Category: Good Transit

Suspended Railways

Suspended railways are not a common mode of transportation. In Europe, the best-known example is the Wuppertal Suspension Railway, opened in 1901. Two examples exist in Japan, which is more willing to experiment with nonstandard rail technology. With essentially just these three examples in normal urban rail usage, it is hard to make generalizations. But I believe that the technology is underrated, and more cities should be considering using it in lieu of more conventional elevated or underground trains.

The reason why suspended trains are better than conventional ones is simple: centrifugal force. Train cars are not perfectly rigid – they have a suspension system, which tolerates some angle between the bogies and the carbody. Under the influence of centrifugal force, the body leans a few degrees to the outside of each curve:

 

If the train is moving away from you, and is turning left, then the outside of the curve is to your right; this is where the body leans in the image on the right. This is because centrifugal force pushes everything to the right, including in particular the carbody. This increases the centrifugal force felt by the passengers – the opposite of what a tilt system does. A train is said to have soft suspension if this degree of lean is large, and rigid suspension if it is small. The depicted image is rotated 3 degrees, which turns 1 m/s^2 acceleration in the plane of the tracks into 1.5 m/s^2 felt by the passengers; this is the FRA’s current limit, and is close to the maximum value of emergency deceleration. There are no trains with perfectly rigid suspension, but the most recent Shinkansen trains have active suspension, which provides the equivalent of 1-2 degrees of tilt.

On a straddling train, this works in reverse. A straddling train moving away from you turning left will also suspend to the right:

 

It’s almost identical, except that now the floor of the train leans toward the inside of the curve, rather than to the outside. So the suspension system reduces the lateral acceleration felt by the passengers, rather than increasing it. By softening the suspension system, it’s possible to provide an arbitrarily large degree of tilt, limited only by the maximum track safety value of lateral acceleration, which is not the limiting factor in urban rail.

This is especially useful in urban rail. Longer-distance railroads can superelevate the tracks, especially high-speed tracks, where trains have to be reliable enough for other reasons that they never have to stop in the middle of a superelevated curve. Some urban rail lines have superelevation as well, but not all do. Urban rail lines with high crowding levels routinely stop the trains in the middle of the track to maintain sufficient spacing to the train ahead; this is familiar to my New York readers as “we are being delayed because of train traffic ahead of us,” but the same routinely happens in Paris on the RER. This makes high superelevation dicey: a stopped train leans to the inside of the curve, which is especially uncomfortable for passengers. High superelevation on urban rail is also limited by the twist, i.e. the rate at which the superelevation increases per linear meter (in contrast, on intercity rail, the limiting factor is jerk, expressed in superelevation per second).

Another reason why reducing curve radius is especially useful in urban rail is right-of-way constraints. It’s harder to build a curve of radius 200 meters in a dense city (permitting 60 km/h with light superelevation) than a curve of radius 3 km outside built-up areas (permitting 250 km/h with TGV superelevation and cant deficiency). Urban rail systems make compromises about right-of-way geometry, and even postwar systems have sharp curves by mainline rail standards; in 1969, the Journal of the London Underground Railway Society listed various European limits, including Stockholm at 200 meters. The oldest lines go well below that – Paris has a single 40-meter curve, and New York has several. Anything that permits urban rail to thread between buildings (if above ground), building foundations (if underground), and other lines without sacrificing speed is good; avoiding curves that impose 30 km/h speed limits is important for rapid transit in the long run.

Suspended railways are monorails, so they run elevated. This is not inherent to the technology. Monorails and other unconventional rail technologies can go underground. The reason they don’t is that a major selling point for monorails is that their sleek structures are less visually obtrusive when elevated. But underground they can still use the same technology – if anything, the difficulty of doing emergency evacuation on an elevated suspended monorail is mitigated on an underground line, where passengers can hop to the floor of the tunnel and walk.

I’d normally say something about construction costs. Unfortunately, the technology I am plugging has three lines in regular urban operation, opened in 1901, 1970, and 1988. The 1988 line, the Chiba Monorail, seems to have cost somewhat more per km than other contemporary elevated lines in Japan, but I don’t want to generalize from a single line. Underground there should not be a cost difference. And ultimately, cost may well be lower, since, at the same design speed, suspended monorails can round tighter curves than both conventional railroads and straddle monorails.

Despite its rarity, the technology holds promise in the most constrained urban environments. When they built their next new metro lines, disconnected from the older network, cities like New York, London, Paris, and Tokyo should consider using suspended railroads instead of conventional subways.

Fare Integration

I said something on my Patreon page about fare integration between buses and trains, in the context of an article I wrote for the DC Policy Center about improving bus service, and got pushback of the most annoying kind, that is, the kind that requires me to revise my assumptions and think more carefully about the subject. The controversy is over whether fare integration is the correct policy. I still think it is, but there’s a serious drawback, which the positive features have to counterbalance.

First, some background: fare integration means that all modes of public transit charge the same fare within the same zone, or between the same pair of stations. Moreover, it means transfers are free, even between modes. Fare integration between city buses and urban rail seems nearly universal; big exceptions include Washington (the original case study) and London, and to a lesser extent Chicago. Fare integration between urban rail and regional rail is ubiquitous in Europe – London doesn’t quite have it, but it’s actually closer than fare integration between buses and the Underground – but does not exist in North America. In Singapore there is fare integration. In Tokyo, there are about twelve different rail operators, with discounted-but-not-free transfers between two (Tokyo Metro and Toei) and full-fare transfers between any other pair.

The reason North American commuter rail has no fare integration with other forms of transit is pure tradition: railroaders think of themselves as special, standing apart from mere urban transit. We can dispense with the idea that it is a seriously thought-out fare system. However, lack of integration between buses and trains in general does have some thought behind it. In London, the stated reason is that the Underground is at capacity, so its fares are jacked up to avoid overcrowding, while the buses remain cheap. In Washington, it’s that Metro is a better product than the buses, so it should cost more, in the same way first-class seats cost more than second-class seats on trains. Cap’n Transit made a similar point about this in the context of express buses.

There are really three different questions about fare integration: demand, supply, and network effects. The first one, as noted by Patreon supporters, favors disintegrated fares. The other two favor fare integration, for different reasons.

Demand just means charging more for a product that has higher demand. This is about revenue maximization, assuming fixed service provision: people will pay more for the higher speed of rapid transit, so it’s better to charge each mode of transportation the maximum it can bear before people stop taking trips altogether, or choose to drive instead. It’s related to yield management, which maximizes revenue by using a fare bucket system, using time of booking as a form of price discrimination; SNCF uses it on the TGV, and in its writeups for American high-speed rail from 2009, it said it boosted revenue by 4%. In either case, you extract from each passenger the maximum they can pay by making features like “don’t get stuck in traffic” cost extra.

Supply means giving riders incentives to ride the mode of transportation that’s cheaper to provide. In other words, here we don’t assume fixed (or relatively fixed) service provision, but variable service provision and relatively fixed ridership. Trains nearly universally have lower marginal operating costs than buses per passenger-km; in Washington the buses cost 40% more per vehicle-km, and perhaps 2.5 times as much per unit of capacity (Washington Metro cars are long). Using the fare system to incentivize passengers to take the train rather than the bus allows the transit agency to shift resources away from expensive buses, or perhaps to redeploy these resources to serve more areas. If anything, the bus should cost more. There are shades of this line in incentives some transit agencies give for passengers to switch from older fare media to smart cards: the smart card is more convenient and thus in higher demand, but it also involves lower transaction costs, and thus the agency incentivizes its use by charging less.

The network effect means avoiding segmenting the market in any way, to let passengers use all available options. The fastest way to get between two points may be a bus in some cases and a train in others, or a combined trip. This fastest way is often also the most direct, which both minimizes provision cost to the agency and maximizes passenger utility. This point argues in favor of free transfers especially, more so than fare integration. Tokyo fares are integrated in the sense that the different railroads charge approximately the same for the same distance; but transfers are not free, and monthly passes are station to station, with no flexibility for passengers who live between two parallel (usually competing) lines.

The dominant reason to offer integrated fares is network effects, more so than supply. Evidently, I am not aware of transit agencies that charge more for buses than for trains, only in the other direction. That fare integration allows transit agencies to reduce operating costs mitigates the loss of revenue coming from ending price discrimination; it is not the primary reason to integrate fares.

The issue at hand is partly frequency, and partly granularity. A typical transit corridor, supporting a reasonably frequent bus or a medium-size subway station, doesn’t really have the travel demand for multiple competing lines, even if it’s a parallel bus and a rail line. Fare disintegration ends up reducing the frequency on each option, sometimes beyond the point where it starts hurting ridership.

In Washington it’s especially bad, because of reverse-branching. The street network makes it hard for the same bus to serve multiple downtown destinations (or offer transfers to other buses for downtown service). Normally, riders would be able to just take a bus to the subway station and get to their destination, but Washington plans buses and trains separately, so two of the trunk routes, running on 14th an 16th Streets, reverse-branch. The hit to frequency (16-18 minutes per destination off-peak) is so great that even without fare integration it’s worthwhile to prune the branches. But such situations are not unique to Washington, and can occur anywhere.

The required ingredients are a city center that is large enough, or oriented around a long axis, with a street network that isn’t a strict grid and isn’t oriented around the axis of city center. New York is such a city: if it didn’t have fare integration, buses would need to reverse-branch from the north to serve the East Side and West Side, and from anywhere to serve Midtown and Lower Manhattan.

The granularity issue is that there isn’t actually a large menu of options for riders with different abilities to pay. This is especially a problem in American suburbs, with nothing between commuter rail (expensive, infrequent off- and reverse-peak, assumes car ownership) and the bus (in the suburbs, a last-ditch option for people below the poverty line). I wrote about this for Streetsblog in the context of Long Island; there’s also a supply angle – different classes of riders travel in opposite directions, so it’s more efficient to put them on one vehicle going back and forth – but this is fundamentally a problem of excessive market segmentation.

This also explains how Tokyo manages without fare integration between different rail operators. Its commuter rail lines are not the typical transit corridor. With more than a million riders per day (not weekday) on many lines, there is enough demand for very high frequency even with disintegrated fares. A passenger between two competing lines can only get a monthly pass on one, but it’s fine because the one line is frequent and the trains run on time.

The rest of the world is not Tokyo. Branches in Outer London and the Paris suburbs aren’t terribly frequent, and only hit one of the city centers, necessitating free transfers to distribute passengers throughout the city. They also need to collect all possible traffic, without breaking demand between different modes. If RER fares were higher than Metro fares, some areas would need to have a Metro line (or bus line) paralleling the RER, just to collect low-income riders, and the frequency on either line would be weaker.

The demand issue is still real. Fare integration is a service, and it costs money, in terms of lost revenue. But it’s a service with real value for passengers, independently of the fact that it also reduces operating costs. The 99.5% of the world that does not live in Tokyo needs this for flexible, frequent transit choices.

When Buses are a Poor Guide to Corridor Demand, Redux

Generally, the best guide to where a city should build rail lines is where the busiest buses are. However, there are exceptions. I have written two posts about this giving examples of exceptions, and am going to give a third exception; I also intend to write a separate post soon giving a fourth exception.

The first post, from four years ago, deals with cases where the bus alignment has to stay on a major street, but some major destinations are just away from the street; a subway can deviate to serve those destinations. Examples include Old Jaffa in Tel Aviv near the north-south spine of bus lines 1 and 25, and Century City near the Wilshire corridor. Here, buses are a good guide to corridor demand, but the rail line should serve microdestinations just outside the corridor.

The second post, from last year, is more properly about corridors. It describes street networks that are hostile to surface transit, by featuring narrow, meandering streets. The main example is Boston, especially the Green Line Extension, in a rail right-of-way in a city infamous for its labyrinthine streets. Another example is the Evergreen extension in Vancouver, serving Coquitlam; the bus the extension replaced, the 97-B, meandered through Coquitlam since the streets were so poorly configured, while the extension uses a short tunnel and runs parallel to a railroad.

In this post I’d like to expand on a point I made, obliquely, in the Voice of San Diego. In San Diego, there’s an under-construction light rail extension, in a rail right-of-way, into an area with not-great bus ridership. Consult the following map:

Preexisting light rail (“Trolley”) is in black, the extension (of the Blue Line) in blue, the parallel north-south arterial in purple, and two buses in green and red. The bus ridership on Ingraham is very low: the bus route running on it, 9, has 1,500 riders per weekday (source). The top bus in San Diego, the 7 (going north of downtown, then east), has 11,000. So on the surface, this suggests there isn’t much demand for north-south transit in that area of the city, called Pacific Beach.

But that’s wrong, because in an auto-oriented city like any US city except New York, the major streets are determined by car access. The relentless grids of so many North American cities – Chicago, Los Angeles, Toronto, Vancouver – are not just where the buses go, but also where the cars go. Even in Manhattan, if you have the misfortune to find yourself going east-west in a car, you will probably use one of the major two-way streets, like 14th or 42nd, which are less clogged than the one-way streets in between. Non-gridded street networks for the most part obey this rule too – the commercial streets tend to be the wider ones used by car through-traffic.

Freeways throw a wrench into this system. They offer a convenient route for cars, but are abominable for commerce. Locations 5 minutes by car from the freeway are good; locations right along the freeway are not, unlike ones right along an arterial road. The main car route from Pacific Beach to the CBD is taking an east-west arterial to the I-5, not going south on Ingraham. This means that the demand for north-south traffic actually shows as strong commerce on east-west streets, hosting bus routes 27 and 30, and not on Ingraham. The 27 has weak ridership, and the 30 has strong ridership but not right along the I-5. But in a sense it doesn’t really matter, because, like the car- and bus-hostile narrow streets of old city centers, the freeway-centric road network in that part of San Diego suppresses bus ridership relative to future rail ridership.

In the presence of rail, the strong routes are the ones orthogonal to the rail line. Here, the 27 and 30 already preexist; there is a planned Trolley stop at the intersection with the 27, and presumably the 30 will be rerouted to serve that intersection rather than to duplicate the trains along the freeway. (I tried talking to the transit agency about this, but didn’t get any useful answers.) So the decent east-west bus ridership in Pacific Beach is actually an argument in favor of a north-south rail extension.

Like every exception to a general rule, this is not a common scenario. So where else are there cases where this special case holds? The necessary elements are,

  1. The city must be auto-oriented enough that car access is crucial to nearly all commercial drags. In Paris, it doesn’t matter how you reach the Peripherique by car, because car ownership is so low.
  2. The city should not have a strong mainline rail network, which leads to a hierarchical transit network (buses feeding train stations), in which both buses and cars use the same major streets to reach train stations. This means that Sydney and Melbourne are out, as are German cities short of Berlin and Munich’s transit mode shares.
  3. The city must have a strong network of urban freeways, disrupting the street network to the point of siphoning traffic away from the surface streets that would otherwise be the main routes.

As it happens, all three elements are present in Tel Aviv. North-south travel within the region uses Ayalon Freeway, inconveniently east of the traditional city center; the city has been building a CBD closer to the freeway, but it’s still not quite there. This suggests that traffic is suppressed on the north-south arterials to the west – Ibn Gabirol (hosting the planned second line of the subway) and Dizengoff (possibly hosting the third) – is suppressed, and those streets require subways. This is in part why, before the Red Line began construction, I argued in favor of putting a north-south subway under Ibn Gabirol, and not under freeway-adjacent Namir Road, where the Red Line goes.

In the future, this pattern suggests that Tel Aviv should make sure to build north-south subways under Ibn Gabirol and Dizengoff, and extend them north. The significance of the northern direction is that the effect I’m describing in this post only works when car ownership is high; Israel is poor enough that car ownership is not universal, and in the poorer southern suburbs it is low enough that the buses do give a good guide to corridor demand, whereas in the northern suburbs everyone owns a car. There is likely to be suppressed transit demand in Herzliya, Ramat HaSharon, and northeastern Tel Aviv (including Ramat HaHayal, an edge city with many tech jobs). Thus ridership on a subway line going elevated over Sokolov in Ramat HaSharon and Herzliya, or on Raoul Wallenberg to Ramat HaHayal, is likely to be higher than present-day bus ridership suggests.

An American example is Washington’s suburbs. The Metro extensions are planned with little regard for bus ridership. While the Silver Line is bad for multiple reasons – high construction costs, service to too far exurbs, too much branching on an overloaded trunk – the extension to Tysons Corner is its one good aspect. There is no point in discussing bus ridership at an edge city like Tysons – conventional buses wouldn’t be following the same route that the cars follow, and freeway express buses almost universally have trivial ridership.

Finally, Vancouver. While Vancouver itself is gridded, its suburbs are much less so. In the suburbs served by the Trans-Canada Highway, especially Surrey, it’s likely that car traffic mostly follows roads feeding the highway. People drive to their jobs in Downtown, Central Broadway, Metrotown, or any of Surrey’s internal centers; there aren’t a lot of park-and-rides at SkyTrain stations, which instead emphasize transit-oriented development, and in Surrey there are actually more park-and-ride spaces at the freeways, with express bus access, than at the one SkyTrain stop with parking, Scott Road. This suggests that there is suppressed bus ridership in Surrey and Langley parallel to the Trans-Canada, along Fraser Highway. Extending SkyTrain in that direction is on a distant priority list for the region, and this theory suggests that it should be moved up, to be just behind the Broadway subway to UBC.

Anti-Infill on Surface Transit

I wrote about infill stops on commuter rail two weeks ago, and said I cannot think of any example of anti-infill on that mode. But looking at Muni Metro reminded me that there is need for anti-infill on surface transit. This is called stop consolidation normally, and I only use the term anti-infill to contrast with the strategy of adding more stops on commuter trains.

The root of the problem is that in North America, transit agencies have standardized on 200-250 meters as the typical spacing between bus stops. In Europe, Australasia, and East Asia, the standard is instead 400-500 meters. Even without off-board fare collection, the difference in speed is noticeable. In Vancouver, the difference between the local 4 and the express 84 is substantial: on the shared segment between Burrard and Tolmie, a distance of 4.8 km, the 84 makes 5 stops and takes 10 minutes, the 4 makes 18 stops and takes 16 minutes. A bus with the normal first-world stop spacing would make 10-12 stops and take, linearly, 12-13 minutes. 23 km/h versus 18 km/h.

With off-board fare collection, the impact of stop spacing on speed grows. The reason is that a bus’s stop penalty consists of the time taken to stop and open its doors, plus the time it takes each passenger to board. The former time is independent of the fare collection method but depends on stop spacing. The latter time is the exact opposite: if the stop spacing widens, then there are more passengers per bus stop, and unless the change in stop spacing triggers changes in ridership, overall passenger boarding and alighting time remains the same. Another way to think about it is that judging by Vancouver data, there appears to be a 30-second stop penalty, independent of ridership. Off-board fare collection increases bus speed, so the 30-second stop penalty becomes more important relative to overall travel time; the same is true of other treatments that increase bus speed, such as dedicated lanes and signal priority.

In New York, there aren’t a lot of places with local and limited-stop buses side by side in which the limited-stop bus has on-board fare collection. One such example is the M4, meandering from Washington Heights down the 5th/Madison one-way-pair, over 15.3 km. At rush hour, the local takes 1:45, the limited-stop takes 1:30: 9 vs. 10 km/h. But the limited-stop bus runs local for 6 km, and over the other 9.3 km it skips 26 local stops if I’ve counted right. The B41 has a limited-stop version over 8.3 km (the rest is local), skipping about 17 stops; the time difference is 10 minutes.

One possible explanation for why the stop penalty in New York seems a little higher than in Vancouver is that the M4 and B41 routes are busier than the 4/84 in Vancouver, so every stop has at least one passenger, whereas the 4 in Vancouver often skips a few stops if there are no passengers waiting. Conversely, the higher passenger traffic on buses in New York comes from higher density and more traffic in general, which slows down the buses independently of stopping distance.

On subways, there’s reason to have more densely-spaced stops in denser areas, chief of which is the CBD. On surface transit, it’s less relevant. The reason is that absolute density doesn’t matter for stop spacing, except when expected ridership at once station is so high it would stress the egress points. What really matters is relative density. Putting more stops in an area means slowing down everyone riding through it in order to offer shorter station access times to people within it. On surface transit, relative density gradients aren’t likely to lead to variations in stop spacing, for the following reasons:

  1. Historically, surface transit stop spacing was always shorter than rapid transit stop spacing because of its lower top speed and the faster braking capabilities of horses vs. steam trains; often people could get off at any street corner they chose. So it induced linear development, of roughly constant density along the corridor, rather than clusters of high density near stations.
  2. If there is considerable variation in density along a surface transit line, then either density is medium with a few pockets of high density, which would probably make the line a good candidate for a subway, or density is low with a few pockets of higher density, and the bus would probably skip a lot of the low-density stops anyway.

Most importantly, the 400-meter standard is almost Pareto-faster than the 200-meter standard. In the worst case, it adds about 4 minutes of combined walking time at both the start and the end of the trip, for an able-bodied, healthy person not carrying obscene amounts of luggage. The breakeven time on 4 minutes is 8 skipped stops, so 3.2 km compared with the 200-meter standard. Bus trips tend to be longer than this, except in a few edge cases. In New York the average unlinked bus trip is 3.4 km (compare boardings and passenger-km on the NTD), but many trips involve a transfer to another bus or the subway, probably half judging by fare revenue, and transfer stations would never be deleted. If the destination is a subway station, guaranteed to have a stop, then the breakeven distance is 1.6 km.

This also suggests that different routes may have different stop spacing. Very short routes should have shorter stop spacing, for example the 5 and 6 buses in Vancouver. Those routes compete with walking anyway. This may create a spurious relationship with density: the 5 and 6 buses serve the very dense West End, but the real reason to keep stop spacing on them short is that they are short routes, about 2 km each. Of course, West End density over a longer stretch would justify a subway, so in a way there’s a reason short optimal stop spacing correlates with high bus stop density.

The situation on subways is murkier. The stop penalty is slightly higher, maybe 45 seconds away from CBD stations with long dwell times. But the range of stop distances is such that more people lose out from having fewer stops. Paris has a Metro stop every 600 meters, give or take. Some of the busiest systems in countries that were never communist, such as Tokyo, Mexico City, and London, average 1.2 km; in former communist bloc countries, including Russia and China, the average is higher, 1.7 km in Moscow. The difference between 600 meters and 1.2 km is, in the worst case, another 1.2 km of walking, about 12 minutes; breakeven is 16 deleted stops, or 20 km, on the long side for subway commutes.

One mitigating factor is that subway-oriented development clusters more, so the worst case is less likely to be realized, especially since stops are usually closer together in the CBD. But on the other hand, at 1.2 km between stations it’s easy for transfers to be awkward or for lines to cross without a transfer. London and Tokyo both have many locations where this happens, if not so many as New York; Mexico City doesn’t (it’s the biggest subway network in which every pair of intersecting lines has a transfer), but it has a less dense network in its center. Paris only has three such intersections, two of them involving the express Metro Line 14. Even when transfers do exist, they may be awkward in ways they wouldn’t have been if stop spacing had been closer (then again, Paris is notorious for long transfers at Chatelet and Montparnasse).

In all discussions of subway stop spacing, New York is sui generis since the lines have four tracks. On paper its subway lines stop every 600-700 meters when not crossing water, but many trains run express and stop every 2 km or even more. Average speed is almost the same as in Tokyo and London, which have very little express service, and it used to be on a par until recent subway slowdowns. This distinction, between longer stop spacing and shorter stop spacing with express runs, also ports to buses. Buses outside the US and Canada stop every 400-500 meters and have no need for limited-stop runs – they really split the difference between local and limited buses in North America.

On a subway, the main advantage of the international system over the New York system is obvious: only two tracks are required rather than four, reducing construction costs. On a bus line, the advantages are really the same, provided the city gives the buses enough space. A physically separated bus lane cannot easily accommodate buses of different speeds. In New York, this is the excuse I’ve heard in comments for why the bus lanes are only painted, not physically separated as in Paris. Mixing buses of different speeds also makes it hard to give buses signal priority: it is easy for buses to conflict, since the same intersection might see two buses spaced a minute apart.

Buses also benefit from having a single speed class because of the importance of frequency. In Vancouver, the off-peak weekday frequency on 4th Avenue is an 84 rapid bus every 12 minutes, a 44 rapid bus every 20 minutes, and a local 4 every 15 minutes. The 84 keeps going on 4th Avenue whereas the 4 and 44 divert to Downtown, but the 4 and 44 could still be consolidated into a bus coming every 10 minutes. If there were enough savings to boost the 84 to 10 minutes the three routes could vaguely be scheduled to come every 5 minutes on the common section, but without dedicated lanes it’s probably impossible to run a scheduled service at that frequency (pure headway management and branching don’t mix).

The example of 4th Avenue gets back to my original impetus for this post, Muni Metro. Only diesel buses can really run in regular surface mode mixing different speed classes. Trolleys can’t. Vancouver runs trolleys on the local routes and diesels on the limited routes. At UBC, it has different bus loops for diesels and trolleys, so people leaving campus have to choose which type of bus to take – they can’t stand at one stop and take whatever comes first.

On rail, this is of course completely impossible. As a result, American subway-surface trolleys – the Boston Green Line, SEPTA’s Subway-Surface Lines, and Muni Metro – all run at glacial speed on the surface, even when they have dedicated lanes as in Boston. In Boston there has been some effort toward stop consolidation on the Green Line’s busiest branch, the B, serving Boston University. This is bundled with accessibility – it costs money to make a trolley stop wheelchair-accessible and it’s cheaper to have fewer stops. Muni Metro instead makes one stop every 3-5 accessible (on paper), but keeps stopping at all the other stops. It would be better to just prune the surface stops down to one every 400-500 meters, which should be accessible.

If you view rail as inherently better than bus, which I do, then it fits into the general framework: anti-infill on surface transit has the highest impact on the routes with the best service quality. Higher speed makes the speed gain of stop consolidation more important relative to travel time; trolleywire makes it impossible to compensate for the low speed of routes with 200-meter interstations by running limited-stop service. Even on local buses, there is never a reason for such short stop spacing, and it’s important for North American cities to adopt best industry practice on this issue. But it’s the most important on the highest-end routes, where the gains are especially large.

Commuter Rail Infill Stops

This is a close second option in a poll I conducted among my Patreon backers. Thanks to everyone who participated. The winning option, about branching and transfers, I covered last week.

Modernizing commuter rail to run it like rapid transit means a lot of things. It means high all-day frequency, fare integration, good transfers to local transit (which requires fare integration), and ideally through-running in order to hit multiple business districts. In North America, these are absent, resulting in low ridership. So let’s posit that these problems are already being solved: commuter rail is being run frequently, the lines are electrified, the fares are the same as on local transit with free transfers. What should the stop pattern look like? This is not a purely hypothetical discussion, because in Toronto the under-construction RER system includes high off-peak frequency, electrification, and through-running, with fare integration under consideration.

So let’s imagine a city with modernized regional rail, maybe in the early 2020s. Trains run every 15 minutes off-peak, charge the same fare as local transit, and run fast EMUs, on track that’s good for 130 km/h outside station throats. The stop pattern, expressed in kilometers out of city center, is any of the following:

Line Stop #1 Stop #2 Stop #3 Stop #4 Stop #5 Stop #6
Chicago Metra Electric 1.3 2.3 3.6 4.3 5.2 9.5
Chicago UP-North 4.5 10.5 15.1 17.7 19.3 21.4
GO Transit Lakeshore West 3.2 10.8 15.4 20.6 26.9 34.4
GO Transit Lakeshore East 8.4 13.8 17.1 20.3 26.6 33.6
SEPTA Paoli/Thorndale Line (PRR Main Line) 8.7 9.7 10.9 11.9 13.7 13.7
Metrolink Antelope Valley Line 9.3 17.5 24.9 35.4 48.3 55.1
Metrolink Orange County Line 14.4 27.1 35.2 41.3 50.2 53.5

(Metrolink data comes from measuring on Google Earth, the rest comes from Wikipedia.)

Two patterns emerge:

  1. Metrolink and GO Transit have very wide stop spacing. GO has straight track it owns outright on the Lakeshore lines, and Metrolink is straight with few curves on the Orange County Line (but freight owns much of the route) and straight until stop #4 on the Antelope Valley Line, Sylmar. EMUs could average 90 km/h on these lines, counting schedule padding.
  2. SEPTA and Metra have wide stop spacing in the core but very narrow spacing in the suburbs; I discussed this issue for Metra in an old post comparing its stop distribution through stop #12 with that of the RER. Metra Electric has a few inner stops, e.g. for the convention center (stop #4), but then there’s a 4-km gap from stop #5 to stop #6 (Kenwood).

Both patterns are compatible with modernized rail operations. But both have problems with dealing with passenger demand. Consider what happens to a transit user in Burbank (stop #2 on Antelope Valley), or Ravenswood on the North Side of Chicago (stop #2 on UP-North), or Danforth and Main (stop #1 on Lakeshore East). Such a passenger would get an incredibly fast train to the CBD, running either nonstop or with one stop. Demand would boom. But is this really the most efficient way of running transit? Not really. This is for the following reasons:

  • The downstream locations would still be very attractive infill train stations, with potential for high ridership. After all, they’d get fast service, too.
  • If you get a 1-stop, 10-minute train ride to work, then adding four more stops to turn it into a 15-minute ride sounds like an imposition (it raises trip times by 50%), but it really isn’t, because most likely your actual commute is 30 minutes, with 10 minutes of walking at each end.
  • With fare integration, buses should really be feeding the major train stations. Making every bus feed a small number of stations with fast commuter rail service compromises the rest of the network, whereas siting train stations at the intersections with the major grid buses in cities like Toronto, Chicago, and Los Angeles facilitates transfers better.

As a result of these principles, my proposal for Electrolink in Los Angeles, built out of the Antelope Valley and Orange County Line, involves extensive infill stops. See map below:

I drew even more extensive (and somewhat fanciful) maps for Los Angeles and Chicago, with more infill, but I want to focus on my Electrolink map, because it showcases some caveats.

Of note, there is much more infill on the Antelope Valley and Ventura County Lines than on the Orange County Line. This is because there is less residential density near the Orange County Line, and much more industrial land use. Los Angeles has a strong manufacturing sector, using the railroad for freight access, so residential upzoning near potential infill station locations is speculative. In the San Fernando Valley the land use near the railroads is not great, but there is a decent amount of residential density beyond the near-railroad industrial uses, there are strong bus corridors intersecting the railroads (and potential for light rail); the corridors also have less freight, so it’s easier to kick out industrial uses from station sites and do residential and commercial upzoning.

In New York and Boston, there are other caveats, explaining why my various regional rail proposals for these cities call only for mild infill. The biggest caveat is that there exist parallel subway lines. Boston’s Old Colony trunk passes through relatively dense areas in Dorchester and Quincy, with just three stops: JFK/UMass at km-point 3.7, Quincy at km-point 12.7, Braintree at km-point 17.6. But the Red Line runs parallel to the trunk making more stops, enabling commuter rail to work as an express overlay. Thus, only the busiest locations deserve a commuter rail stop, and those are precisely the three existing stops. In Somerville, the Green Line Extension plays a similar role, providing local service that commuter rail would otherwise have to provide under any modernization scheme. As a result, my proposal for how to run the Old Colony Lines and the Lowell Line through Somerville is more intercity rail than local commuter rail.

In contrast, the Worcester Line has no parallel subway except on the innermost few km, so it’s already getting two infill stops (Boston Landing and West Station) and I’ve called for several more. The same is true of the Fairmount Line, which is expanding from five stops including the endpoints to nine.

There is an analog for this in Paris, on the RER. Within the city and La Defense, the RER A mostly runs as an express overlay for Metro Line 1, stopping at the major stations, omitting just Bastille, which is too close to Gare de Lyon. But the RER B really has two separate stop regimes. North of Chatelet, parallel to Line 4, it expresses to Gare du Nord, and then doesn’t stop again until reaching the suburbs. But south of Chatelet, all trains make 5 stops in 5 km to Cite-Universitaire, even ones that run express in the suburbs; this is the older part of the line, much of which predates the Metro, so Line 4 was built along a different alignment via Gare Montparnasse.

In New York, the commuter trunks going north and east are closely parallel to the subway, which is often four-tracked. Since the subway already provides relatively fast service, with stops every 2-3 km, commuter rail should be even faster, with sparser stops. The principles here are,

  • Infill stops are more justified at intersections with major orthogonal bus or rail corridors or in dense, transit-deprived areas. Areas with little residential development are to be categorized based on redevelopment potential.
  • Infill stops are less justified parallel to a subway line. The faster the subway is, the faster commuter rail should be.
  • Infill stops are more justified on a shorter line than on a longer line. Here, “shorter” and “longer” do not mean the length of the line to the endpoint, but the length to the endpoint of local service, if the infill stops would not be served by express trains.

Metro-North is parallel to the four-track Lexington Avenue Line, which has four tracks. Between 125th Street and Grand Central, the 4 and 5 trains make just two intermediate stops, at 86th and 59th Streets. Metro-North runs nonstop between 125th and Grand Central, and because the 4 and 5 exist, it has no reason to make more stops, even at 59th for additional service to Midtown

In the Bronx the trunk line isn’t so close to the subway, but already makes multiple stops. There may be plausible infill in Morrisania between Melrose and Tremont. But even that is marginal – for one, Melrose, Tremont, and Fordham are all located at the intersections with high-ridership east-west bus routes, whereas nothing in between is. This distinction between an inner and outer part of the same line also holds for the Atlantic Branch: west of Broadway Junction it parallels the four-track A/C, so no infill is needed, but farther east it parallels the slower J/Z and isn’t even that close to the subway, so infill is useful.

Going east, the LIRR Main Line is parallel to the Queens Boulevard Line, like the Lex a four-track line. There is no real point in infill, except at Sunnyside Junction, where the line meets the Northeast Corridor. The Port Washington Branch is a shorter line than anything on the Main Line, even the Hempstead Branch (but not by much), and isn’t as close to the 7 as the Main Line is to the Queens Boulevard Line; the 7 is also slower. This means an infill stop or two may be justified – my map has three (at Queens Boulevard, Broadway, and Junction), but that may be too much.

It’s the west direction that is the most speculative, toward New Jersey. I have called for new Hudson tunnels to feature a station at Bergenline (building a station in the existing tunnels would disrupt current service and slow down express trains) based on the above principles. Additional infill is possible, but only subject to transit-oriented development plans alongside the line. The land use from just west of Bergen Hill, including Bergenline, to just east of Newark, is a combination of industrial warehouses and wetland preserves. The warehouses should be redeveloped, but until there is rezoning, it is pointless to add more stops. Moreover, Secaucus Junction is already in the middle of the warehouse area, so rezoning should start from there, and if the newly-built residential neighborhood grows big enough so as to justify a second station, a second station can be added later.

The upshot is that even though New York has very wide stop spacing on commuter rail near the core, it does not need as much infill as Los Angeles or Chicago. What about Toronto, the original impetus for the post? There, Metrolinx is already considering minor infill. But if the principles emerging from how I think about infill in the US and on the RER are correct, Toronto needs far more infill. The Lakeshore lines are not really close to the subway: they run east-west, as does the Bloor-Danforth Line, but Lakeshore West is about 2 km from Bloor, and Lakeshore East is mostly 1 km from Danforth, with just a short segment within walking distance. The inner areas of Lakeshore West are very dense, with some blocks at 30,000 people per km^2, and only served by buses and slow mixed-traffic streetcars; even some areas along Lakeshore East are fairly dense, more than 10,000/km^2. Toronto’s bus and streetcar grid hits or can be extended to hit several potential station locations, offering better connections than riding to the Bloor-Danforth Line and then changing to Yonge to reach the CBD.

The one drawback in Toronto: the commuter lines are very long. Not all trains have to make all stops, but if there’s one stopping pattern making 3 stops in 15 km and another making 12, then it isn’t really possible to mix them on the same tracks at high frequency. The core lines have four tracks, but Lakeshore needs to eventually mix four classes of trains: local commuter rail, longer-range commuter rail, intercity rail, freight. There are ways around four-way mixture (for example, there is little freight on Lakeshore in Toronto proper, where the local trains would run), and intercity trains can probably share tracks with long-range commuter trains. It’s solvable, just like the three-way track-sharing between local, express, and eventual high-speed trains around New York, but it isn’t trivial.

In general, North American commuter trains make too few stops in the urban core. Tellingly, while I can come up with many examples of lines that require infill, I can’t name five good examples of anti-infill, where a station served by commuter trains full-time should be closed. But not all commuter lines are equally good candidates for infill stops, and there are large networks, such as Metro-North, where the current stop spacing is fine, just as there are ones, such as GO Transit and some Metra lines, where some inner segments could plausible see the number of stops quadruple.

Line Spacing, and Intersections Without Transfers (Hoisted from Comments)

This post is inspired by two separate things. The first is my work on a fantasy subway map for Lagos; here is the current live version. There are twelve radial lines, all serving the western half of Lagos Island, converging on nine transfer stations. Under the principle that whenever two lines intersect there should be a transfer station, this greatly constrains the paths the lines can take. Result: the path between two CBD stations, Eko Bridge and Leventis, carries ten tracks underneath it. This is under a wide street, and it might be possible with a double-deck four-track-wide tunnel and two more tracks deep-boring around it, but it’s not easy to construct.

The second inspiration is a post by Brian Stokle about subway line spacing. Brian looks not at spacing between successive stops on one line, but at spacing between parallel lines, averaging a few North American examples. The average is a little higher than half a kilometer, narrower than the typical stop spacing. On Twitter, Joshua Mello notes Boston’s spacing was narrower; in comments, I add examples from New York and Paris, which are a bit narrower than Brian’s examples but wider than Boston (New York is one block in Midtown, so 280 meters, and Paris is 300 between Metro 3 and Metro 8 and 9).

These two examples together illustrate the tradeoff in subway construction. Most subways have a stop every 1-1.5 km; newer systems are at the high end of this range, mostly because of the demographic weight of China. It’s normal for stop spacing to tighten in the core, but not to a large extent. In Tokyo, the average stop spacing is 1.2 km, and in Central Tokyo it’s perhaps 800 meters. In London, the Tube lines seem to tighten from an average of 1.2-1.5 km to 600-800 meters in Central London.

At the same time, subway line spacing is necessarily short. The reason is that modern CBDs are geographically small. Midtown is maybe 4 km^2, from 30th to 60th Streets and from between 2nd and 3rd Avenues to between 8th and 9th. The Paris CBD, from just west of Les Halles to just east of Etoile, is also about 4 km^2 (see job density on PDF-p. 6 here). The Tokyo CBD, defined around Otemachi, Nihonbashi, Hibiya, Shimbashi, and increasingly Roppongi, is maybe 5-6 km^2, in a metro area of 38 million people.

Subway networks in such CBDs are necessarily crowded. The CBD is where people want to go. A subway line can get away with skirting it – Paris M4 does, and is in a near-tie with M1 for highest ridership per km. But avoiding it entirely is a ridership killer, except specifically for circumferential lines concentrating off-CBD travel: in Paris this suppresses M10 ridership, and in New York, it suppresses ridership on the J/Z (even though they serve Lower Manhattan) and the L (even though it serves Union Square). This means that the CBD of a large city will have many subway lines converging on a relatively small area. New York has its five north-south lines through Midtown.

Ensuring that every pair of intersecting subway lines has a transfer in this environment is difficult. Line spacing is usually narrower than station spacing, requiring kludges like the block-long walkways in New York, such as between Times Square at 42nd/7th and Port Authority at 42nd/8th. Paris managed to have an almost perfect network – before M14 was built, it only had one missed connection, between M9 and M12 (built by a competing private company) – but only by having very short station spacing, unusual even by the standards of the early 1900s, ruling out significant suburban extensions of the kind that are routine in London and Tokyo.

The situation in smaller cities is actually easier. The CBD is very small, often smaller than a square kilometer, but there are fewer lines, so it’s easier to make sure lines intersect properly. It’s also much easier to get line spacing right outside the CBD, where there’s less intense demand, allowing line spacing compatible with stop spacing on any intersecting or circumferential line.

The fundamental issue here is really about planning for the future. It’s not hard to gets lines 1, 2, and 3 to intersect nicely, or even lines 1-6. But beyond that, a city will often find itself in a situation where the best street alignment for line 7 happens to be right between two stations on line 1, spaced too far apart for a transfer. This is what happened to Tokyo. In New York, the three constituent systems (IRT, BMT, and IND) were each internally planned cohesively, so when two lines within the same system intersect, there’s a transfer, and, with difficulty, the IRT/BMT intersections have transfers as well. But the IND connects poorly to the other two systems, sometimes deliberately, and the IND’s layout made future extensions and service changes break transfers. My proposal to reduce reverse-branching in New York runs into the problem of breaking the transfers designed by the IND around a specific service plan.

When lines are designed together, it’s easier to avoid this problem. Paris M8 and M9 share a route through the center, as they were built simultaneously as the street is wide enough for four tracks. In contrast, building a line under or next to an existing line is much more difficult; New York did it anyway, under Sixth Avenue, but this led to cost overruns that doomed the IND’s early plans for further expansion. It is also difficult to build a new station under an existing transfer station, as it usually requires underpinning; in Paris, this problem means that transfer stations tend not to have closely-aligned platforms, requiring long walks between lines. When I’m proposing running multiple lines in the same tunnel in Lagos, this is from the point of view of assuming coordinated planning, with sequencing that allows entire streets to be dug up at once.

However, in reality, even coordinated design has its limitations. Subway networks take multiple decades to build, and in the interim, the city changes. Planners can attempt to use zoning to shape city development in a way that facilitates further expansion, but some tendencies are too uncontrollable. For instance, high-income neighborhoods tend to commercialize; I mentioned Roppongi as a growing part of the Tokyo CBD earlier, which is an example of this trend. The hottest new part of New York commercial development, the Meatpacking District, is really not a subway hub. This means that even if a city plans out lines 1-12 to share tunnels appropriately, it may not be able to control where there will arise the most demand for line 13. Coordinated long-term planning makes things easier, but it will not solve the basic problem of optimal subway spacing and CBD size.

Rapid Transit in the Third World

Last month, I committed to producing a subway fantasy map for Lagos via a Twitter poll. I’m working on this, but before I go into Lagos itself, I want to talk about the third world in general. Good transportation in poor countries is of independent interest, but it also has some applications to thinking about solutions for rich countries, such as the countries my readers live in. The reason is that every principle of good transportation planning has edge cases, exceptions, and assumptions, and it is critical to evaluate these in the largest variety of situations. Understanding transportation in the United States can yield insights about Europe and vice versa; likewise, understanding the first world can yield insights about the third and vice versa.

The epistemological principle I use is that if I believe that a high concentration of factor A makes solution B work better, then a low concentration of factor A should make solution B work worse. I used that in a post about high-speed rail in Sweden, arguing against it due to the absence of factors that make it work better, namely, linear population distribution. Many good design principles formulated in rich countries depend on those countries’ high incomes, and are less relevant to countries that are only about as wealthy as the US and northwestern Europe were in 1900.

Everything is terrible

On nearly every indicator of technology or living standards, every poor country is worse than every rich country. There are some exceptions involving middle-income countries (for example, Russia and China have very good rail freight), but not in low-income countries. I wrote a piece in YIMBY recently describing the state of New York and Vienna in the early 20th century, which had very high crowding levels; much of the same story can describe many third-world cities today, especially in India, where tight zoning limits housing supply to the point of overcrowding. In Mumbai, the average residential floor space per person is 9 square meters, compared with 55 in Manhattan.

Pollution levels are very high as well, because of the combination of high population density and heavy industry (especially in North India), as well as the proliferation of cars. The amount of pollution caused by 50 or 100 cars per 1,000 people in a dense city where the cars don’t have catalytic converters can be many times worse than that caused by the 200 mostly diesel-powered cars per 1,000 people of Paris, or the 250 cars per 1,000 people of New York. The low motorization levels of lower-middle-income cities like Cairo, Lagos, or Mumbai aren’t a barrier to traffic, either: those cities routinely have traffic jams, just as the United States started having jams in the 1920s. These cities have centralized employment in the CBD, not a lot of road capacity coming in, and a culture in which the middle class drives (or is driven by chauffeurs).

This creates an urgency for improving public transportation in low-income countries that does not exist in the developed world. Third-world countries that build subways spend a much higher share of their GDPs on them than Europe and Japan do, and some, such as India and Bangladesh, spend more than the United States. If Paris hadn’t built the RER, Franciliens would drive or take the slower Metro; if Shanghai hadn’t built the Metro, Shanghainese would still be living in tiny apartments and riding buses in crawling traffic; if Lagos doesn’t build a metro, Lagosians will keep facing multi-hour commutes. The same situation also creates an urgency for improving other areas the government can invest in; good government, capable of making these investments at reasonable cost, without too much corruption, is crucial for economic and social development.

Concrete before electronics

The cost of advanced signaling systems, such as driverless technology, is approximately the same everywhere in the world, in exchange rate terms. The cost of civil infrastructure construction is approximately the same in PPP terms, and if anything may be a little lower in poor countries. The cost of labor that advanced technology avoids is proportional to wages. This means that the electronics-before-concrete principle is less valid in poorer countries, and is sometimes not valid at all. There are practically no driverless metros in developing countries; the only examples I can find of lines in operation include two lines in Sao Paulo and one in Manila, with a small handful more under construction. Brazil is middle-income, and the Philippines are lower-middle-income rather than poor.

This principle also extends to countries with existing rail lines that they could expand. Investments in concrete – additional tracks, grade separation, relief lines – are more valuable than in developed countries, while investments in electronics are less valuable. A city with a desperate transportation situation can expect that every rapid transit line it builds will fill quickly. Tunnels are in a way more future-proof than precise schedules and resignaling.

Regulate cars, not buses

A recurrent feature of transportation in poor cities without rapid transit or BRT is the minibus. It goes by various names; the most famous to the first-world reader is probably the Nairobi matatu, but it also exists in Lagos as the danfo, in the Philippines as the jeepney, and in Jakarta as the angkot. These vehicles are not popular with the segment of the population that the government listens to: they are typically noisy and dirty and the drivers are aggressive. The governor of Lagos State recently announced a plan to ban the danfos, saying they don’t meet the international standards of a great city and should be replaced with air-conditioned buses. This is while the city is still working on its first metro line.

In Delhi, attempts to give buses road priority met an intense backlash from high-income drivers. There was a failed lawsuit openly stating that car drivers’ time was more important. Eventually Delhi scrapped the system entirely.

In contrast, the most successful public transit in cities that were recently poor or low-income, such as Singapore or Seoul, is in an environment where state policy restrained cars and not buses. Singapore has had congestion pricing since in the 1970s, the first city in the world to implement this scheme, and levies high taxes on cars, as does Hong Kong. Seoul restrained domestic consumption, including of cars, in its period of early industrialization from the 1960s to the 1980s.

Nigeria has 60 cars per 1,000 people. Lagos has maybe 150. To a large majority of the city’s population, cars are traffic, not transportation. Numbers in other third-world megacities vary but are not too different: Cairo has about 200 as of 2011, Delhi about 170, Jakarta about 300. (Some car and population numbers are a few years out of date; caveat emptor.) Traffic restraint is the correct policy given massive traffic jams and growing pollution levels, and the sooner the city starts, the better it will look in a generation.

Plan for growth

Developing-world cities are going to be much larger and richer in 30 years than they are today. National population growth rates range from moderate in India and Bangladesh to explosive in Nigeria, Kenya, and Tanzania. Moreover, all of these countries have low urbanization rates today and fast migration from the villages to the cities, setting up fast urban population growth even where national population growth isn’t so high. Economic growth projections are dicier, but at least one estimate through 2024 is quite optimistic about India and East Africa.

The high-density context of most cities in question rules out any auto-based development pattern. The population density of the eastern half of the Indo-Gangetic Plain, from Delhi downriver to Bangladesh, is about 1,000 people per km^2, comprising nearly 600 million people. Nowhere in the developed world is this density seen outside city regions. Lombardy has 400 people per km^2, and is as hemmed by mountains as North India, producing large-scale thermal inversions; with high levels of car traffic and heavy industry, it is one of the most polluted regions of Europe. Southern Nigeria is not so dense, but with fast population growth, it eventually will be. Egypt’s population density along the Nile is well into the four figures.

This also has implications for how rapid transit should be built. A metro line that passes through lightly-populated areas will soon sprout dense development around it, just as the early lines did in late-19th century London and early-20th century New York. Most New York railfans are familiar with the photo of farmland next to the 7 train in the 1910s; between 1900 and 1930, New York’s population doubled, while Queens’ population grew by a factor of 7. Such growth rates are realistic for some developing-world cities. For the same reason, it is worthwhile investing in grade-separated rights-of-way now, when they are cheap.

Another implication concerns capacity. Even Nairobi, which is not a megacity, can expect to become one soon, and requires many different rapid transit lines entering its center. Some of these can be accommodated on existing roads, as els or relatively easy subways under wide streets, but not all can. When the roads are wide enough, cities should consider four-track structures, since the relative construction cost of four-tracking is low for an el or a cut-and-cover subway.

Four-tracking has one additional benefit: local and express service, which is of critical importance in the very largest cities. In forums like Skyscraper City, Tokyo railfans often express concerns over China’s subways, which have no express tracks and little to no commuter rail, since they offer no path through the center faster than about 35 km/h (Tokyo’s express commuter lines, like Tokaido and Yokosuka, approach 60 km/h).

The final implication is that it’s fine to build a central business district from scratch. Shanghai is doing this in Lujiazui, but that is the wrong location, on the wrong side of a riverbend, with only one Metro line serving it, the overcrowded east-west Line 2; a north-south rail line would have to cross the river twice. A better location would have been People’s Square, served by Lines 1, 2, and 8. This is of especial relevance to cities whose traditional center is in a difficult location, especially Lagos but also Dar es Salaam.

BRT is not rapid transit

The failure of Delhi’s BRT line is in some sense atypical. The line was compromised from the start, and global pro-BRT thinktank ITDP expressed criticism from the start. However, other BRT projects draw cause for concern as well. Dar es Salaam’s BRT is instructive: the first phase cost about $8.5 million per km in exchange rate terms, or about $27 million per km in PPP terms, comparable to an average European light rail line or to an American BRT boondoggle. A hefty chunk of this cost comes from importing Chinese-made buses, which are priced in exchange-rate terms and not in PPP terms.

All else being equal, higher incomes strengthen the case for rail vs. BRT and lower incomes weaken it, since one of the major advantages of rail is fewer drivers per unit of passenger capacity. However, there is a countervailing force: the bulk of the cost of rail construction is local construction, priced in PPP terms, and not imported capital, priced in exchange rate terms. Trains still cost more than buses per unit capacity, but the bulk of the cost premium of rail over BRT is not the vehicles, and a weak currency reduces this premium.

And for all of the global marketing, by ITDP and by Jaime Lerner, the Curitiba mayor who invented modern BRT, BRT is not rapid transit. It is surface transit, which can achieve comparable speed to a tramway, but in a dense city with heavy traffic, this is not high speed. The busiest Parisian tramways, T1 and T3, average about 18 km/h. Modern rapid transit starts at 30 km/h and goes up as construction standards improve and stop spacing widens. BRT is still a useful solution for smaller cities, but in the larger ones, which need more speed, grade-separated rapid transit is irreplaceable.

Don’t neglect mainline rail

How are people going to travel between Jakarta and Surabaya, or between Lagos and Kano, or between Nairobi and Mombasa? They’re not going to fly; the capacity of air traffic is not high. They’re not going to take a vactrain. The only real solution is a high-speed rail network; Indonesia is already building HSR from Jakarta to Bandung, using Chinese technology, with plans for a further extension to Surabaya.

The most difficult part of building a new intercity rail network from scratch is serving the big cities. This is the big advantage of conventional rail over maglev or vactrains: it can run on legacy tracks for the last few kilometers. (In poorer countries, which import technology from richer ones, another advantage is that conventional rail isn’t vendor-locked.) Between this and the need to also accommodate medium-speed intercity rail to smaller cities, it’s important that developing-world cities ensure they have adequate right-of-way for any future system. Trunks should have a minimum of four tracks, with intensive commuter rail service on the local tracks, in a similar manner to Mumbai.

It is also important to build the metro to be mainline-compatible, in electrification and track gauge. It is wrong for India (and Pakistan) to build a single kilometer of standard-gauge metro; everything should be broad-gauge. Russia, where everything is on Russian gauge, does this better. African mainline rail networks are usually narrow-gauge and weak, and in some places (such as East Africa) are being rebuilt standard-gauge. Southeast Asia runs the gamut, with reasonable service in Jakarta, which is running frequent electric commuter rail using second-hand Japanese trains; this suggests future metro lines in Jakarta should be built narrow- rather than standard-gauge, to allow Tokyo-style through-service to commuter rail.

Conclusion

The biggest developing-world cities have problems with air pollution, traffic, overcrowding, and long commutes – precisely the problems that rapid transit is good at solving. They have equally great problems with infrastructure for electricity, running water, and sewage, and with access to health care, education, and such basic consumer goods as refrigerators. And they have limited tax capacity to pay for it all.

This makes building good transit – cost-effective, future-proof, and convenient enough to get high ridership – all the more critical. The smallest cities today may be able to get away with looking like smog-ridden midcentury Los Angeles, but even medium-size ones need to plan on models starting from New York or London or Tokyo, and the biggest ones, especially Lagos, should plan on looking like something that doesn’t really exist today.

To that effect, third-world governments need to absorb massive amounts of knowledge of good practices developed in Western Europe and high-income East Asia (and to a lesser extent Russia and China). But they cannot implement them blindly, but have to learn how to adapt them to local conditions: chiefly low incomes, but also weak currencies, import-dependence in technology, high expected future growth, and (in many cases) high expected population density. Nothing prevents a poor country from doing transit well: China, still a middle-income country, has more high-speed rail ridership than the rest of the world combined, and subway ridership per capita in Beijing, Shanghai, and Guangzhou is healthy. But India, Pakistan, Nigeria, and other poor countries with big cities have their work cut out for them if they want to solve their transportation problems.

The Yamanote Line: a Ring or a Radial?

Note: I am going to take some suggestions for post topics in the future. This post comes from a Twitter poll I ran the day before yesterday.

The Yamanote Line in Tokyo is a ring. Trains go around the ring as on any other circular rail line. However, the line is not truly circumferential, since it serves as a north-south trunk through Central Tokyo. In that way, it contrasts with fully circumferential rings, such as the Moscow Circle Line, Seoul Metro Line 2 (see update below), and the under-construction Paris Metro Line 15. It’s really a hybrid of radial and circumferential transit, despite the on-paper circular layout. In previous posts I’ve attacked one kind of mixed line and given criteria for when another kind of mixed line can work. In this post, I’m going to discuss the kind of mixed line Yamanote is: why it works, and in what circumstances other cities can replicate it.

Consider the following diagram:

The red and blue lines are radial. The other three are hybrids. The yellow line is radial, mostly, but skirts city center and acts as a circumferential to its west; this kind of hybrid is nearly always a bad idea. The pink line is radial, but at the eastern end bends to act as a circumferential at the eastern end; this kind of hybrid is uncommon but can work in special cases, for example if Second Avenue Subway in New York is extended west under 125th Street. The green line is a Yamanote-style ring, offering radial service through city center but also circumferential service to the south and west.

On this map, the green line ensures there is circumferential service connecting what are hopefully the major nodes just west and south of city center. It doesn’t do anything for areas north and east of it. This means that this line works better if there is inherently more demand to the west and south than to the east and north. In Tokyo, this is indeed the case: the Yamanote ring offers north-south circumferential service west of Central Tokyo, through what are now the high-density secondary business districts of Ikebukuro, Shinjuku, and Shibuya. East of Central Tokyo, the only really compelling destinations, judging by subway ridership, are Oshiage and Asakusa, and neither is as big as Ikebukuro, Shinjuku, or Shibuya. Toyosu has high subway ridership, but is close enough to the water that it’s hard to build a circumferential through it.

Such a mixed line also becomes more useful if the radial component is better. The radial line can’t extend very far out, since the line needs to form a ring, so it should connect to very high-density neighborhoods just a few stops outside city center, or else provide additional service on an overloaded radial trunk. The Yamanote Line benefits from looking less like a perfect circle and more like upside-down egg, with two elongated north-south legs and two short (one very short) east-west legs; it extends its radial segment slightly farther out than it would otherwise be. In Tokyo, of course, all rail lines serving the center are beyond capacity, so the Yamanote Line’s extra two tracks certainly help; in fact, the two radial lines going north and south of Tokyo Station on parallel tracks, the Tohoku and Tokaido Lines, are two of the three most overcrowded in the city. (The third is the Chuo Line.) There’s even a dedicated local line, Keihin-Tohoku, covering the inner segments of both lines, making the same stops as Yamanote where they are parallel, in addition to the more express, longer-distance Tokaido and Tohoku Main Line trains.

Finally, there should not be radials that miss the mixed line; this is always a danger with subway lines that are neither pure radials nor pure circumferentials. Yamanote avoids this problem because it’s so close to the water at Shimbashi that the north-south subway lines all curve to the west as they go south, intersecting the ring. It’s actually the east-west lines that cross the Yamanote Line without transfers, like Tozai and Hanzomon; the north-south lines intersect the line with transfers.

The obvious caveat here is that while the Yamanote Line functions very well today, historically it did not originate as a circumferential in an area that needed extra service. It was built as a bypass around Central Tokyo, connecting the Tokaido and Tohoku Line at a time when Tokaido still terminated at Shimbashi and Tohoku at Ueno. Tokyo Station only opened 30 years later, and the ring was only completed another 10 years after that. Shinjuku only grew in the first place as the junction between the Yamanote and Chuo Lines, and Ikebukuro and Shibuya grew as the terminals of interwar private suburban railways. When the line opened, in 1885, Tokyo had 1.1 million people; today, the city proper has 9.5 million and the metro area has 38 million. The early rail lines shaped the city as much as it shaped them.

Nonetheless, with the economic geography of Tokyo today, the Yamanote Line works. Even though the history is different, it’s a useful tool for mature cities seeking to build up their rail networks. Provided the principles that make for the Yamanote Line’s success apply – stronger demand for circumferential service on one side of city center than on the others, demand for supplemental inner radial service, and good connections to other lines – this layout can succeed elsewhere.

Waterfront cities should take especial note, since they naturally have one side that potentially has high travel demand and one side that has fish. In those cities, there may be value in running the radial closest to the shoreline in a ring with an inland line.

This does not mean that every waterfront city should consider such a line. On the contrary: non-examples outnumber examples.

In Toronto, using two mainline tracks and connecting them to a ring to provide subway relief could have worked, but there are no good north-south corridors for such a ring (especially on the west), and the only good east-west corridor is Eglinton, which is being built incompatible with mainline rail (and has too much independent value to be closed down and replaced with a mainline link).

In Chicago, the grid makes it hard to branch lines properly: for example, a ring leaving the Red Line heading west at Belmont would necessary have to branch before Belmont Station, cutting frequency to the busiest station in the area. Plans for a circle line from last decade also faced limited demand along individual segments, such as the north-south segment of the Pink Line parallel to Ashland; ultimately, the planned line had too small a radius, with a circumference of 16 km, compared with 34.5 for Yamanote.

In Tel Aviv, there just isn’t any compelling north-south corridor outside the center. There are some strong destinations just east of Ayalon, like the Diamond Exchange and HaTikva, but those are already served by mainline rail. Beyond that, the next batch of strong destinations, just past Highway 4, is so far from Central Tel Aviv that the line would really be two radials connected by a short circumferential, more the London Circle Line when it was a full circle than the Yamanote Line, which is just one radial.

So where would a Yamanote-style circle be useful outside Tokyo? There are semi-plausible examples in New York and Boston.

In New York, it’s at the very least plausible to cut the G off the South Brooklyn Line, and have it enter Manhattan via the Rutgers Street Tunnel, as a branch of the F, replacing the current M train. There is no track connection enabling such service, but it could be constructed just west of Hoyt-Schermerhorn; consult Vanshnookraggen’s new track map. This new G still shouldn’t form a perfect circle (there’s far too much radial demand along the Queens Boulevard Line), but there are plausible arguments why it should, with a short tunnel just west of Court Square: namely, it would provide a faster way into Midtown from Williamsburg and Greenpoint than the overcrowded L.

In Boston, there is a circumferential alignment, from Harvard to JFK-UMass via Brookline, that can get a subway, in what was called the Urban Ring project before it was downgraded to buses. Two of the busiest buses in the region, the 1 and 66, go along or near the route. An extension from Harvard east into Sullivan and Charlestown is pretty straightforward, too. Beyond Charlestown, there are three options, all with costs and benefits: keep the line a semicricle, complete the circle via East Boston and the airport, and complete the circle via the North End and Aquarium. The second option is a pure circumferential, in which South Boston, lying between East Boston and JFK-UMass, would get better service north and south than west to Downtown. The third option cuts off East Boston, the lowest-ridership of the radial legs of the subway, and offers a way into the center from South Boston and Charlestown.

Of note, neither New York nor Boston is a clear example of good use of the Yamanote-style ring. This style of mixed line is rare, depending on the existence of unusually strong circumferential demand on just one side (west in Boston, east in New York), and on the water making it hard to build regular circles. It’s an edge case; but good transit planning revolves around understanding when a city’s circumstances produce an edge case, in which the simplest principles of transit planning (“every subway line should be radial or circumferential”) do not apply.

Update 5/16: commenter Threestationsquare reminds me that Seoul Metro Line 2 is the same kind of ring as Yamanote. The north leg passes through City Hall, near the northern end of the Seoul CBD, providing radial east-west service. The south leg serves a busy secondary commercial core in Gangnam, Tehran Avenue; Gangnam Station itself is the busiest in Seoul, and has sprouted a large secondary CBD.

Slotting Intercity Trains on Regional Lines

In 2011, Clem Tillier and Richard Mlynarik put out sample schedules for modernized Caltrain service, with an applet anyone could use to construct their own timetables. I played with it, and one of the schedules I made, a trollish one, had room for local and express regional trains, but not intercity trains; intercity trains would be slotted with express regionals, and make the same stops. This was a curious exercise: intercity trains would be high-speed rail, which should not slow down to make every express regional stop. But more recently, as I’ve worked on schedules for Boston and New York, I’ve realized that when the regional trains are fast, there is merit to slotting legacy (but not high-speed) intercity trains together with them.

The origin of this pattern is the problem of slotting trains on busy railroads. There are many lines that are not really at capacity, but cannot easily combine trains that run at different speeds. One solution to the problem is to build extra tracks and give the intercity trains a dedicated pathway. This works when there is heavy intercity traffic as well as heavy regional traffic, but four-tracking a long line is expensive; Caltrain and California HSR ended up rejecting full four-tracking.

Another solution, favored for Caltrain today instead of full four-tracking, is timed overtakes. I have argued in its favor for Boston-Providence and Trenton-Stamford for high-speed rail, but it requires more timetable discipline and makes it easier for delays on one train to propagate to other trains. It should be reserved for the busiest lines, where there is still not enough traffic to justify long segments with additional tracks (that would be four tracking Boston-Providence and six-tracking Stamford-New Rochelle and Rahway-New Brunswick), but there is enough to justify doing what is required to run trains on a tight overtake schedule. It is especially useful for high-speed trains, which tend to be the most punctual, since they use the most reliable equipment and have few stops.

But on lower-ridership intercity routes, the best solution may be to force them to slow down to the speed of the fastest regional train that uses the line. On the timetable, the intercity train is treated as a regional train that goes beyond the usual outer terminal. This option is the cheapest, since no additional infrastructure is required. It also boosts frequency, relative to any solution in which the intercity train does not make regional stops: since the intercity train is using up slots, it might as well provide some local frequency when necessary. These two benefits together suggest a list of guidelines for when this pattern is the most useful:

  1. The intercity line shouldn’t be so busy that a slowdown of 10 or 15 minutes makes a big difference to ridership relative to the cost of overtakes. Nor should it be especially fast.
  2. The regional line, or the most express pattern on the regional line if it has its own local and express trains, should have wide stop spacing, such that the speed benefit of running nonstop is reduced.
  3. The regional line should connect long-distance destinations in their own right, and not just suburbs, so that there is some merit to connecting them to the intercity line. These destinations may include secondary cities, airports, and universities (but airports would probably be intercity stops under any pattern).
  4. The regional and intercity lines should be compatible in equipment, which in practice means either both should run EMUs or both should run DMUs (locomotives are obsolete for passenger services).

Both Switzerland and Japan employ this method. In Switzerland, the fastest intercity trains in the Zurich/Basel/Bern triangle run nonstop. But intercity trains going north or east of Zurich stop at the airport, interlining with regional trains to create a clockface pattern of trains going nonstop between the airport and the city.

In Japan, high-speed services run on their own dedicated tracks, with separate track gauge from the legacy network, but legacy intercity services are integrated with express regional trains. An intercity trip out of Tokyo on the Chuo Line starts out as a regular express commuter train, making the same stops as the fastest express trains: starting from Shinjuku, the Azusa sometimes stops at Mitaka, skips Kokubunji, and stops at Tachikawa and Hachijoji. Beyond Hachijoji, some trains make regional express stops, others run nonstop to well beyond the Tokyo commuter belt. On the Tokaido Line, the intercity trains (the Odoriko) skip stops that every regional train makes, but they still stop at Shinagawa and Yokohama, and sometimes in some Yokohama-area suburbs.

In North America, there are opportunities to use this scheduling pattern in New York, Boston, and Toronto; arguably some shorter-range intercity lines out of Philadelphia and Chicago, such as to Reading and Rockford, would also count, but right now no service runs to these cities.

In Toronto, GO Transit already runs service to Kitchener, 100 kilometers from Union Station. For reasons I don’t understand, service to Kitchener (and to Hamilton, a secondary industrial city 60 km from Toronto) is only offered at rush hour; in the off-peak, commuter trains only run closer in, even though usually intercity lines are less peaky than commuter lines. There is also seasonal service to Niagara Falls, 130 km from Toronto. As Metrolinx electrifies the network, higher frequency is likely, at least to Hamilton, and these trains will then become intercity trains running on a regional schedule. This works because GO Transit has very wide stop spacing, even with proposed infill stops. Niagara Falls is a leisure destination, with visitors from all over the Greater Toronto Area and not just from Downtown, so the extra stops in the Toronto suburbs are justified. Right now, Niagara Falls trains make limited stops, about the same number in the built-up area as the express trains to Hamilton but on a different pattern.

There are no infill stops planned on Lakeshore West, the commuter line to Hamilton and Niagara Falls. It is likely that future electrification and fare integration will create demand for some, slowing down trains. The line has three to four tracks (with a right-of-way wide enough for four) and is perfectly straight, so as demand grows with Toronto’s in-progress RER plan, there may be justification for local and express trains; express trains would make somewhat fewer stops than trains do today, local trains would stop every 1-2 km in the city and in Mississauga. Intercity trains could then easily fit into the express commuter slots; potential destinations include not just Hamilton and Niagara Falls, but also London.

This is unfriendly to high-speed trains. However, Canada is not building high-speed rail anytime soon; if it were, it would connect Toronto with Montreal, using Lakeshore East, and not with points west, i.e. London and Windsor. London and Windsor are small, and a high-speed connection to Toronto would be financially marginal, even with potential onward connections to Detroit and Chicago. A Toronto-Niagara Falls-Buffalo-New York route is more promising, but dicey as well. Probably the best compromise in such case is to run trains on a four-tracked Lakeshore West line at 250 km/h; the speed difference with nonstop trains running at 160 km/h allows 15-minute frequency on each pattern without overtakes, and almost allows 12 minutes. Alternatively, express trains could use the local tracks to make stops, as I’ve recommended for some difficult mixtures of local, express, and intercity trains on the Northeast Corridor in New York.

In Boston, the Northeast Corridor is of course too important as an intercity line to be slowed down by regional trains. Thus, even though in other respects it would be great for merging intercity and regional service, in practice, overtakes or four tracks are required.

However, all other intercity-range commuter lines in Boston should consider running as regular commuter trains (electrified, of course) once they enter MBTA territory. These include potential trains to Hyannis on Cape Cod, 128 km from South Station; Manchester, 91 km from North Station; and Springfield, 158 km from South Station; as well as existing trains to Portland, 187 km from North Station. Hyannis, Manchester, and Portland all feed into very fast regional lines: my sample schedule and map have trains to Hyannis averaging 107 km/h and trains to Manchester averaging 97 km/h. Trains to Haverhill, the farthest point on the line to Portland with any Boston-bound commuter traffic, average 88 km/h.

Springfield is more difficult. The Worcester Line is slower, partly because of curves, partly because of very tight stop spacing in the core built-up area. Once under-construction infill is complete, Auburndale, 17 km out of South Station, will be the 7th station out, and another infill station (Newton Corner) is perennially planned; my schedule assumes 3 additional stations, making Auburndale the 11th station out. On the line to Hyannis, the 11th station out, Buzzards Bay, is at the Cape Cod Canal, 88 km out. There is room for four tracks for a short segment in Allston, but in the suburbs there is no room until past Auburndale, which constrains any future high-speed rail plan to Albany. Low-speed intercity trains would have to slow down to match commuter rail speed, because the alternative is to run commuter rail too infrequently for the needs of the line. Average speed from South Station to Worcester is 70 km/h, even with express diesels today, so it’s not awful, but here, slowing down intercity trains is a less bad option rather than a good one.

In New York, as in Boston, intercity trains fit in regional slots away from the Northeast Corridor. Already today there are intercity trains running on the LIRR, to the eastern edge of Long Island, much too distant from the city for commuter traffic. Those trains run nonstop or almost nonstop, and are infrequent; if the entire LIRR were electrified, and express trains were eliminated, locals could match the express speed today thanks to reduced schedule padding, and then some trains could continue to Greenport and Montauk providing perhaps hourly service. Service to Danbury and Waterbury on Metro-North is of similar characteristics.

The New Jersey end is more interesting. Right now, there is no significant intercity service there, unless you count the Port Jervis Line. However, New Jersey Transit is currently restoring service on the Lackawanna Cutoff as far as Andover, and there remain proposals to run trains farther, to Delaware Water Gap and Scranton. Those would be regular express diesel trains on the Morris and Essex Lines, presumably stopping not just at Hoboken but also at important intermediate stations like Newark Broad Street, Summit, and Morristown.

If service were electrified, those trains could run, again on the same pattern as the fastest trains that can fit the Morristown Line (where I don’t think there should be any express trains), going to New York and onward to whichever destination is paired with the shorter-range commuter trains on the line. The same is true of other potential extensions, such as to Allentown, or, the favorite of Adirondacker in comments, a line to West Trenton and onward to Philadelphia via the West Trenton SEPTA line. There’s not much development between the edge of the built-up suburban area at Raritan and either Allentown or the Philadelphia suburbs; but intercity trains, averaging around 90 km/h, could succeed in connecting New York with Allentown or with the northern suburbs of Philadelphia, where a direct train doing the trip in an hour and a half would be competitive with a train down to 30th Street Station with a high-speed rail connection.

The characteristics of intercity lines that favor such integration with regional lines vary. In all cases, these are not the most important intercity lines, or else they would get dedicated tracks, or overtakes prioritizing their speed over that of commuter trains. Beyond that, it depends on the details of intercity and regional demand. But by default, if an intercity line is relatively short (say, under 200 km), and not so high-demand that 200+ km/h top speeds would be useful, then planners should attempt to treat it as a regional line that continues beyond the usual terminus. Alternatively, the commuter line could be thought of as a short-turning version of the intercity line. Planners and good transit advocates should include this kind of timetabling in their toolbox for constructing integrated regional rail schedules.

Where is Electrification Warranted?

At the beginning of the month, I published a piece in Voice of San Diego calling for medium-speed rail investment in the Los Angeles-San Diego corridor, centering electrification. This was discussed in a 500-comment thread on California HSR Blog, in which area rail activist Paul Dyson ripped into my plan, arguing (among other things) that electrification is costlier and less useful than I think. Instead of reopening the debate on that particular corridor, I want to discuss a more general set of guidelines to when rail lines should be electrified.

I haven’t said so in these exact words, but I think North American rail authorities and activists underrate electrification. As a result, I find myself persistently prescribing electrification and defending it when it’s already on the table, even as I attack other rail investments as wasteful. On social media and in blog comments I find myself having to constantly explain to people that no, a $20 billion New York regional rail plan should not use dual-mode locomotives but rather spend $250 million on New Jersey-side electrification.

A year and a half ago I wrote about why small, dense countries should fully electrify. The reasons laid out in that post are included in the guidelines below, but there are some additional circumstances justifying electrification.

Narrow stop spacing

Each train has a stop penalty – a total amount of time it loses to making each stop. The penalty is based on dwell time, line speed, and train acceleration and braking performance. If the line speed is 130 km/h, then the penalty excluding dwell time is about 35 seconds for a FLIRT and 80 seconds for a diesel GTW. This 45-second difference per stop is the same if there is a stop every 3 km or if there is a stop every 50 km.

Stop spacing is narrower on commuter lines than on intercity lines, so electrification usually starts from commuter rail. The first mainline electrification in the world was in Paris on the commuter lines serving Gare d’Orsay; subsequently the commuter lines in Paris, London, Tokyo, Berlin, New York, Philadelphia, and other major cities were wired. In many of these cases, commuter rail was electrified decades before intercity mainlines: for example, Japan started electrifying Tokyo’s innermost commuter lines in the 1900s and completed them in the 1920s and early 30s, but took until 1956 to electrify the first intercity line, the Tokaido Line.

However, in some dense regions, even the intercity lines have many stops. Cities in Israel, Belgium, the Netherlands, and Switzerland are just not very far apart, which blurs the distinction between regional and intercity lines somewhat. Switzerland is all-electrified, and my post from 2015 argued that the first three should be, too. In the US, there are specific regions where continuous sprawl has led to the same blurring: the Northeast Corridor, Southern California, Central and South Florida, New England. All are characterized by high population density. New England has closely spaced cities, whereas the LA-San Diego corridor and corridors within Florida have so much sprawl that there have to be several stations per metro area to collect people, reducing stop spacing.

Frequent sharp curves between long straight segments

Electric multiple units (EMUs) can make use of their high acceleration not at stations, but also at slow restrictions due to curves. They are also capable of higher cant deficiency than top-heavy diesel locomotives, since they have low center of gravity, but the difference for non-tilting trains is not so big. A uniformly curvy line does not offer EMUs much advantage, since all trains are slow – if anything, the lower the top speed, the less relevant acceleration is.

The big opportunity to accelerate is then when a mostly straight line is punctured by short, sharp curves. Slowing briefly from 130 km/h to 70 km/h and then speeding back up costs a FLIRT on the order of 15 seconds. A diesel train, whether powered by a locomotive or by diesel multiple units (DMUs), can’t hope to have the required power-to-weight ratio for such performance.

Mountains

EMUs’ better acceleration profile makes them better-suited for climbing hills and mountains. Modern EMUs, especially low- and medium-speed ones optimized for high acceleration, can effortlessly climb 4% grades, at which point DMUs strain and diesel locomotives require helper engines. When the terrain is so mountainous that tunnels are unavoidable, electric trains do not require ventilation in their tunnels. As a result, some long rail tunnels were electrified from the start. The combination of uphill climbs and tunnels is literally toxic with diesels.

Cheap, clean electricity

Electrification has lower operating costs and lower greenhouse gas emissions in areas where the electricity is powered by cheap hydro or geothermal power than in areas where it is powered by fossil fuels. Switzerland became the only country with 100% rail electrification because it had extensive hydro power in the middle of the 20th century and was worried about relying on coal shipments from Nazi Germany during the war.

This is especially useful in far northern countries, like Sweden and Canada, which have low population density and little evaporation, leading to extensive hydro potential per capita. Despite its low density, Sweden has electrified about two thirds of its rail network. In the US, this is the most relevant to the Pacific Northwest.

But in the future, the falling cost of solar power means that clean electricity is becoming more affordable, fast. This favors electrification in more places, starting from sunny regions like most of the US.

Small installed diesel base

A rich or middle-income country building railroads for the first time, or expanding a small system, needs to build new yards, train maintenance crews, and procure spare parts. It should consider electrifying from the start in order to leapfrog diesel technology, in the same manner many developing countries today leapfrog obsolete technologies like landline phones. In contrast, a larger installed base means electrification has to clear a higher bar to be successful, which is why Japan, France, and other major core networks do not fully electrify.

The US situation is dicey in that it does have a lot of diesel equipment. However, this equipment is substandard: reliability is low, with mean distance between failures (MDBF) of about 45,000 km on the LIRR compared with 680,000 on new EMUs (source, pp. 30-31); the trains are very heavy, due to past FRA regulations; and the equipment is almost universally diesel locomotives rather than DMUs, which makes the acceleration problem even worse than it is for GTWs. Total acceleration and deceleration penalty on American diesel locomotives is not 80 seconds but 2-2.5 minutes.

Because North America underrates electrification, some people who self-identify as forward-thinking propose DMUs. Those require new maintenance regimes and facilities, creating an entire installed base from scratch instead of moving forward to EMUs.

Globally, the installed diesel base for high-performance lines is vanishingly small. The technology exists to run diesel trains at more than 200 km/h, but it’s limited in scope and the market for it is thin.

Through-service to electric lines

Whenever a diesel line is planned to run through to an electric line, it should be a prime candidate for electrification. Dual-mode locomotives exist, but are heavy and expensive; dual-mode multiple units are lighter, but are still boutique products.

This is especially true for the two biggest investments a network can make in passenger rail: RER tunnels, and HSR. RER tunnels involve expensive urban tunneling. When a kilometer of urban subway costs $250 million and a kilometer of catenary costs $2 million, the economics of the latter become stronger. Not to mention that RERs are typically short-hop commuter rail, with frequent stops even on the branches. HSR is a different beast, since it’s intercity, but the equipment is entirely electric. Running through to a diesel branch means towing the train behind a diesel locomotive, which means the expensive HSR traction equipment is idle for long periods of time while towed; this is at best an interim solution while the connecting legacy line is wired, as in the line to Sables d’Olonne.

Nearly complete electrification

Areas where the rail network is almost completely electrified benefit from finishing the job, even if individually the diesel lines are marginal candidates for electrification. This is because in such areas, there is a very large installed electric base, and a smaller diesel base. In small countries the remaining diesel base is small, and there are efficiencies to be had from getting rid of it entirely. This is why the Netherlands and Belgium should finish electrification, and so should Denmark and Israel, which are electrifying their main lines.

This is somewhat less applicable to larger countries, such as Sweden, Poland, and especially Japan. However, India is aggressively electrifying its rail network and planning even more. Note that since networks electrify their highest-trafficked lines first, the traffic can be almost completely electrified even if the trackage is not. For example, Russia is about 50% electrified, but 86% of freight tonnage is carried on electric trains, and the share of ton-km is likely higher since the Trans-Siberian Railway is electrified.

This also applies to networks smaller than an entire country. Commuter rail systems that are mostly electrified, such as the LIRR, should complete electrification for the same reason that mostly electrified countries should. In New England and Southern California, regional rail electrification is desirable purely because of the acceleration potential, and this also makes full electrification desirable, on the principle that a large majority of those two regions’ networks have enough potential traffic to justifying being wired without considering network effects.

Recommendations

Every place – a country, an isolated state or province, a commuter rail system – that is at least 50-60% electrified should consider fully electrifying. The majority of the world that is below that threshold should still wire the most important lines, especially regional lines. Capital-centric countries like Britain and France often get this wrong and focus on the intercity lines serving the capital, but there are low-hanging fruit in the provincial cities. For example, the commuter rail networks in Marseille, Lyon, and Bordeaux are almost entirely electrified, but have a few diesel lines; those should be wired.

In North America, electrification is especially underrated. Entire commuter rail networks – the MBTA, Metra, Metrolink, MARC/VRE, GO Transit, AMT, tails on the New York systems – need to be wired. This is also true of short-range intercity lines, including LA-San Diego, Chicago-Milwaukee, Boston-Portland, Toronto-Niagara Falls, and future New York-Scranton. It is important that good transit activists in those regions push back and support rail electrification, explaining its extensive benefits in terms of reliability and performance and its low installation cost.