La criminalità sembra essere fortemente concentrata in un ristretto numero di micro aree di una città. Studi condotti in diverse città degli Stati Uniti mostrano come il 50% degli eventi criminali si concentrino nel 3%-6% dei segmenti stradali delle città stesse. Partendo da questi risultati, Weisburd, Groff e Yang si sono interrogati sulla effettiva presenza di una legge delle “concertazioni criminali” che sia applicabile a diverse città e che rimanga stabile nel tempo. Infatti, nonostante la generale diminuzione dei tassi di criminalità a Seattle, gli autori hanno riscontrato che, negli ultimi 16 anni, la stessa percentuale di eventi criminali si concentra in un egual numero di segmenti stradali della città. Questi risultati sono confermati da un altro studio condotto a Tel Aviv-Jaffa (Israele), suggerendo la presenza di una sorta di “normale livello di criminalità” tra città a livello micro. Il presente studio mira a testare la presenza di “concentrazioni criminali” in un contesto differente rispetto a quello degli Stati Uniti, dove tale ipotesi non è ancora stata testata e dove non sono ancora stati sviluppati studi quantitativi a livello di segmento stradale. In particolare, è stata condotta un’analisi sui segmenti stradali nella città di Milano (Italia) ed è stata confermata la presenza di micro-concentrazioni criminali. Inoltre, per capire le principali cause della presenza di tali concentrazioni nella città di Milano, sono stati elaborati dei modelli di regressione binomiale negativa (negative binomial regressions models). I risultati dimostrano come i fattori di disorganizzazione sociale sembrano avere una maggior influenza sulla criminalità a livello di segmento stradale, se comparati ai fattori appartenenti alle teorie dell’opportunità. / There is a strong evidence that crime is tightly concentrated in a small number of micro places in urban areas. Indeed, studies conducted in different U.S. cities show how 50% of crime events are concentrated in about 3% to 6% of street segments. Moving from these findings, Weisburd, Groff and Yang raise the issue as to whether there is a law of crime concentrations, applicable across different cities and stable over time. Indeed, despite the general decrease of crime trends in Seattle, the authors find that almost an equal number of street segments in the city produce the same proportion of crime in the 16-year period under study. These results were confirmed in Tel Aviv-Jaffa (Israel), suggesting the presence of a sort of “normal level of crime” among cities at micro level. This study aims at testing the presence of crime concentrations outside the U.S., in a different context, where this hypothesis has not yet been tested and quantitative studies at street segment level have not yet been developed. In particular, a street segment analysis was conducted in Milan (Italy) and the presence of crime concentrations was confirmed. In addition, in order to understand the main determinants of crime concentrations in Milan, a set of negative binomial regressions models were run. Findings show how social disorganisation factors seem to have stronger influence on crime at street segment level, compared to opportunity factors.

The objective of the thesis is to provide a better understanding of the safety conditions inurban environments, particularly related to those found in transport nodes, in this case,underground stations, and surrounding areas1. First, the study starts with an analysis of theoverall city, identifying concentrations of crime in the urban fabric and then focusing on thecriminogenic conditions at and around underground stations. The analysis combines the useof Geographical Information Systems (GIS), statistical techniques and data of different typesand sources. Regression models were used to assess the importance of the environmentalattributes of underground stations on crime rates. Findings show that violent and propertycrimes show different hotspots at different times. Crime patterns tend to follow people’sscheduled patterns of routine activity. The socio-economic composition of the surroundingenvironment of the stations has a significant impact on crime at these transport nodes, butmore important were attributes of the physical and social environment at the stations. Forinstance, low guardianship and poor visibility at the stations together with mixed land-usesin the surrounding areas induced crime rates at the stations. It is therefore suggested thatintervention to improve safety conditions at the stations should focus on a holistic approach,taking into account the station and surrounding areas, but also being aware of crimevariation on specific places at specific times. / <p>QC 20130207</p> / Safety in transport nodes: the influence of environmental attributes on crime and perceived safety