Abstract Epidemiological researchers have indicated that youth violent injury (YVI) is a significant public health issue in the U.S. Rates of youth violence are higher in urban environments compared to suburban and rural settings. Declining economic resources and out-migration from many urban centers often create environmental, social, and economic conditions associated with YVI. CPTED is a youth violence prevention strategy that changes physical and social environments to promote defensible space and deter YVI. Physical CPTED strategies include territoriality (defined ownership), surveillance (sightlines, lighting), access control (paths, entryways), and target hardening (locks, fencing). Social CPTED strategies include cohesion (neighborhood problem solving, conflict resolution), culture (community events and commemorations), connectivity (linkages with community agencies), and participation (residents' engagement in planning and implementation). We apply Busy Streets Theory (i.e., positive neighborhood social processes, including resident interaction and participation, that foster social resources to create safe environments) to understand the effectiveness of physical and social CPTED strategies in reducing YVI. We will use data from our original Crime Prevention Through Environmental Design (CPTED) study to examine our data in more-depth to understand how CPTED may operate to prevent YVI in an urban corridor. We extend our research with new aims because we examine: 1) the intensity of physical and social CPTED strategies on YVI; 2) the underlying mechanisms (i.e., changes in physical disorder, resident engagement and perception) that links CPTED to YVI reduction; and 3) test the synergistic effects of physical and social CPTED on YVI reduction. We conducted our original study in Flint, MI, an economically challenged city with high rates of violent crime, in partnership with a local coalition (University Avenue Corridor Coalition- UACC) of residents, community groups, churches, hospitals, and two small universities. We will evaluate the effect of physical and social CPTED strategies across 441 street segments in the UACC area with a focus on YVI from emergency room treatment records and police incident victimization data. We will also investigate whether physical and social CPTED improves residential community engagement, perceptions about the neighborhood, and physical disorder that may be associate with YVI. Lastly, we will examine the interaction of social and physical CPTED strategies to understand they may operate together to enhance the influence of each other for preventing YVI.