# Investigating and Modeling of Cooperative Vehicle-to-Vehicle Safety Stopping Distance
## 2 Related Work  
CAVs are an essential part of the future of automotive transport. They will allow vehicular networks to be formed through mutual awareness and vehicular cooperation between all vehicles on the road, sharing data between one another and with the network infrastructure. The goal of CAVs is to work towards increasing road efficiency and road safety [11]. Vehicular Ad-Hoc Networks (VANETs) are a type of vehicular network formed of nodes that are communicating information via messages. SAE International defines one of these as the Basic Safety Message (BSM), which is vital for safety-related information, such as location, speed, heading, and general operation details. The type of message utilized for this is usually defined as a broadcast message [12]. The BSM is also known as a Cooperative Awareness Message (CAM) in some countries but is predominantly the same in the context of usage [13]. One technology that has been accepted by the CAR2 CAR Consortium to be a part of VANETs is DSRC or 802.11p/OCB (Out of the Context of a Base-station) [14; 15]. DSRC is a vitally important component to support various types of communication; it is also subject to considerable research efforts. DSRC is commercially available but highly expensive [16]. To counter the high-cost of commercial devices, we previously designed a laptop-based testbed [17] and an SDR-based testbed [10], with the latter being utilized for the simulations in this paper. Many authors have looked at different ways of utilizing V2V for safety-related scenarios. [PERSON] and [PERSON] [18] conducted a study into rear-end collision warning system based on simulators, but this was tailored more towards driver behavior. [PERSON] et al. [19] produced an in-depth review of collision avoidance systems, including both sensors and communication, that details the benefits of each. Two independent studies have been conducted to analyze the performance of V2V or Ad-Hoc performance in vehicular communications. [PERSON] and [PERSON] [20] carried out User Datagram Protocol (UDP) performance tests over different field test scenarios with findings that long-range communication has poor performance in terms of reliability and that reliability can also be affected by packet size. The work by [PERSON] et al. [21] is a simulation test aimed toward the Physical (PHY) and Medium Access Control (MAC) layers, and they proposed using a non-traditional channel access algorithm known as Self-Organized Time-Division Multiple Access (STDMA). In Reference [22], [PERSON], [PERSON], and [PERSON] studied how V2V can be used in truck platooning; however, this work mainly focused on the data rate and message delivery ratio. The work showed results for how differing antenna positions on the vehicle can greatly change the reliability of V2V. There are two similar works regarding the reliability and packet loss in DSRC testing. [PERSON] and [PERSON] [23] gathered data from 3000 vehicle tests to investigate the effects of the Inter Packet Gap (IPG), whilst, on the other hand, in Reference [24], [PERSON] and [PERSON] sought to devise a way of fundamentally defining communication reliability and proposing these ideas in terms of DSRC. [PERSON] et al. [25] chose to research into Vehicle to Infrastructure (V2I) and conducted a measurement campaign comparing the 802.11a protocol with 802.11p, in both Line of Sight (LOS) and Non-LOS conditions. They found that 802.11p in the V2I environment suffers fewer consecutive losses than that of 802.11a. Safety distance is another area that has had a lot of research conducted and differs to stopping distance as this is the distance gap between vehicles used for reacting as situations arise. [PERSON] et al. [26] performed an in-depth analysis into the various types of safety distance indicators, such as various Time to Collision (TTC) algorithms, deceleration-based indicators, and distanced-based indicators.