A blast load of vehicle, especially the Under Body Blast (UBB) case is the specific kind of thread for occupant safety. The risk of injury is caused by great amount of energy transferred in a short time to a vehicle structure and further to a body of  passenger. In the paper, similarity and differences between road collision and blast load of vehicle is discussed. The dynamic load of the occupant’s body was presented and evaluated with the use of biomechanical criterion Dynamic Response Index (DRIz). The load intensity determined with DRIz was compared for a few points on the loaded vehicle structure and the body of the occupant simulated by an Anthropomorphic Test Device (ATD). An examples of numerical investigation of the blast load of the vehicle were presented.