In parallel with the renovation of the Szajol-Püspökladány railway line, a new road underpass was constructed at the Püspökladány end of the Karcag station. The underpass connects the city of Karcag to the No. 4 main road (Road 3401). The reinforced concrete bridge structure was built by closing off one track on the railway line, which handles significant traffic.

The underpass was constructed with retaining walls, serving both to support the excavation and to prevent groundwater infiltration. The total length of the underpass is 255 meters, and its width is 17 meters. The soil was removed after the completion of the bridge structure (Milan method). Following the excavation, the inner U-frame was constructed. The thickness of the bottom slab ranges from 1.40 to 0.60 meters, while the thickness of the side walls varies between 0.65 and 0.40 meters.