Recent upgrading and realignment work on the Main Trunk Rail route between Ohakune and Horopito has required the replacement of the previous Hapuawhenua Viaduct with a 414 m long bridge on a 420 m curve and at a 1.57% gradient. Expected seismic performance has been given particular consideration in the design of the new bridge and the designers believe that the structural arrangement chosen has led to an economic solution providing excellent and predictable seismic behaviour even for very large earthquakes.