Intervehicle Communication (IVC) is attracting considerable attention from the research community and the automotive industry, where it is beneficial in providing intelligent transportation system (ITS) as well as drivers and passengers' assistant services. ITS that aim to streamline the operation of vehicles, manage vehicle traffic, assist drivers with safety and other information, along with provisioning of convenience applications for passengers such as automated toll collection systems, driver assist systems and other information provisioning systems.
In this context, Vehicular Ad hoc NETworks (VANETs) are emerging as a new class of wireless network, spontaneously formed between moving vehicles equipped with wireless interfaces that could have similar or different radio interface technologies, employing short-range to medium-range communication systems. A VANET is a form of mobile ad hoc network, providing communications among nearby vehicles and between vehicles and nearby fixed equipment on the roadside.
Vehicular networks are a novel class of wireless networks that have emerged thanks to advances in wireless technologies and the automotive industry. Vehicular networks are spontaneously formed between moving vehicles equipped with wireless interfaces that could be of homogeneous or heterogeneous technologies. These networks, also known as VANETs, are considered as one of the ad hoc network real-life application enabling communications among nearby vehicles as well as between vehicles and nearby ?xed equipment, usually described as roadside equipment.
Active Road Safety Applications :
Active road safety applications are those that are primarily employed to decrease the probability of traffic accidents and the loss of life of the occupants of vehicles  . A signi?cant percentage of accidents that occur every year in all parts of the world are associated with intersection, head, rear-end and lateral vehicle collisions. Active road safety applications primarily provide information and assistance to drivers to avoid such collisions with other vehicles. This can be accomplished by sharing information between vehicles and road side units which is then used to predict collisions.
Such information can represent vehicle position, intersection position, speed and distance heading. Moreover, information exchange between the vehicles and the road side units is used to locate hazardous locations on roads, such as slippery sections or potholes. Some examples of active road safety applications are given below as
Intersection collision warning:
In this use case, the risk of lateral collisions for vehicles that are approaching road intersections is detected by vehicles or road side units. This information is signaled to the approaching vehicles in order to lessen the risk of lateral collisions.
Lane change assistance:
The risk of lateral collisions for vehicles that are accomplishing a lane change with blind spot for trucks is reduced.
Overtaking vehicle warning:
Aims to prevent collision between vehicles in an overtake situation, where one vehicle, say vehicle1 is willing to overtake a vehicle, say vehicle3, while another vehicle, say vehicle2 is already doing an overtaking maneuver on vehicle3. Collision between vehicle1 and vehicle2 is prevented when vehicle2 informs vehicle1 to stop its overtaking procedure.