Depicting routes and centralities

preparing and investigating Road Centre Lines for Angular Segment Analysis in two Brazilian cities

Résumé

Axial and RCL (Road Centre Lines) models are street network representations used as base for space syntax Angular Segment Analysis (ASA) studies of centralities in cities. Although RCL is widely adopted for ASA, steps to treat RCL seem uncompleted. On the other hand, in Brazil many studies maintain axial models for ASA, despite standardization and updating limitations. Understanding models’ importance as it affects results, and in order to advance more confidently in studies, this paper compares axial and different modes of Open Street Map RCL ASA for two medium-to-large sized north-eastern Brazilian cities (Joao Pessoa and Natal). Closeness and betweenness centralities (i.e., measures of integration and choice) are studied for the city and their old city centres, as well as interrelations between centralities for different scales. Although all models work differently, they capture city centralities and scale dynamics, pointing towards natural urban voids in both cities accentuating routes movement hierarchies. Understanding some limitations in RCL simplifications proposed so far, a further procedure is presented that yielded good results in terms of route depiction and highlighting city centralities reading, while allowing more standardized and easily updated city models, especially relevant for rapidly changing Brazilian cities.