With　the　recent　rapid　increase　in　the　number　of　motor　vehicles　on　roads,　traffic　accidents　have　increased,　and　emergency　reporting　processes　have　become　essential.　In　this　paper,　a　key　agreement　protocol　for　a　real-time　traffic　sharing　system　is　proposed　for　Vehicular　Ad-Hoc　Networks　(VANETs),　in　which　a　broadcast　center　authenticates　the　legitimacy　of　a　user　when　they　report　an　emergency　and　issues　a　certificate　of　emergency　to　other　users.　This　study　uses　a　digital　signatures　mechanism,　key　agreement　and　authentication　scheme　to　satisfy　the　security　requirements　for　a　VANET.　Burrows-Abadi-Needham　logic　(BAN　logic)　is　applied　to　prove　that　the　proposed　scheme　achieves　secure　authentication.　The　proposed　protocol　ensures　the　privacy　of　the　communication　between　fleets　and　provides　a　mechanism　for　immediate　emergency　reporting.　The　experiment　results　show　that　the　proposed　scheme　is　feasible　and　meets　security　requirements.　©　2013　IEEE.