The objective of this paper was to analyze the effect of yellow-safety-line designs on the behavior of passengers at the platform edge in metro stations. To achieve this, an experimental approach, based on observation, was used in existing metro stations in Santiago and Valparaiso, Chile. The experiments were carried out for different widths of the yellow safety line: 5 cm, 10 cm, 24 cm, and 40 cm. In addition, the material was also changed to include yellow adhesive tape, PVC material with yellow pods, and carbon- and fiberglass-reinforced material with yellow pods. The experiments considered a mock-up to represent the hall entrance of the train and its adjacent platform, in which 25 participants were recruited, some of whom had reduced mobility. The results obtained from the experiments showed that the greater the width of the yellow safety line at the edge of the platform, the greater the level of compliance that was achieved. In addition, surveys were carried out with the passengers who participated in the experiment; the majority felt more comfortable and safer for a width of 24 cm. Some participants highlighted the phenomenon of “safety offers comfort”. In conclusion, the results of this research will allow the generation of new design and safety standards for the train–platform interface, which can then be tested in existing stations. Future research is expected to study the space occupied by different types of passengers and to study accessibility in other circulation spaces of metro stations.