Fro vehicles with 12-speed manual transmission, the function of suppressing voltage surge, which occurs when the electromagnetic valve for transmission shift operates, is not adequate, and therefore, noise from the electromagnetic valve may affect the device that converts the signals from the speed sensor and transmits them to the speedometer etc. If this occurs, the converted values from the device may become abnormal, which could cause the speedometer, the tachograph, the speed display equipment and/or the speed limiter to stop functioning.