Sunday, January 31, 2016

The Price of Anarchy in Transportation Networks

Great paper with an interesting application of Braess’s paradox to transportation: closing roads can reduce travel delays.

Youn, H., Gastner, M. T., & Jeong, H. (2008). Price of anarchy in transportation networks: efficiency and optimality control. Physical review letters, 101(12), 128701.

Uncoordinated individuals in human society pursuing their personally optimal strategies do not always achieve the social optimum, the most beneficial state to the society as a whole. Instead, strategies form Nash equilibria which are often socially suboptimal. Society, therefore, has to pay aprice of anarchy for the lack of coordination among its members. Here we assess this price of anarchy by analyzing the travel times in road networks of several major cities. Our simulation shows that uncoordinated drivers possibly waste a considerable amount of their travel time. Counterintuitively, simply blocking certain streets can partially improve the traffic conditions. We analyze various complex networks and discuss the possibility of similar paradoxes in physics.
Hyejin Youn also has some more recent and equally interesting papers on urban scaling laws, in case you're interested.

credit: Youn et al (2008)

Related paper:

Friday, January 29, 2016

Getting updates from this blog

Dear readers, if you like this blog, recommend it to your friends. If you didn't like this blog, recommend it to your enemies. That's fine also.

If you want to receive our updates, you can do this using 3 different alternatives:

1 - Twitter: 

2 - Facebook page:  

3 -  Subscribe to our RSS Feed in a reader. I'd strongly encourage you to use Feedly

Thursday, January 28, 2016

Household composition in London: age and spatial distribution

This is a quite nice way to put a lot of info in a concise and beautiful figure. It comes from ‘The Information Capital’, a book by James Cheshire and Oliver Uberti.

click on the image to enlarge it

Monday, January 25, 2016

PhD Feelings

This is how doing a PhD can feel in one image

via Gif Porn

Saturday, January 23, 2016

Thursday, January 21, 2016

Monday, January 18, 2016

Car-centric Brasilia

Brasilia is great for cars, but less so for people.

"We are not Amsterdam"

On the same topic, there is an interesting piece at the Guardian and a 6-min documentary on how the Dutch got their cycling infrastructure:

Thursday, January 14, 2016

Map of real estate prices in Sao Paulo

Great interactive map with real estate prices in Sao Paulo, Brazil. The data used in the map is available here and covers 200 thousand properties announced for sale in a real state agency website (Properati).

credit: Properati

Wednesday, January 13, 2016

TSU Seminars: Urban Mobilities in the Smart City

From January to March 2016, the Transport Studies Unit (TSU) at the University of Oxford will host a lecture series on the theme of ‘Smart Cities’. This series will gather a range of world – leading academics and urban policy practitioners to debate some of the key issues raised by smart cities for urban transport and mobility futures.

The program is available here and we'll have the participation of some great researchers, including Gillian Rose, Michael Batty, Paul Newman, Geoff Vigar and others.

Transport Studies UnitUniversity of Oxford

Sunday, January 10, 2016

Sex is another good reason to stop climate change, apparently

Hotter temperatures reduce sex drive and lower birth rates, according to a recent study published as a NBER Working Paper. There is a good summary of the paper here. I kind of liked the conclusion in the abstract.

Barreca, A., Deschenes, O., & Guldi, M. (2015). Maybe Next Month? Temperature Shocks, Climate Change, and Dynamic Adjustments in Birth Rates (No. w21681). NBER Working Paper.

Dynamic adjustments could be a useful strategy for mitigating the costs of acute environmental shocks when timing is not a strictly binding constraint. To investigate whether such adjustments could apply to fertility, we estimate the effects of temperature shocks on birth rates in the United States between 1931 and 2010. Our innovative approach allows for presumably random variation in the distribution of daily temperatures to affect birth rates up to 24 months into the future. We find that additional days above 80 °F cause a large decline in birth rates approximately 8 to 10 months later. The initial decline is followed by a partial rebound in births over the next few months implying that populations can mitigate the fertility cost of temperature shocks by shifting conception month. This dynamic adjustment helps explain the observed decline in birth rates during the spring and subsequent increase during the summer. The lack of a full rebound suggests that increased temperatures due to climate change may reduce population growth rates in the coming century. As an added cost, climate change will shift even more births to the summer months when third trimester exposure to dangerously high temperatures increases. Based on our analysis of historical changes in the temperature-fertility relationship, we conclude air conditioning could be used to substantially offset the fertility costs of climate change.

Saturday, January 9, 2016

How (much) can population aging affect transit fares in Sao Paulo?

warning of belated self-promotion: This is a paper I published with colleagues last year in the Brazilian Journal of Population studies. The study  was published in Portuguese only, but the abstract should give a good summary of what we have done.

Pereira, R. , et al. (2015). The effects of population aging and fare concessions on public transport fares in São Paulo Metropolitan Area. Revista Brasileira de Estudos de População, 32(1), 101–120.

Abstract: Students, children under 4 years old and people aged 65 and over are entitled to partial or full concessions on urban trips in public transport systems in Brazil. These concessions are not covered by public funding, but rather through cross-subsidies from other passengers who pay full fare. In this study, we estimate the effect population aging will have on public transport fares over the next four decades in the metropolitan area of São Paulo (MRSP), the largest metropolitan area in Brazil. The analyses in this paper are based on data from a Household Travel Survey carried out in 2007, and on official population projections developed by IBGE (Brazilian Institute of Geography and Statistics) and Seade Foundation for the years 2020, 2030 and 2050. Considering the different periods of population projection, we adapt the technique of direct standardization to simulate expected changes in the composition of public transport trips in terms of paying and non-paying passengers. The results indicate that, in the short term (2020), the population aging expected to occur in São Paulo should have a modest effect on the total number and age composition of trips in the public transport system in the region. In the medium and long terms, however, the expected growth in the proportion of non-paying passengers could result in an increase in fare prices by about 10% and 20% if the current cross-subsidization mechanism is maintained.

Thursday, January 7, 2016

How much faster you could travel today compared to 1914

A couple of months ago, Intelligent Life magazine published a great isochronic map from 1914 showing how much time (in days) it used to take to travel to anywhere in the planet if you departed from London.

The team at Rome2rio have recently updated the map to 2016, which does a great job in showing how the world has gotten incredibly "smaller", though I would rather say "faster". I haven't found any information on which datasets they have used to do this though.

Wednesday, January 6, 2016

Monday, January 4, 2016

Big Data and Cycling

A fresh new study reviewing Big data and cycling, by Zaltz Austwick and colleagues.

Big Data has begun to create significant impacts in urban and transport planning. This paper covers the explosion in data-driven research on cycling, most of which has occurred in the last ten years. We review the techniques, objectives and findings of a growing number of studies we have classified into three groups according to the nature of the data they are based on: GPS data (spatio-temporal data collected using the global positioning system (GPS)), live point data and journey data. We discuss the movement from small-scale GPS studies to the ‘Big GPS’ data sets held by fitness and leisure apps or specific cycling initiatives, the impact of Bike Share Programmes (BSP) on the availability of timely point data and the potential of historical journey data for trend analysis and pattern recognition. We conclude by pointing towards the possible new insights through combining these data sets with each other – and with more conventional health, socio-demographic or transport data.

This paper is part of special issue in Transport Reviews on Cycling as transport, edited by Elliot Fishman. You might want to take a look.

Saturday, January 2, 2016

Urban Picture

Oxford under the winter Milky Way

image credit: Yunli Song, via Cheli Cresswell and Will West