In metropolitan areas, when a highway underpass project is being planned to go beneath an existing railway corridor, there are a number of concerns that could have an impact on the project. For example, will the underpass construction impact the existing railway operations? How to maintain the construction safety in both rail and highway operations? This paper brings construction technology using I-girder systems to provide a solution for highway underpass projects constructing beneath the existing rail corridors. The I-girder systems have been proved as a reliable method for highway underpass construction without the interruption of railway operations. This type of I-girder systems has been widely used in several countries as a temporary "bridge" structure in support of dynamic rail movements during underpass construction. Depending on the spans of underpass structures, a contractor can decide the number of I-girder units to be assembled and installed on site. This paper describes the construction procedures of the I-girder systems installation and daily inspection processes. A case study is used to demonstrate the applicability of I-girder systems in ensuring underpass construction smoothly while maintaining existing railway operations in a safety manner. During the construction of underpass, the contractor encountered geotechnical issues that had a severe impact on the construction safety and the integrity of foundation. This paper further discusses strategies that were used to mitigate the potential building collapses and foundation failures. It is concluded the method of I-girder systems is capable of supporting railway dynamic movements during highway underpass construction.