When the regional COVID-19 and traffic trends were analyzed in this study, the traffic in Seoul, Gyeonggi, and Incheon showed smaller changes compared with the other regions. This is because the Korean citizens, including overseas students, started returning to the country as COVID-19 began rapidly spreading overseas, such as in Europe and the US (Cho, 2020). The number of Korean citizens returning from overseas and requiring control was estimated to be 210 000 individuals, making the risk of a resurgence of COVID-19 considerably high. Indeed, 23.8% of the confirmed cases in Seoul in the third week of March were individuals returning from abroad (Young-kyung et al., 2020). Thus, Seoul, Gyeonggi, and Incheon, which are closer to the airport and the residences of many citizens returning from abroad, showed increased COVID-19 and traffic trends compared with other regions. In particular, Incheon showed a positive linear relationship between traffic and new confirmed COVID-19 patients, prompting increasing concern about a secondary COVID-19 outbreak in this region compared with others.