While Jacobs’s arguments are persuasive, her critics say there is little evidence to show that these factors are linked with vibrant city life. That changed last year when urban scientists in Seoul, South Korea, published the result of a 10-year study of pedestrian activity in the city at unprecedented resolution. This work successfully tested Jacobs’s ideas for the first time.
However, the data was gathered largely through pedestrian surveys, a process that is time-consuming, costly, and generally impractical for use in most modern cities.
De Nadai and co have come up with a much cheaper and quicker alternative using a new generation of city databases and the way people use social media and mobile phones. The new databases include OpenStreetMap, the collaborative mapping tool; census data, which records populations and building use; land use data, which uses satellite images to classify land use according to various categories; Foursquare data, which records geographic details about personal activity; and mobile-phone records showing the number and frequency of calls in an area.
De Nadai and co gathered this data for six cities in Italy—Rome, Naples, Florence, Bologna, Milan, and Palermo.
Their analysis is straightforward. The team used mobile-phone activity as a measure of urban vitality and land-use records, census data, and Foursquare activity as a measure of urban diversity. Their goal was to see how vitality and diversity are correlated in the cities they studied.
The results make for interesting reading. De Nadai and co say that land use is correlated with vitality. In cities such as Rome, mixed land use is common. However, Milan is divided into areas by function—industrial, residential, commercial, and so on. “Consequently, in Milan, vitality is experienced only in the mixed districts,” they say.
The structure of city districts is important, too. European cities tend not to have the super-sized city blocks found in American cities. But the density of intersections varies greatly, and this turns out to be important. “Vibrant urban areas are those with dense streets, which, in fact, slow down cars and make it easier for pedestrian to cross,” say the team.
Jacobs also highlighted the importance of having a mixture of old and new buildings to promote vitality. However, De Nadai and co say this is less of an issue in Italian cities, where ancient buildings are common and have been actively preserved for centuries. Consequently, the goal of producing mixed areas is harder to achieve. “In the Italian context, mixing buildings of different eras is not as important as (or, rather, as possible as) it is in the American context,” they say.
Nevertheless, the team found that a crucial factor for vibrancy is the presence of “third places,” locations that are not homes (first places) or places of employment (second places). Third places are bars, restaurants, places of worship, shopping malls, parks, and so on—places where people go to gather and socialize.
The density of people also turns out to be important, too, just as Jacobs predicted. “Our results suggest that Jacobs’s four conditions for maintaining a vital urban life hold for Italian cities,” conclude De Nadai and co.
They go on to summarize by saying: “Active Italian districts have dense concentrations of office workers, third places at walking distance, small streets, and historical buildings.
”That’s an interesting study that has the potential to have major impact on city planning. The lack of an evidence-based approach to city planning has resulted in numerous urban disasters, not least of which was the decline of city centers in the U.S. in the 1950s, 1960s, and later.