Development of numerical method-based simulation systems is presented. Two types of system development are shown. The former system is developed using conventional structured programming technique. The system incorporates a classical FD hydrocode. The latter system incorporates object-oriented design concept and numerous novel elements are included. Two explicit finite difference models for large deformation of several material characteristics are developed. The models are capable of handling impulsive and constant load, impact and gravitational force, etc. Their capabilities of handling relatively complex shapes, which are not possible to deal with using classical FD models, are shown and discussed. A robust algorithm is suggested to describe general stress-strain relationship, ranging from elastic-perfecdy plastic to multiple elastic modulii and plastic modulii with or without strain rate sensitivity. Hysteresis and Bauschinger effects are included as well. Development of contact-impact treatments is presented. Three novel contact elements are designed, developed and validated. Node-node and node-element contacts are formulated with all the elements developed. The contact-impact treatments include a novel method in handling potential voids and overlaps at contact intersection. Rigid Coulomb’s friction model is incorporated to handle sliding conditions. Formulation of a novel revolute joint element is illustrated and several possible methods are suggested for handling bending limits. Incorporation of resistive moment and damping effects are presented. The numerical stability of the revolute element is discussed and a stability criterion is proposed. The latter simulation system is used to model an idealised human body. Information from literatures, such as height and weight ratio of human segments, and resistive moment of human joints, is incorporated into the human model. Simulations are carried out according to a 2k factorial design of experiment to find the main effect(s) contributed to human head/brain injury when subjected to frontal collision. A simple motorcycle model based on Malaysian KRISS 110 motorcycle is developed as well. The human model is successfully integrated into the motorcycle model. Possibility of solving such model with the developed simulation system is studied.