Barcelona

[Read in English]

[En 2016 visité Barcelona por primera vez.  Esta es una traducción española del artículo que escribí entonces.]

Barcelona tiene el tipo de sistema de transporte público que impresiona a un norteamericano a primera vista: un metro grande, autobuses agradables con numerosos tramos de carril exclusivo, dos funiculares prácticos, trenes de cercanías y dos redes de tranvía…

Es la forma habitual en que la mayoría de la gente resume un sistema de transporte, ¿verdad? Una lista de las tecnologías en uso, que no dice nada sobre lo fácil que es moverse por la ciudad. ¿Te has fijado en que, cuando dije «dos redes de tranvía», sonó al principio como si eso fuera mejor que una sola red de tranvía? Lo contrario es cierto, por supuesto, y de hecho están trabajando para convertirlas en una sola.

Al final, lo que importa no es la diversidad de tecnologías, sino lo fácil que es llegar a los lugares, y esto requiere otro tipo de turismo de transporte. En lugar de ir a una ciudad para maravillarse con las tecnologías —prefiriendo los tranvías a los autobuses sin importar a dónde van, y subiéndose a cada funicular, góndola y curiosa barquita— yo prefiero el turismo de acceso: intento ir realmente a lugares y experimentar lo fácil o difícil que resulta. (Sigo experimentando la casualidad afortunada, claro, pero esta destaca con mayor nitidez cuando se ve contra el fondo luminoso de la intención.)

Solo viajar con intención me hizo notar la rareza del metro de Barcelona. El mapa completo de la agencia de transporte está aquí, y a continuación incluyo una sección. También puede gustarte la versión más austera de Jug Cerovic aquí. La red es complicada en parte porque muestra líneas de metro (L), líneas de tranvía (T) y líneas regionales de cercanías (R), pero para este propósito me centraré en las líneas de Metro (L).

Un poco de matemática sencilla: en una red en cuadrícula óptima, las líneas siguen más o menos rectas y se cruzan entre sí más o menos perpendicularmente. En esta red cambias de dirección haciendo un transbordo. La perpendicularidad maximiza el área de la ciudad a la que cada transbordo te puede llevar.

Las cuadrículas de transporte pueden ser estándar o polares, pero casi siempre son alguna fusión sutil de ambas. La cuadrícula polar surge cuando hay un gran centro en el que la red converge lógicamente, porque los destinos deseables se concentran allí más densamente.

Una vez que reconoces estos patrones, notas lo coherentes que son la mayoría de las redes de metro. Incluso aquellas que son apaños hasta cierto punto suelen haber sido remendadas todo lo posible para crear alguna fusión apropiada de los efectos de cuadrícula radial y estándar.

Pero entre los metros que he conocido, la red del metro de Barcelona parece inusualmente caótica en su estructura, dando a menudo la impresión de serpentear sin intención.

En el mapa de arriba, por ejemplo, fíjate en la línea azul intermedia que entra en el área del mapa por la izquierda en la estación de Pubilla Cases. Esta es la Línea 5. Atraviesa el mapa con resolución de izquierda a derecha, pero a dos tercios del camino a través de la ciudad, en La Sagrera, parece distraerse, girando de repente 120 grados y dirigiéndose hacia las colinas en la parte superior del mapa.

La red también está llena de líneas que se encuentran tangencialmente en lugar de cruzarse. Por ejemplo, aquí tienes un diagrama solo de las Líneas 5 y 2 (azul oscuro y morada, respectivamente) tocándose tangencialmente en la estación (no señalada) de la Sagrada Família:

Hay numerosos casos como este. En cada caso tendrías una red más coherente —más capaz de conectar a más personas con más destinos y con menos transbordos— si las líneas intercambiaran trayectos en este punto, cruzándose una sobre la otra en lugar de tocarse tangencialmente.

De nuevo, la mayoría de los metros son apaños hasta cierto punto. Es poco probable que alguien vivo hoy en Barcelona merezca culpa por los extraños patrones del flujo del metro. Siempre hay razones históricas para que las cosas hayan terminado como están. Si quieres seguir esa historia, aquí tienes un vídeo entretenido.

Pero mientras tanto: ¿tienes en la cabeza alguna idea recibida del estilo de «los metros europeos son tan fantásticos que ¿por qué iba alguien a coger el autobús?»? Recuerdo cuando muchos europeos solían creer esto, pero hoy en día la mejora de las redes de autobús es una de las tendencias europeas más importantes. La necesidad de una red de autobús racional puede ser aún más urgente si tu metro va dando tumbos como un borracho, incapaz de seguir una línea recta.

Lo estupendo de la nueva red de autobuses de Barcelona, entonces, no es solo que sea una cuadrícula, sino que de verdad quiere que sepas que es una cuadrícula, y lo rectas que son las líneas que la componen:

Las nuevas líneas tienen números precedidos por «H» o «V» para «horizontal» o «vertical». (Vertical es bastante literal: no solo arriba-abajo en mapas estándar como este, sino también hacia arriba a las colinas o hacia abajo al mar.) Estas líneas frecuentes están además numeradas en secuencia lógica a lo largo de la ciudad, de modo que, a medida que conoces la red, un número te recuerda aproximadamente dónde se sitúa cada línea dentro de la cuadrícula y, por tanto, para qué es probable que sea útil.

La idea es que la gente debería poder mantener una noción de toda la red en cuadrícula en la cabeza. Si simplemente recuerdas qué significan H y V, y la secuencia en la que están numeradas, dispones de una enorme cantidad de información sobre todo el sistema. Cuando ves cualquier autobús numerado de esta manera, tienes un sentido general de hacia dónde va, o al menos a lo largo de qué eje. Y cuando oyes el número de una ruta de autobús, puedes formarte fácilmente una idea general de dónde se encuentra.

Hay libertad en este tipo de legibilidad. Podrías medirla en términos del número de lugares útiles a los que puedes llegar dividido por los bytes de información que necesitas recordar para tener un mapa funcional de cómo llegar allí. Cualquiera que haya navegado por Manhattan conoce la diferencia entre la cuadrícula regular en la mayor parte de la isla (alta utilidad/byte) frente al laberinto sin patrón de calles en el extremo sur (baja utilidad/byte). Las ciudades europeas tienden a ser especialmente difíciles en este sentido.

Hablo mucho de la red de autobuses de Barcelona porque es uno de los mejores ejemplos de la divulgación de la legibilidad a escala de red, una idea casi inaudita en otras partes del mundo. (Quizá relacionado, también tiene un artículo en Wikipedia que la describe con el mismo respeto que cabría esperar al hablar de una red de metro.)

Barcelona pudo dar con su red de autobuses en cuadrícula, en parte, porque las cuadrículas legibles y orgullosas ya eran su idea de planificación urbana más célebre. La mayoría de los trazados de calles europeas carecen en gran medida de cuadrícula y son irregulares. Pero en una visión sistematizadora rival de la de Haussmann en París, la Barcelona del siglo XIX adoptó un único patrón en cuadrícula para su rápida expansión alrededor del núcleo medieval.

Foto de Alhzeiia vía Wikipedia

A este plan se le suele llamar el distrito del Eixample, pero es realmente un principio más que un lugar. (La palabra catalana eixample significa «extensión» o «área ampliada».) La nueva cuadrícula recorre la ciudad a lo largo de unos 7 km (4,5 mi). Por tanto cubre muchos barrios, uniéndolos no solo con un trazado de calles perfectamente regular, sino también con el detalle más distintivo de la cuadrícula: las esquinas «achaflanadas» que crean pequeños espacios cuadrados en cada gran intersección.

Ahora que Barcelona está empezando a cerrar muchas de estas calles al tráfico rápido de coches, estos pequeños rombos serán los próximos grandes espacios públicos en una ciudad ya rica en ellos. Y una gran red de autobuses, cuyo patrón en cuadrícula a escala de toda la ciudad puedes recordar, y que para justo a la vuelta de la esquina, te llevará allí.

Gracias a mi amigo barcelonés Andreu Orte por el contexto, incluido el diagrama de las Líneas 5/2.

Jacob Lynn is currently a data scientist at Booking.com, and was previously Chief Information Officer at public transit start-up Via Analytics.

Bus network redesigns have been making waves in the transit world over the past few years. The new Houston bus network represented a massive redeployment of resources, and early returns suggest that bus ridership is increasingly roughly as expected, though ridership is also subject to broader economic forces. Portland’s 1982 grid restructuring was critical to the early success of the new light rail system. But Barcelona’s recently redesigned bus network, the Nova Xarxa, has [despite this Human Transit post] received less attention outside Europe than it probably deserves. New research indicates that the network started inducing new demand as soon as it was deployed. Even though it is only partially complete, the Nova Xarxa is demonstrating the potential of transfer-oriented high-frequency bus networks for providing an anywhere-to-anywhere mobility solution for a city.

Prior to the redesign, Barcelona had a spaghetti-like tangle of routes with many stops, low speeds, and generally low frequencies. In other words, like most bus systems, it was biased towards coverage over ridership. Of course, in conjunction with the Metro network and the suburban Rodalies commuter rail, transit has a very high mode share in Barcelona overall. But city officials felt like they were not making the best use of their bus system. Could something be done?

A central section of the local bus network in Barcelona.

Enter the Nova Xarxa. (NB: Nova Xarxa means “new network” in Catalan, and Xarxa is pronounced “sharsha.”) Carlos Daganzo developed a simple mathematical framework to model a “hybrid” transit network, which combines features of grid and radial networks. The model could be optimized to minimize a combination of transit agency and user costs, including travel and wait time. This abstract model was then applied to the specific situation in Barcelona to determine the target spacing between routes in the grid, spacing between stops on a route, service frequency, and other parameters of the network. It turned out that a grid-like network with very frequent service, stop spacing of about 400 meters, and about 20 lines would serve the city well.

Once these basic organizing principles had been determined, Transports Metropolitans de Barcelona (TMB), the city’s transit agency, got to work developing the actual routes. The resulting network has been remarkably faithful to the original grid vision. (The Nova Xarxa was previously discussed on Human Transit in 2010 and again in 2016.)

The current Nova Xarxa, which is about 60% complete.

By design, a grid network depends critically on transfers between routes to enable anywhere-to-anywhere urban travel. Transfers between bus routes have a bad reputation among the public, to the point where there is a large academic literature quantifying exactly how awful it is to have to wait for the bus, particularly when connecting between routes. But in big urban metro rail networks, transfers between lines are commonplace and often only a mild inconvenience. The key difference is the amount of time you have to wait for your connection. Many metro lines run at intervals of 4 to 8 minutes, making the wait for the next train much more palatable. So, if the buses come sufficiently frequently, the thinking goes, the “transfer penalty” may disappear, and the system will function as a well-connected network rather than as a collection of individual lines. (Of course, the transfer experience differs between a metro system and a bus network due to other environmental factors, but generally speaking, if the wait time is short, those other factors will matter less too.)

The Nova Xarxa is designed with this principle in mind, with scheduled headways between 3 and 8 minutes for the entire system. The currently deployed Nova Xarxa routes all have scheduled headways of 6 to 8 minutes, and most current NX routes are intended to have shorter headways once the full network is deployed. Shorter headways are enabled by several factors. Increased spacing between stops, as well as dedicated bus lanes where space permits, have provided key speed increases. Some intersections have traffic signals which prioritize buses. New articulated buses were purchased that increased capacity and in some instances (e.g. line H12) enabled faster multi-door boarding. Removal of overlapping routes allowed redeployment of existing resources. But the network redesign was not intended to be cost-neutral, and some of the frequency increases have come from simply running more buses.

The Nova Xarxa has been deployed in four phases. In each phase, pre-existing routes that had been superseded by the new routes were removed or redesigned to focus on local service. Five routes were initially deployed in October 2012, five new routes were added in November 2013, and three more were added in September 2014. Three more were deployed in February 2016, but data from that period was not included in this report’s analysis. The full deployment of the Nova Xarxa will consist of 28 lines, and it is currently more than half complete. The detailed routes for the 12 final lines were recently proposed by TMB, and should be deployed during 2017 and 2018.

A group of researchers, including Hugo Badia of the Universitat Politècnica de Catalunya and Juan Argote and Carlos Daganzo from UC Berkeley, presented an analysis of ridership on the Nova Xarxa at the recent Transportation Research Board meeting in D.C. (As noted above, Daganzo worked with the city of Barcelona on the initial high-level network concept in 2010, but was not thereafter involved in the detailed design or deployment of the Nova Xarxa.) The research is publicly available as a working paper and is currently under review at TRB Part A. TMB provided the researchers with their key dataset: total bus boardings, broken down on a per-route, per-month basis, over the entire period of the new network. The dataset did not include detailed records of individual boardings, so the proportion of transfers could not be determined directly. But the phased deployment of the network allowed the researchers to use a clever technique.

Boardings on the Phase 1 routes generally reached a fairly stable level within a few months, but then jumped up sharply when Phase 2 was deployed, and then again when Phase 3 was rolled out. The authors infer that the increase in boardings on the Phase 1 routes was caused by riders who were transferring to and from the new routes. When the new routes opened, the old routes immediately became more useful, because they now provided access to more destinations with a short transfer. The researchers formalized this intuition into a simple statistical model, which allowed them to decompose each route’s ridership into two components: baseline demand for the route itself, and transfer demand for connecting routes.

Monthly validations on the NX, with routes grouped by their phase of deployment. As new phases were deployed, boardings on routes from previous phases jumped up, almost certainly due to transfers to and from the new routes.

So how much do transfers matter? The authors estimate that 26% of boardings on the current Nova Xarxa comes from transferring passengers — and once the entire network is deployed, they project that bus-to-bus transfers will represent 44% of boardings. This will be much higher than other major bus networks that overlay rail transit networks, such as Melbourne (16%), Boston (1.5%), London (13%), and New York (3%). (Note that this indicator is not always made public by transit agencies, and different agencies measure it in different ways.) Furthermore, comparing ridership on old routes to their new replacements suggests that corridor ridership has increased by 6% to 24%, due to a combination of increased connectivity, ease of use, and improved level of service. This figure should also increase as the rest of the network is rolled out.

Other factors have contributed to the success of the new network. In the early modern period, Barcelona, as the key city of Catalonia, was repressed by the centralized Spanish monarchy, fortified against revolt, and penned in behind its medieval city walls. Once these walls were removed in the mid-1800s, the city of Barcelona expanded dramatically beyond its medieval core under a strongly gridded street plan, known as L’Eixample. Thus, the idea of the “grid” has a strong resonance with the shape of the city for its citizens. Barcelona city officials have indicated that they believe that the disruptive Nova Xarxa plan faced less political resistance thanks to this intuitive preference for grids.

Beyond any speculative psychological considerations, Barcelona is a city of relatively spatially uniform population and job density. Within the city, there is no strong central business district generating demand for highly radial transit. Furthermore, the city is geographically constrained by mountains to the northwest, the Mediterranean to the southeast, and the Llobregat and Besòs rivers on the other two sides. Thus the overall urban density is quite high. Demand for space-efficient modes in Barcelona is intrinsically high and isotropic, making the Nova Xarxa a natural fit.

These results should not be too surprising. But it is rare that the real world provides us with such a clear-cut opportunity to test the principles of network design. Barcelona’s experience strongly suggests that a dense network with sufficient frequency for painless transfers can unlock anywhere-to-anywhere travel.

The authors of the original analysis, Hugo Badia, Juan Argote, and Carlos Daganzo, provided very useful feedback on early drafts of this article.

For just two days, over a weekend, I’ve visited Barcelona for the first time.

It has the sort of public transit system that will impress a North American at first: a large metro, pleasant buses with numerous stretches of exclusive lane, two practical funiculars, commuter trains, and two tram networks …

That’s the usual way most people summarize a transit system, isn’t it?  A list of technologies in use, which says nothing about how easy it is to get around the city. Did you notice how, when I said “two tram networks,” it sounded at first like that’s better than one tram network? The opposite is true, of course, and indeed they’re working on making it just one.

In the end, what matters is not the diversity of technologies, but how easy it is to get places, and this requires a different kind of transit tourism. Instead of going to a city to marvel at the technologies – picking trams over buses regardless of where they go, and riding every funicular, gondola, and odd little ferry – I prefer access tourism: I try to actually go places, and experience how easy or hard that is.  (I still experience serendipity of course, but it’s in sharper relief when seen against the bright background of intention.)

Only traveling with intention made me notice the oddness of the Barcelona metro. The transit agency’s full map is here, and a slice is coming up below.  You may also enjoy Jug Cerovic‘s more austere version here.  The network is complicated partly because it shows metro lines (L), tram lines (T) and regional commuter rail lines (R) but for this purpose I’ll focus on the Metro lines (L).

Some simple math: In an optimal grid network, lines keep going more or less straight, and intersect each other more or less perpendicularly.  You change direction in this network by making a connection.  The perpendicularity maximizes the area of the city that each connection could take you to.

Transit grids can be standard or polar, but are almost always some subtle fusion of the two. The polar grid arises when there’s a huge center on which the network logically converges, because desirable destinations are packed most tightly there.

Once you recognize these patterns, you notice how coherent most metro networks are. Even those that are kludges to a degree have usually been patched as much as possible to create some appropriate fusion of radial and standard grid effects.

But among the metros I’ve encountered Barcelona’s metro network seems unusually chaotic in its network structure, often seeming to meander without intention.

On the map above, for example, look at the medium blue line that enters the map area on the left at Pubilla Cases station.  This is Line 5.  It heads resolutely across the map from left to right, but two-thirds of the way across the city, at La Sagrera, it seems to get distracted, suddenly turning 120 degrees and heading for the hills at the top of the map.

The network is also full of lines meeting tangentially instead of crossing.  For example, here’s a diagram of just Lines 5 and 2 (dark blue and purple, respectively) touching tangentially at (unmarked) Sagrada Família station:

There are numerous cases like this.  In each case, you would have a more coherent network — more likely to connect more people to more destinations with fewer transfers — if the lines traded paths at this point, crossing over each other rather than touching tangentially.

Again, most metros are kludges to some degree.  It’s unlikely that anybody alive in Barcelona today deserves blame for the odd patterns of the metro’s flow.  There are always historical reasons for why things have ended up as they are.  If you want to follow that history, here’s a fun video.

But meanwhile:  Does your head contain some received wisdom along the lines of: “European metros are so fantastic that why would anyone take buses?” I can remember when many Europeans used to believe this, but today, bus network improvement is one of the most important of European trends. The need for a rational bus network may be even more urgent if your metro is staggering around drunkenly, unable to follow a straight line.

What’s great about the new Barcelona’s bus network then, is not just that it’s a grid, but that it really wants you to know that it’s a grid, and how straight its constituent lines are:

The new lines have numbers preceded by “H” or “V” for “horizontal” or “vertical”.  (Vertical is quite literal: not just up-down on standard maps like this one, but also up to the hills or down to the sea.)  These frequent lines are also numbered in logical sequence across the city, so that as you get to know the network, a number reminds you of roughly where in the grid each line sits, and thus what it’s likely to be useful for.

The idea is that people should be able to keep a sense of the whole grid network in their heads.  If you just remember what H and V mean, and the sequence in which they’re numbered, you have an enormous amount of information the whole system. When you see any bus numbered this way, you have a general sense of which way it’s going, or at least along which axis.  And when you hear a bus route number, you can easily form a general sense of where it is.

There’s liberty in this kind of legibility.  You could measure it in terms of the number of useful places you can get to divided by the bytes of information you need to remember to have a workable map of how to get there.  Anyone who’s navigated Manhattan knows the difference between the regular grid across most of the island (high usefulness/byte) vs the patternless warren of streets at the south end (low usefulness/byte).  European cities tend to be especially challenged in this regard.

I talk about Barcelona’s bus network a lot because it’s one of the best examples of the marketing of network-scale legibility, an idea that’s almost unheard of in other parts of the world.  (Perhaps related, it also has a Wikipedia article that describes it with the same respect you’d expect in discussing a metro network.  Someone should translate it into English.)

Barcelona may have come upon its grid bus network, in part, because proudly legible grids were already its most celebrated urban planning idea. Most European street patterns are largely gridless and irregular. But in a systematizing vision rivaling that of Haussmann in Paris, 19th century Barcelona embraced a single grid pattern for its fast expansion around the medieval core.

Photo by Alhzeiia via Wikipedia

This plan is usually described as the Eixample district, but it’s really a principle rather than a place.  (The Catalan word eixample means “extension” or wider area”.)  The new grid flows across the city over a distance of about 7km (4.5mi). It therefore covers many neighborhoods, uniting them not just with a perfectly regular street pattern but also with the grid’s most distnctive detail: the “cut off” corners that create little square spaces at each major intersection.

Now that Barcelona is beginning to close many of these streets to fast car traffic, these little diamonds will be the next great public spaces in a city already rich with them. And a great bus network, whose citywide grid pattern you can remember, and that stops just down the street, will take you there.

Thanks to my Barcelona friend Andreu Orte for background, including the Line 5/2 diagram.