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Safety berms (also called safety bunds or windrows), widely employed in surface mining and quarry operations, are typically designed based on rules of thumb. Despite having been used by the industry for more than half a century and accidents happening regularly, their behaviour is still poorly understood. This paper challenges existing practices through a comprehensive investigation combining full-scale experiments and advanced numerical modelling. Focusing on a Volvo A45G articulated dump truck (ADT) and a CAT 773B rigid dump truck (RDT), collision scenarios under various approach conditions and different safety berm geometries and materials are rigorously examined. The calibrated numerical model is used to assess the energy absorption capacity of safety berms with different geometry and to predict a critical velocity for a specific scenario. Back analysis of an actual fatal accident indicated that an ADT adhering to the speed limit could not be stopped by the safety berm designed under current guidelines. The study highlights the importance of considering the entire geometry and the mass and volume of the material used to build the safety berm alongside the speed and approach conditions of the machinery. The findings of the study enable operators to set speed limits based on specific berm geometries or adapt safety berm designs to match speed constraints for specific machinery. This will reduce the risk of fatal accidents and improve haul road safety.