Trajectory simulation codes are widely used for assessing and zoning rockfall hazards in view of land use planning. Theses tools may also be used to estimate the benefit in terms of risk reduction derived from the construction of protection structures such as embankments. This paper investigates the relevance of currently used trajectory analysis tools for this purpose through a real case study. The trajectory analysis is first used to assess the hazard and define the embankment geometry. In a second time, it is used to assess the embankment protection efficiency after its insertion in the digital terrain model. Results reveal abnormal trajectories in the vicinity of the embankment suggesting limitations related to both the spatial resolution of the terrain model and to the rebound models. To cope with these limitations, an innovative approach is proposed and evaluated for improving the ability of the simulation code in assessing the residual hazard down the embankment.