Small-scale unmanned aerial vehicles (UAVs) are considered to support vehicular networks in the form of air-to-ground communication. In this paper, we consider a VLC based air-to-ground communication channel where the small-scale UAV provides multiple access to a cluster of cars. The simulation results reveal that the UAV position influences the capacity of each car with the cars that are closer to the UAV achieving higher capacity. Furthermore, the optimum location of the UAV is found to be the location closer to the car with high data rate demand. Another result of the paper is that larger number of cars in the system leads to smaller improvement in the sum capacity compared to non-optimized UAV position scenario.