The definition of “Digital Twin” is credited to Grieves who defines it as “the Digital Twin is a set of virtual information constructs that fully describes a potential or actual physical manufactured product from the micro atomic level to the macro geometrical level. At its optimum, any information that could be obtained from inspecting a physical manufactured product can be obtained from its Digital Twin.” In Grieves and Vickers (2017) the definition is further refined to also describe exchange of data between the real-world physical system and its digital “clone,” and the extensive review in manufacturing by Jones et al. (2020) provides good background of basic definitions of the most popular terms.
Applications of travel behavior models are sophisticated levels qualifying them as Digital Twins of cities as evidenced in many applications of activity-based travel demand forecasting (see multiple chapters in Goulias, 2002). Dynamic microsimulation in software for transportation policy analysis are the Digital Twins that are used to test behavioral models and policy actions in scenarios in transportation planning.
Grieves, M., & Vickers, J. (2017). Digital twin: Mitigating unpredictable, undesirable emergent behavior in complex systems. InTransdisciplinary perspectives on complex systems(pp. 85-113). Springer, Cham
Goulias, K. G. (2002). Transportation systems planning: methods and applications. CRC Press.
Jones, D., Snider, C., Nassehi, A., Yon, J., & Hicks, B. (2020). Characterising the Digital Twin: A systematic literature review. CIRP Journal of Manufacturing Science and Technology, 29, 36-52.