A system and method provided on an ego-vehicle for assessing potential threats in a vehicle collision avoidance system, and/or to plan safety-allowed vehicle trajectories for vehicle path planning. The method includes detecting objects in a predetermined vicinity around the ego-vehicle, and determining the relative velocity or other measure between each detected object and the ego-vehicle. The method defines a virtual dynamic safety shield around each detected object that has a shape, size and orientation that is determined by predetermined properties related to the current state of traffic around the ego-vehicle. The method also defines an action grid around the ego-vehicle. The method assesses the threat level of a potential collision between each detected object based on how the shield for that object and the action grid interact. The interaction between the shields and the grid induces actions aimed at aborting collisions and allows for trajectory planning.