Category: Regional Rail

West Station is an Overbuilt Mess

Boston has been on a commuter rail infill binge lately; it has opened four stations on the Fairmount Line this decade, with general success, and is now eying the Worcester Line, where the MBTA has already opened a single in-city station called Boston Landing. The next station to be opened is called West Station, serving Allston, a middle-class urban neighborhood home to Boston University. Unfortunately, the West Station project has suffered from budget and schedule overruns: the current projection is $90 million, where past stations in the area have opened for about $15-25 million each, and construction will start next decade and only wrap up by 2040.

The cause of the extreme cost is poor design. The station as currently proposed is an overbuilt mess. It is development-oriented transit, sited next to an area that Harvard wishes to redevelop as a new campus, and the compromises made between good rail service, intermodal bus-rail connections, and encouraging development make the project fail at all of its objectives. The idea of an infill station in Allston is solid and the MBTA should keep working on the project, but it should do it right – that is, maximize passenger utility while also slashing the budget by a factor of about 4.

I encourage readers to look at a presentation about the status of the project from May, and at another presentation from June, which was sent to members of the media and neighborhood.

Intermodal integration done wrong

The West Station site is roughly in the center of the new development. Unfortunately, it is poorly-located relative to the street network. With its hierarchy of major and minor streets, Boston is not forgiving to wrong station siting: buses would have to meander to reach the site.

The busiest bus in the area, and among the busiest in the region, is the 66. See image below:

The Red and Green Lines of the subway are in their respective colors (and the Green Line’s branches are surface light rail), the Worcester Line is in purple with its existing stations marked alongside the proposed West Station site, and the 66 bus is in black. The dashed purple line is the disused Grand Junction Railroad – see below for more explanation.

North of the West Station site, the bus could still reach the platforms relatively easily, as the plan includes mapping new streets over the entire site. But to the south, the streets are narrow and practically unusable. All north-south through-traffic is funneled through Harvard Avenue – anything else would meander at speeds not much higher than that of walking.

What’s more, the zigzag in the image above comes from a detour to the center of Allston, called Union Square. The West Station site would move service farther away from Union Square, forcing it to either abandon its single busiest stop or have a more circuitous route. Serving both West Station and Union Square requires running two separate north-south bus routes sharing much of their southern legs, which is bad for frequency. Already the 66 runs every 10 minutes off-peak in one direction and every 14 in the other; this is worse than the minimum acceptable on such a key route, and any further reduction in frequency through route splitting is unacceptable.

Finally, the station design as shown in the presentations includes ample room for bus bays, so that buses can terminate at the station. Such a layout may be appropriate at the center of a small town with timed bus-rail transfers; in the middle of the city, it is pointless. The 66 crosses the rail tracks and has no use for terminal berths. Nor is there any need for terminating buses running parallel to the tracks – passengers could walk to another train station on the Worcester Line or on the Green Line.

The MBTA has never released any public plan for a bus redesign around West Station. It talks about intermodal transfers but refuses to give any details, and it’s likely these details don’t even exist yet. There are occasional excuses, such as intercity buses (why would they terminate there instead of continuing to South Station?), buses to Kendall Square (they don’t need bus bays either), and buses to Longwood (Longwood is south of the Worcester Line and would be better-served by a commuter rail-to-Green Line transfer near Fenway Park).

Track design for maximum conflict

The latest option for West Station is called the flip option. The diagrams below are from the June presentation, pp. 8-10, going west to east:

There are to be two bypass tracks (“WML Express”), located where the current mainline is. There are also to be three tracks with station access, both on the other side of the railyard. The tracks serving the platforms cross the bypass tracks in a flat junction, forcing dependency between the inbound and outbound schedule. The flat junction is not especially quick, either – it is a long ladder track, requiring inbound local trains to South Station to make two slow diverging moves in succession.

The MBTA is planning to spend tens of millions of dollars on station platforms in Newton turning the line into full double-track all the way from Boston to Worcester, freeing the schedule from such dependency, but at the same time it’s planning to add new conflicts.

While the diagrams label two tracks as freight tracks, there is little to no freight on that portion of the line. A freight rail spur in the area, serving Houghton Chemical, was just removed in preparation for the project. The line can and should be designed exclusively around the needs of regional passenger trains, for which the most important thing is continuous operation of double track, preferably with no flat junctions with oncoming traffic, and not any ancillary frills.

The Grand Junction tangential

The MBTA has grandiose plans to use the Grand Junction Railroad to allow trains from Allston and points west to avoid South Station entirely. The Grand Junction provides a bypass to the west of Downtown Boston, which currently sees no passenger service but is used for non-revenue moves between the South Station and North Station networks. There are periodic plans to reactive service so as to enable trains from the west to serve Cambridge and North Station instead. In the flip option, all local trains are required to go to the Grand Junction or switch back to the mainline using the ladder track.

Consult the following table, sourced to OnTheMap, for the number of jobs accessible within walking distance of the various station sites:

Station Walkshed boundaries Jobs
South Station Essex, Tremont, State, the harbor 119,191
Back Bay Hereford, Belvidere, Columbus, Arlington, Storrow 62,513
Kendall Binney, Third, Wadsworth, Memorial, Mass Ave, Windsor, Bristol 29,248
North Station Blossom, Cambridge, State, Prince, the river 33,232

Jobs accessible on the existing mainline outnumber ones accessible via the Grand Junction by a factor of about three. It is not technically sound to avoid city center on an urban rail line, much less a suburban one. Only if the line is a consistent circumferential line is there a good reason to go around the center.

A far-future subway duplicating the 66 route may succeed. The same may be true of a shuttle using the Grand Junction, but such shuttle may well need extensive new track – West Station is not necessarily the best south-of-Charles footprint (turning east toward BU to form a loop with a future North-South Rail Link is better). In contrast, the current plan for diversion of Newton trains toward a secondary job center and away from Downtown Boston has no chance of getting substantial ridership.

The railyard as an obstacle

For a project so focused on redevelopment, West Station does not do a good job encouraging construction in the area. It plans to keep the railyard in the middle, and even forces local and express trains to go on opposite sides of it. But the railyard is an obstacle not only to sound railway operations but also to redevelopment.

Building anything over rail tracks is complicated. New York supplies a few such examples: the link mentions the difficulties of Atlantic Yards, and to that I will add that the construction of the Hudson Yards towers cost around $12,000/m^2, compared with $3,000-6,000 for Manhattan supertall office towers on firma. Hudson Yards has managed to be financially successful, albeit with tax breaks, but it’s located right outside Midtown Manhattan. Allston’s location is not so favored. The cost penalty of building over railyards is likely to make air rights unviable.

There is still an extensive portion of the site that’s on firma. However, if the point is to maximize redevelopment potential, the city and the state must discard any plans for air rights. The railyard should go in order to increase the buildable area.

In lieu of parking at a railyard in a desirable near-center location, trains should circulate back and forth between Boston and Worcester. The MBTA keeps saddling itself with capital costs because it likes running trains one-way to Downtown Boston in the morning and then back to the suburbs in the afternoon, parking them near South Station midday. This is bad practice – trains are not just for suburban salarymen’s commutes. Urban infill stations in particular benefit from high all-day frequency and symmetric service. If the MBTA needs space for train parking, it should sell the railyard in Allston and charge Allston land prices, and instead buy space in Framingham and Worcester for Framingham and Worcester land prices.

West Station, done right

Thanks to delays and cost overruns, West Station is still in preliminary design. There is plenty of time to discard the flip option as well as the original plan in favor of a route that maximizes intermodal connections at minimum cost. A better West Station should have all of the following features:

  • A simple four-track design, either with two stopping tracks and two bypass tracks or four stopping tracks and two island platforms, depending on long-term plans for train timetables
  • High design speed, as high as the rest of the line for nonstop trains, as the tracks are straight and do not require any speed restriction
  • Retention of double-track rail service throughout construction, even at the cost of more disruption to the Massachusetts Turnpike
  • No at-grade conflicts in opposing directions: tracks should go slow-fast-fast-slow or fast-slow-slow-fast rather than slow-slow-fast-fast
  • No bus bays: crosstown buses (that is, the 66) should stop on the street crossing the station right above the tracks, with vertical circulation directly from the bus stop to the platform in order to minimize transferring time
  • Subject to site availability, platforms reaching Cambridge Street for a connection to the present-day 66 and a shorter walk to Union Square
  • Elimination of the railyard to make more room for development, and if the line needs more yard space, then the state should find cheaper land for it in Framingham and Worcester

There is no reason for such a project to cost more than past infill stations built in Boston, which have cost around $15-25 million, about the same range as Berlin. By removing unnecessary scope, the MBTA can make West Station not only cheaper and easier to build but also more useful for passengers. The idea of an infill commuter rail station in Allston is good and I commend the MBTA for it, but the current plan is overbuilt and interferes with good rail and bus operations and needs to be changed immediately, in advance of engineering and construction.

Assume Nordic Costs: London Edition

A month ago I made maps proposing some subway and regional rail extensions in New York and noting what they would cost if New York could build as cheaply as the Scandinavian capitals. Here is the same concept, but with London rather than New York. Here is everything in a single large map:

A full-size (74 MB) map can be viewed here.

Solid lines are existing or under construction, that is Crossrail and the Battersea extension; proposed lines are dashed. Commuter rail lines, that is Thameslink, the soon-to-open Crossrail, and four additional Crossrail tunnels labeled 2 through 5, are always depicted as having separate stations from the other modes, to avoid confusion where one Crossrail station has connections to two adjacent Tube stations (such as Farringdon-Barbican and Moorgate-Liverpool Street). It has many additional interchanges between lines and branches, including some that were left out on purpose, like a Crossrail 1 connection to Oxford Circus, omitted from the under-construction line to discourage riders from using the oversubscribed Victoria line; with four more cross-city lines, the capacity problems would be lessened substantially.

The overall picture is sparser than my New York map. The total projected cost of all of these projects, including some allocated for redoing stations on commuter branches to be given to Tube lines, is £6.8 billion, compared with $37 billion for the New York maps. The reason is that unlike New York, London already has excellent coverage thanks to extensive branching – what it needs is core capacity, which consists of city center tunnels that have high cost per kilometer but need not be long.

There is considerable overbuilding planned in London. Crossrail 2 as depicted on my map is a 6.5 km tunnel between the approach to Victoria Station and the approach to Kings Cross. But as planned, Crossrail 2 extends to a long tunnel parallel to the South West Main Line, a four-track line in a right-of-way that could if truly necessary accommodate six, as well as a long tunnel going north to take over the Lea Valley Lines, which on my map go into Crossrail 5. With gratuitous suburban tunnels and extremely high British construction costs, the budget for Crossrail 2 is around £30 billion, about 20 times what Scandinavia might spend on such a project. Even allowing for the possibility that crossing under three lines at once at Bank is more complex than crossing under two at T-Centralen, this is a difference of a full order of magnitude, counting both total required tunnel length and cost per km.

In addition, there is network simplification. On the Tube this consists of segregating the Northern line’s Bank and Charing Cross branches (already in planning pending the Battersea extension and reconstruction of Camden Town) and through breaking the Circle line into separate Metropolitan and District lines. The latter was estimated by a British blogger to cost £5 billion, based on a rubric in which the Met/District transfer at Aldgate (or Tower Hill) should by itself cost £1 billion; Crossrail and Second Avenue Subway stations cost around half that much, and the more complex T-Centralen and Odenplan stations on Citybanan cost less.

On mainline rail, the service plan is supposed to be deinterlined, as is Transport for London’s long-term goal. The slow tracks of the various mainlines feeding into Central London turn into Crossrail branches, or occasionally Underground extensions, such as Hayes and the Hounslow Loop. The fast tracks stay on the surface to avoid interfering with high-frequency regional metro service. For historic reasons Thameslink mostly stays as-is, with a combination of fast and stopping services, but the curve toward London Bridge should not be used – instead, passengers should have access to Crossrail 3 plus interchanges to the City at London Bridge and a new infill station at Southwark.

London owes it to itself to understand why its construction costs are so high that instead of solving its transport capacity problems with multiple cross-city tunnels in a decade, it’s taking multiple generations to build out such a system. There’s a lot of ongoing discussion about the last-minute delays and cost overruns on Crossrail, but the absolute costs even before the overrun were very high, the highest in the world outside New York City – and Crossrail 2 is set to break that record by a margin.

Assume Nordic Costs

I wrote a post last year proposing some more subway lines for New York, provided the region could bring down construction costs. The year before, I talked about regional rail. Here are touched-up maps, with costs based on Nordic levels. To avoid cluttering the map in Manhattan, I’m showing subway and regional rail lines separately.

A full-size 52 MB version of the subway map can be found here and a 52 MB version of the regional rail map can be found here.

Subways are set at $110 million per km underground, outside the Manhattan core; in more difficult areas, including underwater they go up to $200-300 million per km, in line with Stockholm Citybanan. Lacking data for els, I set them at $50 million per km, in line with normal subway : el cost ratios. The within-right-of-way parts of Triboro are still set at $20 million per km (errata 5/30: 32 out of 35 km are in a right-of-way and 3 are in a new subway, despite what the map text says, but the costs are still correct).

Overall, the subway map costs $22 billion, and the regional rail one $15 billion, about half as high as the figure I usually quote when asked, which is based on global averages. This excludes the $2 billion for separated intercity rail tracks, which benefit from having no stations save Penn (by the same token, putting the express rather than local lines in the tunnel is a potential cost saving for Crossrail 2). It also excludes small surface projects, such as double-tracking the Northern Branch and West Shore Line, a total of 25 and 30 km respectively, which should be $300-550 million in total, and some junction fixes. There may also be additional infill stations on commuter rail, e.g. at intersection points with new subway extensions; I do not have Nordic costs for them, but in Madrid they cost €9 million each.

The low cost led me to include some lines I would not include elsewhere, and decide marginal cases in favor of subways rather than els. There is probably no need for the tunnel connecting the local tracks of Eighth Avenue and Fulton Street Lines, but at just $1.2 billion, it may be worth it. The line on Northern Boulevard and the Erie Main Line should probably be elevated or in a private right of way the entire way between the Palisades and Paterson, but at an incremental cost of $60 million per km, putting the Secaucus and East Rutherford segments underground can be justified.

In fact, the low cost may justify even further lines into lower-density areas. One or two additional regional rail tunnels may be cost-effective at $300 million per kilometer, separating out branches like Port Washington and Raritan Valley and heading to the airports via new connections. A subway line taking over lanes from the Long Island Expressway may be useful, as might another north-south Manhattan trunk feeding University Avenue (or possibly Third Avenue) in the Bronx and separating out two of the Brighton Line tracks. Even at average costs these lines are absurd unless cars are banned or zoning is abolished, but at low costs they become more interesting.

The Nordic capitals all have extensive urban rail networks for their sizes. So does Madrid: Madrid and Berlin are similar in size and density, but Berlin has 151 km of U-Bahn whereas Madrid has 293 km of metro, and Madrid opened a second Cercanías tunnel in 2008 for around $100 million per km and is planning a third tunnel for next decade (source, PDF-pp. 104-108). Things that are completely ridiculous at American costs – say, any future subway expansion – become more reasonable at average costs; things that are completely ridiculous at average costs likewise become more reasonable at Nordic or Spanish costs.

Amtrak is Blocking MBTA Electrification

Ten years ago, Amtrak began putting out its outrageously expensive proposals for high-speed rail on the Northeast Corridor. Already then, when it asked for $10 billion to barely speed up trains, there was a glaring problem with coordination: Amtrak wanted hundreds of millions of dollars to three-track the Providence Line so that its trains could overtake the MBTA’s commuter trains between Providence and Boston, even though the same benefit could be obtained for cheaper by building strategic overtakes and electrifying the MBTA so that its trains would run faster. Unfortunately, Amtrak has not only displayed no interest in coordinating better service with the MBTA this way, but has just actively blocked the MBTA.

The issue at hand is MBTA electrification: the MBTA runs an exclusively diesel fleet. These trains are slow, polluting, and unreliable. Lately they have had breakdowns every few thousand kilometers, whereas electric trains routinely last multiple hundreds of thousands of kilometers between breakdowns. The current scheduled trip time between Boston and Providence is about 1:10 on the MBTA with a total of nine stops, whereas Amtrak’s southbound trains do the same trip in 35 minutes with three stops, leading to a large schedule difference between the trains, requiring overtaking. Fortunately, modern electric multiple units, or EMUs, could make the same stops as the MBTA in about 45 minutes, close enough to Amtrak that Amtrak could speed up its trains without conflict.

The MBTA would benefit from electrification without any reference to Amtrak. Connecting Boston and Providence in 45 minutes rather than 70 has large benefits for suburban and regional travelers, and the improved reliability means trains can follow the schedule with fewer unexpected surprises. The line is already wired thanks to Amtrak’s investment in the 1990s, and all that is required is wiring a few siding and yard tracks that Amtrak did not electrify as it does not itself use them. With the diesel locomotives falling apart, the MBTA has begun to seriously consider electrifying.

Unfortunately, the MBTA has made some questionable decisions, chief of which is its attempt to procure electric locomotives rather than self-propelled EMUs. The MBTA’s reasoning is that EMUs require high platforms, which cost about $10 million per station, which is a small but nonzero amount of money on the Providence Line. As a result, it neglected any solution involving buying new EMUs or even leasing them from other railroads for a pilot project. It’s only looking at electric locomotives, whose travel time benefits are about half as large as those of EMUs.

And yet, Amtrak is blocking even the half-measures. The MBTA sought to lease electric locomotives from Amtrak, which uses them on its own trains; Amtrak quoted an unreasonably high monthly price designed to get the MBTA to lose interest. As of last week, the MBTA put the plan to lease electric locomotives for its electrification pilot on hold. No plans for purchase of rolling stock are currently active, as the MBTA is worried about lead time (read: having to actually write down and execute a contract) and does not know how to buy lightly-modified European products on the open market.

As far as Amtrak is concerned, speeding up the MBTA is not really relevant. Yes, such a speedup would improve Amtrak’s own scheduling, removing a few minutes from the Northeast Corridor’s travel time that would otherwise cost hundreds of millions of dollars. But Amtrak has time and time again displayed little interest in running fast trains. All it wants is money, and if it can ask for money without having to show anything for it, then all the better. Coordinating schedules with other railroads is hard, and only improves the experience of the passengers and not Amtrak’s managers.

The MBTA’s decisionmaking is understandable, in contrast, but still questionable. It was worth asking; the MBTA is no worse for having received an unreasonable offer. However, it is imperative that the MBTA understand that it must be more proactive and less hesitant. It must electrify, and commit a real budget to it rather than a pilot. This means immediately raising the platforms on the stations of the Providence Line that do not yet have level boarding and buying (not leasing) modern EMUs, capable of running fast schedules.

Even with some infill, there are only seven low-platform stations on the mainline and two on the branch to Stoughton, none in a constrained location where construction is difficult. This is at most a $100 million project, excluding the trains themselves. The MBTA could operate the Providence Line with seven to eight trainsets providing service every 15 minutes and the Stoughton Line with another four providing the same. Procuring trains for such service would cost another $250 million or so, but the MBTA needs to buy new rolling stock anyway as its diesel locomotives are past the end of their useful lives, and buying EMUs would pay for itself through higher ridership and lower operating expenses coming from much faster trips.

The MBTA is fortunately salvageable. It has a serious problem in that the state leadership is indecisive and noncommittal and prefers a solution that can be aborted cheaply to one that provides the best long-term financial and social return on investment. However, it is seriously looking in the right direction, consisting of better equipment providing higher-quality service to all passengers.

Amtrak is unfortunately not salvageable. An intercity railroad whose reaction to a commuter railroad’s attempt to improve service for both systems is to overcharge it on rolling stock proves that it is ignorant of, indifferent to, and incurious about modern rail operations. A chain of managers from the person who made the decision to offer the MBTA bad lease terms upward must be removed from their positions if there is any hope for improved intercity rail in the Northeastern United States.

Optimization

This post may be of general interest to people looking at optimization as a concept; it’s something I wish I’d understood when I taught calculus for economics. The transportation context is network optimization – there is a contrast between the sort of continuous optimization of stop spacing and the discrete optimization of integrated timed transfers.

Minimum and maximum problems: short background

One of the most fundamental results students learn in first-semester calculus is that minimum and maximum points for a function occur when the derivative is zero – that is, when the graph of the function is flat. In the graph below, compare the three horizontal tangent lines in red with the two non-horizontal ones:

A nonzero derivative – that is, a tangent line slanting up or down – implies that the point is neither a local minimum nor a local maximum, because on one side of the point the value of the function is higher and on the other it is lower. Only when the derivative is zero and the tangent line is flat can we get a local extreme point.

Of course, a local extreme point does not have to be a global one. In the graph above, there are three local extreme points, two local maxima and one local minimum, but only the local maximum on the left is also a global maximum since it is higher than the local maximum on the right, and the local minimum is not a global minimum because the very left edge of the graph dips lower. In real-world optimization problems, the global optimum is one of the local ones, rather than an edge case like the global minimum of the above graph.

First-semester calculus classes love giving simplified min/max problems. This class of problems is really one of two or three serious calc 1 exercises; the other class is graphing a function, and the potential third is some integrals, at universities that teach the basics of integration in calc 1 (like Columbia and unlike UBC, which does so in calc 2). There’s a wealth of functions that are both interesting from a real-world perspective and doable by a first-semester calc student, for example maximizing the volume of some shape with prescribed surface area.

My formulas for stop spacing come from one of these functions. The overall travel time is a function of walking time, which increases as stops get farther apart, and in-vehicle time, which decreases as stops get farther apart. A certain stop spacing produces the minimum overall trip time; this is precisely the global minimum of the travel time function, which is ultimately of the form f(x) = ax + b/x where a and b are empirical parameters depending on walking speed and other relevant variables.

Continuous optimization

The fundamental fact of continuous optimization, one I wish I’d learned in time to teach it to students, is that at the optimum the derivative is zero, and therefore making a small mistake in the value of the optimum is not a big problem.

What does “mistake” mean in this context? It does not mean literally getting the computation wrong. There is no excuse for that. Rather, it means choosing a value that’s slightly suboptimal for ancillary reasons – perhaps small discontinuities in the shape of the network, perhaps political considerations.

Paul Krugman brings this concept up in the context of wages. The theory of efficiency wages asserts that firms often pay workers above the bare minimum required to get any workers at all, in order to get higher-quality workers and incentivize them to work harder. In this theory, the wage level is set to maximize employer productivity net of wages. At the employer’s optimum the derivative of profit is by definition zero, so a small change in wages has little impact to the employer. However, to the workers, any wage increase is good, as their objective function is literally their wage rather than profits. They may engage in industrial action to raise wages, or push for favorable regulations like a high minimum wage, and these will have a limited effect on profits.

In the context of transit, this has the obvious implication to wages – it’s fine to set them somewhat above market rate since the agency will get better workers this way. But there are additional implications to other continuous variables.

With stop spacing specifically, the street network isn’t perfectly continuous. There are more important and less important streets. Getting transit stops to align with major streets is important, even if it forces the stop spacing to be somewhat different from the optimum. The same is true of ensuring that whenever two transit lines intersect, there is a transfer between them. This is the reason my bus redesign for Brooklyn together with Eric Goldwyn involved drawing the map before optimizing route spacing – the difference between 400 and 600 meters between bus stops is not that important. For the same reason, my prescription for Chicago, and generally other American cities with half-mile grids of arterial roads, is a bus stop every 400 meters, to align with the grid distance while still hewing close to the optimum, which is about 500.

When I talked about stop consolidation with a planner at New York City Transit who worked on the Staten Island express bus redesign, the planner explained the philosophy to me: “get rid of every other stop.” In the context of redesigning a single route, this is an excellent idea as well: the process of adding and removing bus stops in New York is not easy, so minimizing the net change by deleting stops at regular intervals so as to space the remaining stops close to the optimum is a good idea.

The world of public transit is full of these tradeoffs with continuous variables. It’s not just wages and interstations. Fares are another continuous variable, involving particular tensions as different political factions have different objective functions, such as revenue, social rate of return, and social rate of return for the working class alone. Frequency is a continuous variable too in isolation. Top speed for a regional train is in effect a continuous variable. All of these have different optimization processes, and in all cases, it’s fine to slightly deviate from the strict optimum to fulfill a different goal.

Discrete optimization

Whereas continuous optimization deals with flat tangent lines, discrete optimization may deal with delicate situations in which small changes have catastrophic consequences. These include connections between different lines, clockface scheduling, and issues of integration between different services in general.

An example that I discussed in the early days of this blog, and again in a position paper I just wrote to some New Hampshire politicians, is the Lowell Line, connecting Boston with Lowell, a distance of 41 km. The line is quite straight, and were it electrified and maintained better, trains could run at 160 km/h between stops with few slowdowns. The current stop spacing is such that the one-way trip time would be just less than half an hour. The issue is that it matters a great deal whether the trip time is 25 or 27 minutes. A 25-minute trip allows a 5-minute turnaround, so that half-hourly service requires just two trainsets. A 27-minute trip with half-hourly service requires three trainsets, each spending 27 minutes carrying passengers and 18 minutes depreciating at the terminal.

A small deterioration in trip time can literally raise costs by 50%. It gets to the point that extending the line another 50 kilometers north to Manchester, New Hampshire improves operations, because the Lowell-Manchester trip time is around 27-28 minutes, so the extension can turn a low-efficiency 27-minute trip into a high-efficiency 55-minute trip, providing half-hourly service with four trainsets.

In theory, frequency is a continuous variable. However, in the range relevant to regional rail, it is discrete, in fractions of an hour. Passengers can memorize a half-hourly schedule: “the inbound train leaves my stop at :10 and :40.” They cannot and will not memorize a schedule with 32-minute frequency, and needing to constantly consult a trip planner will degrade their travel experience significantly. Not even smartphone apps can square this circle. It’s telling that the smartphone revolution of the last decade has not been accompanied with rapid increase in ridership on transit lines without clockface schedules, such as those of the United States – if anything, ridership has grown faster in the clockface world, such as Germany and Switzerland.

Transit networks involving timed connections are another case of discrete optimization in which all parts of the network must work together, and small changes can make the network fall apart. If a train is late by a few minutes and its passengers miss their connection, the short delay turns into a long one for them. As a result, conscientious schedule planners make sure to write timetables with some contingency time to recover from delays; in Switzerland this is 7%, so in practice, out of every 15 minutes, one minute is contingency, typically spent waiting at a major station.

But this gets even more delicate, because different aspects of the transit network impact how reliable the schedule is. If it’s a bus, it matters how much traffic there is on the line. Buses in traffic not reliable enough for tight connections, so optimizing the network means giving buses dedicated lanes wherever there may be traffic congestion. Even though it’s a form of optimization, and even though there’s a measure of difficulty coming from political opposition by drivers, it is necessary to overrule the opposition, unlike in continuous cases such as wages and fares.

Infrastructure planning for rail has the same issues of discrete optimization. It is necessary to design complex junctions to minimize the ability of one late train to delay other trains. This can take the form of flying junctions or reducing interlining; in Switzerland there are also examples of pocket tracks at flat junctions where trains can wait without delaying other trains behind them. Then, the decision of how much to upgrade track speed, and even how many intermediate stations to allow on a line, has to come from the schedule, in similar vein to the Lowell Line’s borderline trip time.

Continuous and discrete optimization

Many variables relevant to transit are in theory continuous, such as trip time, frequency, stop spacing, wages, and fares. However, some of these have discontinuities in practice. Stop spacing on a real-world city street network must respect the hierarchy of more and less important destinations. Frequency and trip times are discrete variables except at the highest intensity of service, perhaps every 7.5 minutes or better; 11-minute frequency is worse to the passenger who has to memorize a difficult schedule than either 10- or 12-minute frequency.

New York supplies a great example showcasing how bad it can be to slavishly hew to some optimal interstation and not consider the street network. The Lexington Avenue Line has a stop every 9 blocks from 33rd Street to 96th, offset with just 8 blocks between 51st and 59th and 10 between 86th and 96th. In particular, on the Upper East Side it skips the 72nd and 79th Street arterials and serves the less important 68th and 77th Streets instead. As a result, east-west buses on the two arterials cross Lexington without a transfer.

Just east of Lex, there is also a great example of optimization on Second Avenue Subway. The stops on Second Avenue are at 72nd, 86th, and 96th, skipping 79th. It turns out that skipping 79th is correct – the optimum for the subway is to the meter the planned stop spacing for the line between 125th and Houston Streets, so it’s okay to have slightly non-uniform stop spacing to make sure to hit the important east-west streets.

Frequency and trip times are subject to the Swiss maxim, run trains as fast as necessary, not as fast as possible. Hitting trip times equal to an integer or half-integer number of hours minus a turnaround time has great value, but small further speedups do not. Passengers still benefit from the speedup, but the other benefits of higher speed to the network, such as better connections and lower crew costs, are no longer present.

The most general rule here is really that continuous optimization tolerates small errors, whereas discrete optimization does not. Therefore, it’s useful to do both kinds of optimization in isolation, and then modify the continuous variable somewhat based on the needs of the discrete one. If you calculate and find that the optimal frequency for your bus or train is once every 16 minutes, you should round it to 15, based on the discrete optimization rule that the frequency should be a divisor of the hour to allow for clockface timetable. If you calculate and find that the optimal bus stop spacing is 45% of the distance between two successive arterial streets, you should round it to 50% so that every arterial gets a bus stop.

Getting continuous optimization right remains important. If the optimal stop spacing is 500 meters and the current one is 200 meters, the network is so far from the local maximum of passenger utility that the derivative is large and stop consolidation has strong enough positive effects to justify overruling any political opposition. However, it is subsequently fine to veer from the optimum based on discrete considerations, including political ones if removing every 1.7th bus stop is harder than removing every other stop. Close to the local maximum or minimum, small changes really are not that important.

Circles

Rail services can be lines or circles. The vast majority are lines, but circles exist, and in cities that have them they play an important niche. Owing to an overreaction, they are simultaneously overused and underused in different parts of the world. However, that some places overuse circles does not mean that circles are bad, nor does it mean that specific operational problems in certain cities are universal.

In particular, what I think of as the ideal urban rapid transit network should feature circles once the network reaches a certain scale, as in the following diagram that I use as my Patreon avatar:

Circles and circumferentials

Circles are transit lines that run in a loop without having a definitive start or end. Circumferentials are lines that go around city center, connecting different branches without passing through the most congested part of the city. In the ideal diagram above, the purple line is both a circle and a circumferential. However, lines can be one without being the other, and in fact examples of lines that are only one of the two outnumber examples of lines that are both.

For example, here is the Paris Metro:

Paris has a circle consisting of Metro Lines 2 and 6, which are operationally lines; people wishing to travel on the arcs through the meeting points at Nation and Etoile must transfer. Farther out, there is an incomplete circle consisting of Tramway Line 3, where the forced transfer between 3a and 3b is Porte de Vincennes. Even farther out there is an under-construction line not depicted on the map, Line 15 of Grand Paris Express, which has a pinch point at its southeast end rather than continuous circular service. All three systems are great example of circumferential lines with very high ridership that are not operationally circles.

Another rich source of circumferential lines that are not circles is cities near bodies of water. In those cities, a circumferential line is likely to be a semicircle rather than a circle. This is responsible for the current state of the Singapore Circle Line, although in the future it will be closed to form a full circle. The G train in New York is a single-sided circumferential line to the east of Manhattan, not linking with anything to the west of Manhattan because of the combination of wide rivers and the political boundaries between New York and New Jersey.

In the opposite direction – circles that are not circumferentials – there are circular lines that don’t neatly orbit city center. The Yamanote Line in Tokyo is one such example: its eastern end is at city center, so it combines the functions of a north-south radial line with those of a north-south circumferential line connecting secondary centers west of Central Tokyo. London’s Circle Line is no longer operationally a circle but was one for generations, and yet it was never a circumferential – it combined the central legs of two east-west radial mainlines, the Metropolitan and District lines.

We can collect this distinction into a table:

Circle, not circumferential Circumferential, not a circle Circumferential circle
Yamanote Line
Osaka Loop Line
Seoul Metro Line 2
London Circle line (until 2009)
Madrid Metro Line 12
Paris M2/6, T1, T2, T3, future M15
Copenhagen F train
New York G train, proposed Triboro
London Overground services
Chicago proposed Circle Line
Singapore Circle line (today)
Moscow Circle Line, Central Circle
Berlin S41/S42
Beijing Subway Line 2, Line 10
Shanghai Metro Line 4
Madrid Metro Line 6

Operational concerns: the steam era

In the 19th century, it was very common to build circular lines in London. In the steam era, reversing a train’s direction was difficult, so railways preferred to build circles. This was the impetus for joining the Metropolitan and District lines to form the Circle line. Mainline regional rail services often ran in loops as well: these were as a rule never or almost never complete circles, but instead involved trains leaving one London terminus and then looping around to another terminus.

Another city with a legacy inherited from steam-era train operations is Chicago. The Loop was built to easily reverse the direction of trains heading into city center. At the outer ends they would need to reverse direction the traditional way, but there was no shortage of land for yards there, unlike in the Chicago CBD since named after the Loop.

As soon as multiple-unit control was invented in the 1890s, this advantage of circles evaporated. Subsequently rapid transit lines mostly stopped running as circles unless they were circumferential. London’s Central line, originally pitched as two long east-west lines forming a circle, became a single east-west line, on which trains would reverse direction.

Operational concerns: the modern era

Today, it is routine to reverse the direction of a rapid transit train. The vast majority of rapid transit routes run as lines rather than circles.

If anything, there have been complaints that circles are harder to run service on than lines. However, I believe these concerns are all specific to London, which changed its Circle line from a continuous loop to a spiral in 2009. I have heard concerns about the operations of the Ringbahn here, but as far as I can tell the people who express them are doing so in analogy with what happened in London, and are not basing them on the situation on the ground here. Moreover, there are no plans to make the Yamanote Line run as anything other than the continuous loop it is today.

The situation in London is that the Circle line has always shared tracks with both the Metropolitan and District lines. There has always been extensive branching, in which a delay on one train propagates to the entire network formed by these two mainlines. To this day, Transport for London does not expect the lines in the subsurface network to have the same capacity as the isolated deep tube lines: with moving block signaling it expects 32 trains per hour, compared with 36 on isolated lines.

What’s more, the junctions in London are generally flat. Trains running in opposite directions can conflict at such junctions, which makes the schedules more fragile. Until 2009, London ran the Circle line trains every 7 minutes, which was bound to create conflicts with other lines.

The importance of this London-specific background is that the argument against circles is that they make schedules more fragile. If there is no point on the line where trains are regularly taken out of service, then it is hard to recover from timetable slips, and delays compound throughout the day. However, this is relevant mainly in the context of an extensively-branching system like London’s. Berlin has some of that branching as well, but much less so; one of the sources of reverse-branching on the S-Bahn is a line that should get its own cross-city route anyway, and another is a Cold War relic swerving around West Berlin (S8/85).

The benefits of complete circles

The complete circle of the Yamanote Line or the Ringbahn can be compared with incomplete circles, such as the Oedo Line or the various circumferentials in Paris. From passengers’ perspective, it’s better to have a complete circle, because then they can undertake more trips.

Circumferential lines broadly have two purposes:

  1. They offer service on strong corridors that are orthogonal to the direction of city center, such as the various boulevards hosting the M2/6 ring as well as the Boulevards des Maréchaux hosting T3.
  2. They offer connections between two radial lines that may not connect in city center, or may connect so far from the route of the circumferential that transferring via the circumferential is faster.

Both purposes are enhanced when the route is continuous. In the case of Paris, a north-south trip east of Nation is difficult to undertake, as it requires a transfer at Porte de Vincennes. Passengers connecting from just south, on M8 or even on M7, may not save as much time traveling to lines just north, such as M9 or M3, and might end up transferring at the more central stations of Republique or Opera, adding to congestion there.

In contrast, in Berlin the continuous nature of the Ring makes trips across the main transfer points more feasible. Just today I traveled from my new apartment to a gaming event on the Ringbahn across Ostkreuz. At Ostkreuz the trains dwelled longer than the usual, perhaps 2 minutes rather than the usual 30 seconds, which I imagine is a way to keep the schedule. That delay was, all things considered, minor. Had I had to transfer to a new train, I would have almost certainly taken a different combination of trains altogether; the extra waiting time adds up.

Why are circles so uncommon?

The operational concerns of London aside, it’s still uncommon to see complete circles on rapid transit networks. They are the ideal for cities that grow beyond the scale of three or four radial trunks, but there are only a handful of examples. Why is that?

The answer is always some sort of special local concern. If city center is offset to one side of the built-up area, such as in a coastal city, then circumferential lines will be semicircles and not full circles. If there is some dominant transfer point that requires a pinch, then cities prefer to build a pinch into the system, as is the case for Porte de Vincennes on T3 or for some of the lines cobbled together to form the London Overground.

This is similar to the question of missed connections. Public transportation networks must work hard to ensure that whenever two lines meet, they will have a transfer. Nonetheless, missed connections exist in virtually all large rapid transit networks. Some of those are a matter of pure incompetence, but in many, rail networks that developed over generations may end up having one subway line that happens to intersect another far from any station on the older line, and there is little that can be done.

Likewise, it is useful to ensure that circumferential lines be complete circles whenever the city is symmetric enough to warrant circles. Paris, like other big cities with strong transit networks, is good but not perfect, and it is important to call it on the mistakes it makes, in this case building M15 to have a jughandle rather than running as a complete circle.

What Berlin is Building is Not What It Needs to Build

Berlin has a deceptively simple S-Bahn network. There’s the Ringbahn circling city center. There’s the elevated east-west Stadtbahn, which has two tracks dedicated to S-Bahn service and two for everything else, including longer-range regional trains and intercity trains. And there’s the two-track North-South Tunnel, which only carries S-Bahn traffic; longer-range traffic uses the four-track north-south mainline through Berlin Hauptbahnhof, whereas the North-South Tunnel intersects the Stadtbahn one station east of Hauptbahnhof, at Friedrichstrasse.

The main S-Bahn capacity needs in Berlin are east-west; meanwhile, the North-South mainline is underfull, with Wikipedia listing around 7 trains per hour. And yet, Berlin’s big S-Bahn capital project is a new tunnel, dubbed S21, adding yet another north-south track pair through Hauptbahnhof. Fortunately, the project is salvageable, but only if the city and the federal government act quickly, within a few years, to change yet-unbuilt phases to run in the right direction.

Berlin urban rail traffic map

Here is a map of traffic demand on every interstation on the combined Berlin U- and S-Bahn network (source, p. 6):

The numbers are in thousands of passengers per weekday in both directions combined.

The U-Bahn is in blue. It’s a weird-looking network because two lines (U7, running northwest-southeast in the west, and U9, running north-south also in the west) were built in the Cold War to serve West Berlin’s center around Kurfürstendamm, whereas the S-Bahn and the older U-Bahn lines serve the historic center. Since reunification, Germany has made an effort to move the Berlin central business district back to the historic center, and S21 is to reinforce that, serving the western end of Mitte.

Unfortunately, as we see in the green lines, that’s not where the pressing S-Bahn capacity needs are. First, the Stadtbahn is busier than the North-South Tunnel. Second, the busiest branches heading into the city come from the east, with substantially more traffic than from the north and south.

And then there’s the Görlitz Railway. It is the line heading to the southeast, without its own trunk line through the city – it reverse-branches to the two directions of the Ringbahn. Moreover, going north there’s additional reverse-branching, to the Stadtbahn (S9) and around the Ring to the northern branches (S8, S85), with each service running only every 20 minutes. Total traffic across these services is quite high, 107,000 weekday passengers, compared with 144,000 on the Prussian Eastern Railway (S5, S7, S75; S5 is the mainline), 128,000 between the two branches feeding the North-South Tunnel from the south, and 133,000 between the two branches feeding the North-South Tunnel from the north. The brief segment where S9 runs alongside the Ring has 184,000 weekday passengers, the city’s busiest.

S21: what Berlin is actually building

Berlin Hauptbahnhof is a new station. It only opened in 2006, when the North-South Intercity Line opened. The new four-track line has ample capacity for additional S-Bahn traffic, but nonetheless it hosts no S-Bahn trains in regular service. Instead, there are plans for two additional S-Bahn tracks, mostly in tunnel, parallel to the line, with service to Hauptbahnhof:

The map does not show the phasing. The segment from the Ringbahn in the north down to Hauptbahnhof is just about complete, with opening expected soon. The segment from Hauptbahnhof to Potsdamer Platz, which contrary to the map is to be nonstop, is in early stages of construction, and Wikipedia says it is expected to open in 2023.

Farther south of Potsdamer Platz is still not under construction, and frankly should not be built as is. The only real addition this would give to the network is the stop at Gleisdreieck, where the line intersects the east-west U1; the North-South Tunnel intersects U1 without a connection, the only place in the city where there is a missed U-Bahn/S-Bahn connection unless one counts the marginal U9/Stadtbahn miss in which the next station, Zoologischer Garten, is a transfer.

However, the North-South Main Line’s tunnel portal lies just south of Gleisdreieck, and thus it should be feasible if nontrivial to add platforms there for two of the tracks. Farther south, at Yorckstrasse, it is well outside the portal and adding platforms should be fairly easy.

Görlitz Railway S-Bahn: what Berlin should be building

A radial rail network with three lines should aim to have them meet at a triangle in city center. Berlin has two S-Bahn radial lines, and S21 is to add a third. Instead of running parallel to the North-South Tunnel, it should provide a third trunk line. North of Potsdamer Platz the route is already baked in, but farther south, the Görlitz Railway route is a perfect legacy line to link to. It is quite busy, and the likely locations of the intermediate stops between existing infrastructure and Potsdamer Platz are busy U-Bahn stations in their own right.

I was delighted to see this already discussed on the technical transit blog Zukunft Mobilität. It has a long list of potential Berlin rail extensions, some in accordance with current long-term plans, some not. It specifically criticizes S21 for duplicating existing infrastructure, and proposes an extension to the southeast, mentioning that there were plans to that effect in the 1930s. There are two variants, one through Hermannplatz and one through the old route of the Görlitz Railway.

A higher-zoom 11 MB image is available here.

The dashed lines denote under-construction lines, including S21 to Potsdamer Platz, the 4.5-kilometer Siemens Railway to the northwest, and the U5-U55 connection. Dotted lines denote lines I am proposing: either variant connecting S21 toward the southeast, paired with the Siemens Railway as well as two new-build lines through the area of Tegel Airport, which is slated for redevelopment after the Berlin-Brandenburg Airport finally opens. Two branches are depicted toward Tegel, one toward airport grounds to be redeveloped, and one going farther north taking over S25; there are already discussions of a rapid transit line to Tegel, branching off of U6, but this option does not force the outer parts of U6 to contend with reduced frequency.

The two branches should of course not both be built. The main advantage of the southern option is that it hits Hermannplatz, one of the busiest stations in the system: the above diagram of rail ridership shows a large change in U8 demand north and south of the station, and a factsheet from 2010 asserts that it is the second busiest U-Bahn station, closely behind Alexanderplatz. In effect, it functions as an express link from Neukölln to city center. U8 isn’t especially crowded – nothing in Berlin is – but it’s busiest than the North-South Tunnel; this link is at least as justified as the S21 tunnel to the south. This would require about 7 km of tunnel. While S-Bahn tunnels cost more than U-Bahn tunnels, this is deliberately an express line, so keeping costs down to the per-km level of the U5-U55 connection (525 million for 2.2 km) is reasonable, making it a 1.8 billion project or thereabout.

The northern option works differently. It doesn’t hit anything as interesting as Hermannplatz on the way, but it does serve Alt-Treptow, one of the bigger rapid transit deserts inside the Ring. The infill station would also break what is the second or third longest interstation on the Ring. Closer in, it has better coverage in the center – Checkpoint Charlie offers another CBD station in addition to Potsdamer Platz. The cost is more of an open question here. From Görlitzer Bahnhof to Potsdamer Platz it’s about 4 km; east of Görlitzer Bahnhof it’s plausible that the line could reuse the Görlitz Railway’s right-of-way and run elevated, or at worst underground with cut-and-cover. However, the per km cost of the tunnel would be higher, since proportionately more of it is in city center, and it has the same number of stations over shorter length; my vague guess is somewhat less than 1.5 billion.

The Berlin S-Bahn would become a system with three radial lines, meeting at Hauptbahnhof, Friedrichstrasse, and Potsdamer Platz. All reverse-branching would cease: the various branches on the Görlitz Railway, including the existing ones as well as an under-construction one to the airport-to-be, would feed into the S-Bahn trunk, rather than to the Ring or the Stadtbahn. The removal of S25 from the North-South Tunnel would create space for the S8 and S85 services in Pankow to use the North-South Tunnel instead of diverting to the Ring and Görlitz Railway. Potentially, the North-South Tunnel could also be realigned to serve Gleisdreieck, as depicted on the map. Finally, with S9 removed from the Stadtbahn, there would be room to beef up service on S3 and/or end the current practice in which S75 trains from the east stop at Ostbahnhof rather than running through.

Germany isn’t perfect

Writing about North America, I talk a lot about how it can Germanize its regional rail network. But it’s important to understand that while far better than North America, Germany is not perfect. It makes mistakes of many kinds: some involving high construction costs, some involving schedule slips, some involving unnecessary prestige projects. These can mostly be prefaced by “by Continental standards,” though the Berlin-Brandenburg Airport disaster is bad even by the standards of the Anglosphere and its billion-dollars-per-kilometer subways.

The Berlin S-Bahn is a case in point. It has a pretty hefty peak-to-base ratio by German standards – the Ring lines (S41 and S42) run every 5 minutes peak and every 10 off-peak, and a number of other lines have a peak-to-base ratio of 2 as well. It also has a peculiarity in that S75 trains only run east of Ostbahnhof; I can’t tell if there’s a problem with track capacity or demand mismatch, but if it’s the former then it’s strange since peak S-Bahn traffic on the Stadtbahn is only 18 trains per hour (Munich achieves 30 through its central tunnel, with much higher crowding levels), and if it’s the latter then it’s again strange – why not run through to Westkreuz like S5?

S21 is another of these little mistakes. It’s a prestige project on the heels of the construction of Hauptbahnhof, rather than a solution to a transportation need. There are six north-south tracks through Berlin between the S-Bahn and the mainline and they’re not anywhere near capacity; the mind boggles at why anyone would add seventh and eighth tracks before adding fifth and sixth east-west tracks.

Fortunately, the mistake is fixable. Germany’s dragging infrastructure timeline means that there’s often room for modifications to make things more useful. The airport is a lost cause, but S21 is not. From Potsdamer Platz south there’s a good option that adds S-Bahn service exactly where it is needed and simplifies citywide schedules by making it feasible to eliminate reverse-branching. In lieu of building more autobahns, Berlin should commit to building the southeastern extension via Alt-Treptow or Neukölln.

Park-and-Rides (Hoisted from Comments)

My post about the boundary zone between the transit-oriented city and its auto-oriented suburbs led to a lot of interesting discussions in comments, including my favorite thing to hear: “what you said describes my city too.” The city in question is Philadelphia, and the commenter, Charles Krueger, asked specifically about park-and-ride commuter rail stations. My post had mentioned Southeast on the Harlem Line as an interface between commuter rail and the Westchester motorway network, and the natural followup question is whether this is true in general.

The answer is that it’s complicated, because like the general concept of the cars/transit boundary zone, park-and-rides have to be rare enough. If they’re too common, the entire rail system is oriented around them and is not really a boundary but just an extension of the road network. This is the situation on every American commuter rail system today – even lines that mostly serve traditional town centers, like the New Haven Line, focus more on having a lot of parking at the station and less on transit-oriented development. Even some suburban rapid transit lines, such as the Washington Metro, BART, and the recent Boston subway extensions, overuse park-and-rides.

However, that American suburban rail systems overuse such stations does not mean that such stations must never be built. There are appropriate locations for them, provided they are used in moderation. Those locations should be near major highways, in suburbs where there is a wide swath of low-density housing located too far from the rail line for biking, and ideally close to a major urban station for maximum efficiency. The point is to use suburban rail to extend the transit city outward rather than the auto-oriented suburban zone inward, so the bulk of the system should not be car-oriented, but at specific points park-and-rides are acceptable, to catch drivers in suburbs that can’t otherwise be served or redeveloped.

Peakiness and park-and-rides

I’ve harped on the importance of off-peak service. The expensive part of rail service is fixed costs, including the infrastructure and rolling stock; even crew labor has higher marginal costs at the peak than off-peak, since a high peak-to-base ratio requires split shifts. This means that it’s best to design rail services that can get ridership at all times of day and in both directions.

The need for design that stimulates off-peak service involves supportive service, development, and infrastructure. Of these, service is the easiest: there should be bidirectional clockface schedule, ideally with as little variation between peak and off-peak as is practical. Development is politically harder, but thankfully in the main example case, the Northeastern United States, commuter rail agencies already have zoning preemption powers and can therefore redevelop parking lots as high-intensity residential and commercial buildings with walkable retail.

Infrastructure is the most subtle aspect of design for all-day service. Park-and-ride infrastructure tends to be peaky. Whereas the (peakier, more suburban) SNCF-run RER and Transilien lines have about 46% of their suburban boardings at rush hour, the LIRR has 67%, Metro-North 69%, and the MBTA 79%. My linked post explains this difference as coming from a combination of better off-peak service on the RER and more walkable development, but we can compare these two situations with the Washington Metro, where development is mostly low-density suburban but off-peak frequency is not terrible for regional rail. Per data from October 2014, this proportion is 56%, about midway between Transilien and the LIRR.

This goes beyond parking. For one, railyards should be sited at suburban ends of lines, where land is cheap, rather than in city center, where land is expensive and there is no need to park trains midday if they keep circulating. But this is mostly about what to put next to the train stations: walkable development generating a habit of riding transit all day, and not parking lots.

Where parking is nonetheless useful

In response to Charles’ comment, I named a few cases of park-and-rides that I think work well around New York, focusing on North White Plains and Jersey Avenue. There, the parking-oriented layout is defensible, on the following grounds:

  1. They are located in suburban sections where the reach of the highway network is considerable, as there is a large blob of low density, without much of the structure created by a single commuter line.
  2. They are near freeways, rather than arterials where timed connecting buses are plausible.
  3. They are immediately behind major stations in town centers with bidirectional service, namely White Plains and New Brunswick, respectively.

The importance of proximity is partly about TOD potential and partly about train operating efficiency. If the park-and-rides are well beyond the outer end of bidirectional demand, then the trains serving them will be inefficient, as they will get relatively few off-peak riders. A situation like that of Ronkonkoma, which is located just beyond low-ridership, low-intensity suburbs and tens of kilometers beyond Hicksville, encourages inefficient development. Thus, they should ideally be just beyond the outer end, or anywhere between the city and the outer end.

However, if they are far from the outer end, then they become attractive TOD locations. For example, every station between New York and White Plains is a potential TOD site. It’s only near White Plains that the desirability of TOD diminishes, as White Plains itself makes for a better site.

On rapid transit in American suburbia, one example of this principle is the Quincy Adams garage on the Red Line just outside Boston. While the station itself can and should be made pedestrian-friendlier, for one by reopening a gate from the station to a nearby residential neighborhood, there’s no denying the main access to the station will remain by car. Any TOD efforts in the area are better spent on Quincy Center and Braintree, which also have commuter rail service.

Where parking should urgently be replaced by TOD

American suburban rail lines overuse park-and-rides, but there are specific sites where this type of development is especially bad. Often these are very large park-and-ride structures built in the postwar era for the explicit purpose of encouraging suburban drivers to use mainline rail for commuter and intercity trips. With our modern knowledge of the importance of all-day demand, we can see that this thinking is wrong for regional trips – it encourages people to take rail where it is the most expensive to provide and discourages ridership where it is free revenue.

The most important mistake is Metropark. The station looks well-developed from the train, but this is parking structures, not TOD. Worse, the area is located in the biggest edge city in the Northeast, possibly in the United States, possibly in the world. Middlesex County has 393,000 jobs and 367,000 employed residents, and moreover these jobs are often high-end, so that what the Bureau of Economic Analysis calls adjustment for residence, that is total money earned by county residents minus total money earned in the county, is negative (Manhattan has by far the largest negative adjustment in the US, while the outer boroughs have the largest positive one). The immediate area around Metropark and Woodbridge has 46,000 jobs, including some frustratingly close to the station and yet not oriented toward it; it’s a huge missed opportunity for commercial TOD.

In general, edge cities and edgeless cities should be prime locations for sprawl repair and TOD whenever a suburban rail line passes nearby. Tysons, Virginia is currently undertaking this process, using the Silver Line extension of the Metro. However, preexisting lines do not do so: Newton is not making an effort at TOD on the existing Green Line infrastructure, it’s only considering doing so in a part of town to be served by a potential branch toward Needham; and the less said about commuter rail, the better. Mineola and Garden City on Long Island, Tarrytown in Westchester, and every MBTA station intersecting Route 128 are prime locations for redevelopment.

Commuter rail for whomst?

I believe it’s Ant6n who first came up with the distinction between commuter rail extending the transit city into the suburbs and commuter rail extending the suburbs into the city. If the trains are frequent and the stations well-developed, then people from the city can use them for trips into suburbia without a car, and their world becomes larger. If they are not, then they merely exist to ferry suburban drivers into city center at rush hour, the one use case that cars are absolutely infeasible for, and they hem car-less city residents while extending the world of motorists.

Park-and-rides do have a role to play, in moderation. Small parking lots at many stations are acceptable, provided the station itself faces retail, housing, and offices. Larger parking structures are acceptable in a handful of specific circumstances where there is genuinely no alternative to driving, even if the rest of the rail service interfaces with walkable town centers. What is not acceptable is having little development except parking at the majority of suburban train stations.

Stroads and Strails

In 2011, Chuck Marohn of Strong Towns coined the word stroad for a street that functions as a road. Chuck argues that there should be a separation between streets, which are destinations in and of themselves and are to be lined with walkable retail, and roads, which exist to move people between destinations. In contrast, auto-oriented arterials function as both: they are designed for high speed for through-traffic but also have extensive streetside destinations built at automobile scale, hence the portmanteau stroad.

In the last seven years this mentality has become quite popular within online urbanist circles. Unfortunately, it misses why major streets arise in the first place. Moreover, this is not just an issue for cars and car traffic – other modes of transportation want to funnel local and interregional traffic through the same corridors, creating a number of arteries that are in essence strails, like the Berlin S-Bahn. Good planning has to recognize that where people to go through and where people want to go to are often the same, and provide road and rail infrastructure of sufficient size to accommodate.

What is a street, anyway?

The main purpose of a city street is to connect destinations within the city. Major streets routinely form out of trails, post roads, and turnpikes connecting the city with villages that it swallows as it industrializes and grows. Broadway in New York started out as an Indian trail, the Strand grew as a road connecting London with Westminster and had previously been part of an intercity Roman road, Champs Elysees was built as a promenade into the periphery of Paris and gradually filled in with palaces, the Sveavägen/Götgatan axis goes back to the Early Modern era with connections from Stockholm to Roslag to the north and Götland in the south.

Not every street has this intercity or suburban history, but the important ones frequently do. The Manhattan grid was mapped as an entirely urban street network, but the wide north-south avenues were designed for easy access to the Lower Manhattan core from future residential areas. In ungridded cities, usually you can tell which streets are the oldest because they are longer, more continuous, and more commercially developed, and the exceptions come from heavyhanded state planning, like the shift from Rue Saint-Jacques to Boulevard Saint-Michel in Haussmannian Paris.

The importance of through-streets within cities continues even today, and even when cars are not too relevant. People who walk or take transit are likelier to do so on the main streets, and as a result, businesses prefer locating there. In Manhattan there’s even an expression for this: avenue rents versus street rents. In Vancouver, I could walk on any street, but crossing wasn’t any harder on the main streets than on the side streets, and there was more interesting stuff to look at on the main streets; even ignoring zoning, retail would prefer to locate on the main streets because that’s where all the other retail is. There’s a wealth of good restaurants I discovered just by walking next to them, to say nothing of the gaming store on 4th Avenue near MacDonald, which I saw from the bus to UBC.

All of this is magnified in cities that do not have consistent grids, like Paris, Berlin, and even Stockholm. In those cities, zoning does not micromanage use as much as in North America, and yet businesses locate on major streets where possible. Here is a map of the area I live in: the green dot is where I live, and the red dot is a government office I went to last week to register.

Walking east or west, I exclusively use Bernauer Strasse, the street the M10 tramway runs on; walking north or south, I use Brunnen Strasse, which hosts U8. Other streets can function as shortcuts, but with parks and small changes interrupting the grid, they’re less reliable for through-walking. And indeed, they are much quieter and largely residential, with retail mostly at street corners.

The invention of the stroad

The early American roads connected distinct cities, or linked cities with rural hinterlands. Within the cities, they fed preexisting arterial streets. For the most part these arterial streets were fairly wide – they were mapped in the 19th century based on 19th-century design standards, often 30 meters of width, rather than the narrow medieval streets London is famous for – but they still filled with cars fast. Two parking lanes and four moving lanes in a dense city with busy crossings aren’t much. American cities had traffic jams in the 1920s already.

My two go-to references about the history of American roadbuilding – Owen Gutfreund’s 20th-Century Sprawl, and Earl Swift’s The Big Roads – both explain what happened beginning in the 1920s: cities built bypasses. The idea was that the bypasses would segregate through-traffic from urban traffic, separating roads from streets properly.

This never happened. For the same reason preindustrial roads turned into busy streets, bypasses turned into busy auto-oriented streets. Retailers found that the best place to locate was where all the cars were. These bypasses became congested roads themselves, partly due to the induced auto-oriented development and partly due to general growth in car traffic volumes. This trend intensified after WW2, with the freeways leading another cycle of bypasses around congested urban roads becoming congested with urban traffic themselves. Wal-Mart and Carrefour invented the hypermarket in 1962-3, and in the 1960s office space began suburbanizing as well, since traffic conditions were better than in congested city centers.

This is not an obscure history, and Chuck is fully aware of it: among his complaints about stroads is that they reduce the tax base of the city by encouraging retail to decamp for the suburbs. He just fails to follow this through to the logical conclusion: the most intense demand for real estate is near the busiest through-routes. There is no real separation between the street and the road; the best you can do for walkability is run better public transit to the urban core and make sure the roads have street-facing retail rather than front parking lots.

Strails

The principle that the best place for local traffic is where long-distance traffic is is equally true of trains. An intermediate station on an intercity railway sited a convenient commute away from the city will soon fill with suburban travelers. The term commuter itself derives from the discounted commutation tickets American intercity railroads offered regular riders, starting in New York and Boston in the middle of the 19th century.

19th-century railways were not a complex system of branched lines dedicated to regional traffic. Such lines existed, for example the Ligne de Saint-Germain-en-Laye, now part of the RER A, but most of the lines continued onward to long-distance destinations, or had been built with the intention of continuing so. Look at this map of extant London-area railways by year of construction: there aren’t that many branches predating the Late Victorian era, and the branches that do exist tend to be reverse-branches in South London offering service to either a City station like Cannon Street or Blackfriars or a West End station like Victoria. The remainder are loop lines, built to offer four tracks’ worth of capacity on lines that had originally been built with only two, but then both routes filled with local traffic, making it harder to schedule express trains; for an example easily visible on the map, see the Lea Valley lines connecting to Cheshunt.

In contrast with the London loop lines, Prussian State Railways made sure to rebuild the Ringbahn and Stadtbahn to have adequate capacity, that is four tracks, two for local service and two for longer-distance service; the Ringbahn had initially been built with two tracks, but would be expanded to four in the 1880s and 90s. But even here, there are seams. German Wikipedia explains that the Stadtbahn had to take a less desirable route to avoid expensive takings on Leipziger Strasse, and has a winding route with S-curves between Alexanderplatz and Jannowitz Brücke. Moreover, some individual branches only have two tracks even if they are the best intercity routes: the S2 route is the most direct route to Dresden, but with two tracks, heavy local traffic, and only DC electrification, it cannot host intercity trains, and thus intercity trains to Dresden spend 20 minutes out of a 2-hour trip getting around this line.

Berlin at least has the good fortune that four tracks here are enough. Tokyo is so big and strongly-centered that it has ten tracks going south of Tokyo on the Tokaido Line and eight going north on the Tohoku Line, including four for local service, two for Shinkansen service, and two or four for medium-distance express regional trains. Widening railways to serve city centers is expensive, and only done when absolutely necessary, and yet JR East spent considerable money on widening the innermost Tohoku trunk from six to eight tracks.

Even high-speed rail can induce the same development effect as a freeway. It doesn’t have closely-spaced stations, but people might demand stations as a mitigation of construction impact and train noise. The Tohoku Shinkansen diverges from the Tohoku Main Line a few kilometers north of Tokyo, but the local communities demanded local service as well as a mitigation, and as a result Japan National Railways built a four-track line, with two Shinkansen tracks and two local tracks for the Saikyo Line.

Main streets want to be everything

Major streets are the best location for every destination and every mode of transportation. This extends beyond walking. Buses prefer wide streets optimized for higher traffic speed – and the few main streets that are not so optimized, such as the Manhattan crosstown streets (since traffic is optimized for north-south avenue throughput), have buses that win awards for how slow they are. Bicyclists prefer riding on major streets as well, which is why Copenhagen prioritizes bike infrastructure on major streets rather than on side streets – on side streets car traffic is so light and slow that mixed traffic is not so bad, but the desirable through-routes remain the major streets.

The problem is that every mode of transportation requires some piece of the street, whereas street width is finite. Brunnen Strasse is 40 meters wide, and hosts very wide sidewalks including a dedicated path for on-sidewalk cycling, a combination of parallel and angled parking, two moving lanes in each direction, and a generous road median. Even that width does not include dedicated public transit infrastructure: U8 runs underneath the street, leaving the street’s width for sidewalks and roadways.

The same situation occurs on railroads: all uses want the same piece of infrastructure, leading to the usual problems of mixing trains of different speed classes on the same tracks. Freight bypasses are possible, but passenger bypasses are rare – train passengers tend to want to go to the city rather than to some suburb, and unlike cars, trains have prescribed stop patterns. By rail as by road, bigger infrastructure is needed: four tracks for a mixed local and interregional railway, or about 36-40 meters or even more on a main street.

Wide enough streets don’t exist everywhere. New England streets are narrow. Midwestern streets are wider, but at least the one I’m most familiar with, Ann Arbor’s Washtenaw Avenue, is only around 25 meters wide – it only gets up to 40 if one includes setbacks. Road widening would be needed, which is exactly the opposite of what the Strong Towns approach prescribes. Cities this small could mix decent local and intercity rail service on two tracks with timed overtakes, but that would require them to run any passenger rail service to begin with, and to make sure to have enough development near the stations, both residential and commercial, that people would ride the trains.

But on a 30-meter wide street, something has to give. There simply is not enough room for everything. Give pedestrians their 4 or 5 meters of sidewalk in each direction, cyclists their 2 meters of bike lane, and cars their parking lane and two moving lanes, and you’re already at 30-32 meters. You can go with complete streets and reduce the extent of car infrastructure, for example by turning a moving lane per direction into a bus or tram lane, or by getting rid of street parking, but unless you’re in a city with high transit mode share, you’re driving away eyeballs from retailers. Paris can definitely do it, New York and Berlin can do it, even Boston can do it. Can a small American city where planners aspire to run a handful of buses every 15 minutes do it? Probably not.

Corey Johnson’s Report on City Control of the Subway

Yesterday, New York City Council speaker and frontrunner in the 2021 mayoral race Corey Johnson released a document outlining his plan to seek city control of the subway and buses. In addition to the governance questions involved in splitting the state-run MTA between a city-owned urban transit agency and state- or suburb-owned commuter rail, it talks about what Johnson intends to do to improve public transit, befitting a mayor in full control of subway and bus operations. There are a lot of excellent ideas there, but also some not so good ones and some that require further work or further analysis to be made good.

Governance

Johnson proposes to spin the urban parts of the MTA into a new agency, called BAT, or Big Apple Transit. The rump-MTA will remain in control of suburban operations and keep MTA Capital Construction (p. 35), and there will be a shared headquarters. Some cooperation will remain, such as contributions toward cheaper in-city commuter rail fares, but there is no call for fully integrated fares and schedules: the recommendation “all trains and buses in the city will cost the same and transfers will be free” does not appear anywhere in the document.

Johnson also proposes that the BAT board will be required to live in the city and use transit regularly. There is a serious problem today with senior managers and board members driving everywhere, and the requirement is intended to end this practice. Cynically, I might suggest that this requirement sounds reasonable in 2019 but would have been unthinkable until the 2000s and remains so in other American cities, even though it would be far more useful there and then; the off-peak frequency-ridership spiral is nowhere nearly as bad in New York as it is in Washington or Boston.

One strong suggestion in this section involves appointing a mobility czar (p. 36), in charge of the NYC Department of Transportation as well as BAT. Given the importance of the subway, this czar would be in effect the new minister of transportation for the city, appointed by the mayor.

Ultimately, this section tends toward the weaker side, because of a problem visible elsewhere in the report: all of the recommendations are based on internal analysis, with little to no knowledge of global best practices. Berlin has city-controlled transit in full fare union with Deutsche Bahn-run mainline rail, but there has been no attempt to learn how this could be implemented in New York. The only person in New York who I’ve seen display any interest in this example is Streetsblog’s David Meyer, who asked me how DB and Berlin’s BVG share revenue under the common umbrella of the Berlin Transport Association (or VBB); I did not know and although I’ve reached out to a local source with questions, I could not get the answer by his filing deadline.

Finance and costs

This is by far the weakest section in the proposal. The MTA funds itself in large part by debt; Johnson highlights the problem of mounting debt service, but his recommendations are weak. He does not tell New Yorkers the hard truth that if they can’t afford service today then they can’t afford it at debt maturity either. He talks about the need to “address debt” but refrains from offering anything that might inconvenience a taxpayer, a rider, or an employee (pp. 42-43), and offers a melange of narrow funding sources that are designed for maximum economic distortion and minimum visible inconvenience.

In fact, he calls transit fares regressive (pp. 59, 61) and complains about century-long fare increases: real fares have risen by a factor of 2.1 since 1913 – but American GDP per capita has risen by a factor of 7.7, and operating costs have mostly risen in line with incomes.

He brings up ways to reduce costs. In operations these involve negotiations with the unions; even though the report mentions that drivers get paid half-time for hours they’re not working between the morning and afternoon peaks (“swing shift,” p. 48), it does not recommend increasing off-peak service in order to provide more mobility at low marginal cost. There is no mention of two-person crews on the subway or of the low train operator efficiency compared with peer cities – New York City Transit train operators average 556 revenue hours per year, Berlin U-Bahn operators average 829.

In capital construction the recommendations are a mixed bag of good and bad, taken from a not-great RPA report from a year ago. Like the RPA, Johnson recommends using more design-build, in flagrant violation of one of the rules set by global cost reduction leader Madrid. However, to his credit, Johnson zooms in on real problems with procurement and conflict resolution, including change orders (pp. 50-51), and mentions the problem of red tape as discussed in Brian Rosenthal’s article from the end of 2017. He suggests requiring that contractors qualify to bid, which is a pretty way of saying that contractors with a history of shoddy work should be blacklisted; I have heard the qualify-to-bid suggestion from some sporadic inside sources for years, alongside complaints that New York’s current bid-to-qualify system encourages either poor work or red tape discouraging good contractors. Unfortunately, there is no talk of awarding bids based on a combination of technical score and cost, rather than just cost.

Overall the talk of cost is better than what I’ve seen from other politicians, who either say nothing or use high costs as an excuse to do nothing. But it has a long way to go before it can become a blueprint for reducing subway construction costs, especially given the other things Johnson proposes elsewhere in the document.

Accessibility

Another mixed part of the document is the chapter about accessibility for people with disabilities. Johnson recounts the lack of elevators at most subway stations and the poor state of the bus network, featuring drivers who are often hostile to people in wheelchairs. However, while his analysis is solid, his recommendations aren’t.

First of all, he says nothing of the cost of installing elevators on the subway. An MTA press release from last year states the cost of making five stations accessible as $200 million, of $40 million per station. This figure contrasts with that of Madrid, where a non-transfer station costs about 5 million to equip with elevators, and a transfer station costs about 5 million per line served (source, PDF-pp. 11-12). In Berlin, which is not a cheap city for subway construction, the figure is even lower: about 2 million per line served, with a single elevator costing just 800,000.

And second, his proposal for finding money for station accessibility involves using the zoning code, forcing developers to pay for such upgrades. While this works in neighborhoods with ample redevelopment, not all city neighborhoods are desirable for developers right now, and there, money will have to come from elsewhere. For a document that stresses the importance of equality in planning, its proposals for how to scrounge funds can be remarkably inequitable.

That said, in a later section, Johnson does call for installing bus shelters (p. 74). A paper referenced in a TransitCenter report he references, by Yingling Fan, Andrew Guthrie, and David Levinson, finds that the presence of shelter, a bench, and real-time arrival information has a large effect on passengers’ perceived wait times: in the absence of all three amenities, passengers perceive wait time as 2-2.5 times as long as it actually is, rising to a factor of almost 3 for 10-minute waits among women in unsafe areas, but in the presence of all three, the factor drops to around 1.3, and only 1.6 for long waits for women in unsafe areas. Unfortunately, as this aspect is discussed in the bus improvement section, there is no discussion of the positive effect shelter has on people with disabilities that do not require the use of a wheelchair, such as chronic pain conditions.

I do appreciate that the speaker highlights the importance of accessibility and driver training – drivers often don’t even know how to operate a wheelchair lift (p. 63). But the solutions need to involve more than trying to find developers with enough of a profit margin to extract for elevators. Bus stops need shelter, benches, and ideally raised curbs, like the median Berlin tramway stations. And subway stations need elevators, and they need them at acceptable cost.

Bus improvements

By far this is the strongest part of the report. Johnson notes that bus ridership is falling, and recommends SBS as a low-cost solution. He does not stop at just making a skeletal light rail-like map of bus routes to be upgraded, unlike the Bloomberg and de Blasio administrations: he proposes sweeping citywide improvements. The call for bus shelter appears in this section as well.

But the speaker goes beyond calling for bus shelters. He wants to accelerate the installation of bus lanes to at least 48 km (i.e. 30 miles) every year, with camera enforcement and physically-separated median lanes. The effect of such a program would be substantial. As far as I can tell, with large error bars caused by large ranges of elasticity estimates in the literature, the benefits in Eric Goldwyn’s and my bus redesign break down as 30% stop consolidation (less than its 60% share of bus speedup since it does involve making people walk longer), 30% bus lanes, 30% network redesign, 10% off-board fare collection.

There is no mention of stop consolidation in the paper, but there is mention of route redesign, which Johnson wishes to implement in full by 2025. The MTA is in support of the redesign process, and allowing for integrated planning between NYCDOT and the MTA would improve the mutual support between bus schedules and the physical shape of the city’s major streets.

Moreover, the report calls for transit signal priority, installed at the rate of at least 1,000 intersections per year. This is very aggressive: even at the average block spacing along avenues, about 80 meters, this is 80 kilometers per year, and at that of streets, it rises to 200+ km. Within a few years, every intersection in the city would get TSP. The effects would be substantial, and the only reason Eric’s and my proposal does not list them is that they are hard to quantify. In fact, this may be the first time an entire grid would be equipped with TSP; some research may be required to decide how to prioritize bus/bus conflicts at major junctions, based on transportation research as well as control theory, since conditional TSP is the only way to truly eliminate bus bunching.

Reinforcing the point about dedicated lanes, the study calls for clawing back the space given to private parking and delivery. It explicitly calls for setting up truck routes and delivery zones in a later section (pp. 86-87); right now, the biggest complaint about bus lanes comes from loss of parking and the establishment of delivery zones in lieu of letting trucks stop anywhere on a block, and it is reassuring to see Johnson commit to prioritizing public transit users.

Livable streets

This is another strong section, proposing pedestrian plazas all over the city, an expansion of bike lanes to the tune of 80 km (50 miles) a year with an eye toward creating a connected citywide bike lane network, and more bike share.

If I have any criticism here, it’s that it isn’t really about city control of the MTA. The bus improvements section has the obvious tie-in to the fact that the buses are run by the MTA, and getting the MTA and NYCDOT on the same page would be useful. With bikes, I don’t quite understand the connection, beyond the fact that both are transportation.

That said, the actual targets seem solid. Disconnected bike lane networks are not really useful. I would never bike on the current network in New York; I do not have a death wish. I wasn’t even willing to bike in Paris. Berlin is looking more enticing, and if I moved to Amsterdam I might well get a bike.

Conclusion

The sections regarding costs require a lot of work. Overall, I get the impression that Johnson based his recommendations on what he’s seen in the local press, so the suggestions are internal to the city or occasionally domestic; the only international comparisons come from the RPA report or from Eric’s and my invocation of Barcelona’s bus redesign. This works for such questions as how to apportion the MTA’s debt service or how to redesign the bus network, but not so much for questions involving subway capital construction.

New York has a large number of fluent Spanish speakers. It should have no problem learning what Spanish engineers know about construction costs, and the same is true for other communities that are well-represented in the cities, such as Korean-, Russian-, Chinese-, Brazilian-, and Polish-New Yorkers. Moreover, in most big cities that don’t send large communities to New York, such as those of Northern Europe, planners speak English. Johnson should not shy from using the expertise of people outside New York, ideally outside the United States, to get subway construction costs under control.

The speaker’s plan is still a very good first step. The proposed surface improvements to buses, bikes, and street allocation are all solid, and should be the city’s consensus for how to move forward. What’s needed is something to tie all of this together with a plan to move forward for what remains the city’s most important transportation network: the subway.