Due to the development of new highways in metropolitan areas, construction of the road embankments over existing underground structures is inevitable. Since most of these buried structures are old and assessing the structural integrity is not simple, most project agreements allow no additional stresses on the existing underground structures. In this situation, precise stress and deformation analysis are required to assess the effect of the construction of the new embankments and the effectiveness of the stress reduction measures on the existing underground structures. In this study the use of numerical modeling to analyze and design of road embankments constructed over existing underground structures is investigated. Detailed 2D finite difference and finite element analyses were conducted by means of FLAC and SIGMA and the results were compared with the existing analytical approaches in order to determine the efficiency of these stress-deformation analyses. Since the use of expanded polystyrene (EPS) blocks in road embankments is one of the most common methods to reduce the loads on existing underground structures and also the construction time, a light weight embankment in the new Champlain Bridge Corridor project was considered as a case study to evaluate the effectiveness of the proposed analysis approach in design optimization. The results of the analysis show that using numerical modeling with advanced soil models can effectively optimize the design of the lightweight road embankment and significantly reduces the required EPS volume and consequently the construction costs. The outcome of this study provides new insights into the design and construction of road embankments over the existing underground structures in metropolitan areas.