There are two standard reasons why public transit should limit branching. The first is that it reduces frequency on the branches; this is Jarrett Walker’s reason, and distantly the reason why New York doesn’t interline more than two subway services anywhere except 60th Street Tunnel. The second is that it makes schedules more fragile, first because services have to be scheduled more precisely to alternate among branches, and second because delays on one branch propagate to the others. And yet, rail and bus networks still employ branching, due to benefits including better coverage and focusing frequency where demand is the highest. This is especially common on regional rail, where all services are scheduled and often interact with the mainline network, so the second problem of branching is present no matter what. Metro systems instead have less branching, often because they only serve dense areas so that the main benefits of branching are absent. But what about buses?
I posit that bus branching is more valuable in low-density areas than in high-density areas. If an area only has demand for a bus every 30 minutes, and some farther-out places only have demand for an hourly bus, then it’s fine to branch the route in two. The bus would only be useful with some timed transfers at the inner end – maybe it’s feeding a regional train station with a train every half hour – but the Zurich suburbs have half-hourly clockface schedules with timed bus/rail connections and maintain high mode share for how low their density is.
In the other direction, look at Manhattan specifically. I’ve been looking at its bus network even though I’m only supposed to redesign Brooklyn’s. I’ve mentioned before that my epistemology is that if the presence of factor A makes solution B better, then the absence of factor A should make solution B worse. I noticed that the Brooklyn bus network has very little branching: the only route numbers that branch are the B41 and B38, and the only routes with different numbers that share the majority of their lengths are the B67 and B69 (which reverse-branch). However, Manhattan has extensive branching: the M1/2/3/4 share the Madison and Fifth Avenue one-way pair, and the M101/102/103 share the Third and Lexington one-way pair. Understanding why would be useful even if I only care about Brooklyn: if there is a good reason for Manhattan buses to branch then I should consider adding branching in Brooklyn where appropriate, and even if it’s inappropriate, it’s useful to understand what special circumstances make branching good in Manhattan but not in Brooklyn.
As it is, I don’t believe the branching in Manhattan is useful for Brooklyn. This comes from several reasons, at least one of which implies it’s not really useful for Manhattan either, and by extension for other high-density regions.
You can run a bus that comes every half hour on a schedule, making it possible to interline two hourly routes evenly. With some discipline you can go down to 15 minutes, or possibly even 10: Vancouver runs 12-minute limited buses on 4th Avenue on a clockface schedule with on-board fare collection and shared lanes, but there is signal priority at nearly all intersections and relatively little car traffic since the West Side’s street network is rich in arterial roads and distributes cars across other routes (i.e. Broadway, 12th, and 16th Avenues).
In contrast, it’s not really feasible to run buses on a schedule when they come every 5 minutes. There can be a printed schedule, but buses won’t follow it reliably. Once frequency hits about once every 3 minutes, regular street buses bunch so much that adding more buses doesn’t increase passenger capacity, but even in the 5-10 minute range, schedules are less important than headway management, unless the bus has extensive BRT treatments reducing schedule variance. This means that if a bus comes every 10 minutes and is scheduled on headway management, then branching the route means each branch gets service every 20 minutes scheduled on headway management as well. Few passengers would want to ride such a route. This is the worst region for branching, the 7.5-15 minute range in which branches force passengers to use buses that are both infrequent and irregular.
The highest-frequency routes can branch with less risk. If a 5-minute bus branches in two, then each branch gets 10-minute service, at which point reliable schedules are still desirable but not absolutely necessary. How much service do the Manhattan bus trunks run? In the following scheme, peak means the busiest hour in the morning in the peak direction, and off-peak means the lowest frequency between the morning and afternoon peaks, which is usually around 11 am.
M1: 13 buses per hour peak (8 limited, 5 local), 5 off-peak (all local)
M2: 9 peak, 4 off-peak
M3: 6 peak, 6 off-peak
M4: 12 peak (5 limited, 7 local), 6 off-peak (all local)
M101: 6 peak, 6 off-peak (8 in the busiest off-peak hour, 2-3 pm)
M102: 5 peak, 4 off-peak
M103: 5 peak, 4 off-peak
What we see is that Manhattan branches precisely in the worst frequency range. The buses are frequent enough that it’s not possible to run them on a timetable without either much better segregation from traffic than is feasible (even waving away politics) or massive schedule padding, but they still require passengers in Upper Manhattan to wait 10-15 minutes for their specific branch. One might expect that Bus Time would make it easier on passengers by telling them where the bus is, but no, ridership has actually fallen since apps were introduced (and this fall predates the entry of app-hailed TNCs into the city). It turns out passengers like being able to rely on easily memorable clockface schedules, or else on frequencies so high that they only need to wait 5 minutes, not 15.
The street network
Even one-time visitors to New York notice that the avenues in Manhattan are all one-way. This features prominently in the Manhattan bus network, which employs consistent one-way pairs on First/Second, Third/Lex, Madison/Fifth, and Ninth/Tenth. Moreover, again as every visitor to New York knows, Central Park occupies a large blob of land in the middle, interrupting Sixth and Seventh Avenues.
The upshot is that there are more north-south routes north of 110th Street than south of it. This is roughly the branch point on the three trunks that branch (First/Second only carries the M15). In Harlem, there’s demand for buses on Lenox (i.e. Sixth) and Seventh, both of which are two-way there. There’s also commerce on an interpolating route, Manhattan/St. Nicholas, which is effectively 8.5th Avenue in most of Harlem. Farther west, Ninth/Columbus is no longer a useful through-route north of 110th, but instead Tenth/Amsterdam is two-way, and one of the two buses using the Columbus/Amsterdam one-way pair on the Upper West Side, the M11, indeed goes two-way on Amsterdam north of 110th.
This situation occurs very frequently in cities without gridded street networks. One trunk route will split in two, heading to different former villages that were incorporated into the city as it industrialized and grew. Manhattan is unusual among gridded cities in that its avenues are one-way, forcing buses into one-way pairs south of Harlem that, together with Central Park, ensure there are more useful routes north of 110th than south of it. But among cities without a planned street network this is typical.
As a check, let’s look at the bus networks in two ungridded American cities: Boston and Providence. Do they have a lot of interlining, involving one trunk route splitting in two farther out? Yes, they do!
Here is Providence. Going west of Downcity, there are two major routes to Olneyville, Westminster and Broadway, but beyond Olneyville there are four main streets, so each of the two inner corridors carries two bus routes, and one of these four routes even splits in two farther out. Going north, Charles Street carries four routes, branching off at various locations. Going east there’s a bus tunnel to College Hill carrying many routes, but even outside the tunnel, the one-way pair on Angell and Waterman carries three buses, which split in East Providence. And going south and southwest, Broad Street carries multiple routes, and one of its branches, Elmwood, carries two, splitting farther south.
Here is Boston. Unlike in Providence, buses don’t converge on city center, but on subway stations, so the map is much less clean. However, we see the same pattern of trunk routes splitting into branches. For example, going south of Ruggles, many routes go southeast to Dudley and then south on Warren Street, splitting to various destinations in Dorchester, Mattapan, and Hyde Park on the way. Going southwest of Forest Hills we see many routes use Washington Street, some staying on it and branching in Dedham and some veering west to West Roxbury and branching there. Elsewhere in the system we see the same pattern going north of Maverick and Oak Grove, northeast of Malden, west of Harvard (briefly on Mount Auburn), and northwest of Alewife.
One-seat rides and reverse-branching
I have repeatedly criticized the practice of reverse-branching on subway networks, especially New York, in which two train routes share tracks in an outlying area (such as Queens Boulevard) and then split heading into the center (such as Eighth Avenue on the E versus Sixth Avenue on the F). I did so on the same grounds that any branching is suspect: it reduces frequency on specific routes, and makes the schedule more fragile as delays propagate to more of the network. Moreover, the issue of schedule fragility gets worse if many routes share tracks at some point during their journey, whereas with conventional branching there are only two or three branches per trunk and the trunks form self-contained systems. Finally, reverse-branching lacks the main benefit of conventional branching, as it does not concentrate traffic in the core, where there’s most demand.
These issues are present on bus networks, with two modifications:
- The value of one-seat rides is somewhat higher. Transferring between buses is less nice than transferring between subways: in a Dutch study about location decisions, people’s disutility of out-of-vehicle time on buses was 1.5 times as high as on trains.
- Buses can overtake each other and, even without overtakes, run much closer together than trains. The limiting factor to capacity on buses is schedule fragility and bunching and not stopping distances. This means that reverse-branching is less likely to lead to cascading delays – buses do not have a 2-minute exclusion zone behind them in which no buses may enter.
This means that reverse-branching is more defensible on buses than on trains. However, even then, I don’t think it’s a good idea. At least in Manhattan, reverse-branching consists of avenues in Upper Manhattan that have buses going to both the East Side and the West Side: the M7 (serving the Ninth/Tenth pair) and the M102 both run on Lenox, and the M4 and M104 (running on Broadway to Midtown) both run on Broadway in Morningside Heights. These splits both reduce the frequency available to bus riders and should be eliminated. East-west service should be provided with high-quality bus routes on the main streets, especially 125th (which needs a full subway) but also 116th, 135th, 145th, and 155th.
The snag is that grids don’t work well unless they are complete. The Manhattan grid isn’t complete through Upper Manhattan, because 116th and 135th are discontinuous, without a direct connection from Central Harlem to Morningside Heights and West Harlem. However, the M7 route duplicates the 2 and 3 trains, so it’s not necessary for east-west connectivity. The M4 route doesn’t duplicate the subway, but does duplicate the M101, which runs on 125th Street and Amsterdam (and isn’t a reverse-branch because the M11 terminates shortly after 125th), so it’s not useful by itself.
Should buses branch?
There is one solid reason for buses to branch: if the street network has more major routes closer to the center than in outlying areas, then buses running on the outer arterials should come together close to the core. This is common enough on cities with haphazard street networks. It may also be reinforced if there are weak circumferential streets (Sydney is one such example). In contrast, cities with gridded street plans, even broken grids like those of Brooklyn and Tel Aviv, should have little to no bus branching.
If a bus does branch, it should ideally be extremely frequent on the trunk, so that even the branches have decent headway-based service. I’m not willing to commit to a maximum headway, but Barcelona and Toronto both have at worst 8-minute headways on their bus grids, so if that is indeed the maximum then a bus shouldn’t branch if its off-peak frequency is worse than every 4 minutes and better than every 10-20 (the more reliable the timetable is, the lower the upper limit is, since it’s possible to run on a timetable at higher frequency). In my case of interest, Brooklyn, there is exactly one bus route that comes at least every 4 minutes off-peak: the B46 on Utica runs 16 buses per hour in each direction, counting both local and limited (SBS) routes.
The area in which buses absolutely should not branch – strong interconnected networks of arterials (not necessarily grids – Paris’s network counts too), running buses every 5-15 minutes off-peak – is exactly where most strong bus networks are. It’s rare to have a bus that has extremely high frequency all day, because in most functional city such a bus would be a subway already; as it is, Utica has long been New York’s second priority for subway service, after Second Avenue. So for the most part, the places where buses are the strongest are precisely those where branching is the most deleterious. Low-frequency networks, perhaps connecting to a suburban train station with a timed transfer, should add bus branching to their planning toolkit, but high-frequency urban networks should not.
Boston has two main train stations: South Station, and North Station. Both are terminals, about 2 km apart, each serving its own set of suburbs; as a result, over the last few decades there have been calls to unify the system with a regional rail tunnel connecting the two systems. This tunnel, called the North-South Rail Link, or NSRL, would have been part of the Big Dig if its costs hadn’t run over; as it were, the Big Dig reserved space deep underground for two large bores, in which there is clean dirt with no archeological or geotechnical surprises. The NSRL project had languished due to Massachusetts’ unwillingness to spend the money on it, always understood to be in the billions, but in the last few years the pressure to build it intensified, and the state agreed to fund a small feasibility study.
A presentation of the draft study came out two days ago, and is hogwash. It claims on flimsy pretext that NSRL would cost $17 billion for the tunnel alone. It also makes assumptions on service patterns (such as manual door opening) that are decades out of date not just in Europe and East Asia but also in New York. The Fiscal and Management Control Board, or FMCB, discusses it here; there’s a livestream as well as a link to a presentation of the draft study.
The content of the study is so weak that it has to have been deliberate. The governor does not want it built because of its complexity, no matter how high its benefits. Thus, the state produced a report that sandbags a project it doesn’t want to build. People should be fired over this, starting with planners at the state’s Office of Transportation Planning, which was responsible for the study. The way forward remains full regional rail modernization. As for the cost estimate, an independent study by researchers at Harvard’s Kennedy School of Government estimates it at about $5 billion in today’s money; the new study provides no evidence it would be higher. I urge good transit activists in Massachusetts, Rhode Island, and New Hampshire to demand better of their civil servants.
The study says that the cost of a four-track NSRL tunnel under the Big Dig would be $17 billion in 2028 dollars. In today’s money, this is $12 billion (the study assumes 3.5% annual cost escalation rather than inflation-rate cost escalation). It claims to be based on best practices, listing several comparable tunnels, both proposed and existing:
- California High-Speed Rail tunnels (average estimated cost about $125 million per km, not including overheads and contingency)
- Crossrail (see below on costs)
- The M-30 highway tunnel in Madrid (average cost about $125 million per km of bored tunnel in the mid-2000s, or around $150 million/km in today’s money)
- The canceled I-710 tunnel in California (at 7.2 km and $5.6 billion, $780 million per km
- The Spoortunnel Pannerdensch Kanaal (around $200 million in today’s money for 1.6 km of bore, or $125 million per km)
Unlike the other tunnels on the list, Crossrail has stations frustrating any simple per km cost analysis. The headline cost of Crossrail is £15 billion; however, I received data from a freedom of information request showing that the central (i.e. underground) portion is only £11.6 billion and the rest is surface improvements, and of this cost the big items are £2.2 billion for tunneling, £4.1 billion for stations, £1 billion for tracks and systems, and £2.7 billion for overheads and land acquisition. The tunneling itself is thus around $150 million per km, exclusive of overheads and land (which add 30% to the rest of the project). All of this is consistent with what I’ve found in New York: tunneling is for the most part cheap.
With the exception of Crossrail, the above projects consist of two large-diameter bores. The mainline rail tunnels (California HSR and Pannerdensch Kanaal) are sized to provide plenty of free air around the train in order to improve aerodynamics, a feature that is desirable at high speed but is a luxury in a constrained, low-speed urban rail tunnel. The highway tunnels have two large-diameter bores in order to permit many lanes in each direction. The plan for NSRL has always been two 12-meter bores, allowing four tracks; at the per-km boring cost of the above projects, this 5 kilometer project should cost perhaps a billion dollars for tunneling alone.
The stations are typically the hard part. However, NSRL has always been intended to use large-diameter tunnels, which can incorporate the platforms within the bore, reducing their cost. Frequent commenter Ant6n describes how Barcelona used such a tunnel to build Metro Lines 9 and 10, going underneath the older lines; the cost of the entire project is around $170 million per km, including a cost overrun by a factor of more than 3. Vertical access is likely to be more difficult in Boston under the Big Dig than in Barcelona, but slant shafts for escalators are still possible. At the worst case scenario, Crossrail’s station costs are of an order of magnitude of many hundreds of millions of dollars each, and two especially complex ones on Crossrail 2 are £1.4 billion each; this cost may be reasonable for Central Station at Aquarium, but not at South Station or North Station, where there is room for vertical and slant shafts.
It’s possible that the study made a factor-of-two error, assuming that since the mainline rail comparison projects have two tracks, their infrastructure is sized for two urban rail tracks, where in reality a small increase in tunnel diameter would permit four.
Researchers at the Harvard Kennedy School of Government came up with an estimate of $5.9 billion in 2025 dollars for a four-track, three-station NSRL option, which is about $5 billion today. Their methodology involves looking at comparable tunneling projects around the world, and averaging several averages, one coming from American cost methodology plus 50% contingency, and two coming from looking at real-world cost ranges (one American, one incorporating American as well as rest-of-world tunnels). Their list of comparable projects includes some high-cost ones such as Second Avenue Subway, but also cheaper ones like Citybanan, which goes deep underneath Central Stockholm with mined tunnels under T-Centralen and Odenplan, at $350 million per km in today’s money.
But the MassDOT study disregarded the expertise of the Kennedy School researchers, saying,
Note: The Harvard Study did not include cost for the tunnel boring machine launch pit and only accounted for 2.7 miles of tunneling (the MassDOT studies both accounted for 5 miles of tunneling), and no contingency for risk.
This claim is fraudulent. The Kennedy School study looks at real-world costs (thus, including contingency and launch pit costs) as well as at itemized costs plus 50% contingency. Moreover, the length of the NSRL tunnel, just under 5 km, is the same either way; the MassDOT study seems to be doubling the cost because the project has four tracks, an assumption that is already taken into account in the Kennedy School study. This, again, is consistent with a factor-of-two error.
Moreover, the brazenness of the claim that a study that explicitly includes contingency does not do so suggests that MassDOT deliberately sabotaged NSRL, making it look more expensive than it is, since the top political brass does not want it. Governor Baker said NSRL looks expensive, and Secretary of Transportation Stephanie Pollack is hostile as well; most likely, facing implicit pressure from above, MassDOT’s overburdened Office of Transportation Planning scrubbed the bottom of the barrel to find evidence of absurdly high costs.
Massachusetts really does not want or understand electrification. Even some NSRL supporters believe electrification to be an expensive frill that would sink the entire project and think that dual-mode locomotives are an acceptable way to run trains in a developed country in the 2010s.
In fact, dual-mode locomotives’ weak performance serves to raise tunneling costs. Struggling to accelerate at 0.3 m/s^2 (or 0.03 g), they cannot climb steep grades: both the Kennedy School and MassDOT studies assume maximum 3% grades, whereas electric multiple units, with initial acceleration of 1.2 m/s^2, can easily climb 4% and even steeper grades (in theory even 10%, in practice the highest I know of is 7%, and even 5% is rare), permitting shorter and less constrained tunnels.
As a result of its allergy to electrification, MassDOT is only proposing wiring between North Station and the next station on each of the four North Side lines, a total of 22.5 route-km. This choice of which inner segments to electrify excludes the Fairmount Line, an 8-stop 15 km mostly self-contained line through low-income, asthma-riven city neighborhoods (source, PDF-pp. 182 and 230). Even the electrification the study does agree to, consisting of about 30 km of the above surface lines plus the tunnels themselves, is projected to cost $600 million. Nowhere in the world is electrification so expensive; the only projects I know of that are even half as expensive are a pair of disasters, one coming from a botched automation attempt on the Great Western Main Line and one coming from poor industry practices on Caltrain.
A more reasonable American budget, based on Amtrak electrification costs from the 1990s, would be somewhat less than $2 billion for the entire MBTA excluding the already-wired Providence Line; this is the most familiar electrification scheme to the Bostonian reader or planner. At French or Israeli costs, the entire MBTA commuter rail system could be wired for less than a billion dollars.
Another necessary element is conversion to an all-EMU fleet, to increase performance and reduce operating costs. Railway Gazette reports that a Dutch benchmarking study found that the lifecycle costs of EMUs are half as high as those of diesel multiple units. As the MBTA needs to replace its fleet soon anyway, the incremental cost of electrification of rolling stock is negative, and yet the study tacks in $2.4 billion on top of the $17 billion for tunneling for vehicles.
A miscellany of incompetence
In addition to the sandbagged costs, the study indicates that the people involved in the process do not understand modern railroad operations in several other ways.
First, door opening. While practically everywhere else in the first world doors are automatic and opened with the push of a button, the MBTA insists on manual door opening. The MassDOT study gives no thought to high platforms and automatic doors (indeed, the Old Colony Lines are already entirely high-platform, but some of their rolling stock still employs manual door opening), and assumes manual door opening will persist even through the NSRL tunnels. Each train would need a squad of conductors to unload in Downtown Boston, and the labor costs would frustrate any attempt to run frequently (the study itself suggests hourly off-peak frequency; in Paris, RER lines run every 10-20 minutes off-peak).
Second, capacity. The study says a two-track NSRL would permit 17 trains per hour in each direction at the peak, and a four-track NSRL would permit 21. The MBTA commuter rail network is highly branched, but not more so than the Munich S-Bahn (which runs 30 at the peak on two tracks) and less so than the Zurich S-Bahn (which before the Durchmesserlinie opened ran either 20 or 24 tph through the two-track tunnel, I’m not sure which).
Worse, the FMCB itself is dumbfounded by the proposed peak frequency – in the wrong direction. While FMCB chair Joe Aiello tried explaining how modern regional rail in Tokyo works, other members didn’t get it; one member dared ask whether 17 tph is even possible on positive train control-equipped tracks. My expectations of Americans are low enough that I am not surprised they are unaware that many lines here and in Japan have automatic train protection systems (ETCS here, various flavors of ATC in Japan) that meet American PTC standards and have shorter minimum headways than every 3-4 minutes. But the North River Tunnels run 24-25 peak tph into Manhattan, using ASCES signaling, the PTC system Amtrak uses on the Northeast Corridor; the capacity problems at Penn Station are well-known to even casual observers of American infrastructure politics.
A state in which the FMCB members didn’t really get what their chair was saying about modern operations is going to propose poor operating practices going forward. MassDOT’s study assumes low frequency, and, because there is no line-wide electrification except on the Providence Line and eventually South Coast Rail (where electrification is required for wetland remediation), very low performance. MassDOT’s conception of NSRL has no infill stops, and thus no service to the bulk of the contiguous built-up area of Boston. Without electrification or high platforms, it cannot achieve high enough speeds to beat cars except in rush hour traffic. Limiting the stop penalty is paramount on urban rail, and level boarding, wide doors, and EMU acceleration combine to a stop penalty of about 55 seconds at 100 km/h and 75 seconds at 160 km/h; in contrast, the MBTA’s lumbering diesel locomotives, tugging coaches with narrow car-end doors with several steps, have a stop penalty of about 2.5 minutes at 100 km/h.
The presentation makes it very clear what the value of MassDOT’s NSRL study is: at best none, at worst negative value through muddying the conversation with fraudulent numbers. The Office of Transportation Planning is swamped and could not produce a good study. The actual control was political: Governor Baker and Secretary of Transportation Pollack do not want NSRL, and both the private consultant that produced the study and the staff that oversaw it did what the politicians expected of them.
Heads have to roll if Massachusetts is to plan good public transportation. The most important person good transit activists should fight to remove is the governor; however, he is going to be easily reelected, and replacing the secretary of transportation with someone who does not lie to the public about costs is an uphill fight as well. Replacing incompetent civil servants elsewhere is desirable, but the fish rots from the head.
Activists in Rhode Island may have an easier time, as the state is less hostile to rail, despite the flop of Wickford Junction; they may wish to demand the state take lead on improving service levels on the Providence Line, with an eye toward forcing future NSRL plans to incorporate good regional rail practices. In New Hampshire, provided the state government became less hostile to public investment, activists could likewise demand high-quality commuter rail service, with an eye toward later connecting a North Station-Nashua-Manchester line to the South Side lines.
But no matter what, good transit activists cannot take the study seriously as a planning study. It is a political document, designed to sandbag a rail project that has high costs and even higher benefits that the governor does not wish to manage. Its cost estimates are not only outlandish but brazenly so, and its insistence that the Kennedy School study does not include contingency is so obviously incorrect that it must be considered fraud rather than a mistake. Nothing it says has any merit, not should it be taken seriously. It does not represent the world of transportation planning, but rather the fantasies of a political system that does not understand public transportation.
At TransitMatters, we have finally released our regional rail paper, recommending improvements to the MBTA that regular readers of this blog are probably familiar with. Alert readers might even want to probe which parts were written by me and which by others; the main document underwent several edits but some stylistic differences might persist, and the appendices were mostly written individually. We are suggesting the following two-step process:
1. Modernize the system based on best industry practices. This includes full electrification and fleet replacement with electric multiple units (and not electric locomotives), high platforms at all stations, and high frequency all day, every half hour on every branch interlining to support a train every 10-15 minutes on urban trunk lines. In some areas, such as Revere, there should also be infill stops. The capital cost, excluding fleet replacement, should be on the order of $2-3 billion, but the first priority, the Providence Line, is maybe $100 million excluding rolling stock, mostly going to high platforms.
2. Build the North-South Rail Link, with four tracks connecting the South Station and North Station systems. This takes longer than electrification, so planning should start immediately, with the intention of opening somewhat after the entire system is wired. The capital cost should be $4-6 billion, per a study that we’re referencing in our report.
In my mind, regional rail serves three main markets:
1. Local trips on trunk lines, connecting to urban neighborhoods and subway transfer points. The main benefit of regional rail is that it provides an express subway at very high frequency, just as I use the RER to get to Western Paris faster than I would on the Metro. In Boston, areas that would benefit include Forest Hills, Allston and Brighton, Hyde Park, Dorchester and Mattapan along the Fairmount Line, Chelsea, Revere, and Porter Square. Residents of these neighborhoods are likely to travel to other neighborhoods and not just to Downtown Boston.
2. Suburban trips, which are dominated by peak commutes; I complained here that US commuter rail demand is peaky, with 67-69% of suburban trips on the LIRR and Metro-North and 80% on the MBTA occurring in the morning peak compared with around 47% on Transilien, but this is in large part about land use and not just frequency. We’re calling for replacing park-and-rides with town center stations in the report, but absent extensive transit-oriented development, suburban trips are likely to remain peaky and CBD-bound. This is the only market North American commuter rail serves, and its users are territorial about what they view as their trains. However, electrification would speed up these trips materially (the Sharon-South Station trip time would go from 35 to 23 minutes), and the North-South Rail Link would offer North Side suburbs access to the CBD, which is too far from North Station.
3. Intercity trips, which are not peaky except insofar as some people commute. Those tend to dominate off-peak ridership today: per a CTPS study from 2012, about half of the Providence Line’s off-peak ridership originates in Providence itself, which also accords with my observations taking the line on weekends. These trips gain less from high frequency, but need a consistent frequency all day, every day, at worst every 30 minutes, ideally every 15 or 20. Regional rail modernization also speeds these trips the most.
Bear in mind that even though the report just came out, the actual writing was for the most part done in November. This means that the technical aspects of scheduling reflect my thinking in November and not now. At the time, I hadn’t thought about peak-to-base ratios systematically, so my sample schedule for the Providence Line has a train every 15 minutes on each branch (Providence and Stoughton) at the peak and a train every 30 minutes off-peak. I had been assuming a peak-to-base ratio of 2 would be appropriate, by comparison with schedules in Tokyo and on the RER here in Paris. I knew that the ratio was lower in some other places I think highly of, including London and the German-speaking world, but my assumption had been that demand would be so peaky that the maximum acceptable peak-to-base ratio was the correct one.
I’ve argued before that the peak-to-reverse-peak ratio must be 1 or as close to it as practical, in order to avoid parking trains in city center midday. The capacity problems at South Station, which averages a train arrival per platform track per 35 minutes at the peak even though the system is capable of 10-minute turnaround times, come from trains going from the platform tracks to the layover yard during the peak, crossing the station throat at-grade and delaying peak arrivals.
But recently, I started thinking more carefully about operating costs, and wrote this post about peak-to-base ratios. I no longer think peak-to-base frequency ratios higher than 1 are supportable. The marginal labor cost of midday service when there’s a prominent peak is very low, since the railroad would be replacing split shifts with regular shifts, and this encourages running the same frequency during rush hour and midday, if not during the evening and on weekends. And as I explain in the linked post, the cost of rolling stock purchase and maintenance encourages running trains as often as possible. Only energy costs scale linearly with service-km, and those are low: at New England’s current electricity rates, it costs $180 to run a 320-ton 8-car EMU between Providence and Boston each way, and at current fares, inducing 16 extra passengers from the extra frequency is enough to make this pay.
In the report, we talk about American commuter rail operating costs, mostly because that’s what’s available. SEPTA’s are $311/car-hour, whereas those of the LIRR, Metro-North, New Jersey Transit, Metra, and the MBTA are $500-600/car-hour. Per car-km, SEPTA costs about $9 to operate. But a system built around cost minimization, with a peak-to-base ratio of 1 (thus, relatively empty off-peak trains), can get this down to about $2/car-km, or about $180/car-hour.
The reason I think the MBTA could run modern regional rail for $2/car-km, where the RER costs $6/car-km and the Singapore MRT $4-5/car-km, is that the schedule is faster. The costs of rolling stock and labor are based on time rather than distance, and the regional rail system we’re proposing has aggressive schedules, averaging 90 km/h between Boston and Providence. Even energy costs can be contained, since a fast schedule implies relatively few stops. For the same reason it’s easier to make a profit on high-speed rail averaging 200 km/h than on low-speed rail, it’s easier to make a profit on a 90 km/h train at the boundary between regional and intercity scale than on a 40 km/h local train.
In general, I believe that transit planning has to be opportunistic: no city is perfect, so it’s always necessary to find workarounds for some local misfeatures, or ways to turn them into positives. In Boston, the misfeature is very low suburban density, making intense regional service modeled after the RER less useful. The opportunity lies in retooling lines that serve low-density suburbs as intercity lines, connecting Boston with Worcester, Providence, Lowell, Nashua, and Hyannis. With the exception of Worcester, which is on a curvy line, these cities can be connected to Boston at an average speed of 90 km/h or so: the stop spacing is so sparse, and the lines are so straight, that long stretches of 160 km/h are feasible.
But none of this can happen under the present-day operating paradigm. The opportunity I’m describing relies on postwar travel patterns and to some extent even on 21st-century ones (namely, university travel between Providence and Cambridge), which requires reforming frequencies, rolling stock, and infrastructure decisions to incorporate best industry practices that emerged from the 1970s onward. The MBTA can offer a fast, affordable, frequent regional transportation system from as far north as Manchester to as far south as Providence, but for this it needs to implement the regional rail improvements we’re proposing.
Continuing with my series on scale-variance (see part 1), I want to talk about a feature of transit networks that only exists at a specific scale: the Soviet triangle. This is a way of building subway networks consisting of three lines, meeting in a triangle:
The features of the Soviet triangle are that there are three lines, all running roughly straight through city center, meeting at three distinct points forming a little downtown triangle, with no further meets between lines. This layout allows for interchanges between any pair of lines, without clogging one central transfer point, unlike on systems with three lines meeting at one central station (such as the Stockholm Metro).
The name Soviet comes from the fact that this form of network is common in Soviet and Soviet-influenced metro systems. Ironically, it is absent from the prototype of Soviet metro design, the Moscow Metro: the first three lines of the Moscow Metro all meet at one point (in addition to a transfer point one station away on Lines 1 and 3). But the first three lines of the Saint Petersburg Metro meet in a triangle, as do the first three lines of the Kiev Metro. The Prague Metro is a perfect Soviet triangle; Lines 2-4 in Budapest, designed in the communist era (Line 1 opened in 1896), meet in a triangle. The first three lines of the Shanghai Metro have the typology of a triangle, but the Line 2/3 interchange is well to the west of the center, and then Line 4 opened as a circle line sharing half its route with Line 3.
Examples outside the former communist bloc are rarer, but include the first three lines in Mexico City, and Lines 1-3 in Tehran (which were not the first three to open – Line 4 opened before Line 3). In many places subway lines meet an even number of times, rather than forming perfect diameters; this is especially bad in Spain and Japan, where subway lines have a tendency to miss connections, or to meet an even number of times, going for example northwest-center-southwest and northeast-center-southeast rather than simply crossing as northwest-southeast and northeast-southwest.
But this post is not purely about the Soviet triangle. It’s about how it fits into a specific scale of transit. Pure examples have to be big enough to have three subway lines, but they can’t be big enough to have many more. Moscow and Saint Petersburg have more radial lines (and Moscow’s Line 5 is a circle), but they have many missed connections, due to poor decisions about stop spacing. Mexico City is the largest subway network in the world in which every two intersecting lines have a transfer station, but most of its lines are not radial, instead connecting chords around city center.
Larger metro networks without missed connections are possible, but only with many three- and four-way transfers that create crowding in corridors between platforms; in Moscow, this crowding at the connection between the first three lines led to the construction of the Line 5 circle. In many cases, it’s also just difficult to find a good high-demand corridor that intersects older subway lines coherently and is easy to construct under so much older infrastructure.
The result is that the Soviet triangle is difficult to scale up from the size class of Prague or Budapest (not coincidentally, two of the world’s top cities in rail ridership per capita). It just gets too cumbersome for the largest cities; Paris has a mixture of radial and grid lines, and the Metro still undersupplies circumferential transportation to the point that a circumferential tramway that averages 18 km/h has the same ridership per km as the New York City Subway.
It’s also difficult to scale down, by adapting it to bus networks. I don’t know of any bus networks that look like this: a handful of radial lines meeting in the core, almost never at the same station, possibly with a circular line providing crosstown service. It doesn’t work like this, because a small-city bus network isn’t the same as a medium-size city subway network except polluting and on the surface. It’s scaled for minimal ridership, a last-resort mode of transportation for the poorest few percent of workers. The frequency is a fraction of the minimum required to get even semi-reasonable ridership.
Instead, such networks work better when they meet at one city center station, often with timed transfers every half hour or hour. A crosstown line in this situation is useless – it cannot be timed to meet more than one radial, and untimed transfers on buses that come every half hour might as well not even exist. A source who works in planning in Springfield, Massachusetts, a metro area of 600,000, explained to me how the Pioneer Valley Transit Authority (PVTA) bus system works, and nearly all routes are radial around Downtown Springfield or else connect to the universities in the area. There are two circumferential routes within Springfield, both with horrifically little ridership. Providence, too, has little to no circumferential bus service – almost every RIPTA bus goes through Kennedy Plaza, except some outlying routes that stay within a particular suburb or secondary city.
The principle here is that the value of an untimed transfer depends on the frequency of service and to some extent on the quality of station facilities (e.g. shelter). Trains in Prague come every 2-3 minutes at rush hour and every 4-10 minutes off-peak. When the frequency is as low as every 15 minutes, transferring is already questionable; at the typical frequency of buses in a city with a bus-based transportation network, passengers are extremely unlikely to do it.
This raises the question, what about denser bus networks? A city with enough budget for 16 buses running at once is probably going to run 8 radii (four diameters) every half hour, with a city-center timed transfer, and service coverage extending about 24 minutes out of the center in each direction. But what happens if there’s enough budget for 60 buses? What if there’s enough budget for 200 (about comparable to RIPTA)?
Buses are flexible. The cost of inaugurating a new route is low, and this means that there are compelling reasons to add more routes rather than just beef up frequency on every route. It becomes useful to run buses on a grid or mesh once frequency rises to the point that a downtown timed transfer is less valuable. (In theory the value of a timed transfer is scale-invariant, but in practice, on surface buses without much traffic priority, schedules are only accurate to within a few minutes, and holding buses if one of their connections is late slows passengers down more than not bothering with timing the transfers.)
I know of one small city that still has radial buses and a circular line: Växjö. The frequency on the main routes is a bus every 10-15 minutes. But even there, the circular line (bus lines 2 and 6) is a Yamanote-style circle and not a proper circumferential; all of the buses meet in the center of the city. And this is in a geography with a hard limit to the built-up area, about 5-6 km from the center, which reduces the need to run many routes in many different directions over longer distances (the ends of the routes are 15-20 minutes from the center).
There’s also a separate issue, different from scale but intimately bundled with it: mode share. A city with three metro lines is capable of having high transit mode share, and this means that development will follow the lines if it is given the opportunity to. As the three lines intersect in the center, the place for commercial development is then the center. In the communist states that perfected the Soviet triangle, buildings were built where the state wanted them to be built, but the state hardly tried to centralize development. In Stockholm, where the subway would be a triangle but for the three lines meeting at one station, the lack of downtown skyscrapers has led to the creation of Kista, but despite Kista the region remains monocentric.
There is no chance of this happening in a bus city, let alone a bus city with just a handful of radial lines. In a first-world city where public transit consists of buses, the actual main form of transportation is the car. In Stockholm, academics are carless and shop at urban supermarkets; in Växjö, they own cars and shop at big box stores. And that’s Sweden. In the US, the extent of suburbanization and auto-centricity is legendary. Providence has some inner neighborhoods built at pedestrian scale, but even there, car ownership is high, and retail that isn’t interfacing with students (for example, supermarkets) tends to be strip mall-style.
With development happening at automobile scale in smaller cities with smaller transit networks, the center is likely to be weaker. Providence has more downtown skyscrapers than Stockholm, but it is still more polycentric, with much more suburban job sprawl. Stockholm’s development limits in the center lead to a smearing of commercial development to the surrounding neighborhoods (Spotify is headquartered two stops on the Green Line north of T-Centralen, just south of Odengatan). In Providence, there are no relevant development limits; the tallest building in the city is empty, and commercial development moves not to College Hill, but to Warwick.
With a weaker center, buses can’t just serve city center, unless the operating budget is so small there is no money for anything else. This is what forces a bus network that has money for enough buses to run something that looks like a transit network but not enough to add rail to have a complex everywhere-to-everywhere meshes – grids if possible, kludges using available arterial streets otherwise.
This is why bus and rail networks look so profoundly different. Bus grids are common; subway grids don’t exist, except if you squint your eyes in Beijing and Mexico City (and even there, it’s much easier to tell where the CBD is than by looking at the bus map of Chicago or Toronto). But by the same token, the Soviet triangle and near-triangle networks, with a number of important examples among subway network, does not exist on bus networks. The triangle works for cities of a particular size and transit usage intensity, and only in rapid transit, not in surface transit.
Five years ago, I wrote about how American cities’ transit priorities cause them to underrate the neighborhoods with the best potential, which typically are also the poorer ones. Those are the in-between neighborhoods: beyond the gentrified core of the city, which is often within walking distance of the CBD in a small region, but not so far that they’re really suburbs. Instead of serving these neighborhoods, cities that want to look like they’re redeveloping build core connectors, i.e. short-range transit services within the gentrified (or gentrifying) center. I was specifically complaining about two plans, one in Providence and one in New Haven. The Providence plan involved a mixed-traffic streetcar, which has since been downgraded to a frequent bus. It’s this project that I wish to talk about in this post.
First, some background: in the 2000s and early 2010s, Rhode Island realigned I-195. This project, called Iway, rebuilt a segment of the freeway to higher standards, but also moved it so as to no longer cut off the Jewelry District from the CBD (called Downcity). Iway turned the Jewelry District from a post-industrial neighborhood to the next (possibly the only) frontier of gentrification in the city, and state elites needed to decide what to do with all this land. This led to plans to build what was in vogue in the late 2000s and early 2010s: a mixed-traffic streetcar, which would connect the Rhode Island Hospital and Jewelry District with Downcity and continue either north to the train station, or east to College Hill via the East Side Tunnel, a short bus-only tunnel cutting off a steep hill between Downcity and the Brown campus. This was from the start bad transit, and we in the Greater City community were skeptical. The plan was eventually scuttled, and the website’s registration lapsed without any redirect to the new plan, which is BRT.
The new BRT route is going between the train station and the Jewelry District. It’s planned to be very frequent, with a bus every 4-5 minutes, appropriate for the short length of the route, about 2 km between the hospital and the train station. The plan is to build open rather than closed BRT, with several branches interlining on the route. Overall, it looks like RIPTA is doing BRT right. And yet, it’s a terrible project.
The top bus corridor in Rhode Island is the R route (for Rapid), formed from the former 99 and 11 buses, which were by far the top two in ridership. It runs every 10 minutes, between Pawtucket and South Providence, serving some of the poorest parts of an already poor urban area. It has some BRT treatments, including hard-fought signal priority (Governor Carcieri vetoed it six times, and it took until the more progressive Lincoln Chafee replaced him for signal priority to go ahead). But buses run in mixed traffic, and fare collection is on-board. If any route deserves better frequency, it’s this one.
Moreover, the attempt to shoehorn multiple routes through the BRT path is compromising those routes. The R route is already detouring through the train station, which the old 99 route did not serve, and which forces a few minutes’ detour. Another bus, route 1, does not currently serve the train station, but will be rerouted once the BRT path opens; route 1 goes through the East Side tunnel, and making it detour to the train station would give it an especially circuitous path between the East Side and Downcity (the 1 already detours to enter the hospital, which is set back from the street). This, in turn, compromises the usefulness of the tunnel, which is that it interlines several routes between Downcity and Brown, which then go in different direction east of Brown.
There are potentially strong east-west corridors that could receive the R treatment. In the east, off-board fare collection on the buses using the tunnel would considerably speed up service. In the west, there are a few potentially strong routes: Broadway (carrying the 27 and 28 to Olneyville), Atwells in Federal Hill (carrying the 92 fake trolley, which runs through to the East Side and used to use the tunnel), and Westminster/Cranston (carrying the 17, 19, and 31). The highly-branched nature of the routes east of the tunnel makes through-service dicey, and this in turn is a matter of a broken bus network in East Providence. But overall, demand roughly matches that of the strongest corridor on the west, which is either Broadway or Westminster/Cranston, depending on how much branching one tolerates. This would create a second rapid bus trunk between College Hill and Olneyville. So why is the city investing in another route?
It’s not the train station. The train station itself is not a compelling transit destination. It’s too close to Downcity; even with a 5-minute bus frequency, it’s faster to walk from the central bus transfer point at Kennedy Plaza (or to the nearest point on the old 99 route on North Main or Canal) than to transfer to the right bus. It should be served by the routes for which it’s on the way, for example the northwest-bound 50, 56, and 57 routes. It’s unlikely anyone will transfer to a bus to the train station. Nor is it likely anyone will take the 1 from College Hill to the train station: walking downhill takes 15 minutes, and people going to a train station need more reliability than a mixed-traffic bus can provide. Walking uphill is more difficult, and there is less need for reliability, but even then, it seems that most people walk. This means the only real use of the train station connection is for people from the Jewelry District.
This brings me to the Jewelry District itself. The city wants to redevelop it, but it is not yet much of a destination. Nor is Providence itching for new development sites: residential rents are affordable on the East Side, and Downcity commercial property values are so low that the city’s tallest building is empty and was said at appraisal to have no value. So why the rush to give the Jewelry District better public transit than existing neighborhoods that direly need it, like South Providence, Olneyville, and Pawtucket?
The answer is contained in the title of this post. South Providence and Olneyville are in-between neighborhoods. Pawtucket is far enough away that it is getting a $40 million infill station on the Providence Line, but the state is not going to fund frequent service or integrated fares between the line and RIPTA buses. As far as Pawtucket’s predominantly poor and working-class residents are concerned, the train might as well not be there; nor will any gentrifiers move to Pawtucket for service to Boston (they get about the same travel time out of Providence and far better amenities). The focus for the city and the state is on redevelopment, and one can almost see the dollar signs in the eyes of the power brokers who passed this deal.
This neglect of the working class and of Providence’s nonwhite neighborhoods (South Providence is black, Olneyville is Hispanic) is not deliberate. But there is clear disparate impact: the Jewelry District gets BRT, South Providence and Olneyville can drop dead. Like everywhere else in the US, the power structure in Providence discourages investment in the in-between neighborhoods, even comfortable ones like the East Side. The in-between neighborhoods are intact enough that building something there is about providing transportation services, rather than about development and renaissance and the creative capital and other buzzwords. And providing services is too boring, too political, too underappreciated. Better to build something shiny and say “I did that,” even if it’s useless. What the elites consider shiny changes every few years – it was streetcars last decade and is frequent buses today – but the principle is the same: instead of investing for the benefit of residents of Providence and its inner suburbs, the state invests for the benefit of ribbon-cutters.
I support through-running of regional trains: as far as possible, trains should not terminate in major city centers, but instead run through to urban neighborhoods and suburbs on the other side of the CBD. My first blog posts made this point about New York, and over the years I’ve written about this in the contexts of New York, Boston, Washington, Chicago, and Tel Aviv. However, in secondary cities, through-running is not always appropriate policy. If a city is near the edge and not at the center of its metro area, then quite often it’s preferable to run a separate service, which may overlap the primary city’s regional rail system. In some cases, through-running is actively harmful; unfortunately, this is currently done in San Jose and Providence.
Consider the following example city:
The metro area lies on an east-west rail line, and consists of a central city several suburbs; higher-density areas are denoted by darker shades, with the primary CBD in the darkest shade. The city proper also has five secondary CBDs, two of which are on the rail line. On the west, one suburb, really a secondary city, is larger than the rest, and has its own CBD, as job-dense as one of the primary city’s secondary CBDs. With rough symmetry of suburban demand west and east, there is no good reason why trains should not through the primary CBD, and good reasons why they should:
- People in the eastern suburbs may work in the secondary CBD just west of the primary one, and people in the western suburbs may work in the secondary CBD just east of the primary one.
- The primary CBD may not have room to park trains at rush hour without a costly railyard expansion.
- People within the central city may use the line as a rapid transit trunk, to get to either the primary CBD or the two secondary CBDs on the line, as well as to residential neighborhoods not depicted in the diagram.
This is relatively uncontroversial – urban transit is designed along the same guidelines. Also uncontroversial is the question of how far east the commuter line should run: the diagram shows a string of medium-size suburbs, so the line should run as far as the easternmost one, potentially with short-turn runs if the trains at the end are too empty.
The real controversy is how far west to run the service. On the one hand, the secondary city provides a natural outer anchor, with some reverse-peak ridership potential, so there’s an argument for terminating service there. I have criticized the Human Transit model of anchoring as a matter of urban planning, but as a matter of transit planning with fixed urban layout, it is sound; see explanations here and here. On the other hand, there are two smaller suburbs farther west, where people might want to commute to either the primary city or the secondary one, so perhaps service should run farther, with many trains short-turning at the secondary city to avoid running too many empty trains at the western end.
Which of the two options is better – terminating services at the secondary city or continuing onward – depends on the frequency the trunk rail line can support. The reason is that continuing onward requires a very large drop in capacity to avoid empty trains. In the depicted diagram, in relative units, 10% of the western suburbs’ built-up residential area is west of the secondary city; maybe another 10% is the western areas of the secondary city, which could host a station in addition to that at the city’s center. This means that nearly all trains should short-turn; only perhaps one in three or four should continue. If the demand is so intense that a quarter of the base frequency is enough, then trains should continue. But most likely, it isn’t. An individual commuter line with a train every 10 minutes off-peak would be stepped down to every half an hour at the western end, which is borderline; a train every 10 minutes off-peak almost never happens outside Paris, Tokyo, and other enormous systems, except when multiple branches interline to a single trunk.
The alternative is to terminate commuter trains at the secondary city, but then run supplemental service, centered at the secondary city. This supplemental service is not supposed to serve demand into the primary city, handling supercommuters from the western end via a timed transfer (with possible peak through-service), so it can run shorter trains at higher frequency. Sometimes, the secondary city’s CBD must be judged too auto-oriented to be served with commuter rail, and then the correct service pattern is no trains at all west of the secondary city.
In both Providence and San Jose, a situation akin to the above diagram occurs, except without any through-service beyond the primary CBD (respectively, Boston and San Francisco). Of course, San Jose has more residents than San Francisco, 1.03 million compared with 870,000, but it has only 360,000 jobs to San Francisco’s 610,000. Moreover, San Jose’s employment is more dispersed; according to OnTheMap, its CBD’s job density is about comparable to that of Providence’s CBD. Evidently, Caltrain ridership is 13,600 per weekday at San Francisco and 4,200 at San Jose Diridon (PDF-p. 6 here), with both stations located somewhat away from their respective cities’ CBDs. A proper comparison of Providence to Boston is harder to make, since South Station has multiple line and not just the Providence Line, but Providence’s secondary role within New England is well-understood.
In both cities, service runs beyond the secondary city, at reduced frequency. Between San Francisco and San Jose, Caltrain runs 5 trains per hour at the peak, and a train every hour off-peak; but Caltrain also runs three trains per day in each direction south to Gilroy, 47 km to the south (San Francisco-San Jose is 77 km). Between Boston and Providence, a distance of 70 km, the MBTA runs 3-4 trains per hour at the peak and a train every 1.5-2 hours off-peak, but one train per hour at the peak and one train every four hours off-peak continues another 31 km south to Wickford Junction.
Both tails, to Gilroy and to Wickford Junction, are significant drags on the ability of their respective cores to modernize. Ridership is very low: Tamien, just south of San Jose Diridon, has 1,100 weekday riders, but the sum total of all the stations to its south is 559; the two stations south of Providence have between them 454 weekday riders, compared with about 2,300 at Providence and 20,000 on the Providence Line overall (see PDF-pp. 74 and 77 of the 2014 MBTA Bluebook). In both cases, low ridership is a cause of poor service rather than a consequence: Clem Tillier tallied the population and job densities near each Caltrain station and found that, except in the southern neighborhoods of San Jose, there is no real ridership potential on the Gilroy extension; a similar analysis of the Providence Line’s tail has not been carried out, but one of its two stations is in a low-density suburb without many Boston-bound commuters, while Wickford Junction is surrounded by undeveloped land. Caltrain is currently planning to electrify south to Tamien, but there is no justification for continuing electrification further, which means that maintaining Gilroy service would require mixing diesel locomotive-hauled trains with lightweight EMUs; moreover, south of Tamien, the tracks are owned by Union Pacific rather than by Caltrain, and UP has little interest in allowing modern passenger trains on its tracks. In Rhode Island, an additional complication is that the line from Providence down to Wickford Junction is prime high-speed rail territory, and commuter rail ridership is frankly too low to justify complex scheduling with multiple overtakes, unlike the situation farther north in Massachusetts.
In the Bay Area, there is little that can be done, due to the low potential ridership south of Tamien, San Jose’s suburban layout and the distance of Diridon from the CBD, and UP ownership of the tracks. Perhaps a few diesel trains could run to San Jose Diridon with timed transfers to the electrified line from Tamien to San Francisco, but quite likely service could just be canceled. In Rhode Island, Wickford Junction should probably be closed due to low ridership, but Peter Brassard proposed an alternative, a Providence-focused line running short trains at medium frequency (perhaps once every 15 minutes), with very short interstations in order to serve Providence neighborhoods and not just the CBD. Such a line, running at the same average speed as a freight train due to the frequent stops, would interfere heavily with intercity trains, which means that four-tracking the line is a necessary precondition, as discussed here, but this may be worth it given potential local ridership. The most constrained part of the right-of-way is alongside the Route 10 expressway, which requires considerable repairs and is currently being overhauled at high cost.
High-speed rail and rapid transit both change economic geography, in that they compress distances along the lines built, emphasizing connections along the lines at the expense of ones perpendicular to them. I’ve written about this before, giving the example of the division of Uptown Manhattan into East and West Sides. In contrast to the similar implications for economic geography, we see different political treatment of transportation planning: rapid transit is usually planned centrally within a city, together with lower-capacity perpendicular forms of public transit, but there is less centralized planning of high-speed rail and connecting legacy lines.
It’s against this background that I’ve read two recent posts on Itinerant Urbanist, one advocating Northeast-wide intercity rail planning, and one expressing skepticism of plans to run trains from New York to Pittsfield along the Housatonic Railroad, whose southern end hosts the Danbury Branch. In the second post, Sandy shows how, even today, it is faster to get from New York to Pittsfield via Albany, along existing Amtrak routes, than it could be via the curvy Housatonic. The trains from New York to Albany are not HSR, but are some of the fastest in the US outside the Northeast Corridor, and that’s enough to obviate the need for some adjacent lines. But we can extend this analysis further, looking at potential HSR routes and identifying the effect on other regional and intercity lines mentioned in Sandy’s first post.
For our main example, consider Providence-Worcester. There is a direct line, the Providence and Worcester mainline, which hosts no passenger trains. I have previously called for running passenger service on the southern 25 km of the line, from Providence to Woonsocket, and integrating the schedules with MBTA trains to Boston and future HSR; in 2009, the Providence Foundation made a similar proposal, finding that it was possible to slot a reasonable frequency of in-state regional trains between the Providence and Worcester freight trains. Superficially, one might think that trains should not turn at Woonsocket, but go all the way to Worcester, a distance of 69 km, providing a key crosstown link in a New England-wide rail network.
The problem is that the presence of HSR makes the line completely useless for end-to-end traffic. HSR averages between 180 and 260 km/h, whereas regional trains average between 50 and 90, with a few trains overlapping with intercity rail going up to 120. This makes it worthwhile to go two to three times as long as the most direct route, if this can be done on high-speed lines.
It’s 70 km from Providence to Boston; from Boston to Worcester, it’s 71 along the present Worcester Line, while an HSR line following I-90 would be about 65, serving Worcester at an outlying station at the intersection with Route 122 (and the Providence and Worcester line), 6 km outside the legacy station. My attempt to work out a schedule for Providence-Boston gives about 20.5 minutes for nonstop HSR; Boston-Worcester is probably similar, giving 41 minutes plus a short transfer time. (Trains with intermediate stops would stop at Back Bay, and if the transfer can happen there, then it saves about 3 minutes total.) Let’s say the transfers at Boston are not optimized, and the total travel time is 50 minutes.
It is not easy to achieve this travel time on the legacy Providence and Worcester line: 69 km in 50 minutes is 83 km/h, and 63 km (from Providence to I-90 and Route 122) is 76. The latter speed is very ambitious, and the former even more so. While there are regional lines in New England that could approach 100, this is not one of them. The line hosts some freight traffic, so it requires additional sidings if passenger trains go at intercity rail speeds and not at regional rail speeds, which are similar to freight speeds. There is a significant commuter market at the Providence end, requiring more stops in Providence and its inner suburbs: the end-to-end travel time in the schedule I constructed for Providence-Woonsocket is 26 minutes, an average speed of 59 km/h. To get to I-90 in 50 minutes, trains would need to average 94 km/h north of Woonsocket; achieving this makes it almost impossible to stop anywhere in Massachusetts except Worcester, which defeats the purpose of the line. Worcester-Woonsocket is not important enough a travel market to reopen a passenger rail line for. For the same reason, there is no hope of achieving sufficient speed by including a mix of local and express trains: there’s not enough demand to support multiple service patterns.
The Providence-Worcester example is somewhat unfair in that it’s unlikely such a line could be activated without interstate cooperation in intercity rail planning. The same cooperation that could restore service on the Providence and Worcester line would first push for faster intercity trains on the Northeast Corridor, which would be the first step in obviating this direct line. I bring this up because it’s a very clean example of how the presence of HSR allows for circuitous routings on some city pairs, and how this should be reflected in rail planning. There are less clean examples, pitting a unified system with HSR as a trunk and branches feeding the trunk against potential in-state projects and priorities:
1. Unless HSR fares are designed to discourage this, the fastest way to get to New York from suburbs far out along the New Haven Line, and to a lesser extent the Northeast Corridor Line in New Jersey, would be to take commuter rail to New Haven or Trenton and then backtrack on HSR. This changes the optimal service patterns, away from express trains to New York and toward local trains in the outer service area, and this in turn influences planning for capacity improvement. For example, fitting HSR and commuter trains on existing tracks in New Jersey probably requires giving up express service south of Rahway, but at the outer end of the line, around Princeton Junction, going out to Trenton and backtracking on HSR would make this not as onerous as commuters may initially think. On the level of station design, the presence of backtracking means that stations may need to be reconfigured to have more access points from northbound to southbound platforms, to make transfers easier.
2. New Jersey Transit has plans from last decade to reactivate passenger rail service along the West Trenton Line. The presence of HSR makes West Trenton a less useful commuter rail station, to either Philadelphia or New York. In Philadelphia it remains useful if one wants to go to destinations on the Reading side of SEPTA, such as Temple University, or even Market East, but in New York, the nearest job center to West Trenton is Newark, which is on the Northeast Corridor. This means that better transit service from West Trenton to Trenton becomes a greater priority than direct rail service from West Trenton to New York.
3. There is a secondary rail line from New London to Norwich, passing next to Mohegan Sun. It is not very useful if intercity trains remain as they are, but the presence of HSR makes it a good feeder, and also allows trains to beat express buses for trips from New York to the casino.
4. It is vanishingly unlikely Pennsylvania will try to build in-state rail service to Erie. However, if it does, Erie-Pittsburgh service would be similar to Providence-Worcester service, with Cleveland fulfilling the same function as Boston in New England.
Many people have heard that certain regions are well-suited for these projects, for example the Northeast Corridor is unusually good for HSR because it links four major cities and several medium-size ones on a single line. By implication, there has to be a flip side, i.e. regions that are poorly-suited for HSR and cities that are poorly-suited for new rapid transit. If there weren’t – if every region were like the Northeast Corridor – then the ridership models would just have higher first-order estimates. Several proposals I’ve seen in comments and on my blogroll in the last few days are in areas where the urban geography makes it harder to justify such projects. These and a few others are the examples I will use in this post.
As usual, there’s a caveat that difficult does not equal bad. Some of these ideas are worth pursuing, but have more challenges that their easier counterparts do not, and if those challenges are solved, then they can perform well. One of the biggest success stories of modern rail investment, the TGV, is in an urban geography that’s not particularly conducive to rail: France’s secondary cities surround Paris in all directions (although Lyon and Marseille are collinear with Paris), the stub-end layout of stations in Paris and many other cities forces awkward branching, Lyon needed a business district to be built from scratch around Part-Dieu. France made this work, and it’s possible some of the projects on this list can be made to work in similar vein.
High-Speed Rail in Sweden
Project: greenfield HSR lines connecting Stockholm with Sweden’s major secondary cities, Gothenburg and Malmö.
The problem: Stockholm, Gothenburg, and Malmö do not lie on a straight line. The three cities are quite small by the standards of more populated countries: Stockholm has a bit more than 2 million people, Gothenburg has a bit less than a million, Malmö has 700,000. A line connecting just two of them, or even a Y-shaped line, is unlikely to get enough ridership to justify the construction costs of full HSR. There are no large intermediate cities: the largest, Linköping, has about 100,000 people. As noted above, French urban geography is not great for HSR, either, but at least the LGV Sud-Est could serve both Lyon and Marseille, and France’s greater population ensures that its secondary cities are large enough to generate enough traffic to fill an HSR line.
As a silver lining, Malmö is adjacent to Copenhagen, and the difficult part, bridging the Øresund, has already been done. While international lines tend to underperform, the tight cultural and economic connections between the Scandinavian countries make it likely that international projects within Scandinavia would be exceptions to the rule. Copenhagen would add another 2 million people at the end of the line. However, even that is unlikely to generate enough ridership to pay for 500-odd kilometers of greenfield HSR (plus a connection to Gothenburg).
Because of its poor urban geography for conventional HSR, Sweden has investigated cheaper solutions, allowing higher speeds on legacy track or on greenfield tracks built to lower standards. As a result, there is research into the possibility of high-speed tilting trains, running faster than the 250 km/h Pendolino. This research is likely to be useful in the UK and US, where the urban geography is better-suited for HSR but fully greenfield construction is obstructed by suburban development near the rights-of-way and by high construction costs, but the original context was faster speeds within Sweden.
High-Speed Rail in the Pacific Northwest
Project: greenfield HSR connecting Portland, Seattle, and Vancouver. This is not officially proposed anywhere that I know; current plans focus on incremental improvements to the Amtrak Cascades. However, every American HSR fantasy map I’ve seen (including the ones I’ve drawn) includes this link, since at least superficially based on city populations it would succeed.
The problem: getting out of the major cities involves a slog on curvy legacy track in areas where it’s hard to straighten the right-of-way. Heading north of Seattle, the route goes along the water, in terrain that is too hilly for an easy inland cutoff all the way to Everett, 50 km north. Getting out of Vancouver is also hard, because of suburban development in Surrey, and becomes even harder if one wants the Vancouver station to be Waterfront rather than Amtrak’s current stop, the less centrally located Pacific Central. The Northeast Corridor is said to have slowdowns near the major stations, leading to proposals to bypass them with new tunnels, but at no point are there 50 nearly-continuous km of low curve radii; the New Haven Line does not look as curvy, while the Shore Line farther east is easy to bypass on I-95.
The Seattle-Portland segment is much easier: the route heading south of Seattle is not constrained, and north of Portland it is possible to run alongside I-5. However, the most important intermediate cities, Tacoma and Olympia, can only be served with exurban stations, since getting into their centers would require the mainline to detour on curvy alignments.
Through-Run Commuter Rail in Chicago
Project: there are many proposals by transit activists to construct new infrastructure to enable through-running on Metra, analogous to Crossrail, SEPTA Regional Rail, the Paris RER, and multiple S-Bahns. Details differ, but other than the lines through Union Station, through-running generally means connecting Metra Electric to some of the lines feeding into Union Station from the north or the Union Pacific lines; UP-North is especially notable for serving dense neighborhoods and not having any freight traffic.
The problem: the layout of the lines entering the Chicago central business district makes it hard to build a coherent network. What I mean by coherent is that commuter lines can make multiple CBD stops to serve different CBDs, or different parts of the same CBD: in New York, a Penn Station-Grand Central connection would let trains serve both the West Side and the East Side. Look at the map proposed by Sandy Johnston, in the second link above: there is no station on the Near North Side, there is no connection from the West Loop stations to the Loop, and effectively lines are still going to be split between lines bound for the West Loop and lines bound for the Loop in the through-run system.
None of this is the fault of any of the people drawing these maps. To serve both the West Loop and the Loop, a line would have to go east-west in the vicinity of Union Station, where there is no legacy line pointing in the right direction. The options boil down to a long greenfield east-west subway, and an awkward transition to the preexisting east-west lines, BNSF (which is too far south) and UP-West (which is too far north), which to add another complication carry heavy freight traffic.
A system prioritizing north-south connections runs into different dilemmas, concerning the tradeoff between service to the Near North Side and easier connections to the rest of the North Side Metra lines. A north-south line connecting UP-North to Metra Electric through the Near North Side would be beautiful, and miss all other Metra lines and most L lines. Sandy’s proposal has Metra Electric swerving west to meet UP-North just north of its terminus at Ogilvie Transportation Center, meeting all L lines and potentially the North Side Metra lines but missing the job centers in the West Loop and Near North Side.
Rail to LaGuardia
Project: construct some rail extension to LaGuardia Airport. Which rail extension varies based on the proposal. The most mainstream proposal, in the sense that it was supported by Giuliani until it was torpedoed by neighborhood opposition, would have extended the Astoria Line east to airport grounds. More recent proposals from various activists have included not just the Astoria Line extension, but also a Northeast Corridor spur, an AirTrain from the Astoria Line, an AirTrain from Jamaica with JFK connections, a subway shuttle under Junction, and a subway running from the airport to 125th Street along the route of the M60 bus.
The problem: all of the above ideas face the same pair of problems. At the airport end, the airport competes with other urban destinations, rather than complementing them by lying on the same straight line with them. An extension from the west, such as the Astoria Line extension, needs to choose between serving the airport and serving the Astoria Boulevard corridor, which has high residential density and no nearby subway service; Astoria Boulevard itself is so wide that as with Queens Boulevard, an elevated line in its middle would be an improvement. Farther east, there is nothing that a LaGuardia extension could be continued to, because of Flushing Bay. An extension across the bay going to Flushing or College Point could be useful, but an extension of the 7 to College Point would be even more useful and avoid underwater tunneling. The bay, and more generally the Long Island Sound, dooms any proposal for a loop returning to the mainline, in the manner of Zurich Airport, while a spur would again compete for capacity with more important lines. Compare this with LAX, which, going along the Harbor Subdivision, is collinear with Inglewood, the Slauson corridor, and Union Station, and would have an easy connection to El Segundo.
At the other end, the question with every airport extension is, what does it connect the airport to? The answer for LaGuardia has to be the Upper East Side, where as I remember most riders originate; but there is no good way of connecting to the Upper East Side, which has no east-west subway line, and shouldn’t, as there are perhaps a hundred kilometers of higher-priority tunnels in the region. A connection to 125th Street is ruled out by the fact that Second Avenue Subway has an even better connection to 125th. The Astoria Line serves the Midtown hotel cluster well, and has a connection to the Lexington trains to the Upper East Side, but I doubt that it can beat a taxi across the bridge in non-rush-hour traffic.
Providence East Side Tunnel
Project: restore rail service through the East Side Rail Tunnel, with a new connection to Downcity at the western end and connections to new or restored rail lines in and beyond East Providence. In Jef Nickerson’s version, the trains are light rail and drop to the surface at the Downcity end. In mine, they continue elevated through Downcity, with a new station replacing Providence Station for both commuter and intercity rail. All versions include a stop at Thayer Street for Brown University service, should one be constructable at reasonable cost.
The problem: there’s no real need for local or regional service from the east along the tunnel (intercity service could be sped up by about half a minute to a minute by avoiding curves in Pawtucket). Light rail service would run into the problem of incredibly spread-out suburbanization east of Providence. Commuter rail would run into separate problems: the legacy lines go along the water in East Providence and don’t serve the town itself well; beyond East Providence, the line going north serves the same suburbs as the existing Providence Line minus Pawtucket, while the line going south would need extensive and costly restoration work to get to Fall River, and only passes through small and low-density intermediate points.
Cutting off Providence Station to move the city’s main station to the south is useful, but the only rail from Providence to Pawtucket and Woonsocket goes due north of Downcity and would be left out of this system. Shoehorning it to the same station that leads to the East Side Tunnel would produce every adverse impact of viaducts on cities: heavy visual impact coming from elevated-over-elevated grade separation, squeal coming from low curve radii, takings of condo buildings near the existing Providence Station.
So, you have your urban rail line. It’s mostly above ground, so constructing new express overtakes is feasible. It has decent frequency, and carries trains to destinations at a variety of distances from city center. But it’s not an overcrowded subway line that brushes up against line capacity, requiring all trains to run at the same speed. Do you run express trains?
I’m going to focus on regional rail in this post, since with two Tokyo-area exceptions, proper subways are incapable of running express trains without dedicated express tracks due to their high frequency. On a line with a train every 10 minutes it’s feasible to mix trains of different speeds with timed overtakes; on a line with a train every 2 minutes, it’s not. I’m going to use the LIRR and Caltrain as examples, and then apply the derived general principles to other cases in the US, including future regional rail schemes.
The basic tradeoff of express service is that it provides faster service to the express stations at the cost of frequency at the local ones. This can be done in two ways: expresses that stop once every few stations, and local-then-express patterns. Jarrett Walker calls this limited versus express, based on bus service patterns; with trains, both types are called express. The subway in New York, the Chuo Rapid Line, Seoul Subway Line 1, and Caltrain baby bullets are examples of the first kind; the Caltrain limited-stop trains and the peak-hour trains on some LIRR lines are examples of the second kind.
Express trains of either kind but especially the first reduce line capacity, even with very long overtake segments. If train X overtakes train L, then there needs to be an available slot ahead of train L, and after the overtake there’s a slot opening up behind L. The Chuo Rapid Line runs a mixture of local (“rapid”) and express (“special rapid”) trains for most of the day, but at rush hour, there are only local trains, peaking at 28 trains per hour; on the shoulders of rush hour, there are some express trains, with total traffic of about 20 tph. The LIRR runs 23 tph on the Main Line at the peak, so this is an issue, which the LIRR unsatisfyingly resolves by running trains one-way at rush hour. It’s less an issue on Caltrain given constructable overtake locations, but right now the overtake locations are inconvenient and the trains are pulled by diesel locomotives, increasing the stop penalty and reducing the capacity of a mixed local-express line.
The second kind of express service is bad industry practice and should not be used. It avoids the capacity problems of the first kind at low traffic levels, but at high traffic levels the speed difference is still too large. It is used when the trains are a special CBD shuttle and makes it impossible to serve passengers who are cheap to serve, i.e. those getting off short of city center. Caltrain’s limited-stop trains do this because of capacity problems during rush hour, when they need to get out of the baby bullets’ way. The LIRR does this because of a cultural belief that trains exist only to shuttle people from Long Island to Manhattan and back; due to the same belief, it runs trains one-way at rush hour rather than giving up on rush hour express runs as JR East does.
The first kind of express service may or may not be warranted. It depends on the following questions:
1. What is the line’s expected traffic level? Low traffic, up to about 4 tph for a regional line, favors an all-local configuration to prevent cutting local stations’ frequency unacceptably. Very high traffic favors all-local configuration for capacity reasons, or else investment into long overtakes or even full four-tracking. Intermediate traffic, in the 6-12 tph range, is the best zone for express trains.
2. Have local trains already been sped up by use of good industry practices? Level boarding, high-acceleration EMUs, better track maintenance allowing higher speeds between stations, good timetable adherence allowing less schedule padding, and infrastructure preventing delays on one train from cascading to others allowing even less padding can all significantly reduce the speed difference between local and express trains. In some extreme cases, a local train can end up not much slower than an express train hauled by a diesel locomotive.
3. How long is the line, and how many stations does it have? Longer lines and shorter interstations both favor express trains, all else being equal. Intercity rail, which also has higher stop penalties because of the higher line speed, deserves more than one stopping pattern even at low frequencies.
4. How big is the difference between minor and major stations? It is crucial not to confuse current ridership with ridership potential, since lines with express service often pick winners and losers, after which the better-served express stations steal riders who live closer to bypassed minor stops. This is common on Caltrain, where some but not all express stops are major job centers.
5. Can intercity trains plausible substitute for express service?
It is question 4 that makes the difference in many cases. On the LIRR, the Main Line has a clear distinction between major stops (Mineola, Hicksville) and minor ones (all the rest). The Montauk Line does not. Note the ridership levels of the stations, going eastward from Jamaica to the end of electrification:
Queens Village: 791
Floral Park: 1495.5
New Hyde Park: 1725.5
Merillon Avenue: 766.5
Carle Place: 386
Cold Spring Harbor: 2083
Deer Park: 2708.5
Central Islip: 1787
St. Albans: 93.5
Rockville Centre: 3425
Massapequa Park: 1672.5
There are three ends of electrification: Babylon, Huntington, and Ronkonkoma. All have markedly more ridership than nearby stations, especially Ronkonkoma, though in all cases it’s an artifact of their being the ends of electrification, with many people driving in from farther east. Ronkonkoma has nothing nearby that justifies its ridership level, the highest of any suburban LIRR station; it’s a park-and-ride that has a lot of ridership because it’s the end of electrification and has express service.
In contrast, in Mineola and Hicksville, there really is a concentration of activity justifying their status. Both have trivial transit usage as job centers, but there’s enough of a core, especially around Mineola, to justify higher service, and Hicksville is also the junction of the Main Line with the Port Jefferson Branch: see the census bureau’s OnTheMap tool.
But there are no special stations on the Montauk Line. Excluding St. Albans, which is in New York itself and has to compete with cheaper and more frequent if slower bus-to-subway options, the ratio between the busiest and least busy stations is 2.4:1. A similarly flat situation occurs east of Hicksville, excluding the two end-of-electrification stations.
What this means is that the LIRR should only run local trains on the Babylon Branch and east of Hicksville, while maintaining express service on the Main Line west of Hicksville when there’s enough capacity for it. A similar analysis of other lines in the New York area should give the following answers:
Hempstead, West Hempstead, Long Beach, and Far Rockaway Branches: all local due to short length.
Port Washington Branch: probably all local due to short length, but if additional local stations are added in Queens, then some express trains to Great Neck may be warranted.
New Haven Line: very long, sharp distinction between major and minor stops all the way but especially west of Stamford, high frequency, four tracks give enough capacity for everything. The current configuration of nonstop trains to Stamford continuing as local to New Haven and local trains turning at Stamford is fine, except that the express trains should also stop at New Rochelle (a junction with the Hell Gate Line, which deserves service, but also a major stop in and of itself, with the third highest weekday ridership of Metro-North’s suburban stations) and maybe also Greenwich; HSR overtake considerations may require stopping also at Rye and Port Chester.
Harlem Line: generally favors local trains, except that White Plains is a major job center and thus a far more important stop than all others, independently of its better service. There are four tracks south of Wakefield, favoring express trains, but conversely charging subway fares and allowing free transfers to the subway would lead to a ridership spike as people switch from the overcrowded 4 and 5 trains. There’s a big dropoff in ridership north of North White Plains, so the current configuration of locals that turn at North White Plains and expresses that go nonstop south of White Plains is fine, as long as off-peak frequency is raised.
Hudson Line: favors express trains because of length and four-tracking. Although on paper there are more and less important stations, this is an artifact of service patterns. The secondary stations in Yonkers serve higher density than the busier stations in the proper suburbs, and the dense parts near Tarrytown are actually in Sleepy Hollow, about equidistant from the Tarrytown and Philipse Manor stations: see the New York Times’ population density map.
Erie Lines and West Shore Line: probably all local since the population density thins too uniformly going north, with Paterson as the major exception. There are somewhat denser anchors at the outer ends of some lines – Spring Valley and Nyack – but Harlem Line-style nonstops run against a capacity problem, coming from the fact that this part of the network is necessarily highly branched.
Rest of New Jersey Transit: the main lines (Northeast Corridor, Morristown) are very long and have some distinguished suburban job and population centers (Metropark, New Brunswick Morristown) deserving express service, but the branches (North Jersey Coast, Montclair, Gladstone) do not. However, the fare structure and off-peak frequency lead to much less ridership on the inner-urban segments in Newark, Orange, etc., than would be expected based on population density. In addition, the difference between major and minor stops is fairly small on all lines when taking electrification into account, sometimes as small as on the Babylon Branch: see ridership data per line and per station.
Although my initial decision in my regional rail plan to pair the Erie lines with the Atlantic and Babylon Branches of the LIRR was aesthetic, creating a northwest-to-southeast line, in reality the systems are fairly similar in their characteristics. More or less the same can be said about the Staten Island-Harlem system. There are no direct connections to intercity rail except at Jamaica and in the Metro-North tunnel to Grand Central, the lines pass through urban or dense-suburban areas, the interstations are fairly short, and there’s relatively little distinction between major and minor stops. (White Plains is the major exception, and Paterson is a secondary one.) This makes the Lower Manhattan-based system much more RER-like than the Penn Station-based one, which is longer-distance and practically intercity at places.
Finally, the same set of questions in the other three major Northeastern cities generally lead to the conclusion that no express trains are needed.
In Boston, there’s too little difference between major and minor stops on each line (see PDF-page 70) – somewhat more than on the Babylon Branch, but much less than on the LIRR Main Line. The most prominent major station is Salem, but the low-ridership stations farther in on the Rockport/Newburyport Line are in working-class suburbs; the ridership there is depressed because of fare and schedule issues coming from competition with buses, and good regional rail would get much more additional ridership from Lynn and Chelsea than from Salem and the suburbs farther out.
In Washington, current traffic demand is so low that express service would seriously eat away at the frequency offered to local stations. MARC and VRE ridership is so low that any analysis of travel demand has to start from geographic and demographic information rather than from preexisting ridership; the only major outlying destination on any of the lines is Baltimore, which can be connected to Washington by intercity rail, and which conversely has much less Washington-bound commuter traffic than the Washington suburbs. The closest thing to justifiable express service is that when the commuter lines closely parallel Metro, they should have wider stop spacing.
In Philadelphia, on most lines, express service eats away at frequency too much. The one exception is the PRR Main Line, with the SEPTA Main Line a possibility. Many lines have sharp differences between local and express stations: for example, Cornwells Heights on the Trenton Line is much busier than the rest. But a combination of low frequency and lack of easy overtakes (on the Trenton Line, the inner tracks should be mainly used by intercity trains, with only the occasional regional rail overtake if required) makes this not useful. The PRR Main Line actually has less difference between major and minor stops than many others, but it is longer and has short interstations and higher frequency. The SEPTA Main Line has the frequency to support multiple stopping patterns, though the population density near the minor stations is high and the problem, as in other Northeastern cities, is high fares and lack of integration with urban transit.
If new high-speed rail construction has to largely follow Interstate corridors, then a new line from New Haven to Boston can serve either Providence on I-95 or Hartford on I-91/84/90, but not both. However, there’s still the possibility of building a completely greenfield alignment between Hartford and Providence; the FRA is investigating this as option 13 of NEC Future and Amtrak is proposing this in the latest update of its Vision. Since the terrain is hillier than on the coast, it requires some investigation as to whether it’s possible to connect Hartford and Providence without excessive tunneling. The answer turns out to be yes, but only at the cost of slowdowns both north and south of Hartford that impose real costs relative to following I-95: construction is likely to be more expensive and travel time including a Hartford stop is 9 minutes longer.
I believe the alignments depicted in this map are near-optimal for New Haven-Providence via I-95 and via Hartford. The New Haven-Hartford alignment is similar to that of Penn Design with two major differences: Penn Design diverges to cut off some curves near Hartford, but to guarantee sufficient curve radius it has to slice a significant chunk of downtown New Britain; and Penn Design also straightens the route in New Haven with a tunnel, which is unnecessary as the time savings do not justify the expense. Amtrak prefers getting to Hartford from Danbury, but to get there from New Rochelle requires long suburban tunnels, which my alignment avoids. I have not seen a detailed Hartford-Providence alignment, and I drew a line based on Google Earth elevation with an eye toward avoiding tunneling, which means there may be some further optimization, for example a rigorous cost-benefit analysis of viaducts versus curve avoidance.
The Hartford-Providence greenfield route has no tunnels except in Providence itself, where the line tunnels under Olneyville for about 2 kilometers. In Connecticut the route has many viaducts, but does not need to tunnel through the inland hills. Rather than giving detailed cost estimates, which are possible but not with sufficient reliability or precision, I am going to qualitatively describe construction challenges for each route and then the differences in travel time, which favor not serving Hartford. The final decision should boil down to the question, what cost is it acceptable to impose on New York-Boston travelers to allow for service to Hartford?
The I-95 route is zero-tunnel. The Hartford route has no tunnels in Connecticut, but requires a tunnel of 1.5-2 km in Providence. There exists an old railroad alignment going around the river and connecting Providence to the west without a tunnel, but the right of way was given away and to restore it would require some urban building demolitions as well as configuring a flying junction under Route 6 while also slowing down trains further.
The I-95 route has significant challenges in river crossings, since it is close to the coast. Three difficult crossings are needed, of the Quinnipiac, the Connecticut, and the Thames. The Connecticut only requires a span parallel to I-95. The Quinnipiac requires a new span parallel to US 1 and I-95 and a new approach from Union Station; there is space for this approach, and the curve radius can be kept to at least 500 meters, but it requires work on active track. The Quinnipiac span can be avoided by using the existing route around the bay, which crosses the river at a much narrower point, but this adds several slow kilometers to the route. Recent construction costs for parallel bridges are $125 million for the four-lane US 1 bridge and $554 million for a signature ten-lane I-95 span; I believe the lower cost is more indicative of the infrastructure required for a two-track rail bridge.
The Thames is the hardest, since the route of I-95 and the terrain make it hard to cross anywhere except downtown New London, a constrained urban location. There is just enough space for a station between the decks, and the alignment may impose further constraints on curve radius. There is more space north of both decks, or alternatively Connecticut could build a third I-95 deck and repurpose one of the existing decks for rail.
The Hartford route has one significant water challenge: crossing the Connecticut in downtown Hartford. There is an existing bridge, but it is single-track and would require a completely new span to be used by high-speed rail. It is also used by freight, but only by a short branch line that could be bought out.
The Hartford route also needs to cross the Scituate Reservoir, adding about 3 kilometers of viaduct. However, there is a choice of where exactly to cross it and not much development on its banks, making construction easier than on I-95 or across the Connecticut in Hartford.
Terrain and viaducts
I-95 is substantially flatter than the inland route. Only two short segments require significant overland viaducts and earthworks: the transition in southern Rhode Island from I-95 to the Shore Line, and the curve west of New London cutting off curvier parts of the Interstate. The transition is in total 16 km long but only about the western 10 km of it are difficult (of which about half require viaducts and half can be done cut-and-fill), and west of New London there are 6 difficult km requiring a viaduct north of the Niantic.
In contrast, the inland route needs to be on viaduct for a significant portion of the Hartford-Providence section. Of particular note is the Quinebaug River valley, about 13 kilometers of route of which most requires extensive grading and viaducts, as well as some takings in the built-up areas of the towns of Brooklyn and Killingly. The Willimantic River-Mansfield Hollow Lake-Natchaug River complex adds another 16 kilometers, some hard and some less hard; the Willimantic itself is in a deep valley requiring a tall viaduct of about 3 km, and the total viaduct length required appears to be about 8 km. The following 12 km, on the crest heading to I-84, require some earthworks, but probably no significant viaducts.
Urban construction challenges
I-95 has an existing route into Providence. Some curve modifications from East Greenwich northward are helpful for keeping speeds up, but the grade-separated route already exists. The main challenge is fitting regional trains if Rhode Island desires to run them: the right-of-way has room for four tracks but only if track centers are narrowed so much as to preclude tilting, reducing cant deficiency to about 125 mm. At the New Haven end, the main challenge is crossing the Quinnipiac, but once the tracks are east of the harbor, suburban development intensity drops rapidly, requiring only occasional grade separations with roads crossing I-95. Conversely, if intercity trains are all routed through Hartford then no new construction is required for any Rhode Island regional rail.
The major problem then is New London. The entire complex of crossing the city and the Thames is the biggest difficulty in the route, as outlined above in the water crossing section. In addition to geometric difficulties, there are also noise abatement issues, since the track geometry still allows very high speeds (the curve drawn above just west of New London looks like it can be eased to about 3 km, allowing 310 km/h). This is what favors putting the tracks between the two I-95 bridge decks instead of to the north.
The inland route has far greater difficulties. First, it needs to carve a partially new route into Providence, hence the Olneyville tunnel; however, it also leaves the Providence built-up area much faster, within about 6 kilometers vs. 24 for the Shore Line. In New Haven and Hartford it can for the most part transition between legacy rail routes and expressway corridors, but a substantial portion of the route is in the suburbs of those two cities, which requires more grade separations and makes curve modification harder. There are also noise abatement issues, though Shinkansen trains skip some urban stations at 300 km/h, so those issues are more about cost than about speed limits.
There are several alignment choices north of New Haven. The one I used on the map follows the Providence and Worcester’s Middletown Branch right-of-way and thence I-91, but it is equally feasible to take a more westerly route via the Amtrak line transitioning either to I-91 or Route 15; both options involve grade crossings and extensive suburban construction. In all cases, the trains are almost continuously in built-up area from New Haven until 19 kilometers east of Hartford. Grade separations have the full cost of urban or dense-suburban construction, and moreover, the transition to I-384 east of Hartford requires some additional takings.
Total new construction
This is the primary advantage of I-95, cost-wise: the track already exists from Kingston north and requires only minor facelifts. The New Haven-Kingston construction is just 124 km, whereas between the splits with the legacy Northeast Corridor in New Haven and Providence the Hartford route is 167 km.
With this in mind, nearly the entire I-95/Shore Line segment between East Greenwich and East Haven can be eased to a curve radius of 4 km. New London, where noise abatement prevents running at full speed anyway, can accommodate slightly lower radius, about 3 km on the western approach. At the New Haven end, the transition to the Quinnipiac bridge right next to the station has radius 500 meters, but the speed restriction is minor since it is so close to the station.
Hartford-Providence can also be eased to quite high curve radius. In Rhode Island, once out of the Providence built-up area, the tracks can maintain a 4-km standard, and until the transition to I-384, the worst radius is 3.1 km around Mansfield. However, from I-384 west, things become far worse: the transition to the east has a radius of 1.2 km and seems impossible to increase further, the transition to the west has a radius of at most about 1 km, and the curve west of the Connecticut bridge is 500 m and is slightly farther away from Hartford than the Quinnipiac bridge curve is from New Haven.
It is south of Hartford that things deteriorate. The worst curves on the legacy lines are in Meriden and can be bypassed, but there is a 1.3-km curve in New Britain, on an S with a 2.3-km curve just south in Kensington that makes it unfixable. At the New Haven end there’s a curve on the legacy line, bypassed on I-95 by the Quinnipiac bridge, with radius about 450 m about 2.5 km out of the station.
Overall travel time
The explicit assumptions on trains are aggressive, based as always on the need to keep speeds up in big cities and on the only partially fixable New York-New Haven segment. Trains accelerate like the N700-I (26.74 kW/t, more than any high-speed train that currently exists except the Talgo AVRIL), cant deficiency is 175 mm as on the E5/E6 and on the AVRIL, cant is 200 mm as on the Tokaido Shinkansen, and initial acceleration is 0.89 m/s^2 as on the N700-I. With these performance specs, the minimum curve radius required for a full speed of 360 km/h is 4 kilometers; the Tohoku Shinkansen has such radius and JR East intended to run trains on it at 360 km/h before deciding to reduce speeds to 320 for reasons that are not track geometry.
For simplicity of computation I’m going to ignore grades. Since the I-95 route is flat, with very few grades higher than about 1%, this is justifiable there; it’s a little less justifiable through Hartford because a few segments have 3% grades, but they are also quite limited.
Without any schedule padding, we can set the following speed zones for I-95, measuring from 0 km point in Providence and going southbound:
0-0.6 km: 90 km/h (curve around Providence Station)
0.6-4.5 km: 120 km/h (two 450-m curves)
4.5-7.5 km: 180 km/h (Mashapaug Pond curve is too close to 120 km/h to matter, curve into Cranston is about 1 km)
7.5-17 km: 250 km/h (no curves, trains can achieve 270 in between curves but this would only save 5 seconds)
17-22 km: 220 km/h (curves have radius about 1.4 km and the controlling curve at km-point 17 can be eased a bit)
22-92 km: 360 km/h (full speed to New London)
92-103 km: 310 km/h (speed restriction in New London and the curve north of the Niantic River)
103-162 km: 360 km/h (full speed to East Haven)
162-167 km: 250 km/h (curve around an East Haven hill, though trains can barely accelerate fast enough for it to matter going eastbound)
167-168 km: 100 km/h (New Haven approach)
The time taken to transition between speed zones is the average of acceleration and deceleration time penalty. This gives a technical travel time of 33:40 for nonstop trains. If trains have a top speed of 300 km/h, this raises the technical travel time to 37:28.
Now, let us set speed zones for the Hartford route:
0-0.6 km: 90 km/h (curve around Providence Station)
0.6-4.5 km: 180 km/h (curve north of Hartford)
4.5-6.5 km: 200 km/h (curve into Johnston)
6.5-10 km: 240 km/h (curve west of I-295)
10-57 km: 360 km/h (full speed to the Hampton-Mansfield area)
57-86 km: 310 km/h (Hampton and Mansfield impose a 310 km/h restriction to km-point 67, and trains going eastbound can’t accelerate to 360 before they have to slow down again anyway)
86-88 km: 220 km/h (gentler curve in the transition to I-384)
88-101 km: 200 km/h (transition curve to I-384, further curves on I-384 making speedup between transition curves pointless)
101-103 km: 160 km/h (transition curve)
103-109 km: 200 km/h (minor opportunity to make up time, saves 20 seconds over 160 km/h)
109-110 km: 130 km/h (curve on eastern approach to bridge)
110-112 km: 110 km/h (curve on western approach)
Hartford Station: all trains stop since curves limit time savings from not stopping, as at New Haven and Providence
112-127 km: 250 km/h (New Britain curve, speed increase to 270 km/h in between is possible but saves only about 8 seconds)
127-153.5 km: 270 km/h (Kensington and Berlin curves preclude higher speed)
153.5-155 km: 210 km/h (S-curve precludes easy straightening, and significant speed boost requires significant residential takings)
155-169 km: 250 km/h (this requires straightening the kink around and north of the I-91 underpass, otherwise 210 km/h to km-point 162, 160 km/h to km-point 164, and 200 km/h farther south)
169-172 km: 120 km/h (New Haven approach, legacy line curve)
The travel time is 25:30 for nonstop trains from Providence to Hartford and 16:10 from Hartford to New Haven. With a minute of dwell time at Hartford, this is exactly 9 minutes longer than I-95.
Compatibility with other plans
Although I-95 requires less construction overall than Hartford and the construction difficulties are about comparable, Hartford is more compatible with other intercity rail plans for New England, which reduces the advantage of I-95. Under an I-95 option, it is still useful to serve Hartford (and Springfield), which means the Amtrak Shuttle line needs to be electrified, double-tracked, and partially curve-modified anyway. Under the Hartford option this is not required except to provide regional service to Wallingford and Meriden, so the bypassed parts of the legacy line could be built to lower standards.
That said, 60 km of 160-200 km/h electrified track is still a lot cheaper than 60 km of 250-270 km/h track, which means that this reduces the cost advantage of I-95 but does not eliminate it. Of course 60 km of 250-270 km/h track is cheaper than 60 km of 360 km/h track, but I-95 still involves much less overall greenfield track construction.Hartford is also more compatible with any plans Rhode Island might make for southward commuter rail service. The current plans are too low-ridership to bother accommodating, but future plans might involve higher service levels.
Conversely, I-95 is useful for Shore Line East service, since regional trains could use the Quinnipiac bridge as a shortcut. The tracks cross in East Haven and a track connection could be built; it is likely that there will always be enough capacity for 5 km of track-sharing between intercity and regional trains. I-95 is also useful for the New London connection in case anyone wants to build a New London-Norwich regional train serving Mohegan Sun on the way.
Neither route is particularly expensive by the standards of what both Penn Design and Amtrak think are appropriate budgets. At French construction costs, 124 km of high-speed track with no tunnels, few viaducts, and a mostly preexisting Interstate right-of-way should be about $2.5 billion. Likewise, the cost of 167 km with only 2 km of tunnel and a fair number of viaducts should be less than $4 billion, possibly down to $3.5 billion.
However, in case there’s only enough money for part of the route, construction has to be phased. The Hartford route has no track connections to usable passenger railroads between Hartford and Providence, so the only useful partial construction there is the entire Hartford-Providence segment at once plus electrification of New Haven-Hartford(-Springfield). The I-95 route comes sufficiently close to the legacy track in East Haven and Old Saybrook, giving three segments each of which can be built separately: across the Quinnipiac, from East Haven to Old Saybrook, and from Old Saybrook to Kingston.
Every possible train station on a route deserves an answer to two questions: what is the time advantage gained by skipping it?, and who is served by it?. Stations very close to urban terminals, for example Back Bay, have a very low stop penalty because of low approach speeds, but don’t add much service since people can just ride to the urban terminal. Suburban stations such as Route 128 and even Stamford given necessary track upgrades impose high enough a cost that they should also be skipped by express trains even if there’s a fair number of people who’d use them on the local trains.
Between New York and Boston, there are three stations where the answers to both questions favor express stops: New Haven, Hartford, Providence. With New Haven and Providence, the time cost of serving them is so low given urban curves that the only way to skip them at speed is to build new urban tunnels, which cost a lot of money relative to how much time they save. With Hartford, the situation is the same if all trains go via the inland route that serves it.
However, on some level, the time cost of serving Hartford is 9 minutes, compared with about 2 for Providence. But this is not really comparable, so we can’t just say “9 minutes is too much,” as it would be if a station on a running line imposed a 9-minute stop penalty. If we skip an intermediate station that imposes a time penalty of 4 minutes, the express trains gain 4 minutes but there are still local trains serving it. In contrast, if we go via I-95 we save 9 minutes but have no way of serving Hartford on local trains; trains can branch off north of New Haven and serve Hartford and Springfield at lower speed, but this only connects Hartford to New Haven and points south rather than to Providence or Boston. So we lose something more fundamental than stopping train frequency.
So it’s not enough to say that Hartford should be skipped because it saves the trains 9 minutes. That cost-benefit calculation depends on how important serving Hartford is to people. It’s up to the potential users of Northeast Corridor HSR and the politicians providing the funding to decide whether it’s worth it to connect Hartford with Providence and Boston.