Chile is a country under constant natural threats, as tsunamis, with a huge percentage of the population living in vulnerable coastal cities. However, one marked characteristic in all them is its topographic steep slope, for what the end of the hazard zone is in the the city itself. The blue line aims to be a tsunami security map recognisable from the entire city, allowing to identify the distance to which it is the security zone. The colour of the light is blue in order to achieve a clearly contrast with the traditional urban lights and thus to be recognisable every night. When the blue light is projected from the public lighting posts in areas over the 30 m.a.s.l, the line turns highly visible, revealing and marking the security line as an urban landmark. As it is a visual and not written message, a higher percentage of the population will have access to recognize and learn it, considering children, seniors, residents and tourists. Blue Line aims to improve the citizen’s behaviour.