A Multi-City Urban Population Mobility Study Using Mobile Phone Traffic Data

Abstract

Mobility of population is one of major problems in large metropolitan areas. It affects different social, economic and environmental aspects of a city’s life. Urban mobility is characterised by highly dynamic spatial-temporal variability not detected by census or surveys. Mobile phones allow tracking of the population, giving information about their time–space location. A multi-city population mobility study was carried out in seven main Italian large metropolitan areas for 2 months (1st March to 30th April, 2015), starting from high-resolution gridded population data derived from mobile phone traffic data. Mean daily–nightly variations of population density were calculated during weekdays with increments of population of about 25% on average and peaks up by 200% in hotspot areas. Strong spatial gradients were identified with both accumulation and depletion of population in urban zones of geographical dimensions of 55 and 44%, respectively, of the municipality areas on average. Larger metropolitan areas, such as Rome, Milan, and Turin, show the highest increments of population, while medium-sized cities (e.g., Bari and Palermo) exhibit lower values and weaker gradients of variation of population. By means of a developed mobility factor, three main mobility phenomena (morning and evening commuting, diffuse mobility) occurring during weekdays were identified and characterized.