## 2 Literature Review  
In order to control the spread of the infections or to 'flatten the curve', travel restrictions of different degrees have been adopted by different countries during different stages of the pandemics [5; 8; 23]. As highlighted in recent studies, owing to the reason that the virus spreads mainly through close contact with an infected person, public transport could largely contribute to the spread of infectious diseases [13; 15; 24; 25; 26; 27; 28; 29]. Therefore, passengers are required to follow protective and preventive measures, such as, wearing face masks, and maintaining social distancing while using and waiting for public transport [25]. As explained in [30], physical distancing of more than 1 m, use of face masks, and eye protection have been identified as the most effective preventive measure to reduce the person-to-person transmission of COVID-19. In addition, personnel management and protection, cleaning and disinfection of the surrounding environment, and health education have also been identified as the comprehensive measures to control the spread of Covid-19, particularly when using public transportation [31]. Public transport operators could also play a role to minimize the risk of infection by offering flexible or more frequent services to satisfy user needs while reducing congestion and thereby ensuring social distancing, providing sanitizers, automated opening of doors, ensuring adequate ventilation [3; 12; 14]. A simulation-based study, which used automatic passenger count data in the Minneapolis area in the US, explained that to reduce the risk of disease transmission, the number of passengers inside a bus should be limited to 15 [32]. However, to allow a reasonable waiting time for passengers due to the reduced capacity, the frequency of the service should be increased. In addition to public transport operators, workplaces could also assist to reduce or distribute the passenger volumes in public transport modes (to facilitate social distancing measures) by offering to work from home options and flexible or staggered working hours for the staff [33]. However, it is not guaranteed that the passengers always follow these guidelines stipulated by the governments. For example, as explained by [15], although a majority of buses adhere to the social distancing guidelines, the instructions on using face masks were not completely followed. Thus, in general, the use of public transport modes is discouraged during pandemics [34]. Recent studies based on mobility data and passenger or ticket counts explained that there was a dramatic reduction in public transport use in many countries. For example, public transport users declined by up to 93% in Spain [35], 60% in Sweden [36], 80% in Hungary [37], and 77% in Poland [38]. On the other hand, people limit travelling, particularly by using public transport modes, owing to the perceived fear of infection [39; 40]. Past studies have highlighted that, as perceived by the people, avoiding public transport was one of the most effective precautionary measures to avoid infectious diseases [41]. Globally, a substantial reduction in the use of public transport was observed [17; 42]. A study based on travel diaries and a questionnaire survey conducted in the Netherlands reported that trips that used public transport dropped by more than 90%. This decline was expected because the government as well as public transport operators advised people to use it only when it is extremely necessary [43]. Another questionnaire survey conducted globally stated that the mode share for public transport declined from 36% before Covid-19 to 13% during Covid-19 [42]. This study further explained that the pandemic-related underlying factors, such as infection concern, social distancing, cleanliness, passengers with face masks, were significant predictors of mode choice during Covid-19. Ref. [4] explored the preference between private and public transport mode preference of Indian commuters.