Line-of-sight　(LOS)　blockage　is　a　crucial　problem　in　millimeter-wave　vehicle-to-vehicle　communication　due　to　its　severe　penetration　loss　and　high　vehicle　mobility.　In　order　to　overcome　the　LOS　blockage　problem,　in　this　letter,　we　propose　using　neighbor　vehicles　as　relays　to　forward　the　blocked　traffic　flows.　Specifically,　a　traffic-aware　relay　vehicle　selection　is　investigated.　First,　analytic　hierarchy　process　(AHP)　is　adopted　to　handle　the　situation　that　different　traffic　types　have　different　preferences　on　the　performances　of　rate,　delay　and　data　dropping　ratio.　Second,　we　introduce　a　coalitional　game　(CG)　to　evaluate　the　relative　performances　of　the　relay　vehicles.　Finally,　by　combining　the　results　of　AHP　and　CG,　a　heuristic　relay　selection　scheme　is　devised　by　selecting　the　relay　vehicle　with　the　best　rationality　degree.　Simulation　results　show　that　the　proposed　scheme　can　adapt　to　the　requirements　of　different　traffic　types　and　improve　the　performances　of　rate,　delay　and　data　dropping　ratio　when　LOS　blockage　occurs.