Saturday, May 18, 2019

Biographical note: ITF/OECD award

Hi all. I am so glad to share that I have been honored with the 2019 Young Researcher of the Year Award, by the International Transport Forum (ITF/OECD). As I've said many times, this award speaks volumes about the generous guidance and support I have received from supervisors and colleagues at both Oxford and Ipea to conduct my research. Special thanks to my incredibly  demanding  supportive supervisors Tim Schwanen and David Banister. Thanks!

This is the award-winning paper, where I investigate the future impacts that different scenarios of a major BRT in Rio de Janeiro could have on access to employment opportunities for different income groups. The study also shows that the the equity assessment of transport projects based on accessibility estimates using cumulative opportunity measures with a single time threshold (the most common practice adopted by academic studies and transport agencies) can lead to misleading or partial conclusions. The preprint of the study is available for download here (it includes a spatial regression analysis that didn't make it into the paper because or reviewer #2).

Thanks to the award, I'll be attending the 2019 International Transport Forum Summit in Leipzig next week. The team at ITF will be Twitting about the Summit. I'll be presenting the paper on May 23rd at  5:15pm (local time). Apparently, it will be webcasted on Facebook Live.

Wednesday, May 8, 2019

The reasons two variables can be correlated

A concise illustration, by Thomas Lumley. This reminded me of this quite comprehensive list of some  ridiculous  spurious correlations.

image credit: Thomas Lumley

Friday, May 3, 2019

R Links

  1. The ipumsr package helps import census and survey data from around the world integrated across time and space. I've mentioned IPUMS in the blog before. This is certainly among the most important, ambitious and succeeded open data projects in the world

  2. A rather comphrensive comparison between data.table and dplyr syntaxes and funcitonalities ht via Mara Averick. I have to say I a strong preference for data.table because of computational performance. I also generally find the data.table syntax more easily readable than dplyr. There, I said.

  3. Free Book with code: “Spatio-Temporal Statistics with R,” by Christopher K. Wikle, Andrew Zammit-Mangion, and Noel Cressie

  4. brickr: a package to Build 3D LEGO models in R, by Ryan Timpe

  5. trackeR: a package for handling running and cycling data from GPS-enabled tracking devices, by Hannah Frick

  6. A Cheat Sheet on how to use the Reticulate package for interoperability between Python and R

  7. How to create a gif of a spinning globe using R, by James Cheshire

  8. The R package traveltime allows one to retrieve travel-time information from the Traveltime Platform API to create isochrone maps like these below. Great work by Thomas Russo.

image credit: Thomas Russo

Off to Sweden

Professor Sonia Yeh (Twitter) was awarded with the Håkan Frisingers scholarship for her innovative research on sustainable transport and energy systems. The award is given by the Volvo Research and Educational Foundations (VREF) and the award ceremony will be held next week on May 6 in Gothenburg. Sonia has kindly invited Yusak Susilo and I to join her in the ceremony to celebrate her work and to deliver a public lecture. The program of the event is available here. We will also have a more academic oriented seminar at Chalmers University on May 7 in the morning, for those around. I'll be mostly talking about future directions on accessibility and equity concerns in transport research and policy. Needless to say I am very glad for Sonia's well deserved award and honored by her invitation.

After that I'll be joining some colleagues from Lund University to deliver a seminar at the The Swedish Knowledge Centre for Public Transport (K2) on May 10 at 9h20. We'll be talking about Transport Justice Perspectives: Comparing Calculated and Perceived Accessibility. Pop in if you're in the neighbourhood.

Monday, April 29, 2019

New Center for Demographic Science at Oxford

Oxford University has recently launched the Leverhulme Centre for Demographic Science (they are also on Twitter). The center is led by Melinda Mills and it involves a team with several top researchers dedicated to seven interconnected research programmes:

1. Nowcasting: digital and computational demography
2. Environmental context, demography and climate change
3. Inequality and diversity
4. Sociogenomics: nature and nurture
5. Causal demography
6. Demography, society and global sustainability
7. Ethics, truth and trust

*** The other good news is that they are hiring Assistant Professors and Postdocs. The center also offers scholarships for Masters and PhD students.

Friday, April 26, 2019

The global population pyramid from 1950 to 2100

New piece by Max Roser in Our World in Data, showing how global demography has changed and what we can expect for the 21st century.

In this figure below, curves in blue to green show how the global population pyramid changed from 1950 to today, while shades of yellow show the UN projections for the change expected until 2100.

click on the image to see full size

Friday, April 19, 2019

The rapid growth of shared bikes and e-scooters in the US

In 2018, people took 84 million trips using shared bikes and e-scooters in the US, an astounding growth in the past year largely due to e-scooters. This number and many other interesting stats come from a new report looking at Shared Micromobility in the US in 2018, recently published by the US National Association of City Transportation Officials (NACTO). Hat tip to Tim Papandreou.

Monday, April 15, 2019

Collaborative mapping of paratransit and GTFS data

Jacqueline Klopp (Twitter) and Clemence Cavoli (Twitter) have a new paper reviewing some trends in transportation planning in African cities with a focus on paratransit. The paper also discusses why official transportation planning should engage with paratransit services and how this task can be supported through collaborative mapping projects that open new avenues for data accountability.

The paper is open access (see link below) and it draws attention to, an initiative working "to scale up these mapping efforts and promote open data and sharing, open source tools and exchange and learning between African cities to build local data infrastructure, eco-systems and local capacities". Thanks to this initiative, one can easily find for example the GTFS data of cities such as Nairobi, Maputo, Accra and Cairo and others. Jackie and others are working to build a similar initiative in Latin America and I hope I will soon bring more info about this. Stay tuned.

Klopp, J. M., & Cavoli, C. (2019). Mapping minibuses in Maputo and Nairobi: engaging paratransit in transportation planning in African cities. Transport Reviews, 1-20.

Often called paratransit because of their flexible stops, schedules and routes, minibuses make up the bulk of public transport in African cities. Despite their ubiquity and importance, these systems are poorly understood by transportation planners who tend to focus on large-scale urban infrastructure projects such as highways, commuter rail or bus rapid transit systems. The assumption within much of this planning is that these minibus systems are barriers to change and will become at most secondary “feeder” buses within large-scale projects, but structured plans detailing this vision are lacking. This paper argues that frequent failure to collect data and value important paratransit systems as a critical part of transportation in their own right is deeply problematic from the point of view of equity, access and inclusive and effective planning. We ask whether the growing number of bottom up mapping projects of minibus systems can disrupt this status quo. By comparing two mapping projects, Digital Matatus in Nairobi and the Mapa Dos Chapas in Maputo, we find that inclusive, collaborative mapping can help render these minibuses more visible in planning and provoke more grounded and inclusive “planning conversations” on multi-modal integration, passenger information and minibus upgrading, all key but relatively marginalised aspects of creating accessible, low emission, high quality and safe public transport in African cities.

Thursday, April 11, 2019

Biographical note: AAG PhD thesis award

I am very pleased to share that my PhD thesis was awarded the best 2019 thesis award by the Transportation Geography Specialty Group of the American Association of Geographers (AAG). I am also very honoured that I was nominated a board member of the specialty group. If it could be of interest, my thesis is available for download here and I've created a GitHub repository with the R code used in the data wrangling, mapping and analysis in the thesis. Some of the chapters in the dissertation have been published as papers here, here and here (+ this other one currently under review).

I am very grateful for the the support from my partner Fabiana, from the Institute for Applied Economic Research (Ipea) and to the invaluable guidance from my  demanding  tireless supervisors Tim Schwanen and David Banister

ps. the blog has been less active than usual in the past weeks because I was away attending the AAG annual meeting to receive the award and to present this paper here.

Wednesday, April 10, 2019

off-topic: The first-ever picture of a black hole

Just a few years ago, Katie Bouman (then a PhD student at MIT) presented this TED talk about the massive collective research effort involved in the Event Horizon Telescope Collaboration. Three years latter, today, this collaboration announced the first-ever picture of a black hole. Katie led the creation of a new imaging algorithm that helped make this possible.

Yep, they have found a way to register the image of a black hole that is about 55 million light years away from Earth. The method is truly inventive, involving an array of telescopes across the globe, atomic clocks, cutting edge machine learning and more than 5 petabytes of data. You can see more about it in this short video or in the public announcement made today.

I know this is a bit off-topic in this blog but my inner nerd child is too excited to let this one pass. This is a big day.

Credit: Event Horizon Telescope Collaboration

Sunday, March 24, 2019

GTFS rotuer in R

For those interested in public transport research and planning, there is a new R package to do public transport routing using GTFS data. The gtfs-router package uses the power of C++ and it is quite efficient. This is only the release version of the package (0.01), though. There is a lot of room for improvements but I hope gtfs-router becomes a strong competitor to OpenTripPlanner in a couple of years.

The package was created by Mark Padgham (twitter), who is the author of/contributor to various other transport-related packages such as dodgrbikedata and osmdata. Kudos to Mark!

ps. The capabilities of R for transport research and planning are greater than never. There is a very vibrant and active community with dozens of other packages. Perhaps this should be the topic for a future post.

image credit: Rstudio and smtd

Thursday, March 21, 2019

Ipea Seminar - Infusing Urban and Regional policy with Geographic Data Science

Today we are having Dani Arribas-Bel (Geographic Data Science Lab, University of Liverpool) presenting a seminar at the Institute for Applied Economic Research (Ipea). Daniel (websiteTwitter) will be talking about his research agenda on "Infusing Urban and Regional policy with Geographic Data Science". The seminar will start at 3pm (local time). My apologies this post comes in short notice. This week has been hectic.

Daniel is part of the development team of  PySAL and he is a prolific researcher and also a great enthusiast of open data/software and research reproducibility. In fact, many of his papers (code and data) and teaching material are available on his Github repo.

Summary of the presentation:
The recent explosion in availability of new forms of data poses significant opportunities to how we analyse cities and regions, both in academic and policy contexts. Over the last decade, three families of data have emerged in this context. One is digital traces of individual activity. From credit card transactions, to mobile phone calls, to thoughts and feelings we decide to share through social media, more and more bits of our life are being stored digitally as data that a computer can understand. The second comes from an increasing number of sensors, from traffic controllers to nano-satellites orbiting the Earth, which are constantly recording information about the environment. The third one has existed for longer but has not been available until recently: a few years ago, governments started releasing data on their internal operations that used to be parked in (closed) silos. This presentation will walk through several examples where new forms of data are applied to tackle new questions or obtain new perspectives on long-standing challenges of regional and urban analysis. As part of this whirlwind tour, we will also spend some time trying to understand what the main challenges, methodological advances, and risks that "accidental data” pose are, and will emphasise the tremendous opportunities they unleash.

credit: Dani Arribas-Bel

Tuesday, March 19, 2019

The race for the largest city in the world over the past 500 years

In previous posts, I've pointed out to an incredible open dataset with comprehensive population estimates of human settlements and cities for the past 6,000 years. The talented John Burn-Murdoch used some of these data to create this nice animation showing the changing ranks of the 10 largest cities in the world since 1500. The full code for the animation is available here.

Friday, March 15, 2019

Creating a simple world map of cities in R

Mike (from cool but useless) asked on twitter if there is any package in R with with lats/longs of lots of cities. In fact there is. Here is a simple code to create a world map of cities with population larger than 40K in R using maps::world.cities and ggplot2.

ps. These population data in the maps package refers to 2016 estimates. If you want city population data from previous years, you might remember that we have previously posted about this open dataset with 6,000 years of global urbanization.

Wednesday, March 13, 2019

Racial inequity in who pollutes and who gets exposed to pollution

A recent paper led by Chris Tessum (University of Washington) and published in PNAS brings novel estimates of racial-ethnic disparities in air pollution cause and exposure in the US. They find that air pollution is disproportionately caused by consumption by white Americans, but disproportionately affects Black and Hispanic Americans. The air pollution input-output model used in the paper is freely available and there's an experimental live version of the model running, here. (thanks Marko Tainio for pointing to this paper)

Fine particulate matter (PM2.5) air pollution exposure is the largest environmental health risk factor in the United States. Here, we link PM2.5 exposure to the human activities responsible for PM2.5 pollution. We use these results to explore “pollution inequity”: the difference between the environmental health damage caused by a racial–ethnic group and the damage that group experiences. We show that, in the United States, PM2.5 exposure is disproportionately caused by consumption of goods and services mainly by the non-Hispanic white majority, but disproportionately inhaled by black and Hispanic minorities. On average, non-Hispanic whites experience a “pollution advantage”: They experience ∼17% less air pollution exposure than is caused by their consumption. Blacks and Hispanics on average bear a “pollution burden” of 56% and 63% excess exposure, respectively, relative to the exposure caused by their consumption. The total disparity is caused as much by how much people consume as by how much pollution they breathe. Differences in the types of goods and services consumed by each group are less important. PM2.5 exposures declined ∼50% during 2002–2015 for all three racial–ethnic groups, but pollution inequity has remained high.

credit: Tessum et a..

Saturday, March 2, 2019

Off The Road

It's Carnaval season in Brazil and I'll be in small fisherman village mostly disconnected. The level of activity in the blog will remain lower than usual this week (my Twitter is probably be less affected though).

Marau, Bahia, Brazil

Tuesday, February 26, 2019

TSU/Oxford is recruiting a Departmental Research Lecturer

The Transport Studies Unit (TSU) and the School of Geography and Environment are recruiting a Departmental Research Lecturer. This post is a full-time, 5-year departmental appointment, research intensive position (75% research). More details here.

TSU is a relatively small research group with some brilliant researchers in an incredibly vibrant department at one of the top universities in the world. This is a great opportunity and I would strongly encourage competitive candidates to apply. The closing date  is 29-Mar-2019.

Wednesday, February 20, 2019

How Barcelona is taking city streets back from cars

The team at Vox have produced some interesting videos on urban-related topics. I've posted a few of them here in the blog before. This one below covers the urban planning in Barcelona, which uses superblocks as a means to build more liveable and inclusive urban environments in parts of the city.

This video is actually from 2 years ago but I only saw this video last week (thanks to the recommendation of  Telmo Amand, who was my high-school geography teacher!)

Tuesday, February 19, 2019

Evidence-based transport planning - event in Rio

In case you're around Rio de Janeiro this Feb 21-22, I'll be joining members of ITDP Brazil and others in a conversation about evidence-based transport planning, GTFS data and accessibility modelling. The event will be broadcast live (in Portuguese) at

On the second day, before the closing of the event, I will give a short presentation on the Access to Opportunities Project, the first steps of the project and our plans for the next couple of years. The program of the event (in Portugese) is in these images below. Click on them to enlarge the image. 

Friday, February 15, 2019

Tuesday, February 5, 2019

Urban Picture

A very cold Chicago (2019), processed by Pierre Markuse using Copernicus Sentinel data.

Thursday, January 31, 2019

Travel time to closest healthcare facility in Rio de Janeiro

The map shows how long it takes (in minutes) to travel by public transport and walking to the closest healthcare facility across the city of Rio de Janeiro. The analysis is disaggregated for facilities providing low-, medium- and high-complexity services. 

The first thing to note here is that physical accessibility to public health is relatively high in Rio. Approximately 94% of Rio`s population could reach at least one facility providing low-complexity services under 30 minutes. Under the same time, medium- and high-complexity services could be reached by 81% and 72% of the population, respectively. This is explained to some extent by the spatial planning of healthcare in the region, which has been relatively successful in spreading low- and medium-complexity facilities across the city. The map also gives a good sense of how the distribution of healthcare facilities vis-à-vis the public transport network varies across space, and how access to public health tend to be much lower in the west and particularly in the urban fringes of the city.

ps. This is a map I created for my PhD research but I didn't include it in the thesis in the end . To create this map I used a 2015 dataset of healthcare facilities and the GTFS of Rio's public transport network from March 2017. The dataviz and data wrangling were done in R. In case you're interested in doing similar analyses, I've created a simple tutorial with reproducible example on how to use OpenTripPlanner (OTP) to estimate travel times.

[click on the image to enlarge it]

Thursday, January 24, 2019

Why you should probably share your preprints

Among researchers, a preprint is known as the version of a scientific study that precedes official publication in a peer-reviewed journal or book. In hard sciences and computer science, it is quite common for researchers to put their preprints openly available online, mainly through the Arxiv repository. This practice is also common in Economics, where researchers often publish 'working papers' via SSRN, NBER or their own institutions before getting the paper published in a journal. This practice is becoming more common and there are new repositories popping up in different areas such as biorxiv, chemrxiv and the SocArXiv focused on the social sciences more broadly.

Why you should share your preprints:
Preprints are not meant to replace peer-reviewed publications. Nonetheless they can importantly contribute to (1) speeding up the process of getting your ideas out in the public, (2) increasing the readership of your work, and (3) making your research accessible to people who cannot read articles behind paywalls. I've been sharing the preprints of my last papers on SocArXiv and highly recommend others to do the same. There are a few good reasons to use SocArxiv. One of them is that they create a permanent link and a permanent DOI identification for you preprint. This helps making the manuscript searchable and citable on academic databases.

Be aware, though, that some journals for example do not allow the use of preprints as they claim that this practice undermines the novelty of manuscripts. As a rule, though, social science journals published by Elsevier and Taylor & Francis (Routledge) do not see any problem in authors sharing their preprints before paper submission. There is also an interesting debate about whether preprints undermine the double-blindness of peer review and the differential impacts it might have for the publications of senior and junior researchers. As I've mentioned before, the use of preprints is not without controversy. 

Wednesday, January 16, 2019

The Schrödinger Professor

This permanent/temporary position is also indicated in the author's profile on Google Scholar (I saw this on Twitter via the brilliant Drunkeynesian).

Wednesday, January 9, 2019

New paper out: Future accessibility impacts of transport policy scenarios: equity and sensitivity to travel time thresholds

I'm glad to share that the 3rd paper of my thesis is now published. The study (1) illustrates how one can measure the future accessibility impacts of transport project scenarios; (2) discusses how accessibility analyses can be influenced by the little-known issue of the modifiable temporal unit problem (MTUP); and (3) shows that equity assessments of transport policies based on cumulative opportunity metrics depend on the time threshold chosen for accessibility analysis. One thing in particular I like about this paper is that its findings demonstrate that the most common practice adopted by academic studies and transport agencies when evaluating the accessibility impacts of transportation projects can lead to misleading or partial conclusions if this methodological choice is made uncritically.

The paper will remain open access for the next 40 days or so. Downloaded it here [ungated preprint]. The R scripts used to write this paper and my PhD thesis are available in this GitHub repo.

The accessibility impacts of transport projects ex-post implementation are generally evaluated using cumulative opportunity measures based on a single travel time threshold. Fewer studies have explored how accessibility appraisal of transport plans can be used to evaluate policy scenarios and their impacts for different social groups or examined whether the results of project appraisals are sensitive to the time threshold of choice. This paper analyzes how different scenarios of full and partial implementation of the TransBrasil BRT project in Rio de Janeiro (Brazil) will likely impact the number of jobs accessible to the population of different income levels. The analysis is conducted under various travel time thresholds of 30, 60, 90 and 120 min to test whether the results are sensitive to the boundary effect of the modifiable temporal unit problem (MTUP). Compared to a partial operation scenario, the full implementation of TransBrasil that extends this corridor into the city center would lead to higher accessibility gains due to network effects of connecting this BRT to other transport modes. Nonetheless, the size of the accessibility impacts of the proposed BRT as well as its distribution across income classes would significantly change depending on the time threshold chosen for the accessibility analysis. Considering cut-off times of 30 or 60 min, both scenarios of TransBrasil would lead to higher accessibility impacts in general and particularly for low-income groups, moving Rio towards a more equitable transportation system. However, under longer thresholds of 90 and 120 min, an evaluation of this project would find much smaller accessibility gains more evenly distributed by income levels. The paper highlights how time threshold choice in cumulative opportunity measures can have important but overlooked implications for policy evaluation and it calls for further research on the MTUP in future transport and mobility studies.

Sunday, January 6, 2019

Call for a research assistant in the Access to Opportunities Project at Ipea, Brazil

This is just a reminder that I am hiring a research assistant for the Access to Opportunities Project, at the Institute for Applied Economic Research (Ipea). The researcher will be based in Brasilia (Brazil). We are looking for someone with advanced skills in R. Applications will be open until the 20th of January 2019. More details can be found here (info in Portuguese only). Please, help spread us the word.

More info about the Access to Opportunities Project: The aim of the project is to estimate accessibility to employment opportunities as well as education and health services in the largest urban areas in Brazil. The project focuses on how social and spatial inequalities in access to opportunities relate to urban transportation, housing and land use policies. We are estimating accessibility by public transport, walking and cycling at a high spatial resolution for all of the Brazilian major cities. The project will generate a massive amount of data each year. My plan is to make the data outputs and results publicly available to policy makers and researchers, with whom we will be able to collaborate in the future to analzye particular case studies in Brazil but also to conduct comparative studies involving cities in Brazil and other countries.

Thursday, January 3, 2019

A 195 gigapixel Urban Picture of Shanghai

On this link you can browse around an incredible bird's-eye panorama of Shanghai. The picture has an incredible resolution of 195 gigapixels, which captures tiny details such as people's faces or car plates (ht Lionel Page).

image credit: Billion Pixel Studio

Tuesday, January 1, 2019

Fresh new start

That uplifting feeling that every new year/project is an opportunity to have a fresh new start.

image credit: MonkeyUser