Streets have different forms that are not defined only by their partitions, furniture, and width, but also by their edges as vital features of their spatiality. The relationship between a street and a building impacts the street interface configurations, resulting in various topological characteristics. Thus, the street interface is a physical entity that is produced by the interrelationship between urban morphological elements (street and building), and the way it is formed and used affects the livability of the street. The methods used in the current study contribute to an empirical urban morphological–visual cognitive investigation of arterial street interface configurations, particularly on the ground floor level, to assess potential relations between variations in the physical configurations that influence pedestrian visual perception using mobile eye-tracking glasses. In conclusion, this study contributes to research into developing a spatial framework for arterial street liveability, addressing the pilot case study of Avenida da República in Lisbon.