The 63¿64 GHz band has been set aside by CEPT for inter-vehicle and roadside to vehicle communications (IVC and RVC). Roadside beacons would be spaced along the road at regular intervals. This paper describes the development of antennas at Birmingham University for the Miltrans project, led by BAE Systems in collaboration with Qinetiq and Panorama Antennas. The small sizes of antennas in the mm-wave band make dimensional tolerancing and loss reduction more challenging than meeting the 1.57% bandwidth requirement. Designing for a wider bandwidth can ease the tolerance problem. The selected slot antenna arrays have been demonstrated successfully in the system application.