Vehicular communication systems are networks in which vehicles and roadside units are the communicating nodes, providing each other with information, such as safety warnings and traffic information. They can be effective in avoiding accidents and traffic congestion. Both types of nodes are dedicated short-range communications (DSRC) devices. DSRC works in 5.9 GHz band with bandwidth of 75 MHz and approximate range of 1000 m. Vehicular communications is usually developed as a part of intelligent transportation systems (ITS).
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Safety benefits
The main motivation for vehicular communication systems is safety and eliminating the excessive cost of traffic collisions. According to World Health Organizations (WHO), road accidents annually cause approximately 1.2 million deaths worldwide; one fourth of all deaths caused by injury. Also about 50 million persons are injured in traffic accidents. If preventive measures are not taken road death is likely to become the third-leading cause of death in 2020 from ninth place in 1990. A study from the American Automobile Association (AAA) concluded that car crashes cost the United States $300 billion per year. It can be used for automated traffic intersection control.
However the deaths caused by car crashes are in principle avoidable. The U.S. Department of Transportation states that 21,000 of the annual 43,000 road accident deaths in the US are caused by roadway departures and intersection-related incidents. This number can be significantly lowered by deploying local warning systems through vehicular communications. Departing vehicles can inform other vehicles that they intend to depart the highway and arriving cars at intersections can send warning messages to other cars traversing that intersection. Studies show that in Western Europe a mere 5 km/h decrease in average vehicle speeds could result in 25% decrease in deaths.
Vehicle-to-vehicle
V2V (short for vehicle to vehicle) 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 BMW, Daimler, Honda, Audi, Volvo and the Car-to-Car communication consortium. V2V is also known as VANETs (vehicular ad hoc networks). It is a variation of MANETs (mobile ad hoc networks), 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 December 2016, the US Department of Transportation proposed draft rules that would gradually make V2V communication capabilities to be mandatory for light-duty vehicles. The technology is not completely specified, so critics have argued that manufacturers "could not take what’s in this document and know what their responsibility will be under the Federal Motor Vehicle Safety Standards". PKI (public key infrastructure) is the current security system being used in V2V communications.
Conflict over spectrum
V2V is under threat from cable television and other tech firms that want to take away a big chunk of the radio spectrum currently reserved for it and use those frequencies for high-speed internet service. In the USA, V2V's current share of the radio spectrum was set aside by the government in 1999, but has gone unused. The automotive industry is trying to retain all it can, saying that it desperately needs the spectrum for V2V. The Federal Communications Commission (FCC) has taken the side of the tech companies, with the National Transportation Safety Board supporting the position of the automotive industry. Internet service providers (who want to use the spectrum) claim that autonomous cars will render V2V communication unnecessary. The US automotive industry has said that it is willing to share the spectrum if V2V service is not slowed or disrupted; and the FCC plans to test several sharing schemes.
With governments in different locales supporting incompatible spectra for V2V communication, vehicle manufacturers may be discouraged from adopting the technology for some markets. In Australia for instance, there is no spectrum reserved for V2V communication, so vehicles would suffer interference from non-vehicle communications. The spectra reserved for V2V communications in some locales are as follows:
Key players
Intelligent Transportation Society of America (ITSA) aims to improve cooperation among public and private sector organizations. ITSA summarizes its mission statement as "vision zero" meaning its goal is to reduce the fatal accidents and delays as much as possible.
Many universities are pursuing research and development of vehicular ad hoc networks. For example, University of California, Berkeley is participating in California Partners for Advanced Transit and Highways (PATH).