The purpose is to conduct a pilot exposure-based risk study for selected driver characteristics. The study design will complement the LTCCS by addressing the relative crash risk associated with driver characteristics, including personal data and traits, health and medical issues, driving performance and experience, and impacts of the work environment. A case-control sampling method will be used – the characteristics of crash-involved drivers (cases) will be compared to those of non-crash-involved drivers (controls). The study should provide odds ratios as the measure of the crash risk associated with various factors under consideration.