The　orbital　angular　momentum　(OAM)　technique　has　attracted　much　attention　in　wireless　communications　and　radar　applications.　The　OAM　has　theoretically　infinite　states　that　are　also　naturally　orthogonal　to　each　other.　This　feature　is　useful　to　enhance　spectral　efficiency　in　wireless　backhaul　networks　and　distinguish　spatial　targets　without　beam　scanning.　Leveraging　upon　these　unique　properties,　we　propose　an　OAM-based　bi-static　joint　radar-communications　(JRC)　system　for　a　millimeter-wave　vehicular　application.　In　particular,　we　employ　a　frequency　diverse　array　for　the　bi-static　JRC　and　Laguerre-Gaussian　beam　distribution　for　OAM.　To　recover　radar　parameters　and　communication　symbols　effectively,　we　design　a　multiplexing　and　diversity　strategy　to　resolve　the　identifiability　issues.　Numerical　experiments　validate　the　effectiveness　of　our　proposed　technique.　©　2023　IEEE.