New solutions for intelligent restraint systems, able to recognize vehicle occupants size and position, require that:​ suitable biomechanical models are used;​ initial occupant anatomical segments positions are properly set;​ realistic contact models are used;​ interactions between vehicle and occupants are accounted for;​ models of restraint systems are included in the simulation. Here a procedure for the evaluation of the initial positions of biomechanical models for the simulation of out-of-position occupants is proposed together with a vehicle-occupant integrated numerical environment, which allows modeling vehicle and occupants in complex crash scenarios. This methodology is demonstrated with the analysis of a vehicle rollover with occupants included.