We present a new quality metric called “4S” (smart sensors and social sensibility), which is based on the Greek notion of “phaneron” to measure the gap between technological reality and the sensation perceived by users in so-called smart cities. The aim is to verify the quality of goods and services aimed at citizens when travelling by traditional public transportation, such as buses, trams, funiculars, subways, taxis, etc., in several European cities. At the same time, the interfaces of interactive systems for users who are inexperienced in the use of collective smart devices, but who are experts in the use of individual smart devices for medical purposes, are analyzed. In addition, a style guide is generated for the communicability of phaneron in the interfaces of personal devices. The aim of the guide is multiple. On the one hand, this tool to reduce digital illiteracy and the generational gap of users, at the same time, to facilitate the use of devices concerning the technological avant-garde. Finally, in this research work, disciplines and areas of scientific knowledge belonging to software engineering, artificial intelligence, design, ergonomics, semiotics, social psychology, sociology, pedagogy and ecology converge. This convergence has allowed the development of an updated heuristic table to determine the qualitative academic fields in the study of smart city metrics.