Developing concepts for cooperative awareness was subject of several international research programs in the past years 2 . The main concept for cooperative awareness is the communication of localization information enriched by situation specific content by meanwhile standardized messages like the Cooperative Awareness Message (CAM) in Europe or the Basic Safety Message (BSM) in the US. The concept of cooperative perception extends the state of the art concept of cooperative awareness by integrating perception information from infrastructure perception systems (IPS) 3 and vehicle perception systems (VPS) in the ego-vehicles environment model. In this paper three variants of the Covariance Intersection (CI) method used for state fusion in an Inter-Vehicle Information-Fusion (IV-IF) System are compared. The goal is to figure out which CI method out of the selection is the best choice for an active road safety application described in a recent publication, which was developed within the research project Ko-PER (cooperative perception).