We present an adaptive communication scheme for cooperative active safety system (CASS). CASS uses information communicated from neighboring vehicles via wireless communication in order to actively evaluate driving situations and provide warnings or other forms of assistance to drivers. In CASS, we assume that vehicles are equipped with a GPS receiver, a dedicated short range communications (DSRC) transceiver, and in-vehicle sensors. The information exchanges between vehicles include position, speed, heading, and other vehicle kinematic and dynamic information, and the information is...