Advanced Automatic Collision Notification
Advanced Automatic Collision Notification (AACN) is the successor to Automatic Collision Notification (ACN). The Centers for Disease Control and Prevention and the CDC Foundation partnered with OnStar and the General Motors Foundation to develop procedures to help emergency medical responders determine whether a motorist needs care at a trauma center after a vehicle crash.
Source: Wikipedia — Advanced Automatic Collision Notification (CC BY-SA 4.0)