This paper describes the design of a high-efficiency vehicular roof-mounted antenna for wireless access for vehicular environment (WAVE) communication systems used for ubiquitous intelligent systems. The main objective of the ubiquitous intelligent system's automotive IT technology is to enhance the connectivity among vehicles to ensure seamless communication and to reduce the initial access time using high-performance antenna systems. The efficiency of WAVE communication systems used for ubiquitous intelligent systems depends on the antenna efficiency. The proposed vehicular antenna for WAVE communication systems shows an improvement of approximately 4.77 dB in the return loss, as compared with a conventional antenna system.