his is a Lionel 6-83174 O Scale Double Signal Bridge. Make your layout even more realistic with this bridge equipped with lights that change from green to red to signify approaching trains of possible upcoming blocks. Double the size of our Single signal bridge this bridge spans across two tracks. It features: Spans two tracks Lights change from green to red to warn approaching trains of occupied blocks ahead Compatible with both FasTrack and traditional tubular O and O27 track systems and Use an insulated track section or a 153IR (both sold separately).