Abstract—Autonomous Vehicles (AVs) in the Vehicle-to-Everything (V2X) network are the solution to reducing traffic accidents and collisions. High gain antennas for V2X networks are crucial for enabling the networks to operate effectively. This paper proposes a Vivaldi antenna array with two elements for V2X communication on self-driving vehicles. The antenna is designed on FR4 substrate with a compact size of 51.6 mm × 81.3 mm × 1.6 mm. The proposed antenna can operate at four bands, which have the center frequencies of 3.5 GHz, 3.8 GHz, 5.7 GHz, 7.4 GHz, and the wide bandwidths of 285 MHz, 316 MHz, 933 MHz, 1266 MHz, respectively. Also, the antenna achieves a high gain from 5.2 to 8 dBi and main lobe widths in the E-plane and H-plane, respectively, about 270 and 1000 thanks to adding a triangle director and side slots on the Vivaldi plane. Therefore, the antenna array can provide far and comprehensive coverage when placed perpendicularly to the vehicle's roof. Beside the V2X application, the operation bands of the antenna are suitable for 4G, WiFi, and further communication systems in the future. A test scenario was also performed to further demonstrate the antenna performance. The antenna is designed and simulated by Connected Speech Test (CST) software, and a prototype of the antenna is fabricated. There is agreement between simulated and measured S11 results.