Subgrade design is of paramount importance in assessing the load-bearing capacity of pavement systems. In geographical contexts such as the Indo-Gangetic plain characterized by the prevalence of locally sourced soils that frequently exhibit weakness and insufficient strength, there exists a significant demand for effective and economically viable strategies to enhance subgrade performance. The technique of reinforced soil construction has arisen as a dependable method for augmenting the strength and stability of these compromised soils. Among the diverse array of reinforcing materials, waste plastic has demonstrated notable promise. In India, where municipal solid waste comprises 1–4% plastic by weight, materials such as polyethylene terephthalate (PET) and high-density polyethylene (HDPE) have been employed to improve the load-bearing capacity of subgrade soils used in roadway construction. This paper systematically explores the employment of reclaimed Low-Density Polyethylene (LDPE) strips as a reinforcement mechanism for indigenous alluvial soils sourced from the Ganga and Damodar river basins. The findings of the study indicate that the integration of 0.5% LDPE strips (dimensions of 10 mm × 20 mm) into the soil matrix yields a marked enhancement in subgrade performance, evidenced by a 21% augmentation in unsoaked California Bearing Ratio (CBR) and an 18% increase in soaked CBR. Nevertheless, it was noted that the introduction of additional LDPE strips beyond this optimal threshold resulted in a deterioration of CBR values. The noteworthy 21% enhancement implies that LDPE strip reinforcement has the potential to effectively minimize pavement thickness, thereby presenting a cost-efficient and sustainable approach for highway subgrade reinforcement, while simultaneously addressing waste management issues through the waste-to-wealth paradigm.