A methodology based on a probabilistic reliability analysis was proposed for improving the design of rockfall protection fences by accounting for the variability of the loading cases. The approach allows combining loading cases from rockfall propagation simulations with numerical simulations of rock impacts on the struc- ture. Such a reliability-based approach allows obtaining statistically relevant indi- cators of the efficiency of the fence with a limited number of simulations. The method was illustrated on a real study case for the design of low-energy fences protecting a forest road. The fence was modeled using a discrete element method -DEM- model and 3D trajectory simulations were conducted using the code RockyFor3D. In a demon- stration purpose, two parameters were considered. The probability for the fence to be cleared by the rock was evaluated accounting for the variability of two parame- ters: the rock velocity and its angle of incidence before impact. The parameters were considered either separately or together, considering these variables non cor- related or correlated. The results revealed the interest of the approach in terms of computation cost as well as the importance in accounting for both these parame- ters for designing the structure as well as for estimating the residual hazard, down the protective structure.