Describe the critical role of witnesses in road accident investigations, using the recent tragic incident on I-90 as a focal point. Explore the psychological effects on bystanders who witness such events, including feelings of helplessness or the urge to intervene. Highlight the importance of collecting witness testimony and evidence, such as dashcam footage, to aid law enforcement in piecing together the narrative of the accident. Consider the societal responsibilities of individuals as witnesses and the potential impact on their mental health. Finally, discuss the resources available to support those who have witnessed trauma on the road.