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The Death and Life of Great Italian Cities: A Mobile Phone Data Perspective
Marco De Nadai, Jacopo Staiano, Roberto Larcher, Nicu Sebe, Daniele Quercia, Bruno Lepri
TL;DR
The paper asks whether Jacobs’s four conditions for urban life can be tested beyond the costly collection of activity surveys. It combines mobile-phone activity with Italian census and map data to test those conditions in six Italian cities, finding that they hold in Italy as well.
Problem
Jacobs’s four conditions for urban life lacked joint empirical testing because neighborhood activity data was difficult to collect.
Method
The study uses aggregated mobile-phone records as an activity proxy and combines them with census, land-use, and open map data across six Italian cities.
Results
77% of district-activity variability is explained by simple structural and static features, and Jacobs’s four conditions hold across Italian cities.
Takeaways & Limitations
The results show that Jacobs’s theories are verifiable and remain valid in the European context, while the methodology can support replication at scale.
Takeaways & Limitations
The activity proxy omits temporal dynamics, and full replication is difficult without call records.
Abstract
from arXiv · showhide
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.
1. INTRODUCTION
The paper addresses whether Jane Jacobs’s four diversity conditions for urban life can be empirically tested using mobile phone activity data rather than costly surveys. It operationalizes urban vitality and diversity in six Italian cities and reports that Jacobs’s conditions hold there as well.
- Urban planners investigate what creates urban life, with Jacobs identifying the physical environment as essential to urban vitality.
- Jacobs proposed four conditions: mixed land uses, small blocks, diverse buildings, and dense concentrations of people and buildings.
- Before recent work in Seoul, Jacobs’s four conditions had not been empirically tested together because neighborhood activity data was difficult to collect.
- The study uses mobile phone records to measure human activity and open, aggregated, anonymous map data to derive urban-diversity metrics.
- Across six Italian cities, the authors find that all four conditions for promoting urban life hold in the Italian context.
- The work assesses Jacobs’s diversity conditions, identifies implications and limitations, and proposes a methodology that can support testing her theories at scale.
2. RELATED WORK
Related work has used emerging digital data to study urban dynamics, mobility, and urban theories. This paper extends that line of research by comprehensively validating Jacobs’s four conditions for urban life.
- Urban computing combines computer-science approaches with urban planning, urban economy, and urban sociology.
- Researchers have tested urban theories using social media, online images, videos, and mobile phone data.
- Web crowdsourcing games have been used to study mental maps and the visual qualities people associate with streets.
- Mobile phone data supports studying city dynamics and has been used to map functional uses, identify important places, compare cities, and predict socioeconomic indicators.
- Prior research verified Jacobs’s natural-surveillance theory, linking people diversity and visitors with observations that can discourage crime.
- This study goes beyond crime by comprehensively validating Jacobs’s four conditions for urban life using several data sets.
3. SETS OF DATA
The study combines aggregated mobile-phone activity with open geospatial, census, land-use, infrastructure, and venue data. These sources provide measures of mobility, urban form, population, buildings, land use, and places of activity.
- Mobile phone Internet activity enables passive reconstruction of mobility because phones remain connected through background traffic and push notifications.
- Call records cover six cities, combine TIM and roaming customers, are aggregated every 60 minutes, and span February to October 2014.
- OpenStreetMap represents physical-world elements through nodes, ways, and relations, supporting analysis at the block geographic unit.
- The study uses 2011 Italian Census variables about people and buildings, defined at multiple geographic levels.
- Urban ATLAS supplies land-cover and land-use classes for Large Urban Zones, while the ISTAT infrastructure atlas provides logistic-facility details such as railways.
- Table 1 lists ISTAT variables under study, with the final variable from the industry-and-services census and the others from the population-and-housing census.
- Foursquare venues are organized into hierarchical categories, and the study extracts venue data through the public API.
4. DEATH AND LIFE OF CITIES
Jacobs explains urban life through continual pedestrian activity supported by four mutually necessary forms of diversity. The paper describes how land use, block size, building diversity, and density contribute to that urban vitality.
- Jacobs characterizes urban life as a continual sidewalk ballet of pedestrians and associates used streets with safety.
- Mixed land uses attract people with diverse purposes and can bring activity into different times of day.
- Small blocks create more intersections, slow automobiles, and support mixtures of uses and people.
- Buildings diverse in age and form support varied economic activity, jobs, and tenants.
- Dense concentrations of people and buildings help create lively districts that attract people for different purposes.
- Jacobs treats all four conditions as necessary: density alone cannot create diversity, and mixed use does not flourish with large blocks and low density.
- Vacuums such as transport facilities and parks can either support pedestrian activity as hubs or expose areas to deprivation and criminality when poorly managed.
5. METHODOLOGY
The methodology operationalizes Jacobs’s four conditions through urban-diversity metrics derived from census, map, and place data, alongside mobile Internet activity as a vitality measure. It applies these measures to comparable census districts while accounting for spatial structure, building characteristics, activities, and urban vacuums.
- The study relates urban vitality to diversity using metrics for Jacobs’s four conditions and mobile Internet activity.The metrics are computed from public census and map data, commercial place data, and mobile Internet records.
- Italian census districts average 2.47 km^2 and 10,000 people per km^2, with boundaries based primarily on socioeconomic comparability.The districts contain approximately 13,000–18,000 inhabitants as a loose administrative guideline and are similar in area but smaller in population than Jacobs’s districts.
- Land use: Land-use diversity is measured with LUM, residential/non-residential balance, building height, daily-use activity, and third-place prevalence.LUM ranges from zero for single-use land to one for equal use across three categories; third places are classified into eating/drinking, organized social activities, outdoor, and commercial venues.
- Activities and vacuums: Activity and vacuum measures capture daily or day/night use, third places, and proximity to small parks, large parks, railways, highways, and water areas.Closeness measures use inverse distance, while density measures use surface area in square meters; most variables are not normally distributed.
- Small blocks: Small-block diversity is characterized through average block area, intersection density, and block shape anisotropicity, computed over district blocks and net area.Higher block-shape ratio values indicate less anisotropic blocks and more opportunities for contacts.
- Aged buildings: Building diversity is represented by average building age, age heterogeneity, and average employees per company.Average building age weights each age band by its building count, while higher age standard deviation indicates greater heterogeneity.
6. RESULTS
Across six Italian cities, Jacobs’s four conditions were associated with district activity, though their specific effects varied by urban context. Static structural features explained up to 77% of activity variability, with office concentration, third places, dense streets, historical buildings, and limited highway proximity especially relevant.
- 6.1 Land use: Third places were the strongest land-use predictor, with β = 0.3972 and Spearman’s correlation of 0.8337 with activity density.The result was especially evident where historically separated functions made mixed land use consequential, such as Milan.
- 6.2 Small blocks: Intersection density mattered more than block size: small-block model β = 0.0615, while dense streets were associated with vibrant pedestrian areas.Dense streets may slow cars and make pedestrian crossings easier, supporting the sidewalk interactions emphasized by Jacobs.
- 6.4 Concentration: Office concentration was the most informative concentration measure, adding worker-related vitality to resident-based conditions.The authors interpret office workers as contributing vitality through their presence in a district during work.
- 6.6 Summary: 77% of district activity variability was explained by grouped Jacobs features plus vacuum areas and simple static structural features.Figure 4 identifies concentration, land use, small blocks, and vacuum areas as the grouped predictors underlying this result.
- 6.6 Summary: The relative importance of features was similar in Rome and Firenze, despite their different sizes.The authors use city-specific regression models to compare the largest and smallest cities.
7. DISCUSSION
The discussion argues that Jacobs’s theories are verifiable and relevant in Europe, with practical applications for monitoring urban features and regulatory effects. It also identifies limitations in the activity proxy and data availability.
- City dashboards: Built-environment features linked to district activity could inform city dashboards for policy and design decisions.
- Quantifying regulatory interventions: Urban diversity features can be contrasted before and after zoning changes to track regulatory impacts.
- Place recommendation: Structural diversity features could complement economic analyses when recommending new amenities for neighborhoods.
- Theoretical Implications: Jacobs’s theories are presented as verifiable, still important, and valid in the European context.
- Limitations: The activity measure omits temporal dynamics, while individual call records could reveal stay duration, movement radius, and population segments.
8. CONCLUSION
The conclusion reports that Jacobs’s four conditions were verified in Italian cities using mobile phone and web data. These sources offer a scalable alternative to costly surveys for studying urban life at city scale.
- Jacobs’s four conditions were verified in the Italian context by linking mobile-phone vitality proxies with web-based diversity proxies.
- Web and mobile records provide insights into how urban dwellers experience entire cities rather than only sampled parts.
- Because OpenStreetMap data is globally available and telecom records are increasingly public, the study can be replicated at scale without costly surveys.
- Richer digital traces may enable fine-grained tests of traditional urban theories.