question: To realize a sustainable transportation system, it is necessary to estimate the environmental load caused by transportation. Here transportation demand affects carbon dioxide emissions directly. In general, traffic simulations or scenario-based evaluations have been used to predict transportation demand. However, the COVID-19 pandemic that began in late 2019 has changed transportation demand drastically, and such changes have not been considered in conventional simulation models. Therefore, it is important to quantify the impact of the pandemic on transportation demand and its magnitude. In this study, we developed a model focused on describing the changes in transportation demand caused by the COVID-19 pandemic in Japan. We developed a model using system dynamics because this method is effective in describing socio-technical systems such as transportation demand. Based on related studies, we categorized transportation demand by purpose and modeled it based on the cause-and-effect relationship between the amount of transportation and the prevalence of infectious diseases. To verify the developed model, we compared actual data of 2020 in Japan with the output of the model. We set scenarios with varying parameter values that contribute significantly to changes in transportation demand, such as individual awareness of the pandemic. As a result, the developed model was verified at the behavioral level. This model can be used in developing future transportation systems. © 2022 Elsevier B.V.. All rights reserved.