PROJECT SUMMARY/ABSTRACT Trauma is the leading cause of death for children and adults 46 years and younger, killing more Americans than AIDS and stroke combined. African Americans (OR 1.2, P<0.001), people living in high poverty neighborhoods (OR 1.01, P<0.001), and those enrolled in public health insurance programs (OR 1.53, P<0.001) have increased mortality after trauma when compared to their injured counterparts. Quantifying the equity in access to Emergency Medical Services (EMS) and designated/verified trauma centers (TCs), as well as the extent to which timely access to care improves health outcomes are critical first steps to address this alarming discrepancy. Equitable availability to EMS has yet to be evaluated and equitable access to TCs is understudied. In fact, no one has explored the importance of expeditious availability to emergency health care services such as EMS and timely access to emergent trauma care as key social determinants of health (SDOH). Models to evaluate the role of SDOH as major predictors of these disparities remain untested. Rapid transport to a TC is associated with a 25% reduction in mortality; however, nearly 45 million Americans lack timely access to a verified TC. When compared to white populations, recent data show racial/ethnic minority populations have significantly less access to TC and worse outcomes following trauma. Understanding the factors that determine trauma-related socio-spatial disparities can inform interventions at both the policy and system levels to mitigate the disproportionately large numbers of deaths experienced by minoritized populations. Thus, there is a compelling need for research in these areas to facilitate targeted interventions to eliminate socio-spatial disparities within the pre-hospital phase of the emergency trauma care system to improve patient outcomes. To evaluate socio-spatial disparities in availability and access to both EMS and to TCs among critically injured trauma patients, we will apply the Health Equity Measurable Framework (HEMF) to the pre-hospital phase of the emergency trauma care system (availability to EMS, EMS response time, EMS scene time, EMS transportation time, EMS decision to transport to TCs vs. non-TCs, and EMS total prehospital time) and use large national databases to develop spatiotemporal models to assess drivers of disparities in traumatic injuries. HEMF will be particularly well suited for our proposed study because it is designed to describe SDOH in a causal framework to guide the quantitative analysis of health equity for ongoing pre-hospital trauma care surveillance of the critically injured and subsequent policy development. Our interdisciplinary team will use data science methods and novel analytics to address this critical public health need by identifying health disparities at the level of the pre-hospital emergency trauma care system.