This work is part of a larger research that involves the science of semiotics in order to study road infrastructure (road devices) in road crossings, using the theoretical contributions of Ferdinand de Saussure, Umberto Eco and Charles Sanders Peirce, with the purpose to support the safe mobility of citizens. Pedestrians use the roads for work, study, recreation, and other activities of daily living providing a harmonious and safe way for people to move either on foot, by car, bicycle, public or private transport services. One of these road devices is the traffic light system used to control road traffic at an intersection or road junction. This system’s opti- mal and safe operation is related to the infrastructure of the urban space, which results in safe or unsafe mobility for pedestrians. In this sense, the semiotic interpretation of the state transition diagram for a traffic light system (green-amber- red / red-amber-green light change) is being proposed to recognize whether the road may be a dangerous place for users. The research aims to propose an improvement in pedestrians’ conditions to reduce traffic accidents in the most conflictive and dangerous road intersections. These places were determined by the Secretaría de Salud (2012) and disclosed in its Second Report on the Situation of Road Safety in Mexico City.