Guardrails are designed to improve road safety by reducing the severity of accidents, preventing vehicles from leaving the roadway. 3D model studies could perform simulations that reproduce crash tests, considering the mechanical properties best suited to meet current regulations. This research illustrates a detailed behavior analysis of the individual constituent elements of the barriers and advances some improvements to be applied to their future development, evaluating a new guardrail with a greater elasticity given by a release device and a rhomboid spacer by analysing its dynamics and energy absorption during a road impact. Through experimental tests and FEM models, it was possible to determine the most significant parameters for the dynamic behavior of the new system, such as deformability, torsional and flexural stiffness. The progressive axial and flexural plastic collapse of the structure was studied by analysing the stress and strain states of the components reproducing, through a metal cylinder, the impact of a heavy vehicle with the guardrail at a speed of 3.5 m/s with impact angles of 20°, 45° and 90°. The proposed modifications to the guardrail increased the Acceleration Severity Index (ASI) by 10% and improved impact energy absorption by 39%, significantly reducing structural deformation. In light of the results, the proposed methodology allows the dynamic behavior of the rhomboidal spacer to be characterized through a limited number of experimental tests. In fact, the authors found in the scientific literature the lack of numerical-experimental methodologies to characterize and compare the elastoplastic behavior of different types of spacers.