Thursday, November 29, 2018

Visualizing transport mode share using a ternary colour scheme

This is also a great technique to visualize how transport mode share varies across different neighborhoods of a city. This chart below was created by Ignacio Pérez and it shows the mode split of different communes in Santiago (Chile).

image credit: Ignacio Pérez

Wednesday, November 28, 2018

Academic Outreach

While many academics would like to (or are expected to) develop research with impact on the real world outside the ivory tower, this is how the academic publication process often look like. Via SAS.

Tuesday, November 27, 2018

Using GIFs to explain what various causal inference methods

Nick Huntington-Klein (CSU Fullerton) has created a series of excellent gifs to illustrate what various causal inference methods do to data and how they work. The whole thread on Twitter is worthwhile, specially because learning these econometric methods becomes much easier once we have a solid understanding of the concepts and intuitions behind them. (Thanks Bernardo Furtado for the tip).

obs. Nick created these gifs in R using the gganimate package and the code is available here.

Here's the gif that shows the intuition behind difference-in-differences

Wednesday, November 21, 2018

Widening roads to reduce congestion is like loosening the belt to tackle obesity

A gentle reminder that widening roads to reduce congestion is like loosening the belt to tackle obesity *

Related links:

* UPDATE: Apparently, this metaphor was originally used by the urban planner Lewis Mumford in 1955. “Building more roads to prevent congestion is like a fat man loosening his belt to prevent obesity”.

Thursday, November 15, 2018

The landscape and pulses of dockless bikes in Singapore

Yang Xu ‏(Twitter) and his team at the Hong Kong Polytechnic University have a new research project to understand the usage of dockless bike-sharing system and its relationship with built environment in Singapore. More info about the project in Yang's website.

Nice kickoff video created using

Wednesday, November 14, 2018

PhD thesis officially deposited and available for download

PhD thesis officially deposited! You can download the thesis here and check the R code I used in the data wrangling, mapping and analysis in this GitHub repo.*

ps. Special thanks to my friend Christine Moore for making the deposit.

* If you find any mistakes, let me know and I'll try to find someone to blame for.

Tuesday, November 6, 2018

The top cities by scientific output in 2018

The group Nature has updated the Nature Index and published a special issue raking cities and metro areas by their scientific output. There is a vast literature on cities as engines of growth and creativity because of economies of agglomeration, proximity and face-to-face contacts, social and cultural diversity etc. It's interesting to see how scientific outputs are clustered around major urban areas in the world.

The method they used to define urban clusters, however, is not entirely clear.  It seems a bit odd to me that they put Columbia, Princeton and Yale Universities in the same 'New York' cluster given the distance and commuting ties between these urban areas. My guess is that based on the same criteria, London-Oxford-Cambride (UK) should also be considered as a single cluster but they are treated separately. The same would happen with Sao Paulo-Campinas-Sao Jose dos Campos (Brazil).

In any case, the report brings plenty food for thought, including this brief analysis showing that the top collaborating cities are located in the same country.

Sunday, November 4, 2018

Future access to essential services in a growing smart city

Warning of  shameless  self-promotion:

I'm glad to share that some colleagues at UBC (JeromeMartino and Nuttall) and I have a new paper published. In this paper we analyze how projected population change could affect future accessibility demand to education and healthcare services and transportation equity, looking at the case of Surrey in Canada. One thing in particular I like about this paper is that it looks at how transport accessibility is affected by changes in population growth and spatial distribution while most studies in the literature have traditionally looked at how accessibility levels change due to modifications in the transport network or in the spatial allocation of schools, healthcare facilities etc. The paper will remain open access for the next 50 days. Download it here or send me an email and I'll be glad to share it to you. 

Mayaud, J. R., Tran, M., Pereira, R. H. M., & Nuttall, R. (2018). Future access to essential services in a growing smart city: The case of Surrey, British Columbia. Computers, Environment and Urban Systems. doi:10.1016/j.compenvurbsys.2018.07.005

The concept of accessibility – the ease with which people can reach places or opportunities –lies at the heart of what makes cities livable, workable and sustainable. As urban populations shift over time, predicting the changes to accessibility demand for certain services becomes crucial for responsible and ‘smart’ urban planning and infrastructure investment. In this study, we investigate how projected population change could affect accessibility to essential services in the City of Surrey, one of the fastest growing cities in Canada. Our objectives are two-fold: first, to quantify the additional pressure that Surrey's growing population will have on existing facilities; second, to investigate how changes in the spatial distribution of different age and income groups will impact accessibility equity across the city. We evaluated accessibility levels to healthcare facilities and schools across Surrey's multimodal transport network using origin-destination matrices, and combined this information with high-resolution longitudinal census data. Paying close attention to two vulnerable population groups – children and youth (0–19 years of age) and seniors (65+ years of age) – we analyzed shifts in accessibility demand from 2016 to 2022. The results show that population growth both within and outside the catchments of existing facilities will have varying implications for future accessibility demand in different areas of the city. By 2022, the city's hospitals and walk-in clinics will be accessible to ~9000 and ~124,000 more people (respectively) within a predefined threshold of 30 min by public transport. Schools will also face increased demand, as ~8000 additional children/youth in 2022 will move to areas with access to at least half of the city's schools. Conversely, over 27,000 more people – almost half of them seniors – will not be able to access a hospital in under 30 min by 2022. Since low-income and senior residents moving into poorly connected areas tend to be more reliant on public transport, accessibility equity may decline in some rural communities. Our study highlights how open-source data and code can be leveraged to conduct in-depth analysis of accessibility demand across a city, which is key for ensuring inclusive and ‘smart’ urban investment strategies.