 Epidemiological studies typically focus on causes external to the individual such as traffic density, access to safe walking areas, socioeconomic status, injury rates, legislation for safety (e.g., traffic fines), or even the shape of vehicles which affects the severity of injuries resulting from a collision.Epidemiological data show children aged 1–4 are at greatest risk for injury in driveway and sidewalks.Children aged 5–14 are at greatest risk while attempting to cross streets.