Exploring the similarities between informal and traditional settlements: a methodology and an application

International audienceMost urban growth is taking place in the developing countries of the Global South through informal settlements. This form of development is usually strongly opposed by governments and local administrations. However, several works compared them to vernacular urban centres, such as medieval towns, and praised their human-scale qualities. If this similarity were to be systemically assessed on a larger scale, informal settlements would gain more recognition and legitimation. This, in turn, can potentially impact policy making. In this paper, we propose a replicable methodology based on the use of open data to investigate similarities between informal and medieval settlements, through statistical comparison of metrics of urban form and correlation analysis between densities of amenities and street centrality (a fundamental relationship at the basis of city functioning). This methodology is tested on three informal settlements in Sub-Saharan Africa and three Italian medieval towns. Statistical similarities were found, especially for what concerned aspects of the urban fabric, configurational features, and the relationship between densities of amenities and street centrality. These findings add to the studies that recognise the value of informal settlements. Furthermore, the proposed methodology can be replicated to increase the generalisability of this result and further legitimise informal urban development