In order to develop requirements for designing a pedestrian buck, this study conducted two parametric studies that investigated the effect of the vehicle stiffness characteristics and the area of contact between the pedestrian pelvis and lower limb and a vehicle on pedestrian pelvis and lower limb injury measures. The parametric study for different vehicle stiffness characteristics was conducted using a human finite element (FE) model and simplified vehicle models with different front shapes for which stiffness parameters were varied. With regard to the contact area, a prescribed force model representing the contact force time histories from a vehicle was developed and applied to the human FE model, without using a vehicle model, to allow change in the contact area while maintaining the total force magnitude. It was found that maintaining the peak force magnitude is much more important than the maximum deflection of the stiffness characteristics and that accurate representation of the impacted body region is much more significant than the contact area, in reproducing the maximum injury measures.