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.

Abstract: A snowstorm guard fence structure is constructed by anchoring a wall, which overhangs at an upward slope to a road side, to a supporting wall disposed along one side of the road. The constructed structure can be placed on sides of roads, has a space to discard the snow removed from the road, and also is effective for preventing snow accumulation on the road regardless of the degree of wind velocity and the presence of shelter structures. A jet roof is constructed by disposing a plurality of props on a slant and providing a plurality of panels between the props at spaces for jet openings so that jet openings are gradually narrowed toward the road side. The constructed jet roof is effective for preventing snow accumulation on the road regardless of the condition of wind velocity and the presence of shelter structures.