“Right here waiting”? Distribution of intentional metro travel groups amid COVID-19 in Hong Kong

During COVID-19, people needed to travel and meet as a group physically to gain benefits such as overcoming loneliness. Using multiday continuous smartcard data, we can identify intentional travel groups (ITGs) in cities. Using the 2020 smartcard data of the Hong Kong metro system, we first construct a dataset of probable ITG trips (PIGTs) where two riders swiped in and out at the same stations within one minute during weekends—we choose weekends because there are fewer co-presenting metro commuters entering and/or exiting the same station. Assuming that ITGs would have more PIGTs and smaller exit time difference than those co-presenting by coincidence, we then identified ITGs as those with at least four PIGTs in a month. To see whether and how the pandemic impacted ITGs, we geo-visualize the quantity of the identified ITGs by metro station and between metro stations on three different Sundays before and during the pandemic. The results indicate that ITGs’ distribution by metro station and between metro stations changed notably after the outbreak of COVID-19.