## 1 Introduction
Nevertheless, in the context of applications for energy harvesting technologies gaining popularity, several possibilities  
Figure 1: LED-based lighting solutions integrated in vehicles and in road transportation infrastructures. This wide diffusion facilitates the deployment of the VLC technology. emerge. Thus, light dimming could be used in street lighting applications, informative panels, or advertising displays. In such scenarios, the light source optical power could be adapted in accordance with ambient light, whereas in the case of battery-operated devices, the output light intensity could be corroborated with the remaining available power, including the special case of electric vehicles. This function would be very suitable in auto-dimmable headlights, enabling the vehicle to change the light intensity in order to prevent drivers from sudden glare at night conditions. In this context, the existing literature focused on the usage of the VLC technology in automotive applications provides very few investigations concerning the effect of light dimming on the performances of vehicular VLC applications. On the other hand, these effects have been only partially investigated in indoor applications, pointing out that further investigations concerning the effect of light dimming on the VLC performances are required. In this context, the present article provides an analysis and an intensive experimental investigation concerning the effect of light dimming on automotive VLC performances. This article considers a Vehicle-to-Vehicle (V2V) communication scenario, analyzing the case when the brake lights transmit the data, but the intensity of the modulated light is dimmed to a level that can be considered as taillights by the current regulations. In order to provide a comprehensive investigation, the V2V VLC system operating in light dimming mode is tested in controlled laboratory conditions as well as in outdoor daytime uncontrolled conditions. The experimental evaluation is performed for variable communication distances, different lighting conditions, and variable duty cycles. Additionally, the particular case of dimming the light to such an extent that can be considered \"off\" for the human eye, but the transmission of data is still going on with ultra-short pulses, is analyzed. As far as we know, this article is one of the very few works addressing the issues associated with light dimming in vehicular VLC links. As this topic has been neglected in the existing literature addressing automotive VLC applications, this work provides important evidence that demonstrates the ability of the VLC technology to be compatible with such use scenarios. The rest of this article is structured as follows. Sections 2 and 3 provide an overview concerning the issues associated with light dimming in VLC applications and on the existing solutions to these problems. Section 4 presents the V2V VLC prototype that has been used in the experimental evaluations. Section 5 describes the experimental evaluation procedure and presents the experimental results, whereas Section 6 provides a discussion concerning these results. Finally, Section 7 provides the conclusions of this work.