Han is a Professor of Civil and Environmental Engineering and an Oak Ridge National Lab (ORNL) Collaborating Scientist at the University of Tennessee (UT). His fields of expertise and research interests include traffic engineering, application of advanced technologies to transportation, intelligent transportation systems (ITS), system modeling and simulations, traffic flow theory, traffic operations, transportation data and information systems, emergency evacuation and management, crash records and analysis, transportation logistics, operations research, and 3D visualizations.