I think Urban Ring LRT service via Track 61 presents a weaker case than it first appears. Now, it bears mentioning that capital costs for a Track 61 LRT route would probably be less expensive than a journey via South Station. If given the choice between Track 61 LRT and nothing, I’ll be entirely in favor of the former.

Conclusion

Ultimately, this is a fun thought exercise. The scenario I’ve contrived here presupposes a lot of things, so its “real-world relevance” is somewhat limited. A few final thoughts:

The problems I’ve outlined here will impact any Track 61 proposal; Track 61 will always be on the wrong side of the Mass Pike between Summer and Congress Streets, so you’ll always need to figure out a way to bridge that gap
This conversation becomes radically different if an LRT connection between Seaport and Logan is built — although even then, Track 61 will still be on the wrong side relative to the Transitway
Urban Ring considerations aside, I’d suggest that a Navy Line service to Logan would significantly benefit from the “under-the-garage” platform I propose here, especially if the Transitway is converted to LRT and thus cut off from Logan
The Seaport is centered on two east-west corridors, and there’s an argument to make that almost all services, even circumferential ones, would do well to feed into or otherwise align with those

For all the reasons outlined here, and others, most of my crayon maps going forward will favor both LRT and BRT Urban Ring services that run via South Station, rather than Track 61/Haul Road. At most, I can see Haul Road being useful for express service to Logan that bypasses the Seaport — that, it could do quite well. But for serving the Seaport proper, I think it comes up short.

What I saw on the Green Line Extension

Posted on January 2, 2023 by Riverside

As a holiday treat for myself, I went on a purely recreational trip to see the new Green Line Extension in action. Truth be told, I had a ball. Sitting in the so-called “railfan” seat, peeking out the front window as we sped along the Medford Branch, all of the politics and the delays could be momentarily forgotten, and I could enjoy the moment and say to myself, “Wow, this is so cool!”

The Green Line Extension has been in the works for decades. Its 2022 opening means that the one-seat ride between downtown and Union Square and other Somerville neighborhoods has returned after almost exactly 100 years. It is truly a delight to see it open at last. And make no mistake: any operational or aesthetic shortcomings notwithstanding, the bones of this extension are solid and will last for another 100 years if not longer. This is what long-term public investment looks like.

I took lots of notes and photos. Presented below are some of my observations. It is undisputable that many aspects of GLX remain in progress – there is still lots and lots of ongoing construction, for example. So I’m going to present my observations largely without commentary. I pay a lot of attention to details, and will share some of the particular details I noticed – I defer to more knowledgeable voices to assess the significance (or lack thereof) of those details.

All photos are dated Dec 26 2022. I’m writing this about a week after the fact, so it is possible that some of things have changed since my trip, though given the holidays, that seems unlikely.

Maps

Many maps across the system do not currently show GLX. By my observation, all four of the core Green Line transfer stations – Park St, Government Center, Haymarket, and North Station – have maps that omit the Green Line extension and physical signage that points to Lechmere.

The map at North Station is a typical example:

On closer inspection, someone (or multiple people, given the different ink colors) had tried to add in GLX by hand:

A similar situation on Park Street’s Red Line platform:

Park Street’s Green Line northbound island platform had a map and diagram with a sticker that read “Open Spring/Summer 2022”:

By contrast, all of the GLX stations had updated diagrams:

The GLX stations also all have those lovely neighborhood maps:

Quincy Adams (undergoing renovations) also shows GLX on its map in the paid lobby:

Maps within Green Line cars themselves were a mix, with some showing the extension and others omitting it. (Probably there was a pattern based on the older Type 7 vs newer Type 8 cars, but I wasn’t paying close enough attention to tell.)

Signage and wayfinding

“Stop Requested”

On my trip outbound on the Medford Branch, the operator came on the PA after departing Lechmere and said something to the effect of, “For stops on the Medford branch, please request your stop prior to arrival.” (She said something slightly clearer and more elaborate, but I don’t remember the exact phrasing.) The Stop Request sign lit up at every stop, and we made every stop.

On the inbound journey, there was no announcement. When we pulled in to Magoun Sq, no one had made the request, so the train came to a complete stop, but the doors did not open, and the train set off again.

In full candor, the Stop Request system seems reasonable on the B, C, and E branches, where stations are about 750-1000 feet apart; it does not seem reasonable to me on the D and Medford Branches, where stations are much farther apart, and where the often 10-min wait between trains means that a missed stop costs you an additional 15 minutes of travel time (whether you walk or double back on a train).

I should also note that there is no in-car signage on the Type 8’s to explain to riders how to request stops. (I didn’t specifically check while on a Type 7.) There also was no physical signage that I saw in any station about the presence of a Stop Request policy on the Medford Branch.

Next train indicators

I didn’t get a good photo, but the dot matrix indicators that display when the next train will come (e.g. “Heath St – 3 min”) often would just show something like “Trains every 8-13 minutes” on the inbound Medford Branch. As I understand it, this is because a specific countdown doesn’t begin until the incoming train departs Medford/Tufts. However, given that the travel time from Medford/Tufts is relatively short, that means that the countdown indicator will only ever give a few minutes’ worth of notice.

A similar problem happened on the northbound platform at Park Street: because the indicators only show the next two trains, there was a Union Square train only 3 minutes away, but it wasn’t visible on the board.

Next departure track indicators

At Union Square (and also at Medford/Tufts, though I spent less time there), hanging above the platforms are a pair of arrows which are intended to light up to tell passengers which train will depart first. I didn’t get a great photo of them, but you can somewhat make them out in this one (under the overhang, bracketing a white lit panel):

I departed Union Square multiple times during my trip, but only tried to use the indicators during one of those departures; as it happened, the indicator pointed to the wrong track that time.

Miscellaneous

A sign from the Aug-Sept 2022 Green Line shutdown sits tucked away next to the fare machines at Union Square:

The ramp appears to remain under construction at Union Square. As you can see, a small printed sign notes, “MBTA Ramp Closed, Please Use Elevator”.

But in fact, the ramp was unblocked and appeared open, and had a series of small placards with details about the neighborhood (including some evidence of a Somerville-Saugus rivalry over the origins of marshmallow fluff):

Returning to that first photo of the ramp, you’ll notice that there is also an open staircase on the left, which appears to offer an alternative to both the ramp and the elevator. When you get to the top of the staircase, however, it is sealed off with a chain link fence; I did not see any signage to note this.

Operations

Travel over the Lechmere Viaduct remains slow (at or under 10 mph). There was a small sign at the western end on the outbound track, saying “Resume speed.” Trains really fly on the Medford Branch, though – I would guess at least 35 mph.

The automated announcement at Union Square said, “Doors will open on the left hand side,” but the train had already switched over to the other track – meaning the doors would open on the right. (Trains arrive and depart from both tracks at Union, meaning sometimes the doors will open on the left, and other times on the right.)

On one train as we entered Lechmere, the automated announcement said something to the effect of, “This is Union Square. The destination of this train is Heath St/VA Medical Center.” (Beyond announcing the wrong stop, this announcement also doesn’t make sense in that Union Sq trains now go to Riverside, not Heath.)

The inbound Medford train I was on got stuck at a “red over red” signal at East Somerville station (i.e. just before entering the junction with the Union Square branch). The driver eventually had to reset it manually. I overheard chatter on the radio later that suggested there was still an issue at that signal.

One of the outbound Union Sq trains I took needed to have its destination swapped to Medford; we pulled in to Lechmere, and the operators directed people out on to the platform where we waited for the next train (itself originally for Medford) to pull in. I wasn’t able to figure out why the first train needed to change destinations.

On the Green Line Extension, the signals before switches say, “Stop, check for proper signal & switch”, and have little labels below – right arrow for Union, left arrow for Medford, that kind of thing; I’m sure that will make for a fun “Easter egg” for young railfans for many years to come.

On a very nerdy note: now that B and C trains both terminate at Government Center, the Park St Loop in theory does not see any regularly scheduled use (perhaps for the first time ever?). However, I saw at least one train getting short-turned on the so-called “fence track” at Park St, meaning that the loop continues to be used to short-turn trains to reduce bunching.

Infrastructure

The labels for platform level in the elevators at Union Square and Medford/Tufts used different styles for writing “Green Line” – the label at Union Square omits the space between the words.

One of the two elevators at Medford/Tufts was out of service.

Both doors to the Pedal & Park at Medford/Tufts had placards reading “Tap Charlie Card Here,” pointing to an empty space along the fence, where unconnected hookups were visible on the other side; I couldn’t see any place to tap a Charlie Card.

You get some really cool views of the Commuter Rail Maintenance Facility (Boston Engine Terminal) and the new Green Line maintenance facility from the Lechmere-to-Union viaduct:

I didn’t get good photos, but you also get a really cool view looking west from the Medford-to-Lechmere viaduct, from which you can see the Fitchburg Line commuter rail tracks, the Green Line’s flying junction tracks to/from Union, and the under construction Community Path that flies over everything:

And from the Lechmere-to-Medford viaduct, you get a cool view of the curved viaduct ducking under to go to Union, with the Green Line Maintenance Facility in the background.

While GLX stations are not unique in this regard, it is always cool to see level low-floor boarding, which I tried to capture in this quick shot:

The elevator at Lechmere has a lovely botanical pattern on its glass:

And finally, just before I was about to head home, I managed to snag a ride on one of the new Type 9 trains – I had tried earlier in the day to catch one but had barely missed it, and so had given up; as I was heading down to the Red Line platform at Park, I happened to turn around and see a Type 9 rolling in; so I delayed my departure in favor of a quick excursion up to North Station:

Mapping the Orange & Green Line Closures

Posted on August 19, 2022September 3, 2022 by Riverside

Over the past week, I’ve been iterating on modified versions of the T’s official subway map to illustrate the closures and shuttle services that begin tonight and will continue for 30 days. This map will likely continue to evolve, and I will continue to post the latest revision here. As always, please note that this is not an official map — always refer to the MBTA’s website and to the City of Boston’s website for up-to-date information.

Notes for transit and design nerds

This exercise started relatively simple: show the Orange Line and northern Green Line in some alternate manner to indicate the bustituted segments. This was relatively straightforward: I borrowed design language from the Arborway bustitution in the late ’80s, with a colored outline, white fill, and colored circles for the stops.

On the further advice of someone with better aesthetic sense than I, I shifted the white fill to a lightly colored fill, to better differentiate the lines, and avoid the perception of a total absence of service. The light fill seemed to strike a good balance between maintaining the line’s identity, showing the continued existence of service, and also indicating a significant difference in service.

But, as happens with many projects, I kept on thinking of, “Oh, just one more thing I can add!”

Which brings us to the current design, which pushes the original map’s information design to the limits. I wanted to show:

The bustituted segments
The un-bustituted segments
Text notes on significantly relocated shuttle stops
The one-way service at Haymarket
The early-morning/late-night shuttle to Chinatown and Tufts Medical
The bus routes the T suggests as alternatives to the Orange Line (39, 43, 92, 93, CT2)
The suggested walking transfers between Orange Line and Green Line stations

That is a lot of information to cram onto a diagram that was originally designed to be rather sparse. The current official subway map is an evolution of a design from the early 2000s that primarily showed the rapid transit routes, with commuter rail and ferries being shown secondarily, and limited-access highways being shown tertiarily. In the late 2000s, the key bus routes were added, and a subsequent redesign shifted some parts of the map around while maintaining the same visual language overall.

Evaluating my attempts

Was I successful? Ehn.

I was pleasantly surprised when an earlier version of this map gained a small amount of traction of Twitter, so it’s nice to know that at least some people found it useful. But at a certain point, I fear the level of detail hinders rather than helps. Part of the brilliance of Cambridge Seven Associates’ original “spider map” design was in its simplicity; even if you didn’t memorize the whole thing, the visual concept was highly memorable: four lines, crossing each other in a square and radiating out. That basic schema was easy to recognize and recall, and created a foundation to understand the rest of the system, even if it wasn’t put into one single map.

The eventual addition of commuter rail lines, key bus routes, and now all of the additional information I’ve added here is all very reasonable, especially when done incrementally. But I find myself questioning the ultimate usefulness of the diagram I’ve created. Is it really useful enough for journey-planning? Or is it too confusing to parse?

Simple maps and specific signage

Ultimately, I’ve come to believe that clear and specific wayfinding signage in and around stations is much more important than a detailed system diagram, both under ordinary and extraordinary circumstances such as the Orange Line Closure. (This despite my own love for detailed system diagrams.) In that way, perhaps my earlier, simpler diagrams were more effective.

Shuttle routes only

In this simplest version, the shuttle routes are shown and nothing else:

The advantage of this design is how minimally it alters the original, and (hopefully) how starkly clear the changes are: the most important thing is that the Orange Line and northern Green Line are different and need to be planned around. The question all of this hinges on: can the diagram provide enough information to adequately re-plan the journey? And that’s the part I don’t know.

Walking transfers

The second-simplest iteration added the walking transfers:

Including the walking transfers worked better than I expected. Quite frankly, I’d like to see these added to the official map (though hopefully a little more elegantly than I’ve done here). There are a lot of walking transfers that ought to be indicated on the system diagram, such as the ones I’ve included here, but also additionally:

State – Downtown Crossing
Government Center – Park
Riverway – Brookline Village
Reservoir – Cleveland Circle – Chestnut Hill Ave
Kenmore – Lansdowne

These transfers would not be suitable for everyone — and it should be noted that they are not free transfers under the current model — but if you are able-bodied and have a monthly pass that doesn’t charge per ride, these transfers are useful, speedy, and potentially can relieve congestion on key sections of the network.

Adding these transfers to the map is a good idea in general, but does it help in the case of the Orange Line & Green Line Closures? Again, I’m not quite sure. In most of these cases, I would guess that regular commuters are pretty familiar with the areas in question, and likely are well-aware that, for example, State and Gov’t Center are practically a stone’s throw apart. And if you aren’t a regular commuter… well, the pretty clear (and dire) direction from both the City and the T has been, “Please, stay away.”

Concluding Thoughts

Working on this diagram has been fun. It also has been nice to see positive response from numerous folks on Twitter. (Shout out to Jeremy Siegel at WGBH for sharing it with his followers!) And at least some of those positive responses have made comments to the effect of, “This is easier to understand than the materials the T has put out.” A few comments on Twitter aren’t necessarily a representative sample; however, the negative reaction to the T’s materials have been widespread and resounding — the Boston Globe going so far as to publish a parody of the official closure diagram.

That negative reaction suggests that there is room for improvement in how the T communicates these closures. I’d argue that the positive reaction to my diagram has been driven by its recognizable similarity to the “normal” map, combined with the clear-and-obvious differences that are blatant and draw attention to themselves.

With rumors swirling of partial shutdowns of the Green and Red Lines later this year, perhaps the T might consider adopting a similar strategy to what I’ve presented here.

Inevitabilities in Life: Death, taxes, and decreased frequencies on branches

Posted on May 2, 2022August 14, 2022 by Riverside

In my previous post about branches, I briefly discussed the rapid decrease in frequencies as you add more branches to a trunk line. You might remember a diagram that I showed:

A service level diagram, where the trunk has 15 tph, and then 5 tph branch off, leaving only 10 tph to the next station, after which the line splits into two branches of 5 tph each

In this diagram, the trunkline sees high-frequency headways of 4 minutes (which is better than many subway lines in North America). With such a high frequency, it’s easy to think that there’d be enough trains to serve a bunch of branches.

But as you can see, four-minute headways equals 15 trains per hour. If you have three branches, that means each branch gets 5 trains per hour – which yields 12 minute headways. If these branches are out in suburbia, 12 minute headways might be appropriate, but you’ve nearly reached the limit. If you were to add a fourth branch, each branch would see less than 4 trains per hour, at 16 minute headways, at which point you really no longer have a claim to “frequent service”.

In my last post, I recommended, as a rule of thumb, no more than two branches per line. However, I didn’t explain why. It comes down to a combination of typical throughput capacities, and mathematical inevitabilities.

Divvying up trains-per-hour among multiple branches

Consider this chart:

I will post a text version of this table in the next few days!

On the left side, we have a list of potential trunkline capacities, measured in trains per hour. These indicate how many trains in each direction you can squeeze through your trunkline in an hour. (Don’t worry about converting these numbers to headways – I’ll get to that below.)

For some perspective (most numbers pre-covid):

BART ran 16 tph through its core section from Daly City to West Oakland
CTA ran between 12 and 20 tph on its Red and Blue Lines during peak
WMATA ran 15 tph on its Red Line during peak
MBTA ran 15 tph on its Red Line during peak
London Underground’s throughputs vary widely from line to line, with some lines seeing over 30 trains per hour, following major infrastructure and modernization improvements
Beijing’s subway runs between 30 and 35 tph on several of its routes
Shanghai’s subway runs between 15 and 32 tph on most of its inner routes

All of which is to say, the top few rows represent trunkline capacities that require major investment in transportation infrastructure.

To the right of those trunkline capacities are the number of trains available to each branch, depending on how many branches you have. So, for example, in the first row, a 40 tph trunk will provide 20 tph to two branches, 13.3 tph to three branches, 10 tph to four branches, and so on.

As mentioned before: you’ll notice that, as you move from left to right across the chart, the numbers in each row drop dramatically. In fact, the decrease is literally exponential; you can describe the chart above using

y = n^-x

where n is the capacity of your trunkline in tph, x is the number of branches, and y is the resulting tph per branch.

Decreasing frequencies due to decreasing tph

It’s helpful to start this discussion using tph as a measure, because it’s easier to recognize the patterns in the numbers’ decrease. However, once we convert those tph into headways, it’ll become that much clearer why branching quickly leads to decreased frequencies.

I’ve added some (opinionated) color-coding, meant to suggest the various “levels” of service these different frequencies provide.

The bright green (every 5 minutes or better) represent the highest tier of frequent service an agency might provide. “Turn up and go.”
The pale green (every 5-10 minutes) are still comfortably in the realm of rapid transit, but are probably better suited to off-peak periods and lower-ridership networks. “Turn up and wait a couple minutes and go.”
The yellow (every 10-15 minutes) are the lowest tier of what could be considered “turn-up-and-go,” describing services where riders don’t need to check a schedule when planning journeys. Call this tier “turn up and wait.”
- This tier should be approached cautiously, with careful attention paid to the specific corridor where these frequencies would be deployed.
- (Sadly, consideration should also be given to reliability; if a bus is scheduled to show up every 13 minutes, but one run gets dropped, suddenly you have folks waiting nearly a half-hour for their bus.)
The subsequent tiers are rarely going to be considered “frequent service”; some could be “salvaged” by adhering to a strict clockfacing schedule: a route that reliably comes exactly :13 minutes and :43 minutes past the hour can be a useful service that isn’t “turn-up-and-go”, but doesn’t require consulting a schedule either. These tiers break down something like this:
- Orange = “plan when to leave, but journey whenever”
- Light grey = “plan when to journey”
- Dark grey = “schedule around the schedule”

As you can see, our frequencies drop through the tiers I’ve described above quite quickly. Once you hit the yellow tier, you’re teetering on the edge of frequent service, and once you hit the orange and beyond, you’re definitely over the edge.

Different regions will have different definitions of “high frequency”. For example, it’s pretty rare to wait more than 4 minutes for a tube train in central London; a six-minute headway would be considered sub-par. In Boston, we are sadly accustomed to six-minute peak headways on the Orange Line, while Baltimore’s subway sees peak service every 8 minutes.

It’s worth highlighting that reaching 90-second headways at 40 tph on heavy rail is exceptionally difficult. If you have multiple tracks in the same direction, it becomes more manageable, but a standard two-track subway is nearly impossible to operate at 40 tph per direction, outside of the world’s most advanced subway systems. And notice – even the top examples I listed above, such as Beijing or London, you’re still looking at that second row as your baseline, at around 30 tph. Even in those systems, having more than two branches knocks each branch down into a lower “tier”, meaning it’s not suitable to do within the urban core.

If your crayon map requires shoveling 40 trains per hour through a trunk line, then probably it’s worth trying to plan a second trunk line!

Gaming out examples, and dealing with the unideal real world

Many of the North American systems I mentioned above see 4 minute headways on their core. If we go to that row, we can see two branches gives us 8 min (good so far), three branches gives us 12 min (borderline), and four branches gives us 16 min (no good).

Some North American systems see base headways of 7 or 8 minutes. In that case, our drop-off happens even faster: 2 branches becomes borderline, and 3 branches sinks us with headways longer than 20 minutes.

On the London and Chinese systems mentioned above, trunklines see headways around 2 minutes or better. In theory, those trunklines could accommodate five or six branches; but if you drop the core headways by just one minute, suddenly you can only accommodate three or four branches at similar frequencies.

And that “in theory” caveat is what’s really going to get us. Even if you can squeeze 30 tph through your trunkline to get 2-min headways, if you are feeding that trunk from five branches, that’s five times as many opportunities for delays and disruptions. We just saw above that the difference between a 2-min headway and a 3-min headway is worth two whole branches of throughput. That’s a very thin margin for error – meaning that you need reliability to be extremely high, or else the whole system will unravel, with cascading delays across your network.

The exceptions that prove the rule: North American legacy subway-streetcar networks

There are only two networks that I’m aware of which see sub-10 minute headways on four or more branches, feeding into a trunkline handling 40 tph: the MBTA’s Green Line and SEPTA’s Subway-Surface Lines.

This level of throughput is achieved (see caveat below) mostly because they are light rail lines rather than heavy rail. This means shorter trains which can start and stop faster, and therefore can be run closer together (albeit at lower speeds). The MBTA allows multiple Green Line trainsets to enter certain stations simultaneously, and SEPTA actually treats a couple of its subway stations as “request stops”, with trolleys rolling through non-stop if no one signals to board or alight.

(I haven’t done the math on this, but it would be worth someone calculating the actual capacity of those two systems compared to heavy rail equivalents. It is true that the TPH levels are higher, but since the trains are shorter, I don’t know that you actually end up carrying more passengers.)

The reality, sadly, is that both of these networks are infamous for their reliability issues. (Full disclosure: I’m much more familiar with the MBTA than SEPTA, but I believe most of the T’s problems also exist in Philadelphia.) Delays are common, both on the branches and then resultantly in the core, potentially resulting in less than forty actual trains per hour through the core.

Having four or five branches is somewhat workable on these two systems due to their unusual characteristics. Replicating that success elsewhere would likely require replicating those characteristics as well.

The other exceptions that prove the rule: hybrid rapid transit/commuter rail systems

BART’s core trunkline from Daly City to West Oakland feeds out into four eastern branches (Richmond, Antioch, Dublin/Pleasanton, Berryessa/North San Jose). Likewise, the London Undergroud’s Metropolitan Line runs to four termini in the northwestern suburbs (Uxbridge, Amersham, Chesham, Watford).

Both networks accomplish this by running service to distant suburbs that is more like high-frequency commuter rail than traditional rapid transit service. Each branch on the BART runs every fifteen minutes, which isn’t super unreasonable given that most of those branches travel over thirty miles from downtown San Francisco. (BART is also a pluricentric network, which makes the ridership patterns a bit different than, for example, Chicago’s.)

The Met in London is a bit more complicated, but the concept is similar. Similar to New York, and unlike BART, the Metropolitan is quad-tracked for certain stretches, and therefore runs both local services and express services. During peak hours:

Uxbridge sees 10 tph (6 min) spread across local and express services, with 4 of those trains short-turning at Baker Street
Amersham sees 4 tph (15 min), half of which are express
Chesham sees 2 tph (30 min)
Watford sees 8 tph (7.5 min), again with some short-turns and some expresses

A couple of further notes for context:

Almost all of the Uxbridge branch is also served by Piccadilly trains – 12 tph at peak – providing a robust 22 tph, which creates headways under 3 minutes
The Amersham and Chesham services run together until Chalfont & Latimer, before splitting off and going one stop each to their terminus, meaning most of the branch in fact sees 6 tph; these services are also supplemented by at least 2 tph that run on Chiltern Railways to Amersham and beyond.
Chesham is also the most distant Underground station – 25 miles from Charing Cross in central London, and technically outside of Greater London – well into territory where 30-minute headways might be reasonable
The town of Watford is served by three other stations; the largest of these is Watford Junction, which is less than a mile from the Met station, and sees 4 Overground trains and about 5 London Northwestern Railways trains toward London per hour

So, the Met has a few mitigating factors:

Its branches are supplemented by additional services
Despite four possible termini, really it just has three branches, one of which splits at the very end
The only stations that see 15-minute-or-worse headways are distant suburbs, over 20 miles from the core of London

Like SEPTA and the MBTA, both BART and the Metropolitan also have unusual characteristics that enable them to get away with breaking my “two branches max” rule of thumb.

However, both BART and the Met also have an additional special feature that allow them to have their cake and eat it too… to be continued in the next post!

Branches are not your friend

Posted on April 3, 2022August 14, 2022 by Riverside

When I was a kid, I wanted to send branches everywhere. As a child, it was an easy concept to understand — I knew that branches came (like the Braintree or Riverside branches) and that branches went away (like Watertown), and if the Green Line used to have five branches, maybe it could have six or seven or eight! And if the Green Line could have eight branches, why couldn’t the Orange Line?

Obviously, with age has come a modicum of learned wisdom; I stopped drawing branches everywhere and tried to focus on only sending branches where train service actually was reasonable. But there is more to the picture than that.

It is tempting to think of subway branches like roads. If you build a new road, it means that more places are connected. Providence and Hartford don’t have an interstate highway between them — you have to drive north or south first and pick up Route 84 or Route 95, and then head west. It takes longer than it would if there were an interstate directly between them, which is why you will occasionally hear proposals for one. Two disconnected places ought to have a connection between them.

Rail systems don’t work like that most of the time (and actually road systems don’t either, but that’s a different topic).

There actually is a surprising amount to discuss on this topic! Here are some rules of thumb:

Two branches max

For most systems, do not give an HRT/subway line more than 2 branches. A light rail line, or a commuter/regional rail line, can probably take more, but keep in mind the other rules of thumb below.

One evening I decided to jump down this rabbit hole and did a cursory review of pretty much every heavy rail subway system in the world. Almost none had HRT lines with more than 2 branches. Most of the exceptions were themselves exceptional systems, such as BART or London’s Metropolitan Line, both “subway” lines that act more like commuter rail lines, especially along their branches.

Consider frequencies

Branches have low frequencies, trunks have high frequencies. Trunks should only branch once they are far enough from the urban core that lower frequencies will be feasible.

Most transit systems in North America have a “full-build reach” (even if hypothetical) of a 10 mile radius from the center. Your trunk shouldn’t branch too close to downtown; every city will be different, but in general you’ll want your trunk to branch no closer than 5 miles to the core. If you need to branch closer to the core, you should try to create a second trunk line.

Remember that branching frequencies are almost always a hard-and-fast math problem: If your trunk line can take x trains per hour max, then two branches can each feed no more than 50% of x. That is often going to be enough to knock a “high-frequency” trunk service into a “mid-frequency tier” on the branches. As such, it’s worth conceptualizing a branch as something less than a “full” rapid transit line.

In the diagram below, note how the trunk line has a high frequency of 4 minute headways via 15 trains per hour, but that splitting it up into three branches very quickly drops frequencies to 12 minutes on each branch.

Trunk line capacity should be your starting point

It’s important to recognize that branches are (usually) a game of subtraction, not addition. Your trunk line provides the pool of trains that you can send out to multiple branches. Unless you know that the trunk line is under capacity, you should assume that they are shoveling through as many trains as they possibly can, and can’t add more. So you need to think about redirecting the existing pool of trains, which is why this is a game of subtraction and not addition.

Note that I said this is usually a subtraction game – some newer/younger rail systems will not be at capacity. When that is the case, a branch proposal can work in your favor: proposing the addition of a second mid-capacity branch can combine with the existing mid-capacity service to create high-capacity service in the core (where presumably demand will be higher). Especially in newer metro systems, there may not be sufficient existing demand to justify the capital expenses of expanding the fleet to increase service in the core; adding a branch can broaden your revenue base, and enable the purchase of enough vehicles to run high-frequencies in the core. (Sometimes – these calculations are always going to be complicated.)

Look for short-turn services (and over-capacity extremities)

Transit agencies are incentivized not to run extraneous services. The further out from the core, the lower the demand for service (very much theoretically, but I digress). One solution agencies use are short-turn services, in which some fraction of vehicles do not run the full-length of the route. Sometimes this is done to reduce the number of near-empty vehicles running on the outskirts of the line, and sometimes this is done in order to increase the reliability of service on the inner sections of the line (and sometimes both). Short-turns are very common on bus routes, but do have their role in rail transit as well.

If your trunkline has an existing short-turn service, that is a very strong jumping-off point for a new branch: it points to a confirmed high-frequency trunk/mid-frequency branch demand model, and it doesn’t require additional capacity to be freed up in your trunk, since you aren’t trying to funnel a greater number of trains per hour through. (You will still need to expand your fleet size to maintain existing frequencies, although you may be able to adjust frequencies elsewhere in the network to account for the longer trips your short-turn services will now be taking on the branch).

A simple route diagram, from "Downtown" to "Beltway" to "Suburbia", before and after. Before, half of all trains terminate at Beltway (indicated by the line thinning to halfwidth). After, half of all trains go to Suburbia, and the other half divert after Beltway to East Suburbia, on a new branch.

But be careful – this technique works well if the short-turn is intended to avoid excess capacity on the extremities of the existing service. If the short-turn is intended instead to increase reliability within the core, then extending those short-turns out onto a new branch may jeopardize that reliability. And make sure to take note of the pitfalls of junctions, below.

Be cautious with reverse branching

Be cautious with reverse-branching, which is when a transit service splits into multiple branches going in to the city, rather than going out. (SEPTA’s Broad-Ridge Spur is a good example of this on-paper. In practice, it’s actually a little more complicated, but that’s a post for another time.)

A SEPTA system map with the Broad-Ridge Spur highlighted

http://www.septa.org/maps/system/

Recall what we went through above: branches are lower frequency than trunks. Reverse-branching into an urban core thus means you are reducing frequency precisely in the area you need it most.

Note that I say “be cautious,” not “avoid.” I think that one of the major values of crayon maps is that they sometimes value creativity over feasibility. Reverse-branching is usually more creative than it is feasible, but sometimes it sparks good follow-up ideas. So, I wouldn’t forbid it as a hard-and-fast rule, but it’s good to be aware of its drawbacks.

Junctions are complicated

Junctions where branches come together will always have one of two drawbacks, so be careful where you put them:

If a level junction is used, then you will have capacity limits and sometimes delays, as trains need to wait for each other to cross, and may need to leave a whole signal block free (i.e. the train may not be able to wait right at the junction like a car at an intersection, but may need to be hundreds or thousands of feet away).

A flying junction avoids those problems and should be the standard for any new rapid transit junction. However, flying junctions are much more expensive, and also take up more space — horizontally and vertically — than level junctions. So, as with all things, it’s a trade-off between cost and quality of service. If you want your proposal to be taken seriously, make sure your proposal is ambitious enough to merit building the flying junction.

In conclusion, branches are not your friend

Branches are not the friend of the crayon-mapper. They look great on paper but require a lot of careful planning to be done well; when done poorly, they can be actively detrimental to the individual branches and the system overall. If you really want to use them on a subway network:

No more than two branches
Aim to branch at least 5 miles from the core
Look for segments where there already is reduced service (short-turns) or reduced demand for service (lower density)
If both branches demand full-frequency service, then both branches warrant their own trunklines through the core: i.e. they shouldn’t be branches, but should be separate lines

Post-script on LRT, BRT and mainline rail

All of the dynamics I describe here hold true on other modes of service. However, the cost-benefit calculations work out a little differently because there are different standards for these modes.

LRT

For the most part, LRT is going to have the same struggles as an HRT subway would. The main differences are all knock-on effects of light rail’s shorter and more nimble rolling stock. Shorter trains makes it easier to “fudge” capacity in a trunk line, with multiple trains stopping in a single station at once, and shorter signal blocks allowing trains to run closer together. The shorter signal blocks also mean that flat junctions – while still disruptive – can be mildly less problematic.

LRT also – by virtue of its lower capacity – is sometimes a better fit for serving lower-density regions, which can sometimes mean that the frequency cost of more than two branches is more manageable, especially if combined with a higher frequency on the trunk than you could achieve with larger trains.

Boston and Philadelphia both run a scheduled 40 light rail trains per hour through their tunnels (Philly apparently swings even more than that), with four and five branches respectively. San Francisco runs at a lower frequency (I think) in the Muni Metro subway, also with five branches. All three of these systems are plagued with reliability and other issues. (Muni recently tried to redirect two of its branches out of the subway, but now has returned them to the tunnel). That isn’t to say that these systems can’t be improved, nor am I denying benefits to their approaches. But it’s probably best to think of these as the exceptions which prove the rules.

BRT

BRT comes in lots of flavors, some of which are more amenable to branches than others. Christof Spieler gave an excellent presentation at TransitCon 2022 on the varieties of BRT, and discussed some of the pros and cons of branching on each. In short, I’d say that the more you want your BRT line to act like a subway line, the more you should follow the same rules about branching.

Mainline rail

Mainline rail faces all of the same dynamics I outlined above. The major difference is that the costs of branching don’t always end up being “disqualifying.” If you take a 20tph rapid transit line and give it 10 branches, each branch will get 30 minute headways, which no longer is “rapid transit.” But if you give a 20tph commuter rail line 10 branches, the 30-minute headways on each branch may be perfectly reasonable. The same dynamic is at play — it’s just that the requirements are different and therefore the costs are more acceptable.

On the other hand, some dynamics remain equally if not more problematic. Junctions, for example, will still be disruptive if built flat and costly if built flying. And reverse branching’s impact may be felt even more acutely: many American commuter rail lines run once per hour; split those between two downtown terminals – we’ll call them “Northtown” and “Southtown” –, and commuters now have to wait two hours between trains, which reduces flexibility for riders and may have an overall chilling effect on ridership on both branches.

Consider this fictional system below:

Inspired by the NJ Transit system, four routes of 2 tph each branch out to Burlington (green), Louisburg (red), Toledo (blue), and Millville (purple). Those last two merge at Arroyo, proceding north to Belleview where they are joined by Red, all three of which proceed to Newtown where they are joined by Green. Between Newtown and Riveredge are 8 tph. East of Riveredge, each line splits into two half-width thinner lines, one each to Northtown and to Southtown

At first glance, it looks like a relatively robust commuter rail network. Each suburb sees 30-minute headways, and that segment between Newtown and Riveredge sees rapid transit-frequencies of 7.5 minutes. And every community sees direct service to both Northtown and Southtown.

But most commuters don’t care about going to two different workplaces – their destination is the same everyday. Let’s look at what the network looks like for a Northtown commuter:

A modified version of the map above, showing only services that go to Northtown. Each line is now half-width all the way through.

This paints a significantly different picture. Most suburbs are reduced to hourly service, and the turn-up-and-go frequencies at Newtown are gone.

(To be fair, in this example, most American cities would be thrilled to see commuter rail service at this level – hourly commuter rail is nothing to sneeze at. But I’m keeping the numbers simple to keep the math simple; if most cities start with hourly commuter rail, then reverse branching drops the effective frequency of each branch down to every two hours, which is pretty rough. You get the idea.)

Instead of a robust trunk-and-branch network, reverse-branching reduces this network into two significantly diluted networks operating in parallel.

The same map as above, but for Southtown, shown at 50% size to compare to the Northtown map at right.

The same Northtown map as above, shown at 50% size to compare to the Southtown map at right.