Based on modern tubular signal bridges used by several major Class I lines and modern commuter railroads, this layout-ready signal bridge is ideal for your double-track lines. Each model includes four prewired, micro-LED signal heads with three aspects per head (red, yellow, green). This accurately scaled signal bridge features durable plastic parts and etched-metal walkways. Each supporting leg houses four wires, (one common and one for each LED). The model is ready for hookup to your choice of detection circuitry, sold separately.