Safety is one of the most important concerns in the Intelligent Transportation Systems (ITS). One of the most relevant research areas in safety is the development of Collision Warning Systems (CWS). One goal of the research groups is to take the initiative to decrease the number of collisions occurring on the intersections. In urban zones, traffic lights are utilized to control the traffic flow on some intersections. However, it is not possible to place traffic lights on all intersections due to the enormous economical costs. This paper describes ISAPCI (Intelligent Signaling Approach for Prevent Collisions at Intersections), an ITS based on vehicular ad-hoc networks (VANET) to mitigate collisions at intersections, and to regulate the traffic flow at intersections that are not controlled by traffic lights.