The validity of evaluating FlexPLI peak injury measures has been shown by the correlation of the peak measures between a human FE model and a FlexPLI FE model. However, comparisons of tibia bending moment time histories (BMTHs) between these models show that the FlexPLI model exhibits a higher degree of oscillatory behavior than the human model.The goal of this study was to identify potential improvements to the FlexPLI such that the legform provides more biofidelic tibia BMTHs at the normal standing height. Impact simulations using a human FE model and a FlexPLI FE model were conducted against simplified vehicle models to compare tibia BMTHs. The same series of impact simulations were conducted using the FlexPLI models that incorporated potential measures to identify measures effective for further enhancement of the biofidelity. An additional analysis was also conducted to investigate the key factor for minimizing the oscillation of the tibia BMTH.The results of this study showed that the change of the mass distribution between the bony and flesh parts, along with the addition of the mass compensating for the upper body, provide more biofidelic FlexPLI tibia BMTHs, when used at the normal standing height. It was also found from the additional analysis that the primary factor for the oscillation of the tibia BMTH is the natural frequency of the skin/flesh part, rather than its damping characteristics.