Collisions involving vehicles and semi-trailers often result in severe consequences for both human life and property. This article examines the specific case of a Multi-Purpose Vehicle (MPV) colliding with the side of a semi-trailer, both with and without the implementation of a Side Under-ride Protection Device (SUPD), at a collision speed of 64 km/h. The study aims to assess the effectiveness of the SUPD in enhancing passenger safety. Key metrics, such as passenger compartment intrusion and foot acceleration, are evaluated against the guidelines provided by the Insurance Institute for Highway Safety (IIHS). The results indicate that while the presence of the SUPD slightly reduces passenger compartment intrusion, the levels remain above acceptable limits. Additionally, the foot acceleration surpasses the recommended thresholds, suggesting that the basic SUPD currently equipped on the semi-trailer does not sufficiently protect passengers under the tested conditions. These findings underscore the need for further improvement of the SUPD to meet safety standards and better protect vehicle occupants in side-impact collisions.