###### Abstract  
The use of visible light communications technology in communication-based vehicle applications is gaining more and more interest as the research community is constantly overcoming challenge after challenge. In this context, this article addresses the issues associated with the use of Visible Light Communications (VLC) technology in Vehicle-to-Vehicle (V2V) communications, while focusing on two crucial issues. On the one hand, it aims to investigate the achievable communication distance in V2V applications while addressing the least favorable case, namely the one when a standard vehicle rear lighting system is used as a VLC emitter. On the other hand, this article investigates another highly unfavorable use case scenario, i.e., the case when two vehicles are located on adjacent lanes, rather than on the same lane. In order to evaluate the compatibility of the VLC technology with the usage in inter-vehicle communication, a VLC prototype is intensively evaluated in outdoor conditions. The experimental results show a record V2V VLC distance of 75 m, while providing a Bit Error Ratio (BER) of \(10^{-7}\)-\(10^{-6}\). The results also show that the VLC technology is able to provide V2V connectivity even in a situation where the vehicles are located on adjacent lanes, without a major impact on the link performances. Nevertheless, this situation generates an initial no-coverage zone, which is determined by the VLC receiver reception angle, whereas in some cases, vehicle misalignment can generate a BER increase that can go up to two orders of magnitude. accident prevention; communication-based vehicle safety applications; inter-vehicle communications; long-range; V2V; vehicle misalignment; vehicle-to-vehicle communications; vehicle safety; vehicular communications; visible light communications +
Footnote †: journal: 21 May 2021  
mines [3], where the usage of Radio-Frequency (RF)-based communications could be unsafe. The ubiquitous character of LED light sources also enables the VLC technology to be suitable in Internet of Things (IoT) applications [4; 5]. Due to its ability to provide low latency, energy-efficient and cost-effective connections, the VLC technology has been found to be appropriate for industrial use, including in the Industry 4.0 domain [6]. Although numerous possible applications have been identified, the main usage of VLC technology is limited for now to high data rate indoor applications [7; 8; 9; 10]. Indoor VLC systems have reached a rather high maturity level, with good performances, providing unprecedented data rates that currently go up to a few tens of gigabits per second (e.g., 20 Gb/s in indoor mobile settings [9], 15.73 Gb/s with off-the-shelf LEDs over a 1.6 m link [10]), whereas data rates that can go beyond 100 Gb/s are envisioned [11]. These unique perspectives, together with an inherent ability to provide small size isolated cells, allow the VLC technology to be considered a major candidate in Fifth Generation (5G) and Sixth Generation (6G) mobile and wireless networks [12; 13; 14]. It should be also mentioned that in addition to lighting and communication functions, the VLC technology has the potential to provide high accuracy indoor localization and positioning that reaches centimeter precisions [15; 16], opening the door to a whole new range of applications [17], which in turn increases the need for a better mobility [18; 19] and multi-user connections [20]. A particular use case for VLC technology is its use in vehicular applications. This concept envisions smart or autonomous vehicles that communicate with each other, or with intelligent traffic infrastructure, while using their already implemented LED lighting systems. Such applications have the potential to significantly contribute to a more efficient and safer transportation system.