The Impact of Urban Appearance

We have mentioned the work of Cesar Hidalgo (twitter) in this blog a few times already but he keeps coming up with new interesting research . As many will know, Hidalgo and his team have a project called Place Pulse, in which they use computer vision techniques to analyze snapshots of google street view and crowdsource people's perception on city’s physical appearance. Here are my three highlight of the project so far.

• In its initial phase, the project focused on 19 American cities. Some of the research findings show how perceived safety of streetscapes has strong positive correlation with household income, population density and income inequality (PDF of the paper).
  
  
• In a more recent paper, led by Marco De Nadai (twitter), the authors combine Place Pulse with mobile phone data to show how the safety scores of neighbourhoods in Rome and Milan are also strongly correlated with urban liveliness, and that visual features like greenery and street facing windows contribute to a positive appearance of safety. This is an extension of Nadai's previous work, where he engages more directly with Jane Jacobs's ideas on urban vitality.
  
  
• Finally, the Place Pulse project has been recently updated and expanded to create the first global dataset of urban appearance "...containing 110,988 images from 56 cities, and 1,170,000 pairwise comparisons provided by 81,630 online volunteers along six perceptual attributes: safe, lively, boring, wealthy, depressing, and beautiful". 

The research possibilities here are endless, so I'm sure I'll be posting updates on this project again in the future. Don't forget to input some of your own perceptions to the project.

Testing Jane Jacobs's ideas on urban vitality using mobile phone data

In her influential book - The Death and Life of Great American Cities (1961), Jane Jacobs proposed that cities would only develop vibrant activities and flourish if they met four conditions of diverse urban environment:

1. City districts should serve more than one primary function, what would attract people with diverse purposes at different times of the day; 
   
   
2. Street blocks must be short, to allow pedestrian-friendly environments;
   
   
3. The buildings in a district should be diverse in terms of age and form, what would support diversity of economic activities and residents with of high- and low-income;
   
   
4. A district must have a sufficient density of people and buildings; what would foster “lively” environments that attract people for different purposes.

These conditions have recently been tested in four Italian cities in a paper by De Nadai and colleagues (2016). The authors use a combination of data sources, including socio-demographic information from the Italian Census, Open Street Map and human activity patterns extracted from mobile phone data. Good food for thought !

De Nadai, M. et al. (2016). The Death and Life of Great Italian Cities: A Mobile Phone Data Perspective. In Proceedings of the 25th International Conference on World Wide Web (pp. 413-423). International World Wide Web Conferences Steering Committee.

Abstract:

The Death and Life of Great American Cities was written in 1961 and is now one of the most influential book in city planning. In it, Jane Jacobs proposed four conditions that promote life in a city. However, these conditions have not been empirically tested until recently. This is mainly because it is hard to collect data about "city life". The city of Seoul recently collected pedestrian activity through surveys at an unprecedented scale, with an effort spanning more than a decade, allowing researchers to conduct the first study successfully testing Jacobs's conditions. In this paper, we identify a valuable alternative to the lengthy and costly collection of activity survey data: mobile phone data. We extract human activity from such data, collect land use and socio-demographic information from the Italian Census and Open Street Map, and test the four conditions in six Italian cities. Although these cities are very different from the places for which Jacobs's conditions were spelled out (i.e., great American cities) and from the places in which they were recently tested (i.e., the Asian city of Seoul), we find those conditions to be indeed associated with urban life in Italy as well. Our methodology promises to have a great impact on urban studies, not least because, if replicated, it will make it possible to test Jacobs's theories at scale.

ps. You might want to follow some of the authors on twitter: De Nadai, Staiano, Quercia and Lepri.

credit: De Nadai, M. et al. (2016).

Assorted links

1. What's the connection between a metro’s size and its success in pro sports?
   
   
2. The new issue of the Journal of Transport and Land Use (JLUT) is out!
   
   
3. Bucerius Ph.D. scholarship program in migration studies "Settling Into Motion" offers up to eight scholarships for Ph.D. theses addressing migration in changing societies (thank Joice Vieira for the tip)
   
   
4. Is America Facing a Housing Shortage?
   
   
5. Jacobs’ lasting “Top 10″ observations
   
   
6. Want a Job? Go to College, and Don’t Major in Architecture
   
   
7. 5th stage of the Demographic Transition (?)

(image credit)

Soundtrack: Jazzual Suspects

Should there be a “proper density”?

"Indeed, to anyone who respects consumer sovereignty, there is something a little jarring about Jacobs’s question: "What is the proper density for city dwellings?' " (E. Glaeser)

When it comes to urban planning, it seems there has been a long normative discussion about what should be a “proper density”. In this point I take Glaseser 's words as mine:

"Why in the world should there be a 'proper density'?
A good case can be made that cities succeed by offering
a diverse menu of neighborhoods that cater to a wide
range of tastes."

ps. Jane Jacobs wasn't always right.