This paper is motivated by the need to enhance road safety by mitigating the risks associated with rear-end collisions involving trailers. The aim of this research is to design, develop, and validate a rear underrun protective device (RUPD) for wood transport trailers that fully complies with the safety standards outlined in Regulation No. 58-03. The methods used include a two-stage design process followed by a Finite Element Analysis (FEA) to simulate real-world impact scenarios. The results show that the initial design failed to meet the regulatory deflection limits, while the second, reinforced design successfully restricted deformation to within the required thresholds. In conclusion, this study demonstrates the successful development of a robust and compliant RUPD, providing a viable solution for improving the safety of heavy-duty vehicles on public roads and unpaved terrain.