This study investigates the adequacy of comparing the risk of brain injuries based on the available National Automotive Sampling System/Crashworthiness Data System (NASS/CDS) field data to the risk predicted by Brain Injury Criterion (BrIC) measured from an Anthropomorphic Test Device (ATD) in NHTSA’s Research Moving Deformable Barrier (RMDB) oblique tests (fleet). Finite Element (FE) analysis was utilized to simulate crashes with a given range of Principal Direction of Force (PDOF) and change in velocity (Delta-V) to illustrate their effect on the field vs. fleet risk comparison. The simulation based results indicate that BrIC is highly dependent on PDOF and Delta-V. The methods applied for estimating brain injury risk from the simulation results demonstrate the importance of accounting for the distributions of both PDOF and Delta-V when comparing brain injury risk estimates from the field data versus those calculated from fleet testing.