Wangaratta railway station is being upgraded as part of the Australian Rail Track Corporation (ARTC) Inland Rail project. To facilitate the safe passage of double-stacked trains, the existing Cusack Street bridge needs to be demolished and replaced by a new pedestrian underpass. Open cut excavation is undertaken across the rail tracks, and the underpass is constructed with precast structural modules. In order to minimize the impact of the construction activities on the train services, the whole operation is scheduled to be finished within 60 h. This paper presents the value engineering approach to the design and construction of the pedestrian underpass, and how the geotechnical engineering optimizations led to the successful construction of the underpass during the rail occupation. Comprehensive numerical modelling for geotechnical analysis is demonstrated. The benefits of using the limit equilibrium method and the finite element method in achieving value engineering in design are also discussed. The analytical outcomes from both methods exhibit consistent factor of safety, although the finite element method excels in identifying intricate details in failure mechanisms.