Category: Good Transit

When are Express Trains Warranted? Part 2: Subways

Last week, I wrote about which regional rail lines should run local and express trains and which should only run locals. I gave various guidelines, specific to that mode of transportation. The same question makes a lot of sense for subways (or elevated lines), and is especially important for large cities building new metro networks, typically in developing countries. The key difference is that subway trains almost always run so frequently that the only way to have local and express services is to build four-track mainlines, like in New York. So really, this is a question about when it’s useful to build four-track subways instead of two-track subways.

Costs

The cost of a four-track subway is higher than that of a two-track subway. However, the difference depends on the method of construction. Cut-and-cover four-track subways do not appear to be much more expensive than two-track subways; in the 1900s, New York had little to no cost premium over London or Paris. The First Subway’s underground segments, slightly less than half of which are four-track, cost $39 million per km in today’s money, compared with about $29 million per km in Paris in the same era (see sources in this post). The Metropolitan line in London cost about the same: £1.3 million for 6 km in the early 1860s, or about $30 million per km.

In contrast, boring four tracks appears to cost twice as much as boring two. It’s hard to find examples, since four-track bores are extremely rare; the examples I do know, such as the East River Tunnels and the tunnel carrying the Lexington Avenue Line under the Harlem River, are short. There are bound to be efficiencies in engineering and sitework reducing the cost of boring, just as there are with cut-and-cover, but the majority of the cost of tunneling is the boring and the systems. The majority of the rest is stations, and the local stations can be built for not much of a premium over stations on a two-track line, but the express stations require considerably more excavation.

What this means is that cities that build cut-and-cover should probably aim to build four tracks rather than two. In retrospect, Paris should have built Metro Line 1 with four tracks: the narrowest street segment, Rue de Rivoli, runs for 3 km and is about 20-23 meters wide, which can take four tracks if there are only local platforms, and everything else is at least 30 meters and could take four tracks and express platforms. The only express station under Rivoli would probably be Chatelet, where there is a wide square where the station footprint could expand.

The question of whether to use cut-and-cover today is a separate issue. It’s easier for the first few lines than for subsequent lines, which have to cross under the old lines. Nonetheless, it’s still in use, for example in China; the lack of express tracks on Chinese subways has led to criticism on some railfan forums, particularly by Japanese railfans, who are used to the fast express trains of the JRs through urban areas. But in India, the longest underground segment in Delhi, on the Yellow Line, appears to be bored, running deep under Old Delhi. The one potential pitfall is that bored tunnels, while generally more expensive to construct than cut-and-cover tunnels if wide streets are available, are nimbler, making it easier to build lines to high standards, with wide curves.

Benefits

The two obvious benefits of express subways are speed and capacity. New York averages a decent speed, just under 30 km/h, buoyed by express trains that average about 36 km/h. When frequency on both the local and express tracks is adequate, which it regrettably isn’t most of the time in New York, it’s possible to use cross-platform local/express transfers to improve trip times even for people on the local stations.

The capacity benefits are sometimes compromised by transfers. In New York, the express tracks are consistently more crowded than the local tracks on the main lines, and the Upper West Side in particular sees the city’s most overcrowded trains on the express tracks run alongside the second least crowded on the local tracks. However, on the East Side, the local and express trains under Lexington are both quite full. The number of passengers they carry would overwhelm any two-track line: to carry the same number of passengers on just two tracks at the current peak frequency, each train would need about 2,100 passengers, more per unit of train floor area than the most crowded Tokyo Metro lines.

There are also indirect effect of four-tracking. The most distant stations are presumably express-only, or, if not, passengers will transfer to an express train at the first opportunity. This means that adding local stops does not increase trip times for passengers far out, which in turn argues in favor of tighter stop spacing on local trains, to provide more coverage. Evidently, New York has one of the smallest interstations (on local trains) of any major metro network in the world, surpassed only by Paris, which built the Metro without regard for the suburbs. Second Avenue Subway, built with just two tracks, has wider stop spacing than other Manhattan north-south mainlines, missing 79th Street, with the planned phase 2 stopping at 106th instead of 103rd and 110th.

Network effects

I have hammered repeatedly that metro systems need to avoid three pitfalls of network planning:

  1. Tangential lines, starting as radial farther out but becoming circumferential closer in rather than staying radial and serving city center.
  2. Reverse-branching: a common trunk in an outlying area splitting into branches in city center, the opposite of the more normal branching arrangement.
  3. Missed connections, in which two lines intersect without a transfer.

It is easier to miss connections when the stop spacing is wider, because city centers are so small that line 1 can easily miss the road that line 6 will later run under. The Paris Metro has just one missed connection (M5/M14), and the city made a failed effort in the 1900s to bring Line 5 to what would be the transfer station, Gare de Lyon. New York has only two missed connections among the lines built from 1900 to the 1920s (Junius/Livonia on the 3/L, Bowling Green/Whitehall on the 4-5/RW), both of which are easy to fix; the city’s tens of misses come from a deliberate decision to avoid transfers in the lines built in the 1930s. Systems with wider stop spacing have more opportunities for missed connections, such as Tokyo, Shanghai, and Moscow.

Four-track mainlines short-circuit this problem doubly. First, fewer lines are required to provide the same coverage and capacity. On the eve of the Great Depression, New York had six subway mainlines, three with four tracks and three with two, and 2 billion annual riders. Even if a city insists that all transfer stations be express (which is the case in New York among lines built before the 1930s, though at one station express platforms were only retrofitted decades later), there are fewer potential intersections; at city center, even the express lines are unlikely to have very wide stop spacing.

Moreover, it’s fine to miss transfers on express lines. The reason missed connections are so bad is that the alternative option typically requires a three-seat ride. For example, the 1 passes between Columbus Circle-59th Street and 50th Street without a connection to the E train, leaving connecting passengers with one of two options: ride to Times Square and transfer there, which is both a detour and a very long walk between the platforms, or change to the B or D at 59th and then again to the E at 53rd; the latter option is the faster one, saving about 5 minutes of in-vehicle time and 3 minutes of transfer time.

But if one of the transfers is cross-platform, then a three-seat ride is less onerous. This is especially true if this transfer is local/express on a long shared trunk line, where the transfer stations usually don’t get as crowded as between two separate trunks. This means that it’s possible, if there is no better option, to have local-only transfers. Two of the top stations in New York, 53rd/Lex and Columbus Circle, are local-only transfers.

Scale

Small cities don’t need to think about express trains very much. Transit cities with about 2 million people in their metro areas, such as Vienna, Stockholm, Prague, Budapest, and Hamburg, make do with a handful of metro lines, sometimes supplemented by regional rail. But as they grow, the number of urban rail lines they need grows to the point that a coherent two-track network is too difficult, not to mention too slow. Paris manages to make do with the RER acting as the express layer, but outside India and Pakistan, cities that are just beginning to build their metro networks don’t have large legacy commuter rail networks to leverage for express service. In Africa between the Sahara and South Africa, nearly everything has to be built from scratch, and the same is true of Bangladesh and much of Southeast Asia and Latin America.

Moreover, in developing countries, a large number of cities either are megacities or can expect to grow to that size class soon. This is less true in Latin America, nearly all of which has at- or below-replacement birth rates, already high urbanization rates, and negative net migration (thus, the main case for four-track subways in Bogota hinges on the fact that the city has absurdly wide roads for cut-and-cover, not on future scale). However, in poor countries with high birth rates and low urbanization rates, cities can expect to increase their population many times over in the next few decades. Lagos and Dhaka are already huge, and midsize cities such as Nairobi, Kampala, Dar es Salaam, Addis Ababa, Khartoum, Accra, Abidjan, Douala, and Sanaa can expect to grow to that size class within a generation, as can midsize cities in countries with lower birth rates, such as Chittagong, Hanoi, and Ho Chi Minh City. In such cities, transportation planning should presume much greater scale than may seem warranted today.

A smaller-scale version of this principle can be found in cities that are growing rapidly due to immigration, especially Singapore but also Sydney, Melbourne, Toronto, Vancouver, and Stockholm. Such cities might want to consider infrastructure investments based not on their present-day population levels, but on those that they can expect after 30 more years of high migration rates. Vancouver and Stockholm are too small for express subways no matter what, and Toronto has already built its central spines with two tracks (and is upgrading its regional rail network to act as an express layer), but Singapore, Sydney, and Melbourne should all think about how to plan for the possibility that they will have 10 million people within 50 years.

The MTA’s Bus Redesign Plan

Two weeks ago I wrote about the Brooklyn bus redesign I’m working on with Eric Goldwyn. The MTA, which is aware of our efforts, came up with its own plan. So far details are scant; there is a presentation available online, which talks about goals (“network redesign,” “higher frequency”) but no specifics (“a more gridded network,” “6-minute off-peak frequency on the main routes”).

At least so far, the goals seem solid. The MTA has the following list of improvements:

  • Redesign the network from top to bottom based on customer input, demographic changes, and travel demand analysis. Provide better connectivity and more direct service in every neighborhood
  • Optimize the existing network with community consultation by removing closely-spaced and underutilized stops and making street design changes on select corridors in coordination with NYC DOT
  • Expand off-peak service on strategic routes using a toolbox of service strategies including increased frequency and demand based service adjustments
  • Expand Traffic Signal Priority (TSP) to allow an approaching bus to hold a green light or shorten a red light
  • Seek exclusive busways on priority corridors to give buses full access in major congested areas
  • Identify opportunities for new bus lanes and queue jumps in 2018
  • Advocate for strengthened NYPD enforcement of bus lanes to keep bus stops and travel lanes clear throughout the system
  • Recommend dedicated transit-priority traffic teams to focus enforcement in key areas to ensure buses move quickly through trouble spots
  • Use Bus Lane Enforcement Cameras mounted on buses to automatically identify violations and issue tickets. Advocate for legislation to expand beyond the existing 16 authorized routes
  • Install tap readers to speed up the boarding process so buses spend less time waiting at stops
  • Introduce all-door boarding to allow riders to get on through any door of the bus
  • Explore options for a future cashless system to maximize reductions in boarding time
  • Expand fare enforcement on regular bus service to reduce evasion and restore fare revenue

The main problems only appear toward the end, with the implementation of off-board fare collection and all-door boarding. The insistence on “fare enforcement,” which could mean regular proof of payment (POP) inspections but could also mean worse, such as armed cops (not practiced in New York on SBS but practiced on some other US systems, like BART) or holding the bus during inspection (which New York does practice, unlike Berlin and other German-speaking cities). Overall I’m relatively sanguine about Andy Byford specifically – he’s not American and is not used to American levels of police militarization.

However, another aspect of the POP proposal is troubling: the connection with tap readers. The plan’s full text (which is barely more detailed than what I quote above) mentions that POP should come with the so-called New Fare Payment System, or NFPS, which New York is currently planning to roll out starting in 2019, continuing until 2023. The NFPS is based on worst industry practices cobbled from American and British ideas. Here is my second post ever, discussing the plans for smartcards in New York in 2011. New York ignored (and keeps ignoring) the smartcard implementations in a number of East Asian cities in its zeal to make people treat their credit card as a transit fare card, ensuring the agency can surveil all passengers; perhaps Americans lack the values of freedom and individual privacy of Japan and Singapore.

New York also ignored (and keeps ignoring) the POP implementations in cities with paper tickets, such as most of Central Europe. Smartcards are not required for POP: the German-speaking world has POP with paper tickets, as did Vancouver on SkyTrain and some bus lines even before the Compass Card debacle. In Singapore I saw a ticket inspection on a bus even before EZ-Link; I had a magnetic farecard at the time. Given the enormous waste coming from making passengers line up and pay the driver, it’s imperative to move toward POP as soon as possible, even if it means equipping inspectors with MetroCard readers rather than smartcard readers. MetroCard may only last for five years if the NFPS schedule doesn’t keep slipping, but handheld magnetic card readers are a cheap technology whereas making buses idle while passengers dip cards one at a time is not so cheap.

The zeal to go cash-free is the final troubling aspect of New York’s ideas about fare payment, especially when bundled with the idea that the bank card is the fare card. Not everyone has a local bank account. Tourists don’t (and even cards that are supposed to work abroad don’t always). Low-income city residents don’t, either: 11.7% of New York households have no bank account, and they disproportionately appear to be in poverty, judging by which neighborhoods they are most concentrated in. The MTA has always treated anonymous smartcards as an afterthought, and going cash-free means there is no recourse for the unbanked or even for many tourists.

Nor is cash-free operation even necessary. An on-board farebox is compatible with POP. In this system, riders can board from any door, and the driver will begin moving as soon as all passengers have boarded, even if not all passengers have paid yet. Riders with valid transfers or season passes need not do anything. Riders with a pay-per-ride smartcard and no transfer should tap their card at a validator at any bus door or bus stop (validators are cheap that blanketing the system with them is practically free). The remaining passengers should walk to the farebox and pay there; perhaps some busy stations should get fareboxes, as all SBS stops do in New York today, but if the MTA only expects a few smartcard-free, non-transfer passengers at a stop, then having them pay on board a moving bus should not be a problem.

I’d like to stress that other than the ongoing hiccups of the English-speaking world with fare payment systems (hiccups that it seems to export to Paris), the plan appears good, from what few details the MTA has released. There are plans for increasing the average distance between bus stops, adding more bus lanes, getting serious about signal preemption, raising off-peak frequency, and letting passengers board from all doors. The MTA really is noticing that its bus system is collapsing and really is making serious plans to avert a death spiral.

Buses in Brooklyn: Frequency is Freedom, but 15 Minutes isn’t Frequency

I’ve recently started working part-time on a project for the Marron Institute at NYU about bus restructuring in Brooklyn; at the end of this summer, I expect to release a proposal for service upgrades and a new map. I’m working on this with Marron scholar Eric Goldwyn, who is funded by the TWU, which is worried that ridership collapse may lead to service cuts and job losses, but I’m funded directly by Marron and not by the union.

Some of what’s likely to appear in the final report should be familiar to regular readers of this blog, or of Human Transit, or of the work TransitCenter has been doing. As I wrote in Curbed earlier this year, bus operating costs in New York are unusually high because the buses are slow, as the main operating costs of buses scale with service-hours and not service-km. Thus, it’s important to speed up the buses, which allows either providing higher frequency at the same cost or the same frequency at lower cost. A bus speedup should include systemwide off-board fare collection and all-door boarding (common in the German-speaking world but also in San Francisco), wider stop spacing, dedicated lanes wherever there is room, and signal priority at intersections; the TWU is an enthusiastic proponent of off-board fare collection, for reasons of driver safety rather than bus speed.

While bus speedups are critical, their impact is not as Earth-shattering as it might appear on paper. New York’s SBS routes have all of the above features except signal priority, and do save considerable time, but are still slow city buses at the end of the day. Brooklyn has two SBS routes: the B44 on Nostrand, averaging 15 km/h (local B44: 11.3), and the B46 on Utica, averaging 13.7 (local B46 on the shared stretch: 10.8). Their speed premiums over the local routes are toward the high end citywide, but are still 30%, not the 200% speed premium the subway enjoys. Moreover, the speed premium over non-SBS limited routes is 15-20%; put another way, between a third and a half of the speed premium comes purely from skipping some stops.

I mentioned in my last post that I met Carlos Daganzo at Berkeley. Daganzo was responsible for the Barcelona bus redesign, Nova Xarxa; you can read some details on Human Transit and follow links to the papers from there. The guiding principles, based on my conversation with Daganzo and on reading his papers on the subject, are,

  • Barcelona has high, relatively uniform density of people and jobs, so there’s no need for buses to hit one CBD. Brooklyn has about the same average residential density as Barcelona, but has a prominent CBD at one corner, but as this CBD is amply served by the subway, it’s fine for buses to form a mesh within the subway’s gaps.
  • Nova Xarxa involved widening the stop spacing in Barcelona from less than 200 meters to three stops per km, or a stop every 300-350 meters; Daganzo recommends even wider stop spacing.
  • While Barcelona’s street network is strictly gridded, the buses don’t run straight along the grid, but rather detour to serve key destinations such as metro stops. This is an important consideration for Brooklyn, where there are several distinct grids, and where subway stops don’t always serve the same cross street, unlike in Manhattan, where crosstown routes on most two-way streets are assured to intersect every north-south subway line.
  • The percentage of transfers skyrocketed after the network was implemented, standing at 26% at the end of 2015, with the model predicting eventual growth to 44%, up from 11% before the redesign.
  • The network was simplified to have 28 trunk routes, the least frequent running every 8 minutes off-peak.

The high off-peak frequency in Barcelona is a notable departure from Jarrett Walker’s American network redesigns; the evidence in Houston appears mixed – ridership is about flat, compared with declines elsewhere in the country – but the percentage of transfers does not seem to have risen. Jarrett says in his book that having a bus come every 10 minutes means “almost show-up-and-go frequency” with no need to look at schedules, but his work in Houston and more recently in San Jose involves routes running every 15 minutes.

Moreover, unreliable traffic in these car-dominated cities, in which giving buses dedicated lanes is politically too difficult, means that the buses can’t reliably run on a schedule, so the buses do not run on a clockface schedule, instead aiming to maintain relatively even headways. (In contrast, in Vancouver, a less congested street network, with priority for all traffic on the east-west main streets on the West Side, ensures that the buses on Broadway and 4th Avenue do run on a fixed schedule, and the 4th Avenue buses have a 12-minute takt that I still remember four years after having left the city.)

I’ve talked about the importance of radial networks in my posts about scale-variant transit. I specifically mentioned the problem with the 15-minute standard as too loose; given a choice between an untimed 15-minute network and a timed 30-minute network, the latter may well be more flexible. However, if the buses come every 5 minutes, the situation changes profoundly. Daganzo’s ridership models have no transfer penalty or waiting penalty, since the buses come so frequently. The models the MTA uses in New York have a linear penalty, with passengers perceiving waiting or transferring time on the subway as equivalent to 1.75 times in-motion time; bus waiting is likely to be worse, since bus stops are exposed to the elements, but if the average wait time is 2.5 minutes then even with a hefty penalty it’s secondary to in-vehicle travel time (about 18 minutes on the average unlinked bus trip in New York).

Unfortunately, that high frequently does not exist on even a single bus line in Brooklyn. Here is a table I created from NYCT ridership figures and timetables, listing peak, reverse-peak, and midday frequencies. Five routes have better than 10-minute midday frequency: the B12, the B6 and B35 limited buses, and the B44 and B46 SBSes, running every 7, 7.5, 8, 8, and 6 minutes respectively. In addition, the B41 limited and B103 have a bus every 9 and 7.5 minutes respectively on their trunks, but the B41 branches on its outer end with 18-minute frequencies per branch and the B103 short-turns half the buses. Another 14 routes run every 10 minutes off-peak, counting locals and limiteds separately.

The problem comes from the split into local and limited runs on the busiest buses. The mixture of stopping patterns makes it impossible to have even headways; at the limited stops, the expected headway in the worst case is that of the more frequent of the two routes, often about 10 minutes. The average ridership-weighted speed of Brooklyn buses is 10.75 km/h. An able-bodied passenger walking at 6 km/h with a 10-minute head start over a bus can walk 2.25 km before being overtaken, which can easily grow to 3 km taking into account walking time to and from bus stops. To prevent such situations, it’s important to run buses much more frequently than every 10 minutes, with consistent stopping patterns.

This does not mean that NYCT should stop running limited buses. On the contrary: it should stop running locals. The SBS stop spacing, every 800 meters on the B44 and B46, is too wide, missing some crossing buses such as the B100 (see map). However, the spacing on the B35 limited is every 400 meters, enough to hit crossing buses even when they run on one-way pairs on widely-spaced avenues. The question of how much time is saved by skipping a stop is difficult – not only do different Brooklyn buses give different answers, all lower than in Manhattan, but also the B35 gives different answers in different directions. A time cost of 30 seconds per stop appears like a good placeholder, but is at the higher end for Brooklyn.

The question of how many stops to add to SBS on the B44 and B46 has several potential answers, at the tight end going down to 400 meters between stops. At 400 meters between stops, the B44 would average 13 km/h and the B46 12 km/h. At the wide end, the B44 and B46 would gain stops at major intersections: on the B44 this means Avenue Z, R, J, Beverly, Eastern Parkway, Dean, Halsey, and Myrtle, for an average interstation of 570 meters and an average speed of 14 km/h, and on the B46 this means Avenue U, Fillmore, St. John’s, and Dean, for an average interstation of 610 meters an average speed of 13 km/h. Consolidating all buses into the same stopping pattern permits about a bus every 2.5 minutes peak and every 4 minutes off-peak on both routes.

On the other routes, consolidating local and limited routes required tradeoffs and cannibalizing some peak frequency to serve the off-peak. While it may seem dangerous to limit peak capacity, there are two big banks that can be used to boost off-peak frequency: time savings from faster trips, and greater regularity from consolidating stop patterns. The B82 is an extremely peaky route, running 7 limited and 10 local buses at the peak and just 6 buses (all local) for a four-hour midday period; but there is a prolonged afternoon shoulder starting shortly after noon with another 6 limited buses. Some peak buses have to be more crowded than others just because of schedule irregularity coming from having two distinct stop patterns. Consolidating to about 15 buses per hour peak and 10 off-peak, cannibalizing some frequency from the peak and some from the shoulders, should be about neutral on service-hours without any additional increase in speed.

The sixth post on this blog, in 2011, linked to frequent maps of Brooklyn, Manhattan, and Bronx buses, using a 10-minute standard. There has been some movement in the top buses since 2011 – for one, the B41 route, once in the top 10 citywide, has crashed and is now 16th – but not so much that the old map is obsolete. A good place to start would be to get the top routes from a 10-minute standard to a 6-minute standard or better, using speed increases, rationalization of the edges of the network, and cannibalization of weak or subway-duplicating buses to boost frequency.

I Gave a Pair of Talks in the Bay Area About Regional Rail

Thanks to the invitation of Adina Levin’s Friends of Caltrain, I came to the Bay Area for a few days, giving two talks about regional rail best industry practices in front of Friends of Caltrain, Seamless Bay Area, and SF Transit Riders. My schedule was packed, including a meeting with a world-leading expert in transportation systems in which I learned about the Barcelona bus service changes; a Q&A about both general and Bay Area-specific issues for Bay City Beacon subscribers; and several other meetings.

My two talks were in Mountain View and San Francisco, and used the same slides, with minor corrections. Here are the slides I used in San Francisco; I consolidated the pauses so that each page is a slide rather than a line in a slide. This was also covered in Streetsblog, which gives more background and gives some quotes from what I said during the presentation, not printed in the slides.

Unlike in my NYU presentation last year, I did not include a proposed map of service improvements. The reason is that in the Bay Area, there are more questions than answers about which service should use which piece of infrastructure. This makes fantasy maps dangerous, as they tend to fix people onto one particular service pattern, which may prove suboptimal based on decisions made elsewhere in the system. This is not a huge problem in New York or Boston, where the alignments naturally follow where the stub-end commuter lines are, with only a few questions; but in the Bay Area, the situation is more delicate, because big questions like “can/should Caltrain get a trans-Bay connection from San Francisco to Oakland and the East Bay?” can go either way.

The role of redevelopment in the area is especially important. Unlike New York, Paris, or other big transit cities, San Francisco does not have much density outside the city proper, Oakland, or Berkeley. Moreover, there is extensive job sprawl in Silicon Valley, which contributes to a last-mile problem for public transit; usually first-mile access is a bigger problem and high-end jobs tend to cluster near train stations. But conversely, the high incomes in the Bay Area and the growth of the tech industry mean that everywhere TOD is permitted in the core and the suburbs, it will be built. This impacts decisions about the total size of transit investment.

At present-day development patterns, San Francisco proper really doesn’t need more rail construction except Geary and the Downtown Extension, depending on construction costs. But general upzoning makes Geary worth it even at $1 billion per km and opens up the possibilities of four-tracking Caltrain within the city (which means expanding some tunnels), giving the N-Judah dedicated tracks and a dedicated tunnel under Mission, and extending the Central Subway to the north and northwest. The land use in the Richmond and Sunset Districts today supports a fair amount of transit, but not new subways if there’s no cost control.

New York-Area Governments to Form a Coordinated Transportation Planning Agency

Governors Andrew Cuomo (D-NY) and Phil Murphy (D-NJ) announced that they would cooperate to form a Lower Hudson Transportation Association, or LHTA, to supersede what they described as antiquated 20th-century thinking and bring the region’s transportation into the 21st century. LHTA would absorb the transportation functions of Port Authority, which senior New York state officials speaking on condition of anonymity called “irredeemably corrupt,” and coordinate planning across the region. Negotiations with the state of Connecticut are ongoing; according to planners in New Jersey, the timing for the announcement was intended to reassure people that despite the lack of federal funding for Gateway, a lower-cost modified version of the project would go forward.

But the first order of business for LHTA is not Gateway. The governors’ announcement mentioned that LHTA would begin by integrating the schedules and fares throughout the region. By 2019, passengers will be able to transfer between the New York City Subway and PATH for free, and connect from the subway to the AirTrain JFK paying only incremental fare. Engineering studies for removing the false walls between PATH and F and M subway platforms are about to begin.

Commuter rail fare integration is also on the table. Currently, the fare on the subway is a flat $2.75. On commuter rail, it is higher even within New York City: a trip between Jamaica Station and New York Penn Station, both served by the E line of the subway, is $10.25 peak or $7.50 off-peak on the Long Island Railroad (LIRR). The governors announced that they would follow the lead of European transportation associations, such as Ile-de-France Mobilités in Paris, and eliminate this discrepancy under LHTA governance, which also includes revenue sharing across agencies. Detailed studies are ongoing, but in 2019, LHTA will cut commuter rail fares within New York City and several inner cities within New Jersey, including Newark, to be the same as the subway fare, with free transfers.

Simultaneously, LHTA will develop a plan for schedule integration, coordinating New Jersey Transit, the LIRR, Metro-North, and suburban bus agencies. In order to make it easier for suburban passengers to reach commuter rail stations, the suburban buses will be timed to just meet the commuter trains, with a single ticket valid for the entire journey. Today most passengers in the suburbs drive to the commuter rail stations, but the most desirable park-and-rides are full. Moreover, the states would like to redevelop some of the park-and-rides as transit-oriented development, building dense housing and retail right next to the stations in order to encourage more ridership.

Moreover, the LIRR and New Jersey Transit’s commuter trains currently stub-end at Penn Station in opposite directions. LHTA is studying French and German models for through-running, in which trains from one suburb run through to the other instead of terminating at city center. Planners within several agencies explain that the systems on the Long Island and New Jersey side are currently incompatible – for example, LIRR trains are electrified with a third rail whereas New Jersey Transit trains are electrified with high-voltage catenary – but reorganizing these systems for compatibility can be done in a few years, well before the Gateway project opens.

In response to a question about the cost of this reorganization, one of the planners cited the Swiss slogan, “electronics before concrete.” Per the planner, electronics include systems, electrification, and software, all of which are quite cheap to install, whereas pouring concrete on new tunnels and viaducts is costly. The planner gave the example of resignaling on the subway: the New York Times pegged the cost of modernizing subway signals at $20 billion, and this could increase capacity on most lines by 25 to 50 percent. But the cost of building the entire subway from scratch at today’s costs in New York is likely to run up to $200 billion.

But while the immediate priorities involve fare and schedule integration, LHTA’s main focus is the Gateway project. There are only two commuter rail tracks between New Jersey and Penn Station, and they are full, running a train every 2.5 minutes at rush hour. The Gateway project would add two more tracks, doubling capacity. The currently projected cost for the tunnel is $13 billion, but sources within New York said that this number can be brought down significantly through better coordination between the agencies involved. This way, it could be funded entirely out of local and state contributions, which add up to $5.5 billion. When pressed on this matter, officials and planners refused to say outright whether they expect $5.5 billion to be enough to cover the tunnel, but some made remarks suggesting it would be plausible.

Previous estimates for the costs of Gateway adding up to $30 billion include substantial extra scope that is not necessary. Sources on both sides of the Hudson report that the main impetus for the formation of LHTA was to coordinate schedules in a way that would make this extra scope no longer necessary. “With last decade’s ARC, there was a cavern under Penn Station to let trains reverse direction and go back to New Jersey,” explains one of the planners; ARC was a separate attempt to add tracks to the Hudson rail crossing to Penn Station, which Republican Governor Chris Christie canceled in 2010 shortly after his election. “With Gateway, there was the plan for Penn Station South, condemning an entire Manhattan block for the station for $7 billion. With the plans we’re developing with LHTA we don’t need either Penn South or a cavern to let trains run between stations.”

Moreover, some planners suggested reactivating plans to connect Penn Station and Grand Central as part of Gateway. They refused to name a cost estimate, but suggested that at the low end it could be funded out of already-committed state money. Under this plan, there would be through-running between not just New Jersey Transit and the LIRR but also Metro-North, serving the northern suburbs of New York and Connecticut. Sources at the Connecticut Department of Transportation said they are studying the plan and have reservations but are overall positive about it, matching the reports of sources within New York, who believe that Connecticut DOT will join LHTA within six months.

Officials are optimistic about the effects of LHTA on the region both privately and publicly. The joint press release referred to the metro area as “a single region, in which decisions made in far apart areas of New York nonetheless affect people in New Jersey and vice versa.” Planners in both states cited examples of friends and family in the other state who they would visit more often if transportation options were better. With better regional rail integration, they said, people would take more trips, improving regional connectivity, and take fewer trips by car, reducing traffic congestion and pollution.

Missed Connections

I’ve discussed before the topic of missed connections on subway systems, both here and on City Metric. I’ve for the most part taken it for granted that on a rapid transit network, it’s important to ensure that whenever two lines intersect, they offer a transfer. This seems like common sense. The point of this post is not to argue for this principle, but to distinguish two different kinds of missed connections: city center misses, and outlying misses. Both are bad; if I had to say which is worse I’d say it’s the city center miss, but city center misses and outlying misses are bad for distinct reasons.

A useful principle is that every pair of rapid transit lines should intersect, unless one is a shuttle, or both are circumferential. If the city is so large that it has multiple circular lines at different radii (Beijing has two, and London vaguely has two as well depending on how one counts the Overground), then they shouldn’t intersect, but rapid transit networks should be radial, and every radial line should connect to every other line, with all radial-radial transfers ideally located within the center. City center misses weaken the network by making some radials not connect, or perhaps connect at an inconvenient spot. Outlying misses often permit more central transfers, and their problem is that they make it harder to transfer to the better or less crowded radial on the way to the center. London supplies a wealth of examples of the latter without the former.

What counts as a missed connection?

Fundamentally, the following picture is a missed subway connection:

The red and blue lines intersect without a transfer. Even if a few stations later there is a transfer, this is a miss. In contrast, the following picture is not a missed connection:

It might be faster for riders to transfer between the southern and western leg if there were a station at the exact physical intersection point, but as long as the next station on the red line has a transfer to the blue line it counts, even if the blue line has one (or more) stations in the middle. Washington supplies an example of this non-miss: it frustrates riders that there’s no connection between Farragut West and Farragut North, but at the next station south from the intersection on the Red Line, Metro Center, there is a transfer to the Blue and Orange Lines. London supplies another pair of examples: the Northern line and the Waterloo and City line appear to intersect the District line without a transfer, but their next station north from the physical intersection point, Bank, has an in-system transfer to Monument on the District.

There are still a few judgment calls in this system. One is what to do at the end of the line. In this case, I rule it a missed connection if the terminal clearly has an intersection without a transfer; if the terminal is roughly between the two stations on the through-line, it doesn’t count. Another is what to do about two lines that intersect twice in close succession, such as the Bakerloo and Hammersmith and City lines in London, and Metro Lines 4 and 10 in Paris. In such cases, I rule that, if there’s just one station on the wrong side (Paddington on Bakerloo, Mabillon on M10) then I rule it a single intersection and allow transfers at the next station over, by which standard London has a missed connection (Edgware Road has no Bakerloo/H&C transfer) and Paris doesn’t (Odeon has an M4/M10 transfer).

How many missed connections are there?

In Paris, there are three missed connections on the Metro there is one missed connection on the Metro (update: see comments below): M9/M12, M5/M14, M9/M14. As I discuss on City Metric, it’s no coincidence that two of these misses involve this miss involves Line 14, which has wide stop spacing. Narrow stop spacing makes it easier to connect within line-dense city centers, and Paris famously has the densest stop spacing of any major metro system. M9/M12 and M9/M14 morally should connect at Saint-Augustin and Saint-Lazare, but in fact there is no in-system transfer. M5/M14 should connect at Gare de Lyon, but when M5 was built it was not possible to get the line to the station underground and then have it cross the Seine above-ground, so instead it meets M1 at Bastille, while M14 doesn’t serve since it expresses from Gare de Lyon to Chatelet. A fourth missed connection is under construction: the extension of M14 to the north misses M2 at Rome, prioritizing long stop spacing over the connection to the M2/M6 circumferential.

In Tokyo, there are many misses. I am not sure why this is, but judging by line layout, Tokyo Metro and Toei try to stick to major roads whenever possible, to avoid tunneling under private property, and this constrains the ability of newer lines to hit station locations on older lines. If I understand this map correctly, there are 19 missed connections: Ginza/Hibiya (Toranomon and Kasumigaseki should connect), Ginza/Mita, Ginza/Yurakucho, Ginza/Shinjuku, Marunouchi/Mita (Ginza and Hibiya should connect), Marunouchi/Yurakucho, Asakusa/Yurakucho, Asakusa/Hanzomon, Hibiya/Namboku, Hibiya/Yurakucho (Tsukiji and Shintomicho should connect), Hibiya/Hanzomon, Hibiya/Shinjuku, Hibiya/Oedo, Tozai/Oedo, Tozai/Fukutoshin, Mita/Oedo, Chiyoda/Oedo twice, and Oedo/Fukutoshin. Oedo is particularly notable for being a circumferential line that misses a large number of transfers.

In New York, there are even more misses. Here the culprit is clear: the two older layers of the subway, the IRT and BMT, have just two missed connections. One, 3/L at Junius Street and Livonia Avenue, is an outlying miss. The other is central: Bowling Green on the 4-5 and Whitehall on the R-W should connect. But the newer layer, the IND, was built to drive the IRT and BMT into bankruptcy through competition rather than to complement them, and has a brutal number of misses: ABCD/2-3, ACE/1-2-3, AC-F/2-3-4-5, AC-G/2-3-4-5-BQ-DNR, BD/NQRW, BDFM/NQRW, BD/JZ, E/1, E/F, M/NW, R/7, F/BD-NQ, F/NRW, F-Q/4-5-6, F/NW, G/7, G/JMZ. Counting individual track pairs, this is 46 misses, for a total of 48 including the two IRT/BMT misses; I’m excluding local-only transfers, such as Columbus Circle and 53rd/Lex, and counting the 42nd Street Shuttle as an express version of the 7, so it doesn’t miss the BDFM transfer.

Finally, London only has eight misses. In Central London there are three: the Metropolitan or Hammersmith and City line misses the Bakerloo line as discussed above, and also the Victoria line and Charing Cross branch of the Northern line at Euston. The other five are outlying: the Central line misses the Hammersmith and City line at Wood Lane/White City, and its branches miss the Piccadilly line’s Uxbridge branch three times; the fifth miss is Metropolitan/Bakerloo. But one more miss is under construction: the Battersea extension of the Northern line is going to intersect the Victoria line without a transfer.

The difference between the two kinds of miss

Many misses are located just a few stations away from a transfer. In New York, some misses are just a station away from a transfer, including the G/7 miss in Long Island City, the E/1 miss between 50th Street and 59th Street, and several more are a few stations away, such as the various BDFM/NQRW misses. In London, these include two of the three Central London transfers: there is an H&C/Bakerloo transfer at Baker Street and an H&C-Met/Victoria transfer at King’s Cross-St. Pancras. As a result, not counting the Waterloo and City line, only two trunk lines in the system do not have any transfer: the Charing Cross branch of the Northern line and the Metropolitan/H&C line.

On a radial network, if two lines don’t have any transfer, then the network is degraded, since passengers can’t easily connect. In New York, this is a huge problem: some station pairs even within the inner networks require two transfers, or even three counting a cross-platform local/express transfer. My interest in subway networks and how they function came about when I lived in Morningside Heights on the 1 and tried socializing with bloggers in Williamsburg near the JMZ.

In Paris the three misses are also a problem. Line 4 is the only with a transfer to every other main line. Line 9 intersects every other line, and Line 14 will when its northern extension opens, but both miss connections, requiring some passengers to take three-seat rides, in a city infamous for its labyrinthine transfer stations. Fundamentally, the problem is that the Paris Metro is less radial than it should be: some lines are laid out as grid routes, including Lines 3, 5, and 10; moreover, Lines 8, 9, 12, and 13 are radial but oriented toward a different center from Lines 1, 4, 7, and 11.

In London, in contrast, there is almost no pair of stations that require a three-seat ride. The Charing Cross branch of the Northern line doesn’t make any stop that passengers from the H&C or Met line can’t get to from another line with one interchange (Goodge Street is walking distance to Warren Street). A bigger problem is the lack of interchange to the Central line on the west, which makes the connections between the H&C stations on the west and some Central line stations awkward, but it’s still only a small number of stations on each line. So the problem in London is not network robustness.

Rather, the problem in London is severe capacity limitations on some lines. Without good outlying interchanges, passengers who want to get between two lines need to ride all the way to the center. Most likely, passengers between the Piccadilly and Central line branches to the west end up driving, as car ownership in West London is relatively high. Passengers without a car have to instead overload the Central line trunk.

The same problem applies to misses that are strictly speaking not missed connections because the two lines do not actually intersect. In Paris, this occurs on Line 7, which swings by the Opera but doesn’t go far enough west to meet Lines 12 and 13. In London, the best example is Hammersmith station: the H&C and District lines have separate stations without an interchange, but they do not intersect since it’s the terminus of the H&C line and therefore I don’t count it as a miss. But morally it’s an outlying miss, preventing District line riders from changing to the H&C line to reach key destinations like Euston, King’s Cross, and Moorgate without overloading the Victoria or Northern line.

In New York this problem is much less acute. The only outlying misses are the 3/L and the ABCD/2-3; the 3/L connects two very low-ridership tails, so the only serious miss is on the Upper West Side. There, passengers originating in Harlem can walk to either line, since the two trunks are two long blocks apart, and passengers originating in Washington Heights can transfer from the A-C to the 1 at 168th Street; at the other end, passengers bound for Midtown can transfer at Columbus Circle, using the underfull 1 rather than the overcrowded 2 and 3.

The role of circumferential lines

Outlying transfers are useful in distributing passengers better to avoid capacity crunches, but they are incidental. They occur when formerly competing suburban lines get shoehorned into the same subway network, or when two straight roads intersect, as in Queens. But the task of distributing passengers between radial lines remains important and requires good connections between as many pairs of radials as possible.

The usual solution to this is a circumferential line. In Moscow, there are several missed connections in the center (Lines 3/6, 3/7, 6/9) and one more planned (8/9), but the Circle Line helps tie in nearly all the radii together, with just one missed connection (to Line 10 to the north) and one more under construction (to Line 8 to the west). The point of the Circle Line is to allow riders to connect between two outlying legs without congesting the center. This is especially important in the context of Moscow, where there are only a handful of interchange stations in the center, most of which connect more than two lines.

In London, the Overground is supposed to play this role. However, the connections between the Underground and Overground are weak. From Highbury and Islington clockwise, the Overground misses connections to the Central line, the Victoria line, the main line of the District line, the Piccadilly line, the Hammersmith and City line, both branches of the Northern line, and the Piccadilly line (it also misses the Metropolitan line, but that’s on a four-track stretch where it is express and local service is provided by the Jubilee line, with which there is a transfer). Much of this is an unforced error, since the Underground lines are often above-ground this far out, and stations could be moved to be better located for transfers.

In New York, the only circumferential line is the G train, which has uniquely bad transfers, legacy of the IND’s unwillingness to build a system working together with the older subways. Triboro RX (in the original version, not the more recent version) would play this role better: with very little tunneling, it could connect to every subway line going counterclockwise from the R in Bay Ridge to the B-D and 4 at Yankee Stadium. On the way, it would connect to some major intermediate centers, including Brooklyn College and Jackson Heights, but the point is not just to connect to these destinations in the circumferential direction but also to facilitate transfers between different lines.

Going forward, cities with large metro network should aim to construct transfers where feasible. In New York there are perennial proposals to connect the 3 and L trains; these should be implemented. In London, the missed outlying transfers involve above-ground stations, which can be moved. The most important miss, White City/Wood Lane, is already indicated as an interchange on the map, but does not to my understanding have an in-system transfer; this should be fixed.

Moreover, it is especially important to have transfers from the radial lines to the circumferential ones. These improve network connectivity by allowing passengers to change direction (from radial to circumferential, e.g. from east-west to north-south within Queens), but also help passengers avoid congested city centers like outlying radial-radial transfers. Where circumferential lines don’t exist, they should be constructed, including Triboro in New York and Line 15 in Paris; where they do, it’s important to ensure they don’t miss connections the way the Overground does.

Boston Regional Rail

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.

Transit and Scale Variance Part 3: Grids

This is my third post about scale variance in transit planning; see parts 1 and 2. In part 1, I discussed how good bus networks exist at a certain scale, which can’t easily be replicated at larger scale (where the slowness of city buses makes them less useful). In part 2, I went over a subway planning feature, especially common in the communist bloc, that again works only at a specific scale, namely cities with enough population for 3-4 subway lines; it gets more complex in larger cities, and cannot be imported to bus networks with 3-4 lines. In this post, I will focus on one scale-variant feature of surface transit: the grid.

The grid works only for surface transit and not for rapid transit, and only at a specific scale, so constrained as to never be maximally useful in an entire city, only in a section of a city. This contrasts with what Jarrett Walker claims about grids. Per Jarrett, grids are the perfect form of a transit network and are for the most part scale-invariant (except in very small networks). One of the impetuses for this post is to push back against this: grids are the most useful at the scale of part of a transit city.

Grid Networks Versus Radial Networks

I’ve written a few posts exhorting subway planners to build their networks in a certain way, which, in the most perfect form, is radial. In particular, tangential subway lines, such as the G train in New York (especially when it ran to Forest Hills), Line 10 in Paris, and Lines 3 and 6 in Shanghai, are weak. When the G train was running to Forest Hills, most local passengers would switch from it to the next Manhattan-bound train, leading New York City Transit to send more Manhattan-bound local subways to Forest Hills and eventually to cut back the G to Long Island City. Based on these examples, I contend that on a subway network, every line should be either radial, serving the CBD, or circumferential, going around the CBD.

My post about New York light rail proposes a network with some lines that are neither: in the Bronx, my proposal is essentially a grid, with north-south routes (Grand Concourse, Webster, 3rd) and east-west ones (161st, Tremont, Fordham) and one that combines both (145th-Southern). Regular commenter NewtonMARunner criticized me for this on Twitter. I answered that the lines in my proposal are based on the busiest buses in the Bronx, but this simply shifts the locus of the question to the existing network: if transit lines should be radial or circumferential, then why are the tangential Bx19 bus (145th-Southern) or the Bx40/42 and Bx36 (Tremont, with a long radial eastern tail) so successful?

To answer this requires thinking more carefully about the role of circumferential routes, which by definition don’t serve the most intensely-used nodes. In Paris, Lines 2 and 6 form a ring that misses five out of six train stations and passes just outside the CBD, and yet they are both busy lines, ranking fourth and fifth in ridership per km. The reason is that they are useful for connecting to radial Metro lines and to some RER lines (namely, the RER A and the southern half of the RER B). Tangential lines miss connections much more easily: in the west, Line 10 here has a decent transfer to Line 9 and a somewhat decent one to Line 8, but to Lines 12 and 13 it’s already not very direct. The G train in New York has the same problem to the south – few connections to lines that actually do go into Manhattan.

Consider the following three possible networks:

The radial network is a typical subway network. The full grid lets you go from everywhere to everywhere with just one transfer, at the cost of having far more route length than the radial network. The partial grid no longer lets you go from everywhere to everywhere easily, and has the outer two lines in each service direction missing city center, but still has more overall route-length than the radial network. The principle here is that a grid plan is useful only if the grid can be complete.

The scale, then, is that rapid transit is so expensive that there’s no money for a complete grid, making a radial plan more appropriate. But surface transit, especially by bus, can be spread across a grid more readily. The Bronx’s size, density, and bus ridership patterns are such that a mostly complete grid is feasible within the western two-thirds of the borough, supplemented by the subway. In this environment, a tangential route is fine because it hits all the radial routes it could, and could provide useful two-seat rides to a large variety of destinations.

Are Grids Really Grids?

Chicago has a relentless bus grid. The three busiest north-south routes are the tangential 8 (Halsted), 9 (Ashland), and 49 (Western), which are 22, 29, and 26 km long respectively. None enters the Loop; Halsted, the easternmost, is at the closest approach 800 meters from the Loop, across a freeway. The two busiest east-west routes, the 77 (Belmont) and 79 (79th), are also far from the Loop.

However, I contend that these routes don’t really form a grid, at least not in the sense that passengers ride between two arbitrary points in Chicago by riding a north-south bus and connecting to an east-west bus. Instead, their outer ends form tails, which people ride to the L, while their inner ends are standard circumferentials, linking two L branches. The L in turn is purely radial and doesn’t follow the Chicago grid, with the Blue Line’s O’Hare Branch, the Orange Line, and the Brown Line all running diagonally.

Vancouver is similar. The north-south routes are radial, veering to enter Downtown. The east-west ones are more circumferential than tangential: they connect the Expo and Canada Lines, and most also connect to UBC. The Broadway buses (9 and 99) pass so close to Downtown Vancouver they’re more tangential, but they also offer the shortest path between the Expo and Canada Lines (making them a strong circumferential) while at the same time serving high job density on Central Broadway (giving them some characteristics of a radial).

In the absence of a radial rail network to connect to, long grid routes are less useful. Cities have a center and a periphery, and the center will always get more ridership, especially transit ridership. The outermost grid routes are often so weak that they should be pruned, but then they weaken the lines they connect to, making it necessary to prune even more lines until the grid is broken.

The Optimal Scale for a Grid

A strong transit grid will not form in a city too small for it. There needs to be a large enough center with enough demand for transit ridership to justify more than a purely radial bus network with a timed transfer. At the same time, the city cannot be too big, or else the arterial buses are too slow to be useful for ordinary work and leisure trips, as in Los Angeles.

What’s more, there is no Goldilocks zone, just right for a grid. Chicago is already too big for a bus grid without the radial rail layer. It’s also too big for what Jarrett calls grid accelerators – that is, rapid transit routes that replace bus grid lines: the Red Line is plausibly a grid accelerator, but the other lines in Chicago are not, and if there were L lines only at grid points, then the Red Line and the one east-west route would get overcrowded heading toward the Loop. Even Vancouver, a compact metro area hemmed by mountains and the ocean, relies on the diagonal Expo Line to serve Downtown and doesn’t really have a grid beyond city limits. A less dense city in the same land area could have a grid, but without much traffic or a strong CBD, cars would always beat transit on time and only the poor would ride the bus.

The scale in which grid networks work more or less on their own seems to be that of Vancouver proper, or that of the Bronx. Vancouver is 115 km^2 and the Bronx is 110 km^2; Vancouver’s bus grid spills over to Metrotown and the Bronx’s to Upper Manhattan, but in both cases these are small increases in the relevant land area.

Tellingly, Vancouver still relies on the bus network to feed SkyTrain; the Canada Line is a grid accelerator, but the Expo Line is not. The Bronx is the more interesting case, because it is not a city or even the center of the city, but rather a dense outlying portion of the city with an internal arterial grid. In both cases, the grid is supplementary to the radial rail core, even if the routes that use it have a lot of independent utility (Metro Vancouver has higher bus ridership than rail ridership, and the Bronx buses combined have slightly more ridership than the combined number of boardings on the Bronx subway stations).

Geographical constraints matter as well. The Bronx and Upper Manhattan are hemmed by water and by the administrative border of the city (which also includes a sharp density gradient), and Vancouver is hemmed by water and by a density gradient in the east. This makes it easier to equip both with grids that are close enough to the complete grid in the middle image above rather than the incomplete one in the third image. The Bronx’s lower-density eastern tails happen to meet up with those of Queens, forming circumferential routes, and also have enough north-south subway lines to feed that they remain useful.

In a transit city, the grid cannot come first. Even if there is a street grid, the spine of the network has to be radial as soon as there is demand for more than two rapid transit lines. The role of surface transit remains feeding rapid transit. Grids look attractive, but the optimal scale for them is awkward: large-scale surface transit grids are too slow, forcing the city to have a rapid transit backbone, and if the city is too small for that then the arterial grid provides too good auto access for public transit to be useful.

Transit and Scale Variance Part 2: Soviet Triangles

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.

Transit and Scale Variance Part 1: Bus Networks

I intend to begin a series of posts, about the concept of scale-variance in public transit. What I mean by scale-variance is that things work dramatically differently depending on the size of the network. This can include any of the following issues, roughly in increasing order of complexity:

  • Economies and diseconomies of scale: cars display diseconomies of scale (it’s easier to build freeway lanes numbers 1-6 than lanes 14-20), transit displays the opposite (there’s a reason why the world’s largest city also has the highest per capita rail ridership).
  • Barriers to entry: a modern first-world transit network, or an intercity rail network, requires vast capital investment, beyond the ability of any startup, which is why startup culture denigrates fixed-route transit and tries to find alternatives that work better at small scale, and then fails to scale them up.
  • Network design: the optimal subway network of 500 km looks different from the optimal network of 70 km, and its first 70 km may still look different from the optimal 70 km network. Bus networks look different from both, due to differences in vehicle size, flexibility, and right-of-way quality (surface running vs. grade separations).
  • Rider demographics: the social class of riders who will ride half-hourly buses is different from the class who will ride the subway, and the network design should account for that, e.g. by designing systems that the middle class will never ride to destinations that are useful to the working class. But then marginal rider demographics are profoundly different – sometimes the marginal rider on a low-usage bus network is a peak suburban commuter, leading to design changes that may not work in higher-volume settings.

For a contrasting example of scale-invariance, consider timed transfers: they underlie the Swiss intercity rail network, but also some small-town American bus systems and mid-size night bus networks such as Vancouver’s. I wrote about it in the context of TransitMatters’ NightBus proposal for Boston, giving a lot of parallels between buses and trains that work at many scales.

However, night buses themselves are an edge case, and usually, bus network design is different at different scales. In this post I’d like to go over some cases of changes that work at one scale but not at other scales.

Brampton

The trigger for this post was a brief Twitter flamewar I had earlier today, about Brampton. TVO just published an article praising Brampton Transit for its rapid growth in bus ridership, up from 9 million in 2005 to 27 million in 2017. Brampton is a rapidly growing suburb of 600,000 people, but transit ridership has grown much faster than population. The bone of contention is that current ridership is only 45 annual bus trips per capita, which is weak by the standard of even partly transit-oriented places (Los Angeles County’s total annual bus and rail ridership is about 40 per capita), but is pretty good by the standard of auto-oriented sprawl. The question is, is Brampton’s transit success replicable elsewhere? I’d argue that no.

First, Brampton’s transit ridership growth is less impressive than it looks, given changing demographics. Fast growth masks the extent of white flight in the city: it had 433,000 visible minorities in 2016, up from 246,000 in 2006 and 130,000 in 2001, and only 153,000 whites, down from 185,000 in 2006 and 194,000 in 2001. The TVO article points to racial divisions about transit, in which the white establishment killed a light rail line over concerns about traffic, whereas the black and South Asian population (collectively a majority of the city’s population) was supportive. Ridership per nonwhite resident is still up, but not by such an impressive amount. Brampton’s population density, 2,200 per square kilometer, is high for a North American suburb, and a change in demographics could trigger ridership growth – this density really is okay for both transit and driving, whereas very high density (e.g. New York) favors transit and very low density (e.g. most of the US Sunbelt) favors driving regardless of demographics.

But even with demographic changes, Brampton has clearly gotten something right. I compare ridership today to ridership in 2005 because that’s when various bus improvements began. These improvements include the following:

  • A bus grid, with straighter routes.
  • More service to the airport.
  • Free transfers within a two-hour window.
  • New limited-stop buses on the major trunks, branded as Züm.

The bus grid is not especially frequent. The Züm routes have variants and short-turns, with routes every 10-12 minutes on some trunks and every 20-25 on branches and the lower-use trunk lines.

This isn’t the stuff high ridership is made of. Most importantly, this is unlikely to be the stuff higher ridership in Brampton could be made of. The Toronto region is electrifying commuter rail in preparation for frequent all-day service, called the RER. One of Brampton’s stations, Bramalea, will get 15-minute rail frequency all day; but Brampton Station itself, at the intersection of the two main Züm routes, will still only have hourly midday service. With fast service to Toronto, the most important thing to do with Brampton buses is to feed the RER (and get the RER to serve Downtown Brampton frequently), with timed transfers in Downtown Brampton if possible.

The express buses are specifically more useful for low-transit cities than for high-transit ones. In low-transit cities, the travel market for transit consists of poor people, and commuters who want to avoid peak traffic. Poor people benefit from long transfer windows and from a grid network, whereas commuters only ride at rush hour and only to the most congested areas; in Brampton, where city center doesn’t amount to much, this underlies the express bus to the airport, and the trains that run to Downtown Toronto today.

The marginal rider in Brampton today is either a working-class immigrant who can’t afford Toronto, or a car-owning commuter who drives everywhere except the most congested destinations, such as Downtown Toronto at rush hour, or the airport. Brampton has catered to these riders, underlying fast bus ridership growth. But they’re not enough to lead to transit revival.

Bus grids

The value of a bus grid in which passengers are expected to transfer to get to many destinations rises with the frequency of the trunk lines. In Vancouver and Toronto, the main grid buses come every 5-10 minutes off-peak, depending on the route, and connect to subway lines. Waiting time is limited compared with the 15-minute grids common in American Sunbelt cities with bus network redesigns, such as San Jose and Houston.

The difference between waiting 15 minutes and waiting 7.5 minutes may seem like a matter of degree and not of kind, but compared with bus trip length, it is substantial. Buses are generally a mode of transportation for short trips, because they are slow, and people don’t like spending all day traveling. The average unlinked bus trip in Houston is 24 minutes according to the National Transit Database. In San Jose, it’s 27 minutes. Breaking one-seat rides into two-seat rides, with the bus schedules inconsistent (“show up and go”) and the connections not timed, means that on many trips the maximum wait time can be larger than the in-vehicle travel time.

The other issue coming from scale is that frequent bus network don’t work in sufficiently large cities. Los Angeles can run frequent bus lines on key corridors like Vermont and Western and even them them dedicated lanes, but ultimately it’s 37 km from San Pedro to Wilshire and an hourly bus on the freeway will beat any frequency of bus on an arterial. There’s a maximum size limit when the bus runs at 20 km/h in low-density cities (maybe 30 in some exceptional cases, like low-density areas of Vancouver with not much traffic and signal priority), and cars travel at 80 km/h on the freeway.

This has strong implications to the optimal design of bus networks even in gridded cities. In environments without grids, like Boston, I think people understand that buses work mostly as rail feeders (it helps that Boston’s public transit is exceptionally rail-centric by the standards of other US cities with similar transit use levels, like Chicago or San Francisco). But in sufficiently large cities, buses have to work the same way even with grids, because travel times on surface arterials are just too long. The sort of grid plan that’s used for buses in Chicago and Toronto is less useful in the much larger Los Angeles Basin.