Intelligibility of French historical towns: assessing the impact of 19th century urban interventions

During the 19th century, French cities underwent great transformations in response to insalubrity. Many new streets were created and changed the overall intelligibility of the street network with the creation of boulevards where the defensive town wall used to stand, as well as large avenues to provide better accessibility to the centre of towns. This study aims to assess the impact of these transformations on the urban tissue by measuring the intelligibility of the urban form before and after the transformations. It compares the Napoleonic cadastral maps of Agen, Amiens, Avignon, Dijon, Clermont and Tourcoing with the current cadastre. Intelligibility is measured by the ease of navigation towards the centre of an urban environment and the ease of traversing it as one traces a path between two given points on the map. The choice of paths is examined, highlighting the role of the new streets. This research brings together the cognitive mechanisms that underpin the exploration and decision-making process when navigating urban maps with their syntactic and morphological properties. It examines the motor aspect of decision making during the navigation process. Motor reactions are recorded using technology developed for the quantification of neuromotor impairments. This interdisciplinary approach provides a means to measure and better understand the intelligibility of urban environments.