ISTDM 2021 aims to gather transportation researchers and practitioners across the globe for exploring the frontiers of big data, modeling and simulation to advance transportation research to support the connected, cooperative and automated mobility. With a greater focus on emerging technologies, ISTDM 2021 rebrands the two long-standing transportation symposia: International Symposium of Transport Simulation (ISTS), and the International Workshop on Traffic Data Collection and its Standardization (IWTDCS). During the three-day conference, plenary sessions featuring renowned speakers and interactive breakout sessions will take place at the University of Michigan in Ann Arbor, United States.