Abstract: Guardrails are critical safety facilities in road transportation, and their protective performance directly influences both occupant safety and vehicle structural integrity during collisions. To address the limitations of existing studies, which primarily focus on single vehicle types or specific operating conditions, this study develops finite element models of three representative vehicles-a passenger car, a medium bus, and a heavy truck-colliding with SS-grade steel beam-and-post guardrails, based on SolidWorks modeling and ABAQUS explicit dynamics. Through systematic simulations under various vehicle types, speeds, and impact angles, the deformation modes of guardrails, energy absorption characteristics, and vehicle structural responses were comprehensively analyzed. Results indicate that vehicle geometry and mass significantly affect guardrail performance. Lightweight vehicles induce relatively small guardrail deformation, enabling effective redirection back onto the roadway, whereas heavy trucks often cause severe deformation or even override failure, markedly reducing protective capacity. Furthermore, increases in impact speed and angle exacerbate structural damage to both guardrails and vehicles, with high-speed collisions producing the most critical failures. This study elucidates the failure mechanisms of guardrails under diverse impact conditions, providing theoretical support for guardrail design optimization and a valuable reference for developing scientific protection standards in road traffic safety management.