In this paper, we propose a relay-assisted handover technique for vehicular visible light communication networks where streetlights are configured to serve as Access Points (APs). In the proposed system, the vehicle is served by a relay terminal in the form of a neighbor vehicle in addition to the serving AP if the measured bit error rate becomes higher than a threshold value. We evaluate the system performance using realistic site-specific channel models developed through non-sequential ray tracing features of OpticStudio for various deployment scenarios. The simulation results show that our technique provides a superior performance compared to conventional handover schemes.