This study investigates the application of lightweight fill materials, specifically Expanded Polystyrene (EPS) geofoam, in the construction of highway embankments, focusing on the I-15 Reconstruction Project in Utah. Traditional embankment construction methods often face challenges with soft or loose soils, leading to significant settlement issues. Utilizing geofoam addresses these challenges by providing a highly compressive-resistant, lightweight, and easy- to-handle solution, which prevents excessive loading on underlying soils and structures. This paper presents a comprehensive numerical analysis using PLAXIS 2D to model the stress–strain behaviour and settlement characteristics of the geofoam embankment, comparing the results with field measurements and previous studies. The findings indicate that geofoam significantly reduces settlement and maintains long-term stability, although numerical models sometimes underestimate settlement at greater depths due to complex soil-structure interactions not fully captured in simulations. Additionally, the study highlights the importance of accurate subsoil characterization in predicting vertical stresses. Overall, the research supports the viability of EPS geofoam as an effective material for highway embankment construction, offering insights into its practical benefits, limitations, and potential for broader application in infrastructure projects.