Abstract: A system for traffic signals for one-side passing, which realizes efficient traffic control during abnormal operation of detectors or the night with little traffic density. Traffic signals 6 and 7 are provided with detectors 8 and 9 for detection of passing of vehicles respectively. Both traffic signals repeat traffic lighting in a cycled manner such as green-red, red-red, red-green and red-red by a sensitive controller 10. Owing to an ill-detection switching device 71, if there is no detection signal input by the detector of one traffic signal within a switch holding time after detection signal is input by the detector of the other traffic signal, the green lighting of one traffic signal will be shifted to a fixed-cycle operation until detection signal input by the detector. The traffic signal shifted to the fixed-cycle operation will be restored to the sensitive operation if the detection signal is input by the detector.