Since the World Health Organization (WHO) declared the COVID-19 pandemic, the spread of infections around the world has not abated. The global total number of COVID-19 cases was 0.7 million in March when the WHO announced the COVID-19 outbreak a global pandemic but exceeded 79.2 million in December [1, 2]. With the incessant outbreak of community transmission, clusters of cases, and sporadic infections, coronavirus is still spreading across the world.
The spread of COVID-19 infections was inevitable even in Korea. In the early phase of the pandemic, the rate of increase of cases was relatively low. However, in Daegu, the southern city of South Korea, massive cluster infections occurred at Shincheonji Church of Jesus on February 18, and then cases sharply jumped and spread out from the city. The pandemic moved north to reach Seoul in mid-August and the spread accelerated rapidly with many cases detected in Sarang Jeil Church in Seoul. Figure 1 shows the progress of COVID-19 cases in Seoul between February and September. As of December 24, the number of COVID-19 cases in South Korea reached 53,533 with 756 deaths [3].
With the spread of the coronavirus worldwide, nations implemented a principal policy restricting the movement of people to minimize contact between people as WHO reported that the COVID-19 is rapidly transmitted through human contact and respiratory organs [4]. Asymptomatic “silent spreaders” were found, making it difficult to track the routes of transmission [5]. Wuhan, the Chinese city where the pandemic is believed to have started was effectively sealed off from the rest of the country immediately, and movement between regions in China was strictly banned [6]. In Europe, strict restrictions such as lockdowns, curfews, and permits for movement were imposed by governments [7]. In the United States—with most the coronavirus cases worldwide—heightened mobility restrictions such as stay home order, ban on gathering, and travel restrictions were implemented, depending on the status of each state [8].
The Korean government is implementing social distancing measures instead of strong restrictions on movement to curb the contagion of the COVID-19. Lockdowns and other forms of restrictions on mobility are enforced mandatorily for all residents in a region. However, social distancing is a sort of a campaign, guidance, or recommendation of the Korean government to achieve regulated mobility through citizens’ voluntary cooperation and compliance. From March 22 to April 19, the period of the first wave of the pandemic, “enforced social distancing” was first implemented, and during the second wave, August 16 to September 20—depending on the case severity—phase 2 and phase 2.5 of social distancing were enforced. From late November, social distancing in the phase 2 or higher was imposed to stem the spread of the third wave of the pandemic [9]
Mobility restriction policies of countries and voluntary restrictions—driven by fear of the coronavirus infection—have led to the decrease of transit demand. In France, during the national lockdown, consumer mobility estimated based on the use of payment cards has decreased by 75% compared to 2019 [10]. According to Google Trend data, mass transit demand in ten countries including Italy, Brazil, and the United Kingdom has fallen sharply since the COVID-19 outbreak [11]. In Mexico, the use of automobiles has decreased by 10 to 25 % since the outbreak [12].
Seoul has also witnessed a drastic reduction of transit demand amid the pandemic, which can be measured based on the changes in mass transit system use in Seoul—among the top ten in the world in terms of efficiency and user satisfaction [13]. The population of Seoul was 9,668,465 as of December 2020, and the use of buses and subways surpasses 100 million a month for each. Figure 2 shows the number of bus and subway rides in 2018, 2019, and 2020. As cases of COVID-19 began to rise in late January 2020, mass transit demand fell dramatically and rebounded after March, but still well below the demand recorded in the same periods of 2018 and 2019. Besides, in August, mass transportation demand declined again after the outbreak of cluster infections in Seoul, showing that mass transportation is significantly affected by the pandemic.
Most studies on the decrease of mass transit demand are focused on the effect of governments’ mobility restriction measures. However, there is a lack of studies on the impact of voluntary restriction that significantly affects the decrease of transit demand. That may be attributed to the fact that, as many countries are implementing restrictions on mobility, it is difficult to isolate the effect of citizens’ voluntary restraint of movement.
Data on subway transit demand in Seoul is useful in studying the voluntary mobility reduction during the pandemic as it has three characteristics that are not found in other cities. First, it is a type of mass transit that carries a high probability of infection. Mass transportation involves very high risks of infection because of the high density, diversity of contacts, and potential presence of patients [14]. Hence, when traveling in the subway, passengers are aware of the risk of infection. Second, government did not issue any restrictions on subway use. Without enforced mobility regulation, subway use reflects the voluntary mobility of people. Third, people aged 65 and over can ride a subway for free—following Article 19 of the Welfare of Senior Citizens Act, in Seoul, the elderly aged 65 and over can ride on a subway for free [15]. For the elderly without income earned through economic activity participation, the subway is an essential and most common means of mass transit for leisure. However, after the COVID-19 outbreak, subways were classified as facilities that carry the highest infection risk, and the age group most prone to fatality because of the COVID-19 infection is the elderly group. Therefore, though they have free access to the subway, the most efficient means of movement, the aged cannot ride on a subway train without concern over the COVID-19 impact. As such, the change in the subway ride patterns by the elderly most effectively reflects the risk of the COVID-19 infection.
This study aims to empirically analyze changes in the subway use pattern by older people and the economically active population, amid the risk of COVID-19 infection. First, the period when cases spiked sharply, and other periods were separated for analysis. The Korean government is controlling the social distancing level according to the number of cases. The rise of the social distancing level imposed by the government is intended to heighten citizens’ awareness against the pandemic and cause behavioral change. As such, by focusing on the social distancing level imposed by period, changes in the behavior of each age group associated with changes in social distancing level can be identified. Next, the elasticity of the demand for subway use to the number of COVID-19 cases was measured, determining whether the elderly most vulnerable to the coronavirus are more sensitive to infection than young people. Lastly, through analysis based on the number of subway stations by period, this study attempted to determine whether changes in subway ride decisions are related to fear of COVID-19 infection. In areas near stations for transfer[1] and multiple stations, there is more transit demand because of easy access to the subway. That is, such areas carry a higher risk of infection from more human contacts. Accordingly, if areas with a greater number of stations are found to experience a higher decrease of passengers than areas with a smaller number of stations, that can be interpreted as a behavioral change to avoid COVID-19 infection.
Change in the Pattern of Subway Use Demand Amid the Pandemic in Seoul
The number of deaths because of the COVID-19 infection rises as the age of patients climbs. According to the Center for Disease Control and Prevention data, 80% of death from the coronavirus is associated with people over 65 years old [16]. Reports on case-fatality rate (CFR) in China and Italy found that CFR for people aged under 60 was less than 2% while CFR for the aged over 60 years old rises to 20% [17]. In the United States, the CFR of the aged 65 or older was 3% to 27%, higher than that of younger people [18]. In Korea, COVID-19-related CFR for the older people was like other countries. Figure 3 shows the share of Korean coronavirus cases and CFR by age group. Over 70% of people infected with COVID-19 are aged under 50, whereas people aged over 60 showed a non-linear rapid rise of CFR.
The Seoul Metropolitan Subway with a potentially higher rate of COVID-19 cluster infection has seen users declining significantly since the outbreak of the pandemic. Figure 4 shows changes in the number of rides for passengers aged between 20 and 64 and those aged 65 and older. During 2018 and 2019 before the pandemic, those aged between 20 and 64 recorded 94,130,730 subway rides a month on average, and those aged 65 and older 14,278,200 rides. After the COVID-19 outbreak, people between 20 and 64 used the subway 72,398,975 times a month while those aged 65 and older 10,815,514 times a month, showing a dramatic decrease.
The COVID-19 pandemic has led to changes in hours for the use of the subway and the number of rides. Figure 5 shows a change in the share of the number of subway rides by the hour in 2020 and 2019. Compared with 2019, the subway ride of passengers aged 20 to 64 in 2020 rose by 0.2% to 1% during six to nine O’clock (commute to work), and also rose by 0.5% to 0.9% during five to six O’clock in the afternoon (commute from work). In hours other than those, the use of the subway transit dropped. This is likely to be attributed to the reduction of operating hours of stores owing to social distancing rule and a decrease in the number of permitted persons for meetings and dinners. The subway use for passengers aged 65 and over rose by 0.5% during five to seven O’clock, and the use of subway decreased during hours other than this. Such changes in time for the use of the subway for the aged people who are not constrained by time for their social activities seem to be meant to reduce human contacts and restrict external activities voluntarily to avoid COVID-19 infection.
[1] The number of transfer stations was counted in terms of the number of subway lines available for the station. For instance, for a subway station on three subway lines, the number of stations was counted as three.