The Tennessee Department of Transportation is administered by the state of Tennessee. The department manages facilities in Jackson, Nashville, Chattanooga and Knoxville in Tennessee. It operates an aeronautics division that assists in the design, construction and maintenance of public aviation systems. The Tennessee Department of Transportation also manages a rail and waterways office. The department has a freight and rail office that provides grants for track and bridge rehabilitation projects. In addition, it handles airport improvement projects. The department is responsible for public transportation, planning and promotion, and research and technical assistance. The Tennessee Department of Transportation employs a staff of more than 4,000 people.