PROJECT SUMMARY/ABSTRACT Upwards of 3.8 million concussions occur annually in the United States. Only 44% of concussed individuals reduce their driving at any point following injury despite emergent concerns over post-concussion driving safety, documented driving impairment, and reports of feeling unsafe driving after a concussion. Most concussed individuals who reduce their driving only do so for 24-48 hours following the injury. Driving is a highly complicated activity that requires visual, motor, and cognitive skills, which are commonly impaired after concussion. Concussed individuals cross the centerline more frequently within 48 hours of injury and present with poorer vehicle control throughout the full symptom recovery. Yet, the time course of post-concussion driving impairment has not been characterized. There is a critical need to 1) determine when concussed individuals should return to driving and 2) identify the key concussion assessment predictors of readiness to return to driving. In the absence of formal recommendations, impaired concussed drivers are at risk to themselves and others on the road. The first specific aim is to compare simulated driving between concussed individuals and non-concussed yoked matched controls across five longitudinal timepoints (pre-injury baseline, day 2, day 4, asymptomatic, and unrestricted medical clearance) and daily naturalistic driving from day 2 to day 9. Driving recommendations must be appropriate and necessitated by concussion impairments, since excessively strict recommendations wrongfully strip concussed patients of their independence and may dissuade individuals from seeking medical care. The second specific aim is to identify widely used concussion assessment outcomes that predict simulated driving performance among concussed individuals throughout concussion recovery. To address these aims, 100 concussed and 100 yoked matched control young adult college athletes will complete a simulated driving assessment and a robust concussion assessment battery at pre-injury baseline, day 2, day 4, asymptomatic, and unrestricted medical clearance. Naturalistic driving (measured with in-car global positioning systems) will be captured from day 2 to day 9 (7 days total). This study will determine the acute and subacute time course of post-concussion driving impairment and determine key predictors of post-concussion driving performance. Results from this innovative approach will have a broad and positive impact that will improve the safety of both concussed individuals and the general population, guide the practices of health professionals, inform the future work of researchers, and substantiate the work of policy-makers by providing evidence-based recommendations for managing post- concussion driving.