SCIENCE OFCITIES

NEXT CITY

2016 NEXT CITY

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Next City is a nonprofit organization with a mission to inspire social, economic and environmental change in cities through journalism and events around the world.

Cover photo by Andr P. Meyer-Vitali.

NEXT CITY

Table of Contents

4 Introduction Ariella Cohen

5 What Questions Should We Be Asking About Big Data Sarah Laskow

7 What a Parks Design Does to Your Brain Rebecca Tuhus-Dubrow

9 This City Used Big Data to Beat a Big Rat Problem Henry Grabar

11 Ancient City Ruins Warn Us About Our Urban Future Sarah Laskow

13 What a Massive Indian Festival Can Teach Us About Improving Cities Carlin Carr

15 When it Comes to Making Money, Big Data Reveals that Cities Have a Pattern Zoe Mendelson

17 How A Citys Collective Memory Can Predict the Future Sarah Laskow

19 How Trees Can Make City People Happier (and Vice Versa) Sarah Laskow

21 Heres What Happens When You Let Artists Play With Big Data Rachel Kaufman

23 Theres Now a Formula for the Chaos of Your Commute Zoe Mendelson

Introduction

Jane Jacobs with the math. Thats one way theoretical physicist Geoffrey West describes the burgeon-ing field of urban science. Like Jacobs and so many of us who feel the buzz of city life everyday, West and his fellow scientists of the city believe in the value of urban interaction and believe that these interactions can be quantified.

Over the past two years, our reporters have taken up Wests challenge and explored the math behind Jacobs' urban dance. With the support of the John D. and Catherine T. MacArthur Foundation, we have reported on the algorithms, data and ideas redefining how we understand cities and increasingly, changing how they operate. From Somerville, Massachusetts, where city officials teamed up with computer scien-tists to fight rat infestations with data to Porto, Portugal, where a researcher measuring how the design of a park affects brain waves was able to quantify the calming affects of an afternoon at your neighborhood urban green and inspire new investment in such spaces, the science of cities is changing our communities. This ebook offers a look at the field as it continues to evolve. We hope you find it as fascinating as we do.

Ariella CohenEditor-in-Chief

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5A test of an AeroVironment Puma drone. Some envision a future in which drones fly off to gather information, perform tasks and keep their owners oriented and safe. (AP Photo/BP Alaska)

What Questions Should We Be Asking About Big Data?

SARAH LASKOW | OCTOBER 14, 2014

Huge sets of data, properly organized and analyzed, have the potential, certainly, to improve the way cities oper-ate and the lives of people inhabiting them. But using this data, as David Burney pointed out at the Pratt Institute and Places Journal symposium City by Numbers: Big Data and the Urban Future, is not without risks. There are some unforeseen consequences, he said. It may take us to a place we dont want to be.

Connecting the events presentations and conversations on personal drones, air pollution, desert cities, self-driv-ing cars in near-perpetual gridlock and data sets so big that n = all, the Pratt professor and former New York City commissioner for design and construction said, Some of it is dazzlingly fascinating, but I noticed all day this undercur-rent of anxiety and unease.

Despite the abundance of Big Data boosterism thats emerged in recent years, Anthony Townsend, a senior research scientist at NYUs transportation policy center, pointed out that no one seems to know quite what Big Data does or should mean. It very well may be, as the events description asserted, one of the defining phenomena of our time, but, as Townsend said, I havent had a single conversation where anyone has a precise vocabulary for talking about it.

However, when it came to one of the meetings main questions (as Thomas Hanrahan, the dean of Pratts archi-tecture school, put it), Is Big Data going to help us visualize cities? Does it let us visual the future?, the assembled architects, designers, planners and academics had plenty of ideas.

The designer James von Klemperer described how data had informed the development of projects like One Vanderbilt, in New York City, and a whole neighborhood in London. In the transportation chain, Townsend noted, every step vehicles, markets, places, even people had become, to some extent, programmable. That realization led him to imagine different iterations of the transportation future, which might include everything from a functioning network of solar-powered, self-driving cars to suburban streets abandoned in favor of a data-driven bus rapid transit system.

There were the suggestions, too, on how future city-dwellers might access and create data. Were currently on the horizon of an era where well be interacting with our cities much differently, said Adam Pruden, a Pratt graduate who now works at Frog Design. If right now, there is one interface that rules them all the smartphone soon, Pruden suggested, in the context of Google Glass and the Apple Watch, the smartphone might seem like an outdated, relatively limited tool. And at Frog, he and colleagues had been thinking about an even more advanced sort of interface.

6Drones are already evolving from smartphones, he pointed out. Small, personal drones are incorporating phones gyroscopes, GPS and battery technologies. Im not talking about military drones that attack and shoot mis-siles, Pruden said. Im talking about quadcopter personal drones. You can kind of consider them flying smartphones.

This vision of the future involved drones that tether to their owners but fly off to gather information, perform tasks and keep their owners oriented and safe. (Its not unlike the world of Philip Pullmans The Golden Compass, in which every human has an animal daemon that has some degree of autonomy but cant stray too far from its human.) These drones, Pruden suggested, might monitor air quality and serve as a sort of mobile air filter; act as personal trainer by projecting physical games onto the built environment; help people navigate the city; or detect rain and UV levels and, transforming into a whirring, flying umbrella, protect its owner from the elements.

As fun as it might sound to have a flying phone, Mark Shepard, an artist and architect who created the Sentient City Survival Kit, questioned what might be at stake in a future like that one. As computing leaves the desktop and spills out into the city, he said, data processing becomes embedded in urban space. Few of us are going to take issue with a smart traffic light control system. Some may be bothered by a coupon being beamed to your phone. Many, how-ever, are likely to protest if we are denied access through a subway turnstile when we match the profile of a terrorist.

SARAH LASKOW IS A REPORTER AND EDITOR IN NEW YORK WHO WRITES ABOUT THE ENVIRONMENT, ENERGY, CITIES, FOOD AND MUCH MORE.

7What a Park's Design Does to Your Brain

REBECCA TUHUS-DUBROW | SEPTEMBER 23, 2014

As a student in Poland, Agnieszka Anna Olszewska was fascinated by the way that some landscapes seemed to be more contemplative than others. She wanted to research the reasons behind that calming effect, but she found little encouragement. People told me I can write a novel, I can write a poem about the contemplativeness of landscape, but not a scientific paper. One well-respected landscape architect told her it couldnt be done because of the diversity of human responses: Some of us might find a garden conducive to contemplation; others might prefer the bathroom.

But Olszewska, now a doctoral candidate in landscape architecture and urban ecology at the University of Porto in Portugal, persevered. With a neuroscience professor at the university, she conducted a pilot project that culminated, earlier this year, in a conference paper titled Urban Planning, Neurosciences and Contemplation for Improving Well-being in Our Cities. It combined questionnaire results with measurement of brain waves in an effort to prove that there are certain characteristics of urban parks and gardens that can induce in the visitor the pattern of brain activity that is associated with contemplative or meditative states.

AP Photo/Julie Jacobson

We know that cities can be hectic, stressful places. We also know that green space can have a calming effect on people. But Olszewska is seeking to take our knowledge a step further to enable designers and planners to maxi-mize the serenity of urban green refuges.

In the study, four design experts examined 50 photographs from three urban parks in Portugal and France. The experts were also given a checklist of design features (such as long-distance views, biodiversity, canopied, pan-oramic). They identified which features appeared in each photograph, and also evaluated each settings contemplative-ness. The settings deemed most contemplative had panoramic vistas with long-distance views (more than 400 meters). They tended to include large empty spaces, natural asymmetry, clearings and stimulation to look at the sky. The least contemplative settings, by contrast, usually lacked these features, and instead had characteristics such as paths and enclosed spaces (as in small pocket gardens).

In the second part of the project, subjects were asked to look at the 15 photos of landscapes ranked highest by the experts for contemplativeness. Their brain waves were recorded by electroencephalography (EEG) during this task. The brain activity, Olszewska said, was similar to patterns known to be associated with mindfulness achieved through meditation. She stresses, though, that her research is quite preliminary; subjects werent shown the least contemplative spaces. (She is currently working on a study that includes this kind of control group.)

8The most contemplative landscapes are not necessarily the ones that people would claim to enjoy the most. More stimulating landscapes brightly colored flowers, numerous eye-catching elements may be more immediately attractive. If you imagine the French baroque gardens, they are very geometrical, very organized, said Olszewska. But this kind of environment, however beautiful, may be less relaxing to spend time in.

This is not to say that the opposite extreme wild landscapes is necessarily more contemplative. Olszewska thinks we tend to find those overwhelming. Instead, she hypothesizes that the ideal is a golden middle between too much design and too little.

The small experiment is part of a larger, nascent movement to try to connect neuroscience to architecture and design. The movement for evidence-based design originated in the health care field. One famous finding was that in hospitals historically not the most pleasant places surgical patients whose windows faced natural outdoor scen-ery were discharged sooner and requested fewer painkillers than patients whose windows faced a brick wall. Inspired by this movement, others began to think that there was no reason to limit such thinking to hospitals. It spread to schools, and now, increasingly, the built environment and urban green spaces. Some researchers began to incorporate neuroscience. Much of the interest is focused on contemplativeness. Perhaps, just as hospitals need healing spaces, cities need serene oases to counteract the urban chaos.

Julio Bermudez, an associate professor of architecture and planning at the Catholic University of America, studies how the built environment can induce states of relaxation and mindfulness. In one study, which he presented last week at the second annual conference of the Academy of Neuroscience for Architecture, architects looked at photographs of buildings designed to be contemplative, including the Salk Institute in San Diego and the Pantheon in Rome, as well as ordinary buildings. The contemplative buildings reportedly elicited markedly distinct responses, as measured by func-tional Magnetic Resonance Imaging (fMRI). Bermudez and his co-authors (including a neuroscientist at the University of Utah) concluded that contemplative buildings allow subjects to enter into a meditative state with diminishing levels of anxiety and mind wandering.

In an email, Bermudez speculated about some common features of contemplative design: buildings that frame nature in some way; that exhibit simplicity without being simplistic; and that offer a sense of separation from the rest of their context, among other qualities. Some remarkable cities, he wrote, naturally invite contemplative states. As examples, he cited Santiago de Compostela in Spain and Bodh Gaya in India, as well as parts of Paris, Washington D.C. and San Francisco.

It may be true that, as the landscape architect warned Olszewska, its hard to make blanket generalizations about what people find contemplative, and responses may vary culturally too. Its also notoriously challenging to interpret brain waves conclusively, and this research is in its infancy. But both Olszewska and Bermudez believe there are certain common features that can broadly foster these meditative responses. And rather than write poems, they hope to prove it with the tools of fMRI and EEG.

REBECCA TUHUS-DUBROW WAS NEXT CITYS SCIENCE OF CITIES COLUMNIST IN 2014. SHE HAS ALSO WRITTEN FOR THE NEW YORK TIMES, SLATE AND DISSENT, AMONG OTHER PUBLICATIONS.

9Map: City of Somerville

This City Used Big Data to Beat a Big Rat Problem

HENRY GRABAR | JUNE 23, 2015

In 2012, Somerville, Massachusetts, was facing what Daniel Hadley, now Mayor Joe Curtatones chief of staff, called an onslaught of rats.Year over year, complaints about rats had risen 65 percent. The number of rat-related calls to the citys hotline in the summers of 2012 and 2013 was more than twice what it had been in 2010. (Rat populations boomed during successive mild winters in the Northeast.) The city of 78,000 north of Boston was under siege, and it responded in kind. Somerville declared war on rats.

Now, rat sightings are down an incredible 66 percent year over year thanks to data analysis (and new trash cans).

Somervilles Rodent Action Team (RAT), a group of public health professionals, data analysts and city workers, started by mapping the reported rat sightings the city was receiving, on average, two rat-related calls a day in 2012. They began to see a pattern. As Londons cholera cases clustered around wells, so Somervilles rat sightings were concentrated around food sources.

That might seem obvious, but theres a reason that many municipal anti-rat projects focus on rat reproduction. According to the sterilization company SENES, four male and four female rats can add an incredible 14.5 million rats to the population over their eight-to-nine-month lifetimes. Food sources can seem like a secondary concern. Also around 2012, New Yorks Metropolitan Transit Authority conducted a well-reported sterilization experiment in the subways. (Surveys reported a 3 percent drop in rat sightings that year.)

In Somerville, clamping down on food sources (in concert with a tough winter) produced a shocking success.The city quadrupled the number of waste container licenses it issued to restaurants. It bought 64-gallon trash

cans for every house in the city. After all, if residential garbage pickup and disposal is a municipal service, why not garbage storage? Standardizing the citys bins was first and foremost a RAT initiative, but the result was aesthetically pleasant too.

The primary data source wasnt exactly high-tech: Rats were only reported by calls to the citys 311 line. That tended to mean that neighborhoods with high percentages of homeowners were overrepresented in the raw data, while others seemed to have fewer issues. But by looking at rat reports as a percentage of total calls, the city figured it was getting a more reliable geographic portrait. A comparison with neighboring Boston was instructive. The two cities rat reports seemed to move in concert, to the point where officials could predict the number of calls in Somerville based on the parallel figure in Boston.

Until this year, that is. After the brutal winter, the snowiest in Bostons snowy history, experts expected rat pop-

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ulations to take a hit. Bostons did. But Somervilles rat population declined 40 percent more than that of its neighbor across the Charles.

We tend to think of such data-driven management as a technique reserved for big cities like Chicago and New York, with their in-house analysis teams. Somerville is bucking that stereotype. The city has a five-person department called SomerStat that offers analytical expertise on matters like the budget and public works. Curtatone, who has been mayor since 2004, said that the city already had the data in hand it just didnt have a team to use it.

Skye Stewart, the director of the department, said that resources had previously been allocated based on best estimates or gut feelings. Now, its her team a bunch of data nerds who help out, in turn reducing the citys dependence on expensive outside consultants.

As the new trash bins were distributed to residents, for example, SomerStat helped the citys Department of Public Works determine how many residents had overflowing bins, and how that number varied between garbage routes.

With the right sort of analysis you can save hundreds of millions of dollars, said Hadley, who headed up SomerStat for three-and-a-half years before Stewart took over last summer. In midsize cities, the amount of data is proliferating to the extent that its becoming more cost-effective.

Hes still envious of how a city like New York, which is more than 100 times Somervilles size, can gather and manipulate information about traffic or crime. Somerville, however, may have set the standard in one field: rat reduction.

With the city receiving just a third as many calls as last year, Hadley was triumphant. Ive never seen a drop quite like that, he said.

HENRY GRABAR IS A JOURNALIST IN NEW YORK WHO WRITES THE DREAM CITY COLUMN FOR SALON. HIS WORK HAS ALSO APPEARED IN CULTURAL GEOGRAPHIES, THE ATLANTIC, THE WALL STREET JOURNAL AND ELSEWHERE.

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Ancient City Ruins Warn Us About Our Urban Future

SARAH LASKOW | DECEMBER 30, 2014

The ruins of Tikal are surrounded by a national park 57,600 hectares of rainforest and wetlands. In comparison, the center of the city is small, about 400 hectares of temples, terraces, roads and houses, surrounded by another thousand hectares or so of residential neighborhoods and reservoirs.For years, the protected site in northern Guatemala has been relatively isolated (George Lucas filmed a scene

there for the original Star Wars), and since the Maya left, at the end of the 9th century, almost no one has lived in the area. Now, amid the abandoned temples and tombs, researchers are finding important clues about how the Mayans lived and what the citys demise might signal for our future urban resilience.

Theres been no real settlement there, since the time of the collapse. The forests have grown back and its a reflection of what the Maya left, says David Lentz, a professor at the University of Cincinnati who studies paleoethno-botany and paleoecology. What was intriguing about Tikal was that people had been working there for over a century, and nobody had ever done a good environmental assessment. No one had looked at the plant remains.

Mayan ruins of the city of Tikal (AP Photo/Rodrigo Abd)

When Lentz and a group of colleagues looked, they were able to piece together a picture of how Tikal survived as an urban center. For hundreds of years, they found, the Maya managed their resources sustainably. But that wasnt enough to keep the city from collapsing in the face of climatic change; the changes Tikals residents made to the land may even have made them more vulnerable.

They expanded to the carrying capacity of their landscape, leaving no resilience where something bad came along, Lentz said. Nature is a fickle thing, and things change.

Tikal attracted its first residents sometime in the 6th century B.C. At the heart of the city was a system of springs an important source of water, in an area with no river or lakes and a dry season that could parch crops. Lentz and his colleagues outlined a zone around the city center from which the residents would have extracted resources, taking into account both distance from neighboring towns and Tikals economic dominance.

Over hundreds of years, as the city grew into one of the most important places in the region, the Maya who lived there harvested wood in the surrounding forest. They used some of the newly open land for agricultural and the wood for energy. Most of the food they ate beans, root crops, and maize would have needed to be cooked over a fire; houses at the archaeological site have 70 to 80 fired pots, which would have lasted only about a year kilns eat up substantial amounts of wood, too. But when Lentz and his colleagues estimate how much wood would have been

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required to support the population in Tikals later days, from about 600 to 850 A.D., they found that it was approxi-mately equal to the amount of wood available on a sustainable basis.

The Tikal residents made efficient use of their limited water resources, too. They channeled the water from the springs and built plazas that collected rainwater, channeling both into the reservoir. These technologies allowed the city to expand its agricultural productivity and support a growing a population.

The Maya were not bad conservationists, Lentz points out not at all. They managed to build a relatively large city that lasted for more than a thousand years. What cities do we have in North America that have been around for that long? he says. None. Not even close. They managed their resources very well.

But by the 9th century, they were also using their resources as efficiently as possible, Lentz and his colleague found: One of the conclusions that can be drawn from the evidence generated is that the Maya at Tikal were living quite near or perhaps beyond the sustainable carrying capacity of their highly engineered landscape, they write. There was not a lot of room for error.

Around that time, a dry period swept through the region, which would have strained the most limited of Tikals resources: water. Theres evidence, too, that the sort of changes they had made, clearing forest for agricultural land, exacerbated the effects of the drought.

When you make changes to your environment, sometimes things happens that you dont expect, Lentz says. When the droughts came, because they had exploited the environment to the full extent of their technological capabil-ities, they just were not able to respond. The last monument went up around 869 A.D. By the end of the century, the city was likely largely abandoned.

Its difficult to see this as anything but a parable, warning modern-day cities against the dangers of complacency, of assuming that the technologies that might have allowed expansion and, for many years, supported a good life will also ensure that way of life can continue indefinitely.

Its harder to outline the physical area on which a modern city depends: Food and energy resources come from across the country, across political borders or across oceans, even. But, like the resources on which Tikals residents depended, they are being used at close to capacity and are vulnerable to the effects of the changing climate.

Once you get close to that tipping point, things can fall apart very rapidly, as they did at Tikal, says Lentz. Here was this big city. They had the best architecture, it was the center of the universe. And it was pretty rapidly abandoned.

As much as we talk these days about threats to cities and about resilience, its hard to imagine cities that are thriving today totally abandoned and left to overgrown forests. But one lesson of Tikal is that, if technologies arent adapted or cant adapt to changing climate conditions, a city that was stable for hundreds of years can disappear in just a few decades. And one big advantage that modern cities have isnt that theyre more sustainable or even that they have access to better technology. Its that weve more warning that the climate is changing and clearer knowledge of our own contribution.

We have some understanding of whats going to happen, Lentz says, whereas I think the Maya were probably caught unawares.

SARAH LASKOW IS A REPORTER AND EDITOR IN NEW YORK WHO WRITES ABOUT THE ENVIRONMENT, ENERGY, CITIES, FOOD AND MUCH MORE.

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Devotees gathered for the Kumbh Mela bathing festival in Allahabad in 2013. MIT Media Lab researchers see the festival as an opportunity to study pop-up cities and rapid urbanization. (AP Photo /Manish Swarup)

What a Massive Indian Festival Can Teach Us About Improving Cities

CARLIN CARR | MARCH 31, 2015

Indias orange-robed godmen are rarely the focus of urban planners. But later this year, 40 million religious pilgrims are expected to descend upon Nashik a rapidly growing city a few hours from Mumbai and, almost overnight, swell the modest metro into the largest city in the world.The 20-day Hindu festival, the Kumbh Mela, can attract crowds the size of multiple New York Cities on a single

day. The religious event takes place every three years when devotees make the trek to one of four alternating cities Allahabad, Nashik, Hardiwar or Ujjain to bathe in one of the sacred rivers. While the spiritual seek to cleanse them-selves of sin, urban innovators, policymakers and planners see the population surge as an ideal opportunity to gather data and test new ideas related to pop-up cities and rapid urbanization.

Its a perfect set of problems, says Daniel Goodman, a graduate student in the MIT Media Lab, which helped organize a weeklong innovation sandbox called the Kumbhathon in Nashik earlier this year. The Kumbh Mela doesnt last very long, but during that time it stresses the city on all fronts. It forces us to think about fundamental problems, such as sanitation, food distribution and good utilities.

The Kumbhathon, which was conceptualized by Nashik-based innovator Sunil Khabdbahale and Ramesh Raskar, head of Camera Culture Group at the MIT Media Lab, set out to understand the challenges faced by host cities of the Kumbh Mela and experiment with technologically focused interventions. The group received more than 500 responses on its open, crowdsourced platform that asked the public to identify key areas of concern. Organizers whittled that long list down to 12 target themes that included health, housing, food, payments and transportation.

Understanding the challenges was just the beginning. In January 2015, the Kumbhathon brought together inno-vators from 20 cities across India to get creative with tackling the issues at hand. Participants came from a broad range of fields from computer science to mechanical engineering to business and public health and gathered in Nashik for a week to look more closely at the city, its current and future challenges and brainstorm on best ways to intervene in better managing the soon-to-be megacity. MIT faculty, entrepreneurs and industry experts acted as mentors to the groups, and local experts from Nashik challenged their ideas with personal experiences and knowledge of the current urban landscape. The ideas were also evaluated by technical innovators for deployment, marketability and scalability.

Nashik is an ideal city to study and test the stresses of urbanization and what can be done to prepare for it. The city is the 16th-fastest growing metropolis in the world and one of the fastest growing in India. The Kumbh Mela will

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send that growth into overdrive for a few weeks. Nashik has also been selected as one of Prime Minister Narendra Modis 100 Smart Cities, an initiative launched last year to drive forward technology in urban development around India.

While Indias megacities such as Mumbai and Delhi capture most superlatives, architect Rahul Mehrotra, chair of Harvards Department of Urban Planning and Design, has been urging policymakers and planners to look beyond the major metropolises to the emerging metros such as Nashik. In an article in the Hindu in 2011, he said, Furthermore, it is crucial for us as a nation to focus on our small towns and tier two cities; these will comprise a vast majority of the urban Indian population in the future. These are also places (unlike the megacities and primary towns) that are not locked into unsustainable paradigms and where planners still have possible ways of intervening.

One of the ideas for intervening devised by Kumbhathon participants is an epidemic tracker. Major public health crises, particularly in the wake of the Ebola outbreak, have brought new challenges to developing world cities. Like the Kumbh Mela, these cities often lack accurate data on crowded informal settlements, where disease can spread quickly, making it difficult to react in case of an event. The epidemic tracker monitors the health status of people in real time to check and control disease outbreaks. Up-to-the-minute information could enable medical staff to identify individuals with threatening symptoms and quickly provide them with the necessary care to prevent further infection.

Another major logistical challenge during the Kumbh Mela is food distribution. The Kumbhathon participants devised a system that connects festival-goers with quality food suppliers. Such a model could bolster the Indian food industry and potentially translate into a multibillion-dollar service across India that caters to the lower-income popula-tion, according to one Kumbhathon report. The issue, it said, is that customers have to make risky food transactions, because they often have little or no information about when the food was cooked, who cooked it or the rating of the person who cooked it. Information linkages such as these enhance the experience, safety and running of pop-up cities.

But, urge Kumbhathon organizers, the potential of these innovations go beyond this one event. This is not just to help the Kumbh Mela, says Kumbathon co-founder Khabdbahale. This is about promoting innovation in cities like Nashik. We have a big opportunity here to test ideas for city optimization around India.

CARLIN CARR IS AN URBAN DEVELOPMENT PROFESSIONAL INTERESTED IN INNOVATIVE IDEAS FOR SOCIAL CHANGE.

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When It Comes to Making Money, Big Data Reveals Cities Have a Pattern

ZOE MENDELSON | JANUARY 29, 2016

How are people, infrastructure and economic activity organized and interrelated? In infinite ways depending on infinite dynamic factors. The question borders on absurdly ambitious. But a paper published last week, Scaling and universality in urban economic diversification, examines these connections with notable results. In an effort to measure and characterize the economic diversity of cities and its role in productivity, innovation and economic devel-opment, the authors unexpectedly discovered what they call a systemic behavior common to all cities.

To understand the commonality at work, first think of the city as an ecosystem. Think of types of businesses as species. Ecosystems in the natural world often share common patterns in distributions of species. That got us think-ing, says Hyejin Youn, an Oxford fellow and the lead researcher, maybe [the same consistency] happens in the city too. Only instead of the food web, its people and money and businesses that require one another. (Youn is quick to clarify that this is merely a metaphor and that the human economy is obviously more complicated than simply a con-sumer-resource network.)

Photo by Wouter Engler

Just as ecosystems vary greatly from deserts to tide pools so too do cities. Cities have different abundances of specific sectors. San Joses tech is to Detroits manufacturing. We usually think of cities as unique. Detroit is very different from Silicon Valley, Youn says. Abundances of certain industries are their signatures. But, it turns out, what governs the distribution of those abundances stays the same across the board.

The monster data set the team analyzed for this study was the National Establishment Time-Series, which was created by Walls and Associates, an economic development agency based in Oakland. The set contains more than 32 million establishments nationwide and includes data on employment, sales, business performance, jobs gained and lost, businesses born and failed, and changes in major markets.

They organized the data by 366 U.S. metro regions. They made their unit of analysis the establishment, which they defined as a single physical location where business is conducted. Each is a workplace so theyre the most relevant unit to innovation, wealth generation, entrepreneurship and job creation. (The data set used the U.S. govern-ments North American Industry Classification System to classify the types of businesses to which each establishment belongs.)

The team then parsed out the frequency distribution how many of each type of establishment occurred in each

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city. When they compared these distributions among cities, they found their universal law: Despite widely different mixes of types of businesses and across different-sized cities, the shape of these distributions was completely universal.

Thats the thing that was amazing, says co-author Geoffrey West, whos a professor at the Santa Fe Institute. The distribution of different employment categories, even though the jobs are different, all look the same, which is a statement that the underlying dynamics, processes in every city are the same. People talk about diversity and jobs and businesses and culture but its never been quantified, and its amazing that there are regularities and systematic behaviors.

The team also found that as cities grow, the total number of establishments is linearly proportional to its popula-tion size (more people, more businesses). Seems logical maybe, but they got specific: On average, they found, a new work place is created each time the city size increases by 22 people.

When the researchers tried to measure diversification the rates at which different types of businesses enter the mix things got complicated. The scheme that the researchers used for classification of the data may seem obvious, but was perhaps the trickiest aspect of the study design. It comes down to the muddy question of how to measure or even define diversity.

If sectors are species, imagine that each species has a taxonomy tree: restaurant, fast food restaurant, McDonalds, Burger King, etc. We couldnt go all the way down to specialized cuisines. You have to look at different ways of classi-fication and think about how your results will change depending on the system of units that you use, Youn says. The government invented the NAICS system for trade purposes. It doesnt capture true diversity.

The effect of this classification problem was that their results changed based on what level of the taxonomy tree they used to calculate. If they stopped around the level of fast food coarsely grained data, a broader definition of diversity then they found that diversification slowed considerably once a city reaches a certain size.

But does it? Depends on if you believe a modern art and a classic art museum or a KFC and a Popeyes rep-resents diversity. The researchers needed to correct their model so their conclusions would not be about their arbitrary classification system. The finer grained the data, the more infinite the diversification. So they extrapolated down to the finest grain imaginable. They made imagining the furthest nit-picky branches of taxonomy trees of businesses into numbers. And they were able to show that cities have an open-ended, ever-expanding diversification process as they grow. Cities, in fact, are like fractals.

The study also reveals that with increasing city size, entirely new types of services begin to appear. Youn calls this combination dynamics, and attributes the effect to how in large cities, different sectors collaborate and communicate and fuse. Its progressive specialization, explains co-author Lus Bettencourt, professor of complex systems at the Santa Fe Institute, because you live in a larger ecosystem, you can be more specialized because you find more func-tions around you. Its unlikely youll find an Ethiopian restaurant in a small town, or a glassblowing studio. But its likely youll find one in a big city because there are enough people who are interested in those services and enough special-ized suppliers nearby to make them viable endeavors.

And interestingly, if predictably enough, specific species of businesses are more likely to show up in larger cities, like lawyers and PR firms. They are professions that connect people or help people fight each other or not fight each other, says Bettencourt. Businesses that thrive on connectivity are emphasized in larger cities that are dense networks of businesses and people.

And what exactly is the mysterious force creating these consistent patterns? The human ecosystem. Its people interacting, exchanging ideas, gathering things, needing to eat, West says. Humans have universal needs and actions.

ZOE MENDELSON IS A JOURNALIST IN MEXICO CITY CAMPAIGNING FOR A MORE CHILLER WORLD. HER WORK HAS BEEN FEATURED ON FAST COMPANY, BUZZFEED, UNTAPPED CITIES AND ELSEWHERE.

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Photo by Kamel15

How a Citys Collective Memory May Predict the Future

SARAH LASKOW | MARCH 17, 2015

Imagine, says Alberto Hernando de Castro, you are moving to a city. Maybe its New York, where hundreds of thou-sands of people move in (and move out) every year. You might be moving to find or follow love, to take a job that exists nowhere else or to fulfill a desire maybe whim, maybe a long-held dream to be in this particular place.There is a good reason for every one, for every single person, Hernando says. A big decision for them, appar-

ently small for the city. Most of them, they never meet with each other and probably they never will. But all these moves are correlated, and also with those that happened 20 years ago.

This is one of the key findings of his latest study: that U.S. cities have a memory that goes back 25 years that a citys population dynamics in a particular year have some significant relationship to the population dynamics of every preceding year, going back half a century. In other words, it looks like theres some underlying logic or rule connecting each individual in a city to (seemingly unrelated) movements of the greater population.

Hernando is a theoretical physicist, working to seek out laws, analogous to the laws of physics, that describe the workings of cities a thermodynamics of population flows, for instance. Its heady in the abstract. But look at the gif of Brownian motion (right), the random movement of particles in a fluid.

Its not a such a big stretch from that to people moving in Times Square.It is hard to believe that all these individual decisions have something in common, Hernando says. But that ran-

domness of individual movement isnt the whole story here. The sum of all our decisions, of all our moves, contribute to the entity called the city, he says.

Hernandos work builds on the understanding that started developing earlier in the 20th century, that cities do behave in some regular ways. The relative size of cities in a given country, for instance, fits Zipfs law. This statistical prin-ciple describes relative frequencies within a large set of data: It was first connected to the way we use words the, the most common word, is used twice as frequently as of, the next most commonly used word. With cities, you can halve the population of a countrys largest city and get roughly the population of the second most populous city. The third most populous city has about a third of the population of the first. (New York, 8.4 million; Los Angeles, 3.8 million; Chicago, 2.7 million.)

But Hernando is interested in dynamics: How do cities grow? How do they interact? Or, another way of putting that: How do cities move in time? In space?

In a paper published in 2013, Hernando and his colleagues tried to answer these questions using a large set of

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data describing the population of Spanish cities over decades. They found that these cities memories went back 15 years, and cities influenced each others population dynamics if they were within 80 km (about 50 miles) of each other. This new study looks at the same questions using U.S. census data stretching from 1830 to 2000.

The studys finding about distance that U.S. cities within 200 km (about 125 miles) of each other have an influ-ence on how their respective populations grow and shrink is relatively straightforward. But its also pretty remarkable, if you look at particular examples. Take New York, for example: This rule puts Hartford, Philadelphia and Wilmington but not Boston or D.C. within New Yorks orbit. Bostons connected to Portland, Maine, Manchester, New Hampshire, and Providence. D.C.s in a relationship with Baltimore and Richmond, with Philly on the very edge. In the South, Atlanta gets Athens, Columbus and Chattanooga. In Clevelands radius: Detroit, Ann Arbor, Toledo, Pittsburgh. Chicago: Madison, Milwaukee, Kalamazoo and Bloomington. Los Angeles: Santa Barbara, San Diego. In every case, the statistically derived radius manages to connect cities that make intuitive sense together.

The finding about time is a little bit more complicated to understand. What does it mean that a city has a memory that goes back only 25 years? One way to think about it is that its reminiscent of how we grow as people how long can a persons current behavior be connected to the choices and experiences she made in years past? Last years behaviors surely have more influence than five years past, or 10, or 20. And at some point, our past self becomes disconnected to our present; the 4-year-old has only a tenuous connect to the 40-year-old.

Theres another complicating factor: Hernando and his colleagues also argue that cities can suffer from a post-traumatic amnesia. In the Census data, they found that there were occasional breaks in the connections between present and past points at which the correlation dropped to zero or became negative. They connected those points to two major historical events the Civil War and the stock market crash, essentially by looking at the points where these breaks originated and considering what might have caused them. Its a little bit of a leap in logic, but, to follow the analogy of people to cities dont we say, of the soldier who comes home from war or the victim of a terrible accident, that its like shes a different person? If personal traumas can wipe a person of her past, maybe historical events can do the same to cities.

This might seem a little far from the practicalities of city building, but its in service of a concrete goal: These researchers want to find a set of equations that could forecast demographic and economic trends that could be used all over the world. We want to do it with a mathematical framework, and thus be able to do predictions and simulations, as we do now in physics and other sciences, Hernando says. Our aim is to develop a simulation tool were any policy of potential economic and social plan can be tested in a computer before applying it in real life.

Whats clear from the work so far, he says, is that there is no such thing as short term for demographics. If a policy effects change, the city could be living with that alteration for decades, long after the lawmakers and their staffs have moved on. Individuals might forget the source of the change.

While the implications of this work for free will once troubled Hernando, hes since reassured himself that any one persons behavior is essentially impossible to predict. But predicting what one million people will do is easier. Whatever individuals did or decided, the city as a whole bears some lasting mark of it.

SARAH LASKOW IS A REPORTER AND EDITOR IN NEW YORK WHO WRITES ABOUT THE ENVIRONMENT, ENERGY, CITIES, FOOD AND MUCH MORE.

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How Trees Can Make City People Happier (and Vice Versa)

SARAH LASKOW | FEBRUARY 3, 2015

THe trees out my fourth-floor New York City window were covered in snow a few days ago; now their bare branches are waving in the wind, against the gray-blue of the cloudy dusk sky. Its nice to have them there. Without the trees, my view would be starker, nothing but flat roofs still white with snow and the rectangular out-lines of overlapping buildings farther in the distance. Theyre calming something big and beautiful, that wasnt made entirely by human hands, in a city full of people.

Theres plenty of evidence that hints of nature help us humans live in the urban spaces weve built. About five years ago, one major study showed that, across the world, living in cities is associated with higher levels of depression and other mental health problems; a rash of studies since have shown that people feel like green spaces parks and community gardens, usually help them deal with the stresses of urban life.

Mark Taylor, a public health researcher at the University of Trnava in Slovakia, wondered, though, if there might be a way to establish that connection between nature and mental health without relying on peoples own accounts of their

Photo by Mark Frank and Chloe Carli

well-being. Theres been a fair bit of research that looks at different ways in which people say they feel some kind of benefit of being around natural spaces, he says. But nearly all of that was subjective. You can ask people if they feel better, he says, and plenty might say they do. But how to know for sure?

Taylor decided to take advantage of the wealth of public data available in England, where hes originally from, to see if that connection held. He and his colleagues collected data on two variables: the density of street trees and the number of antidepressant prescriptions in Londons 33 boroughs. (The boroughs average about 20 square miles, with about 250,000 people each; theyre almost small cities of their own.) What they found was that, even after adjusting for factors like unemployment and affluence, the areas that have the most trees along the streets also had fewer prescrip-tions for antidepressants. (Their results are reported in the journal Landscape and Urban Planning.)

We cant say that if you plant an extra 20 trees on every street, everyone will be fine and there will be no mental health issues, says Taylor. This is one more factor to consider. It does seem like people are happier when they have some access to this kind of thing.

But are trees happy living in the city? We ask a lot of our urban forests: They modulate our moods, they shade sidewalks and buildings, they suck up carbon, and they drink the water that runs through the streets after rainstorms.

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Plus, they have to live with us, in these weird environments weve created, where they compete with buildings for sun-light and with wires and pipes and subway tunnels for space underground.

Jess Vogt, a visiting assistant professor at Furman University, in South Carolina, is what she calls a trees and people researcher. Shes interested in how trees and humans live side by side and looks at tree outcomes, people outcomes and the effects they have on one another. One of the main questions she has been trying to answer over the last few years, as she was working toward her Ph.D., is: How can people help street trees thrive and vice versa?

Her project started in Indiana, when Vogt was a grad student there. Keep Indianapolis Beautiful had long wanted to know more about the impacts of its neighborhood tree planting projects. The group, a nonprofit founded in 1976, had heard stories from the neighborhoods theyd worked with, that tree planting had led to bonding and barbecues, says Vogt, and they wanted to know: How well were their planted trees doing? And does tree planting lead to other social goods?

Indianapolis is relatively flat, and not very dense. Neighborhoods right outside the densest part of downtown might be filled with small homes on narrow lots. Vogt and her colleagues looked at these neighborhoods, as well as more suburban-feeling parts of the city where cookie-cutter development might have been designed with few trees and wealthier, well-treed areas. Some of the trees they examined were on tree lawns or boulevards. Some were planted on the edge of a retention pond, or a two-lane road. Some were planted between a neighborhood and a high-way, to dampen noise.

All in all, Vogt and her colleagues looked at 35 projects, in 25 Indianapolis neighborhoods. They documented whether 1,345 trees had lived or died and looked more closely at 616 trees, to see how theyd grown.

One thing the researchers were looking to determine was what sort of variables led to tree success. Much of the research on urban tree growth and survival has been done in greenhouses or focused on the trees growing environ-ment. But Vogt and her colleagues were interested in the impacts that people, out in the real world, would have on the trees too. So they considered variables connected to the trees themselves (like species, the nursery they came from), the trees environment (its growing space, soil conditions); the community itself (homeownership, experience planting trees); and the contributions of institutions (pruning, mulching).

What they found was that all four of these components were connected to growth and survival. In other words, the trees quality of life wasnt just influenced by its immediate surroundings, but by the people they interacted with.

What type of tree was planted didnt matter at all, for survival, for instance. But variables connected to the com-munity, like the percent of people who had moved in within the past five years, did.

And, their study found, the watering strategy the community took up also made a difference. Overall, trees that were cared for by communities that watered collectively did better. But Vogt and her colleagues also found that the watering strategy neighborhoods chose mattered for their own thriving too. Communities that chose a collective water-ing strategy tended to be ones that had come together less often in the past for block parties or crime watches. But after they started caring for the trees together, they started organizing other community events more often.

Vogt is now working on expanding the project to Atlanta, St. Louis, Detroit and Philadelphia to look at, for instance, what happens to the same type of tree, in different cities. But one of the main conclusions of this work so far, she says, is that theres not always one strategy that works best to help trees thrive in the city

Theres no one best way for people to manage our resources, she says. Just like theres no one best way to design a perfect environment for people, theres no one best way to design a perfect environment for trees.

SARAH LASKOW IS A REPORTER AND EDITOR IN NEW YORK WHO WRITES ABOUT THE ENVIRONMENT, ENERGY, CITIES, FOOD AND MUCH MORE.

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Urban Heartbeat, which turns data into sound, was one of three winners in Data Canvas recent Sense Your City competition.

Heres What Happens When You Let Artists Play With Big Data

RACHEL KAUFMAN | MAY 5, 2015

In just a few decades, weve turned into a data-producing species. According to some estimates, there is now more data produced every two days than in all of history prior to 2003. The promise is this: If we could just unlock and understand this data, our cities would be more efficient, our economy more vibrant, our lives better.But data is not an easy thing to grab onto. It can be misinterpreted, skewed or plain wrong. It can contain noise

that obscures the signal.Enter citizen-science-cum-art collaboration Data Canvas, a partnership of San Francisco-based nonprofit Gray

Area, Lift Conference and Swissnex, a public-private organization that encourages innovation exchange between the Bay Area and Switzerland. The idea: Give artists access to massive data feeds and see what they do with it, then project the finished visualizations on giant screens on the sidewalk.

As we were studying what the content might be we thought we needed to create datasets that are real time, says Josette Melchor, executive director and founder of Gray Area. Real-time open data isnt commonly at hand, so the project authors decided to generate their own for their most recent challenge. Thats how [this] turned into the Sense Your City project. The goal was to create real-time data so that we could have more engaging projects that were basically alive.

First, Data Canvas deployed 100 DIY sensors over seven cities in four continents, which are collecting data on temperature, light, noise, dust, pollution and more. A challenge to artists do something interesting with this followed.

The three grand-prize winners were Sonic Particles 2.0 and Urban Heartbeat, both apps that turn data into sound but in different ways, and It Feels Like, a website that lets users compare the weather in, say, Geneva, with the weather in Bangalore, to find when the weather conditions are similar in those two cities.

Some of the projects might leave you with a vague Is this it? feeling. Runner-up Seeing the Air uses visualiza-tions to show how air quality differs in each of the seven Sense Your City cities and how it varies over time. The results, while pretty, show that Genevas air is typically better than Rio de Janeiros, which should not come as a surprise to most people. Or they show that Genevas sensors were placed in generally cleaner areas, or that one of the sensors froze and stopped collecting reliable data. Its hard, really, to know, and even the builders of Seeing the Air admit that the data is collected by off-the-shelf equipment set up by volunteers, and may not be as accurate as industrial equipment.

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Another project renders cities as seriously birds during mating season. The user sets her preferences for temperature, noise, humidity and so forth, and gets a matching ideal city based on those characteristics.

If it all seems a little silly, perhaps it is. But big data as a field is still in its infancy and experimentation across all sectors, from mathematics to the arts, could prove worthwhile as we develop the big data rules we want to set as a society. And the more urbanists of all professions who kick around data, the better the chances for its applications not getting siloed.

Data Canvas, besides being a fun art project, was also an exercise to show people that working with real-time data is actually difficult, says Emina Reissinger, of Swissnex San Francisco. Case in point: Data Canvas gave one of its sensors to CERN, the particle physics research group. It turned out when they installed it, these particle physi-cists switched two sensors, which caused these numbers to be completely off the charts. (They had also mounted the sensor outside, which promptly froze.) We have had scientific advisors who work specifically on environmental sensing . They have told us it is very difficult to work with this kind of data. [Data Canvas] shows people how sensitive it is, and how difficult it is to work with this data and make sense of it.

Smart-city big-data projects have thus far run to the practical: New York City uses data though not real-time sensors to predict which buildings are most at risk for fire; startup SNIPS mines data to predict how full Parisian com-muter trains will be up to three days in advance. Real-time bus arrival apps or signboards have become commonplace in many cities, so much so that their presence is taken for granted.

Real-time data of the sort that Data Canvas is releasing as in, volunteer-generated, real-time data on noise, light, weather and pollution does in fact have practical uses. The TenderNoise project (not part of Data Canvas) tracked noise pollution in San Franciscos Tenderloin district. What this caused was a series of reports to 311, the Department of Public Health responding and having a dialogue with neighbors about the health implications of noise pollution, Melchor says.

Next, Gray Area is working with the Urban Heartbeat project creators to expand it, adding new data streams from private partners who have information on real estate, transportation and more. Visualizations from the project will be displayed on giant, street-level touchscreens at Gray Areas headquarters in the Mission District. Melchor says, Were working on trying to figure out whats relevant to somebody as theyre rushing by on their commute. How do you make people stop and look at data?

RACHEL KAUFMAN IS A JOURNALIST COVERING TRANSPORTATION, SUSTAINABILITY, SCIENCE AND TECH. HER WRITING HAS APPEARED IN INC., NATIONAL GEOGRAPHIC NEWS, SCIENTIFIC AMERICAN AND MORE. SHE ALSO MANAGES ELEVATION DC, A LOCAL SITE COVERING CITY ISSUES IN WASHINGTON, D.C.

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Theres Now a Formula for the Chaos of Your Commute

ZOE MENDELSON | AUGUST 14, 2015

Two physicists are sitting in a car. One says to the other, Traffic is sure chaotic. The other says, Not so sure, buddy.This isnt the start of a joke its the origin story of a series of studies by a team of Colombian and Chilean researchers that prove once and for all, with a mathematical model, that traffic is indeed chaotic, in the dynamic sense.

And it all started with an argument in a car.Chaos theory is a field of math that studies dynamical systems. Dynamical means that even though outcomes

do depend on initial conditions, small differences in initial conditions change outcomes drastically without the interfer-ence of random external elements. Chaotic dynamical systems are by definition unpredictable. Edward Lorenz, a pio-neer of chaos theory, described chaos as, when the present determines the future, but the approximate present does not approximately determine the future.

Jorge Villalobos, dean of the School of Mathematics and Sciences at the University of Ibagu in Colombia,

AP Photo/LM Otero

explains the chaotic nature of traffic like this: Suppose you have a neighbor and you work at the same place. If traffic was not chaotic, it would be possible for both of you to leave within 10 minutes of each other and arrive at work at basically the same time every day without fail. But we know thats not true. Say you leave at 7 a.m. every day and usually arrive around 7:45. Its perfectly possible that leaving at 7:05 could cause you to arrive at 8:30. The chaos of traffic means that small differences in your departure times get amplified hugely.

This may seem obvious. Of course, you can beat rush hour by five minutes or get stuck in it. But this research proves that even without unpredictable levels of traffic or accidents or road construction, travel times would still be impossible to nail down because the nature of traffic itself is chaotic. Factoring in how much other traffic is on the road would count as the interference of random external elements. So, to find out if traffic was chaotic, Villalobos and his team created a model in which a single car interacts with only traffic lights. They found that likelihood of chaos increases when a driver attempts to synchronize his trip with the lights to hit all the greens.

This means, as Villalobos says, If you try to set up the system to minimize your travel time, youre going too near the necessary conditions for chaos to appear. The mechanism that creates chaos is the braking and accelerating of a car attempting to minimize travel time by hitting every green light just as it turns green. If you barely miss it, explains

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Villalobos, you have to brake at the light but not stop, and then accelerate thats why you have chaos. This does not mean trying to minimize your travel time will actually make your trip longer. It could still make it shorter. It just means that you become more susceptible to small differences in your trip resulting in huge differences in your travel time. You become less able to give a reliable ETA.

Think of a pinball machine for an analogy. The machine never changes but no two games are ever the same. You can extract the physics. You can write equations for the motions of the ball (or the car). But the tiniest variation in the way a ball hits a bumper produces a large difference in its trajectory. Its not a perfect metaphor because a human operating the flippers on a pinball machine counts as an external interference, but the bumpers are a way to understand why traffic lights and the slight acceleration-brake combinations they cause create chaos.

Villalobos, who had been working with Juan Alejandro Valdivia on the car chaos models for a few years, was sit-ting on a bus one day in Bogot and realized that the buses, because they add stops into the equation, would make an interesting extension to his research. So he and his team created a model in which a bus travels through a sequence of traffic lights and stops between lights to pick up passengers. They manipulated for how long the bus stopped. Their findings were published in a recent paper in the journal Chaos. They found that buses are likewise susceptible to chaos if their routes are engineered to minimize travel times: synchronized with traffic lights, making stops as short as possible and accelerating as much as possible after stops.

Another of their conclusions could prove useful to transportation planners. Planning a bus route so that the bus stops for longer and consistent amounts of time can significantly increase the predictability of the buss position along its route. Sure, this could make it slower, but its easy to see the benefits of a slightly longer but more predictable commute.

Villalobos and his team are now trying to find out how driver behavior affects the system. They have created a mathematical model for an aggressive driver one always trying to go at the top speed of the bus and a calm driver. Depending on their findings, its possible to imagine a general policy recommendation to all transit authorities: Bus drivers need to chill out, and it also wouldnt be a joke.

ZOE MENDELSON IS A JOURNALIST IN MEXICO CITY CAMPAIGNING FOR A MORE CHILLER WORLD. HER WORK HAS BEEN FEATURED ON FAST COMPANY, BUZZFEED, UNTAPPED CITIES AND ELSEWHERE.

THE SCIENCE OF CITIES COLUMN IS MADE POSSIBLE WITH THE SUPPORT OF THE JOHN D. AND CATHERINE T.

MACARTHUR FOUNDATION.