PROJECT SUMMARY Traumatic injuries caused more than 200,000 deaths and the loss of 2 Million potential life years in the US in 2019. Black, Hispanic, rural, and low-income populations bear a disproportionate burden of injury incidence and mortality. There is mounting evidence that proximity to and capacity of trauma centers are substantial drivers of these disparities, but current evidence does not identify or quantify specific system-level interventions that might reduce health disparities. We propose the following aims to identify strategies to mitigate disparities in trauma outcomes: Aim 1: Examine approaches to trauma system planning in states with and without disparities in trauma outcomes. We will conduct a series of in-depth case studies with a purposive sample of state trauma systems (n=11) identified based on injury mortality trends from 2000-2020. Using document review and semi-structured interviews with stakeholders responsible for trauma system planning in each state (e.g., medical directors, nurse managers), we will examine the overall approach to trauma system planning, and specifically probe for planning decisions intended to address disparities. Aim 2: Identify modifiable trauma system characteristics associated with injury disparities and decompose the structural pathways causing injury disparities. We will conduct a national survey of state trauma systems to identify existing trauma system resources (e.g., infrastructure, personnel), then link survey responses with outcomes data from the Centers for Disease Control and the Agency for Healthcare Research and Quality. After identifying trauma system characteristics associated with injury outcomes among disparities populations, we will use mediation pathway models to decompose the effects of trauma system resource allocation as a determinant of injury disparities. Aim 3: Identify and prioritize strategies to mitigate injury disparities through trauma system planning and resource allocation. We will conduct a Delphi consensus panel with national stakeholders, in partnership with the Coalition for National Trauma Research (CNTR). We will ask panelists to evaluate and prioritize recommendations trauma system interventions to mitigate disparities, drawing from the results of Aims 1 and 2, and from the literature. Impact of proposed work: Our proposed work will facilitate efforts to reduce disparities in injury outcomes by contextualizing current approaches to trauma systems planning, identifying specific trauma care resources that mediate injury disparities, and identifying actionable strategies to address disparities at the trauma system level. Our partnerships with national trauma leaders will support dissemination and implementation throughout the US.