The development of vehicle-to-vehicle (V2V) technologies has progressed to the point of real world testing, and if broadly deployed, they are anticipated to offer significant safety benefits. Efforts by the U.S. Department of Transportation (DOT) and the automobile industry have focused on developing in-vehicle components such as hardware to facilitate communications among vehicles, safety software applications to analyse data and identify potential collisions, vehicle features that warn drivers, and a national communication security system to ensure trust in the data transmitted among vehicles. This book focuses on the V2V technologies expected to offer safety benefits as well as the technical description and identification of policy and institutional issues.