There is a high incidence of TBI among warfighter occupants of vehicles targeted by underbody blasts but little is known about the unique forces involved or the pathophysiology. We hypothesize Acceleration experienced during survivable underbody blasts produces dose-dependent, TBI. Underbody blast-induced acceleration combined with secondary head impact is also military relevant and can be modeled. Neurologic outcome following underbody blast-induced TBI can be improved by force-modifying vehicle hull designs. We will expand our underbody blast animal model of TBI to establish full dose-response relationships and to model the combination of acceleration plus head impact. This research will promote development of engineering- and biomedical-based neuroprotective interventions translatable to warfighter TBI.