As the impact of traffic accidents caused by older adults is significantly large, they are often advised to surrender their driving license. On the contrary, the decrease in the number of human drivers for public transportation is a serious problem in rural areas where populations are aging and declining. With a rapidly aging society, mobility-related problems among the elderly have gained significant attention. To address these issues, dedicated autonomous public transportation is essential, thereby necessitating field-operational tests involving autonomous buses. However, the deployment of autonomous bus-related field-operational tests in Japan is relatively slow as compared to the that in the U.S. and China. This is attributed to the few by-wire controllable bus systems that meet the requirements of Japanese vehicular laws for field-operational tests. To resolve these issues, we propose an autonomous bus using existing joystick driving system solutions. The steering wheel and gas/brake pedals are activated using electric motors of the joystick driving system, thus achieving drive-by-wire. Therefore, we selected this joystick-driving system attached to a bus as the basis for an autonomous bus, to meet the requirements of Japanese vehicular laws. Systems including LIDAR, GNSS, gyro sensors, and cameras enable the bus to be automatically controlled using the proposed driving system. This proposed prototype bus has passed vehicular inspection, and field-operational tests have been performed on public roads using this bus. The results of these tests confirm the viability of our proposed solution.