Wikipedia
Vehicle-to-vehicle (V2V) is an automobile technology designed to allow automobiles to "talk" to each other. The systems will use a region of the 5.9 GHz band set aside by the United States Congress in 1999, the unlicensed frequency also used by WiFi.
V2V is currently in active development by General Motors, which demonstrated the system in 2006 using Cadillac vehicles. Other automakers working on V2V include Toyota, BMW, Daimler, Honda, Audi, Volvo and the Car-to-Car communication consortium.
V2V is also known as VANET ( vehicular ad hoc network). It is a variation of MANET ( Mobile ad hoc network), with the emphasis being now the node is the vehicular. In 2001, it was mentioned in a publication that ad hoc networks can be formed by cars and such networks can help overcome blind spots, avoid accidents, etc. Over the years, there have been considerable research and projects in this area, applying VANETs for a variety of applications, ranging from safety to navigation and law enforcement.
In April 2014 it was reported that U.S. regulators were close to approving V2V standards for the U.S. market.