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Journal of Public Transportation, Vol. 22, No. 1, 2020 1
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
© 2020 Alejandro Tirachini and Oded Cats
https//doi.org/10.5038/2375-091.22.1.1
ISSN: 1077-291X | Licenced under Creative Commons License Attribution - Noncommercial 4.0
e Journal of Public Transportation is published by the Center for Urban Transportation Research
at the University of South Florida
Journal of Public Transportation | scholarcommons.usf.edu/jpt
Vol. 22 No. 1 [2020] pp. 1-21
Journal of Public Transportation
COVID-19 and Public Transportation: Current
Assessment, Prospects, and Research Needs
Alejandro Tirachini
Universidad de Chile and Instituto Sistemas Complejos de Ingeniería, Chile
Oded Cats
Delft University of Technology, the Netherlands
Abstract
e COVID-19 pandemic poses a great challenge for contemporary public transportation worldwide, resulting
from an unprecedented decline in demand and revenue. In this paper, we synthesize the state-of-the-art, up to
early June 2020, on key developments regarding public transportation and the COVID-19 pandemic, including
the different responses adopted by governments and public transportation agencies around the world, and
the research needs pertaining to critical issues that minimize contagion risk in public transportation in the
so-called post-lockdown phase. While attempts at adherence to physical distancing (which challenges the very
concept of mass public transportation) are looming in several countries, the latest research shows that for closed
environments such as public transportation vehicles, the proper use of face masks has significantly reduced the
probability of contagion. e economic and social effects of the COVID-19 outbreak in public transportation
extend beyond service performance and health risks to financial viability, social equity, and sustainable mobility.
ere is a risk that if the public transportation sector is perceived as poorly transitioning to post-pandemic
conditions, that viewing public transportation as unhealthy will gain ground and might be sustained. To this
end, this paper identifies the research needs and outlines a research agenda for the public health implications of
alternative strategies and scenarios, specifically measures to reduce crowding in public transportation. e paper
provides an overview and an outlook for transit policy makers, planners, and researchers to map the state-of-
affairs and research needs related to the impacts of the pandemic crisis on public transportation. Some research
needs require urgent attention given what is ultimately at stake in several countries: restoring the ability of public
transportation systems to fulfill their societal role.
Keywords: COVID-19 virus transmission, sustainability, safety, resilience, public health
2 Journal of Public Transportation, Vol. 22, No. 1, 2020
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
Introduction
e rapid spread of the COVID-19 virus, which became a worldwide pandemic in a matter of weeks, has been
attributed to the hypermobility of our current lifestyle, globalization, and the connectivity and accessibility of
Wuhan, the first epicenter (Musselwhite, Avineri, and Susilo 2020). Since then, the COVID-19 pandemic rapidly
evolved into a situation with profound effects on lifestyle and travel worldwide, ranging from a dramatic
decrease in air travel to an unprecedented increase in teleworking. ese impacts resulted from governmental
measures (e.g., travel restrictions and shutdowns of whole sectors in the economy) as well as individual choices
to refrain from traveling in order to reduce exposure to other people and the risk of contamination.
Urban travel has declined all over the world, but not uniformly for all modes; public transportation has taken
the hardest blow, as shown by survey-based data (Molloy et al. 2020; Astroza et al. 2020). is was in some
cases accompanied by a reduced service supply and exacerbated by the perception of public transportation
as riskier than private or personal means of transport because of the closer contact to other people that is
possible, sometimes unavoidable, in public transportation vehicles and stations. Figure 1 shows the variation on
the use of public transportation hubs based on Google Mobility Reports data (authors own elaboration). e
baseline for the data is the median value for the corresponding day of the week, during the five-week period
between January 3 and February 6, 2020 (Google 2020).
FIGURE 1.
Change in use of public transportation hubs such as subway, bus, and train stations; ve-day moving average between
February 15 and June 5, 2020
Journal of Public Transportation, Vol. 22, No. 1, 2020 3
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
e fact that a person infected with the novel coronavirus COVID-19 is contagious before showing any
symptom (Javid, Weekes, and Matheson 2020; Ferretti et al. 2020) is particularly worrisome for virus exposure
in public places. Several factors contribute to making public transportation stations and vehicle environments
high risk for the COVID-19 contagion (UITP 2020):
1. People are confined in limited space. Contagion risk increases with the level of passenger occupancy in
vehicles and stations. e discomfort associated with traveling in crowded buses or trains has increased
since the COVID-19 pandemic due to the added risk of becoming infected by a potentially deadly virus for
which there is no vaccine yet.
2. ere might be scarce access control to identify passengers or workers who may be sick.
3. e existence of multiple surfaces, such as seats, handrails, doors, and ticket machines, that easily transfer
germs.
Notwithstanding, there are ways to reduce or eliminate the risks associated with all these factors, which are
reviewed in this paper. Moreover, the level of the COVID-19 contagion risk during traveling versus during
activities performed at the places that people visit is unclear, as several variables intervene in determining actual
risk levels in different environments.
Advice by authorities regarding the use of public transportation in response to the COVID-19 pandemic has
been quite varied around the world. On one end of the spectrum, official guidelines explicitly discourage the
use of public transportation. e United Kingdom clearly advises, “You should avoid using public transport
where possible” and “Consider all other forms of transport before using public transport” (DfT 2020). Similarly,
the Netherlands national government advises to use public transportation “only if it is really necessary and you
do not have any other means of transport, and travel outside the rush hours as much as possible” (Rijksoverheid
n.d.). In the United States, it is suggested that employers should “offer employees incentives to use forms of
transportation that minimize close contact with others (e.g., biking, walking, driving, or riding by car either
alone or with household members)” (CDC 2020b). Such positions can be accompanied by strict physical
distancing rules. For instance, during May 2020 in New South Wales, Australia, the capacity of a standard
12-meter-long bus and of a train carriage have been reduced to 12 and 32 passengers, respectively (Terrill 2020).
At the other end of the spectrum, there are countries particularly in Asia that have not imposed strong
restrictions or warnings. In some cities of China, bus capacity has been reduced to 50% only, allowing all
bus seats to be occupied while onboard cameras check capacity compliance (Wong 2020). Metro trains in
Taiwan and South Korea are running with large occupancies at peak periods, well beyond the usual COVID-
19 physical distancing suggestions (one or two meters of distance between people), in countries where mask
use is compulsory in public places and the COVID-19 outbreak has been largely contained. Moreover, as the
economy reopens after lockdown in Singapore, the COVID-19 governmental task force explicitly stated that
social gatherings are still forbidden as of June 8, but physical distancing in public transportation will not be
enforced as long as passengers wear masks and do not talk to each other in order to minimize contagion risks
(How and iagarajan 2020). e differences in recommendations and regulations by countries regarding
public transportation could be explained by the differences in the current prevalence of COVID-19 in their
communities, however more factors are likely at play. e appropriateness of containment measures in each
country will be reassessed as the pandemic evolves.
In this paper, we analyze the critical issues pertaining to public transportation use during the COVID-19
pandemic, some of which provide insights into understanding the various approaches to public transportation
use adopted in different countries, as discussed above. e COVID-19 worldwide crisis is a rapidly evolving event
with rapidly increasing yet limited and inconclusive scientific evidence so far on key issues pertaining to virus
4 Journal of Public Transportation, Vol. 22, No. 1, 2020
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
transmission paths and the effectiveness of prevention measures. We review evidence publicly available through
early June 2020 on several factors relevant to public transportation during the COVID-19 pandemic. en we
use this information as a basis to suggest a research agenda.
Some of the topics discussed refer to the COVID-19 crisis or lockdown period, in which large-scale measures
to contain the spread of the virus were taken by federal, state, and local governments, usually implying the
avoidance of all unnecessary travel by any means of transport. However, most of the discussion is relevant for
the so-called post-lockdown phase, loosely defined as the period after the worst part of the crisis has passed,
when people resume activities that have been paused because of COVID-19. is post-lockdown period
might be prolonged, as it is expected to last for as long as there is no widespread immunity in the population.
Furthermore, there is no certainty that new waves of widespread infection will not emerge after the first crisis.
COVID-19 Eects and New Rules for the Use of Public Transport
The Emergence of Physical Distancing
Respiratory infections such as COVID-19 are transmitted through droplets (5 to 10 μm) and aerosols (smaller
than 5 μm) exhaled from infected individuals when breathing, speaking, coughing, and sneezing (Prather, Wang,
and Schooley 2020). Although there is still plenty of uncertainty about the various ways in which COVID-19
contagion occurs (Leung et al. 2020; Han et al. 2020), airborne transmission in closed environments has been
established by several authors (Morawska and Cao 2020; Shen et al. 2020; Prather, Wang, and Schooley 2020;
Buonanno, Stabile, and Morawska 2020). Consequently, closed environments are generally riskier than open
environments (Nishiura et al. 2020; Qian et al. 2020). Aerosols can accumulate and remain infectious in indoor
air for hours (Prather, Wang, and Schooley 2020), which is the greatest challenge for public transportation and
the resuming of day-to-day human activities in other closed environments during the COVID-19 pandemic. For
example, guidance on the resuming of activities in workplaces highlights the relevance of natural ventilation,
air filtration, and employees following strict hygiene protocols, in addition to the cleaning and disinfection
especially of high-touch surfaces among several other actions (CDC 2020b).
e concept of physical distancing (also called social distancing) has emerged as one of the most widely non-
pharmaceutical measures applied to prevent COVID-19 transmission. e World Health Organization (WHO)
recommends keeping a distance of at least one meter from other persons (WHO 2020b), while other health
organizations suggest a physical distance of two meters to reduce the risk of COVID-19 transmission (CDC
2020a). A distance of at least one meter has been found to significantly reduce the probability of COVID-19
contagion (Chu et al. 2020). e recommendation of physical distancing is, among the non-pharmaceutical
prevention measures, the most significant and consequential for public transportation service deployment and
use, provided that physical distancing strongly reduces the capacity of vehicles and stations to accommodate
travelers. Simply put, physical distancing conflicts with the concept of public transportation (Musselwhite,
Avineri, and Susilo 2020).
Current research suggests that the general advice of keeping a distance of 1.0, 1.5, or 2.0 meters from other
people as a precautionary measure works in outdoor environments with short exposure times, but this physical
distance rule has been challenged for indoor environments where contagion from an infected to a non-infected
person has been reported at larger distances. Shen et al. (2020) report the case of a January 2020 bus trip in
Ningbo, China, where a single asymptomatic infected person is believed to have transmitted the COVID-19
virus to 22 passengers (out of 67 persons in total) over two 50-minute bus rides. In this case, the passengers did
not wear face masks. Current research recognizes that the duration of exposure is also relevant (Prather, Wang,
Journal of Public Transportation, Vol. 22, No. 1, 2020 5
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
and Schooley 2020; SAGE 2020), however as of this writing, it is still unknown how the probability of contagion
increases as a function of the duration of exposure. is is particularly relevant for public transportation use
in order to understand the inherent risks of long trips relative to short trips. All in all, without face protection,
frequent cleaning, and ventilation, public transportation ticks all the boxes as a prime virus spreader: it is
a closed environment where people might be contained for a prolonged period. In this setting, physical
distancing can reduce the number of people infected if the virus is circulating, but by itself does not work to
stop virus spreading if not complemented by other measures such as universal face mask use.
The Use of Face Masks
e use of face masks by asymptomatic persons as a virus containment measure has been a contentious
issue particularly during the first months of the COVID-19 pandemic (Javid, Weekes, and Matheson 2020;
Greenhalgh et al. 2020). Arguments against suggesting the widespread use of face masks include the initial
limited evidence of their efficiency, misuse due to lack of information about how to properly wear them, and
the possibility of adopting risk behaviors when wearing masks (Greenhalgh et al. 2020). For several months, the
World Health Organization (WHO) recommended face mask use only for people with respiratory symptoms
and for healthcare workers (WHO 2020b). On June 5, 2020, WHO revised its guidelines to suggest the use of
non-medical (fabric) masks in public places including public transportation, and the use of medical masks for
vulnerable populations (WHO 2020a). Following WHO, the US Centers for Disease Control and Prevention
(CDC) also originally advised the general public not to wear masks, but this recommendation was updated
in April 2020 to suggest the use of fabric masks in public (CDC 2020a), apparently as a substitute due to
the shortage of surgical masks (Greenhalgh et al. 2020). e efficiency of different fabrics to filtrate aerosol
particulates was tested by Konda et al. (2020), finding that the filtration level could be similar to that of medical
masks when multiple layers are used and when different fabrics are combined (e.g., cotton and silk, cotton and
chiffon).
Even though doubts over the universal use of face masks were prevalent in many countries particularly during
the first months of the COVID-19 crisis, the latest research suggests that universal mask wearing is critical for
the containment of COVID-19. Face masks can significantly reduce the number of infectious COVID-19 viruses
in exhaled breath (Chu et al. 2020; Leung et al. 2020), particularly of asymptomatic people and those with
mild symptoms (Prather, Wang, and Schooley 2020). e filtration capacity of fabric masks was found to be
larger than 80% for particles <300 nm and larger than 90% for particles >300 nm, with particular combinations
of common fabrics including cotton, silk, chiffon, and flannel (Konda et al. 2020). Lately, the “precautionary
principle” has been to suggest the widespread use of face masks during the COVID-19 crisis, given that the
potential gains in public health are likely to largely outweigh the risks involved (Greenhalgh et al. 2020; Javid,
Weekes, and Matheson 2020). At this stage, it is also clear from epidemiological data that countries that have
effectively contained the spread of COVID-19, such as Taiwan, Japan, Hong Kong, Singapore, and South Korea,
have enforced universal mask wearing (Prather, Wang, and Schooley 2020). e effectiveness of widespread
mask adoption among the population in reducing the death rate due to COVID-19 at city or country levels
has also been predicted by simulation models (Eikenberry et al. 2020; Ngonghala et al. 2020). Education on the
proper use of face masks is as relevant as enforcing universal use because improperly fitting masks can reduce
aerosol filtration efficiency by 60% (Konda et al. 2020).
us, the accumulated evidence suggests that face mask use in public transportation can be an effective way
of stopping COVID-19 virus transmission only if proper masks are used and people know how to fit and handle
them correctly. A campaign for face mask use needs both to make sure that proper masks are affordable
6 Journal of Public Transportation, Vol. 22, No. 1, 2020
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
by the general population and that people are educated about their use. Eye protection devices also reduce
the probability of COVID-19 contagion (Chu et al. 2020), however their use has not been enforced for public
transportation passengers. Eye protection could be considered, among other measures, for higher-risk workers
such as bus drivers.
Hygiene, Sanitization, and Ventilation
Regarding enhanced hygiene and cleaning standards, it has been found that the COVID-19 virus remains
infectious from hours to days on different types of surfaces, including plastic and stainless steel (Fa-Chun et
al. 2020; van Doremalen et al. 2020). erefore, physical contact with a contaminated surface is a potential
mode of COVID-19 transmission. is implies frequent cleaning of high-touch surfaces in public transportation
vehicles and stations as a recommended preventive measure. Sanitization of public transportation vehicles
and stations has been widely adopted around the world, with various levels of intensity depending on the
extent of organization and the resources available in each agency. Some guidelines already advise on the
increased hygiene measures that must be put in place for public transportation staff, not only on vehicles and
stations, but also in dressing rooms, meeting rooms, and management offices (GIZ 2020; UITP 2020). Rigorous
evaluations on the effectiveness of these measures are lacking and much needed. In the post-lockdown
period, it might be necessary to have personal protection elements and hygiene measures to reassure staff
and passengers and maintain confidence in the public transportation system, even if the risk of infections is
considered low (UITP 2020). Relevant information should be widely provided to users, including standards of
conduct and hygiene, the correct use of masks, and avoidance of public transportation if a passenger shows
symptoms such as fever and coughing (GIZ 2020).
Whether the use of air conditioning can further spread the COVID-19 virus and lead to transmission at a longer
distance from the source is still unclear and likely depends on using recirculated air. Limited evidence suggests
that air conditioning can play a role in contagion in indoor environments such as restaurants (Jianyun et al.
2020). CDC recommends the use of air ventilation/air conditioning systems on non-recirculation mode (CDC
2020c). Frequent ventilation of closed spaces such as public transportation vehicles is usually recommended as
a preventive measure (Buonanno, Stabile, and Morawska 2020; CDC 2020c; SAGE 2020), which is particularly
relevant for drivers who spend several hours inside vehicles. In the absence of specific guidance about
ventilation in public transportation vehicles, the United Kingdom has recommended following the ventilation
flow rate guidelines for buildings, which is 8-10 l/s/person (litres per second per person) of fresh air, without
recirculation (SAGE 2020).
Economic and Social Eects of the
COVID-19 Outbreak in Public Transportation
Financial Adversity
In a matter of weeks, the COVID-19 pandemic became the largest economic crisis for public transportation
services in decades. e severe decline in public transportation demand due to COVID-19 has been combined
with increased costs due to new hygiene and cleaning standards. Under these conditions, several public
transportation agencies are struggling financially, putting pressure on governments. e largest US public
transit agency, New York’s Metropolitan Transportation Authority (MTA), is seeking a $4 billion bailout due
to the COVID-19 pandemic (Goldbaum 2020). In other countries like Chile, the government has agreed to
compensate bus operators for the loss in demand (up to 80%) in its capital city, Santiago (DF 2020). e
Journal of Public Transportation, Vol. 22, No. 1, 2020 7
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
Dutch government has allocated €1.5 billion for compensating the Dutch Railways (NS) and the three urban
public transport operators in Amsterdam, the Hague, and Rotterdam (NOS 2020). e Swedish government
transferred 3 billion SEK to cover nationwide income losses from reduced ticket sales (Sverigesradio 2020). An
additional problem for public transportation agencies seeking financial relief is that the COVID-19 pandemic
negatively impacts the availability of public funds, given that governments face a large number of social needs
requiring financial support (e.g., unemployment, risk of bankruptcy for small businesses, hospitals, and health
care) while expecting a reduction in tax intakes. In this context, public transportation must compete against
several other social needs for financial support.
Regarding fare payment, new rules for the use of public transportation may have undesired effects on
reducing revenues. Compulsory rear-door boarding can be recommended to avoid contact between drivers
and passengers, if drivers are not physically separated from passengers. is policy has been implemented in
cities such as Santiago and Montreal, as well as in the Netherlands, since March 2020. But in systems that rely
on passengers boarding at the front door for onboard fare payment, rear-door boarding imposes financial
risks such as inducing or forcing free rides. Apart from this issue, traditional ticket inspection, with inspectors
approaching passengers to check if they hold a valid ticket or travel pass, may not be possible due to increased
contagion risk (UITP 2020). is may result in an increase in fare evasion if no alternative payment method is
available.
e largest problem to be faced due to the decrease in demand and the resulting financial pressure in public
transport is the possibility of bankruptcy for public transportation providers, if not rescued. Some countries
may have the means to support public transport, other countries may not. In low-income and developing
countries, public transportation is usually unregulated or poorly regulated, without proper standards of safety
or hygiene and no public subsidies, where driver income depends directly on the number of passengers carried
daily (Tirachini 2019; Gwilliam 1999). e financial conditions of such systems and of the people delivering this
type of public transportation service is highly dependent on the final duration of the COVID-19 crisis.
Social Equity
Working from home during the COVID-19 crisis has been shown to be mostly a privilege of higher income jobs,
as reported in data from different countries including the United States (Valentino-DeVries, Lu, and Dance
2020), Canada (Tanguay and Lachapelle 2020), and Chile (Astroza et al. 2020; MOVID-19 2020). Based on survey
data collected from 20,000 respondents in Germany, the United Kingdom, and the United States, Adams-
Prassl et al. (2020) concluded that less educated workers and women are more negatively impacted by the
ramifications of the pandemic on the labor market. e long-term impacts of the pandemic crisis are expected
to exacerbate disparities not only within countries, but also between countries due to their different levels of
resourcefulness in recovering from the crisis (e Economist 2020).
In this context, the vision of public transportation as a motor of social integration rather than of social
segregation seems more distant today than ever. With the COVID-19 pandemic, people have abandoned public
transportation, but not uniformly: high-income groups have left public transportation in larger numbers. A
recent survey comparing trips made in the last week pre-coronavirus crisis in Santiago versus the first week with
nationwide measures to contain the virus in March 2020 found that people from higher-income households
were the highest number who stopped traveling by public transport. While trips on public transportation fell by
between 30% and 40% for people in the lowest income households, the decrease in public transportation use
was greater than 70% for the highest income households (estimation based on data from Tirachini et al. 2020).
ese numbers quantify the assertion that the people who leave public transportation are mainly those who
8 Journal of Public Transportation, Vol. 22, No. 1, 2020
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
have the option to do so—by working from home, by being able to pay for alternative means of transportation,
and by shopping online—while those who continue to travel by public transportation are largely people
with lower incomes. is difference in the rate of adaptation in travel behavior between different social
groups is likely to continue in some ways throughout the post-crisis period. Consequently, improving public
transportation today is, more than ever, a matter of social equity.
Sustainable Mobility
e sharp reduction in public transportation demand due to the new physical distance behaviors and the fear
of COVID-19 contagion poses several questions for the future sustainability of mobility in cities. Designing a
plan to make public transportation safe for a period of time (post-crisis) that is likely to be prolonged (as long
as there is no widespread immunity to the new virus) requires several coordinated actions from policy makers,
public transportation agencies, workers, and users. e objective should be to ensure that public transportation
is as safe as possible and that it can accommodate and attract more people than those who have no viable
alternative.
If buses and trains are running almost empty in the COVID-19 era, then the economic and environmental
efficiency argument for promoting public transportation is severely challenged, and the only argument
remaining would be providing mobility to those who have to travel because public transportation is their only
option. If new physical distance and occupancy rules are imposed, a valid study is the demand threshold (i.e.,
break-even point) in public transportation vehicle occupancy that makes buses more efficient than private cars
in terms of energy consumption, congestion, and pollution. Consider road space consumption, for example.
Before the onset of the COVID-19 crisis, buses in Santiago carried between 28 and 65 passengers on average
(taking into account peak and off-peak periods), while cars had an average occupancy between 1.4 and 1.5 pax/
veh (SECTRA 2013). erefore, considering a passenger car equivalency (PCE) of two to three cars per bus, it is
estimated that car users occupy between 10 and 15 times more road space than bus users. erefore, average
bus occupancy can be largely reduced while remaining a more efficient mode in the use of road space than
traveling by car.
The Way Forward: Policy Directions and a Research Agenda
In the following, we identify and discuss key directions for potential policy interventions as well as areas that
need advancements in knowledge. is section outlines a research agenda to address an array of identified
research gaps, questions pertaining to public health considerations, and measures to reduce crowding in public
transportation.
Public Health Considerations in Transportation Planning
Incorporating Public Health Considerations into Service Planning
Passenger transportation where people share the same facilities and vehicles is especially prone to virus
spreading when proper measures are not taken. is is particularly true for mass public transit where many
passengers with diverse origins and destinations are traveling in crowded conditions. e question is then, what
costs should the public transportation system bear—in the form of preventive measures and prolonged travel
times—to reduce the public health risks associated with contagion. Although it brings unease, societies have
limits as to how much they are willing to sacrifice to save lives. Regardless of the assumed risk level, this requires
making moral choices, which are by no means new in the transportation policy domain, as pointed out by
Journal of Public Transportation, Vol. 22, No. 1, 2020 9
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
Chorus (2020). ink for instance of deciding whether to invest in a connection that will save passenger hours as
opposed to a safety measure expected to reduce the risk of fatal accidents. Also, in the case of making decisions
in the context of COVID-19, this involves trade-offs between abstract but grave risks versus the experience
and annoyances for many. Hence the need for methods to support evidence-based decision making and for
professionals to convey to decision makers and the public the dilemmas and decisions made.
Physical Distancing in Public Transportation
During the COVID-19 lockdown period, it was generally agreed that travel must be minimized, allowing only
essential or unavoidable trips. As activities resume in the post-lockdown period, it gives rise to the question
of physical distancing in public transport. e scarce empirical research available hitherto does not provide
conclusive evidence on the effect of physical distancing in closed environments such as public transportation
facilities and vehicles. ere is, albeit limited, evidence showing that the relevance of physical distancing in
public transport can be greatly reduced if other non-pharmaceutical measures are enforced, such as the
correct use of face masks, enhanced hygiene, or even a prohibition of talking (Singapore case). On one hand, if
contagion in indoor environments can occur at distances greater than two meters due to airborne transmission,
as reported by Shen et al. (2020) and further discussed in recent epidemiological contributions (Prather, Wang,
and Schooley 2020; Morawska and Cao 2020; Setti et al. 2020), then there is still a risk of virus spreading without
wearing a face mask. In the presence of an infected passenger, physical distancing can help reduce the number
of people infected but not prevent infection altogether when passengers do not wear masks. On the other
hand, the latest epidemiological research shows that masks are effective in preventing or at least significantly
reducing COVID-19 virus spread (Leung et al. 2020; Prather, Wang, and Schooley 2020; Chu et al. 2020). ere
are public transportation systems currently running large occupancies with passenger spacing below the two-
meter physical distance rule and no COVID-19 outbreaks attributed to public transportation when everyone
wears masks, as recently reported for Japan. In that country, it was recently found that most COVID-19
contagion clusters originated in places where people gather, eat, drink, chat, and sing, such as gyms, pubs,
live music venues, and karaoke rooms. No cluster was linked to commuter trains. e fact that close-range
conversation among strangers in public transportation is infrequent has been hypothesized by virologist Hitoshi
Oshitani as one of the explanations for these findings (Normile 2020). is type of result led Singapore to its
decision of not enforcing strict physical distancing rules in public transportation but requiring passengers to
wear face masks and not talk to each other.
Even though the safety gains from universal adoption of face masks are potentially large, it is unknown how
much safer a public transportation vehicle or station is if all passengers wear different types of masks (surgical,
cloth, N95) at different stages of the pandemic, versus if only a subset of them does it. is is a matter of utmost
relevance because it can help in defining a “reasonable” occupancy level for public transport, an element that
has significant economic, operational, and social implications. Put differently, if a physical distance of two
meters does not properly work in public transportation vehicles when people do not wear masks, what should
be the maximum passenger capacity of vehicles if all people use masks properly? e current experience in
large cities in Asia, such as Tokyo and Seoul, shows that a physical distance shorter than one meter in public
transportation seems to work well under universal mask use and high hygiene standards; however, the current
prevalence of the virus in those places is unknown. e evolution of such an approach to public transportation
use, without setting strong physical distancing rules, should be closely followed in the near future to understand
the conditions that would allow for its replication in other cities around the world.
10 Journal of Public Transportation, Vol. 22, No. 1, 2020
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
It is worth stressing that solid evidence on the COVID-19 transmission risk in public transportation under
different use and operation rules (including the adoption of preventive strategies) is still scarce, and new insights
are expected to be gained in the coming months. e problem of new maximum occupancy standards due
to new physical distancing requirements is a multifaceted challenge that depends on the use of face masks,
sanitization, and ventilation, among other factors. However, conditions are likely to be less clear-cut with some
passengers not (properly) wearing masks. We therefore assume in the following that some form of physical
distancing may be needed, which is the current reality in many countries.
Trade-os between Service Eciency, Eectiveness,
and Robustness in the Context of COVID-19
As clearly and painfully demonstrated in this pandemic crisis, the connectivity offered by all modes of
transportation is not only an asset and a catalyst for the exchange of ideas and goods, but also a potential
catalyst for adversity, such as a virus. System robustness is measured in terms of its capacity to withstand shock
and recover functionality. e provision of public transportation services in the era of the pandemic and its
aftermath involves trade-offs between effectiveness (defined in terms of the accessibility and level-of-service
offered), robustness (the health risks associated with traveling by public transport), and efficiency (the amount
of resources needed to offer a given service supply). As is often the case, there is an inherent conflict between
efficiency and robustness since the latter requires designing larger margins and reserves, which imply redundancy
under normal circumstances. is is particularly stressing given the already adverse financial conditions
experienced by many public transport service providers worldwide. In the context of complying with physical
distancing measures and thus a reduced capacity standard, the robust solution will involve not only inefficiency
from an operator’s perspective (i.e., requiring additional resources), but also ineffectiveness since it results in a
deterioration of the level-of-service due to expected less frequency and hence longer waiting times in the post-
crisis phase.
Measuring System Resilience and Its Ability to Restore Functionality
Given the importance of public transportation systems as critical infrastructure and to society at large
(Homeland Security 2010), it is essential to devise measures to mitigate the impacts of virus spreading in public
transportation systems, while maintaining their functionality as critical infrastructure to the extent possible. e
bathtub model proposed by McDaniels et al. (2008) offers a conceptual framework for analyzing the evolution
of system performance in the event of a disruption. In the context of public transport, system performance can
be measured in terms of the original capacity share that is provisioned, total number of passengers transported,
total passenger-km, and total passenger time losses attributed to the disruption. e conceptualization and
analysis of the robustness and resilience of public transportation systems has mostly been limited to supply
performance and passenger accessibility and connectivity (Jenelius and Cats 2015; Bešinović 2020). e pandemic
produced a shock to the system that caused an abrupt reduction in system performance with consequences
to its core functionalities. Some parts of the world are currently experiencing different phases of the recovery
period. e recovery period sees an increase in system performance, although there is no guarantee that
(1) system recovery will follow a monotonic pattern, setbacks such as more restrictive measures introduced
following a so-called “second wave,” and (2) system performance will recover to its original level (i.e., the recovery
may yield a new normal). is calls for the development of concepts and methods to assess system resilience
while encompassing impacts for public health in addition to accessibility, equity, sustainability, and financial
viability.
Journal of Public Transportation, Vol. 22, No. 1, 2020 11
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
Assessing the Spread of Virus in Public Transportation
Understanding and quantifying the spread of virus in public transportation systems is essential for evaluating
the public health consequences of alternative scenarios and strategies. ere is therefore an urgent need to
couple transportation models and epidemiological models in order to analyze the resulting contact graphs
and their spatial consequences (Barabási 2014; Colizza et al. 2007). e contact network reflects the set of
passengers a person potentially encounters during a public transportation journey. e transportation model
will assign travel demand to the service network and that output will be used as input to the epidemiological
model, which then updates the states of segments of the travel demand population in relation to virus carrying.
Each passenger on any given day may be characterized by one of the following states: susceptible (not infected),
infected (and traveling), quarantined (infected and not traveling), and immune (and traveling again). Passenger
demand can then be reassigned to the network to analyze the evolution of the virus spreading and obtain key
performance indicators, such as the share of the passenger population that has been infected or the number
of days needed for nullifying the number of new cases. Since virus spreading requires physical proximity to an
infected passenger, it is essential to analyze individual passenger trajectories and the resulting crowding levels.
Krishnakumari and Cats (2020) demonstrated how this can be done using detailed smart card trajectories. ey
estimated the crowding conditions that each passenger experiences on any segment of the journey and the
probability that a person is in proximity to someone who is infected, based on the trajectories of those assumed
initially infected. Such modeling capabilities allow testing the potential consequences of various demand levels,
service provision, and assumed virus spreading characteristics to support the design of exit strategies and post-
pandemic realities.
Contact Tracing to Reduce the Risk of Virus Spreading in Public Transport
Medical developments such as testing more of the public and faster diagnoses will significantly impact the
potential spread of the virus in public transport by reducing the number of infected passengers traveling
and therefore reducing the health risk to others. To this end, contact tracing can also support shortening
the exposure period for passengers who are potential carriers of the virus prior to diagnosis. Governments
worldwide have introduced or are in the process of introducing contact tracing apps designed to facilitate
this. In the context of public transport, smart card data validations may be used for contact tracing in public
transportation systems as demonstrated by Krishnakumari and Cats (2020) for the Washington DC Metro
system. Passively collected fare data offers a unique source for conducting contact tracing research and
supports the identification of contact networks based on recorded or inferred passenger trajectories. In systems
that require tap-in only and/or offer station-based (rather than vehicle-based) validation, the application of
alighting station and vehicle inference methods will be instrumental.
Avoiding the Crowds: Accommodating Physical Distancing Regulations
Implications of Physical Distancing on Service Capacity
e public transportation sector is currently focusing on adjusting services to adhere to physical distancing
requirements as well as vehicle and station cleanliness, to comply with governmental instructions, and to
reduce public health risks. As discussed above, however, there is currently no conclusive evidence on the
relevance of strong physical distance rules (as two meters is likely not enough in closed environments if people
do not wear masks, and there are public transport systems with large occupancy levels in which everyone
wears masks that have good results). Complying with physical distancing requirements comes at the cost of a
12 Journal of Public Transportation, Vol. 22, No. 1, 2020
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
dramatic decrease in the service capacity offered and consequently the system’s ability to satisfy demand. For
example, assuming that passengers are spaced across platforms and metro trains seeking to ensure a minimum
distance of 1.5 meters (approximately 5 feet) from any fellow traveler, this implies a capacity of 312 passengers,
a reduction of more than 80% for the Washington DC Metro (Krishnakumari and Cats 2020). Similarly, a
maximum capacity of 18-20 passengers can be suggested for a standard 12-meter-long bus as a way to keep
current common distance (GIZ 2020). However, any new COVID-19 induced capacity guidelines should be
revisited and reassessed as the pandemic evolves and robust epidemiological knowledge becomes available.
In many systems, increasing capacity through vehicles per hour or per day (as a way to counterbalance per
vehicle capacity reduction) is not an option, either because services already run at full capacity in peak periods
or because of a shortage in resources (lack of more vehicles, drivers, and operators). is might be particularly
challenging in the upcoming period because of limited budgets due to reduced revenue, reduced driver
availability due to the pandemic itself, or due to the need to protect drivers who are at higher risk (e.g., workers
older than 60 with chronic diseases). ere might also be requirements from drivers’ unions to reduce working
times and the number of shifts during the pandemic to reduce exposure to the virus. Dealing with the possible
absenteeism of staff due to COVID-19 related issues is a common concern of public transportation operators
(UITP 2020).
Redesigning Services to Accommodate Prevailing Demand Patterns
and Capacity Limitations
Public transportation services may be redesigned to more efficiently and effectively accommodate passenger
demand given the new, more restrictive capacity limitations. For example, service frequencies may be reset
to maximize the share of passenger demand that can be accommodated as demonstrated by Gkiotsalitis and
Cats (2020) for the Washington DC Metro network. Service redesign may also extend beyond the reallocation
to existing services to involve changes in service configuration; for example, in terms of stopping patterns and
short-turnings, to better adjust supply to uneven spatial patterns of demand (Tirachini, Cortés, and Jara-Díaz
2011). is calls for the potential introduction of physical distancing constraints into strategic, tactical, and
operational decisions, as well as accounting for their consequences.
Leaving parts of the travel demand unserved has equity ramifications that should be assessed and integrated
into the decision-making process. On-demand transportation services may be used to cater to unserved
demand by line-based public transport. Traveling by means of on-demand shared services is expected to
result in a contact network of limited size (Kucharski and Cats 2020). Furthermore, in addition to transporting
passengers otherwise left behind, on-demand services offer door-to-door transportation for users in risk
groups such as the elderly and for healthcare workers. Arrangements for shared-mobility companies to provide
exclusive services to healthcare workers have already been implemented in countries such as Mexico (Jetty
2020) and Germany (Carey 2020).
Eectively Managing Limited Capacity
ere are several ways to manage scarce resources. One option is to let people queue for these services,
possibly denied several times before they can board a vehicle. is will not only severely prolong travel times,
make service unpredictable, and lead to dissatisfaction, but will also pose public health risks with large crowds
queuing. An alternative is to restrict access. Depending on the service type and fare validation technology,
reservation systems might be deployed committing passengers to travel during certain time periods or on
certain trajectories, or better still, to specific itineraries. is will assist in managing service capacities, thus
Journal of Public Transportation, Vol. 22, No. 1, 2020 13
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
ensuring compliance with physical distancing requirements, and will limit the number of passengers that
each passenger is exposed to over a longer period. However, reservation systems come at the cost of limiting
travelers’ spontaneity (i.e., inducing scheduling delays). e feasibility of such a solution is likely to be limited to
systems where digital billing and subscription capabilities are already available. Access could be based on setting
priorities or even restrictions. For example, trips could be prioritized or restricted to essential workers such
as medical support staff and occupational users who are not able to perform their work remotely, mitigating
some of the social equity ramifications. Certain time periods might be restricted for certain user groups, such
as allowing only the elderly to travel between 10 a.m. and 4 p.m. Such a prioritization or restriction should
be made by the local policy makers. Alternatively, pricing can be used as an instrument to manage capacity.
For example, greater discounts might be offered in the off-peak periods to stimulate passengers who can shift
their departure time to do so and thereby reduce crowding levels in periods when capacity is scarce. Mobility
as a Service (MaaS) ecosystems may play a key role in enabling and facilitating a smooth use of different (new)
modes by providing an integrated platform for information and payments. In addition, there could be a role for
MaaS platforms to facilitate a potential booking system for public transport, and to apply different fares and
priorities for different sectors or risk groups.
Eectively Managing Crowding to Reduce Public Health Risks
Since physical proximity is currently assumed to be the precondition for virus spreading, crowding management
is paramount to combating it. is applies to all areas of the public transportation system, including platforms
and station walkways in addition to vehicles, so as to minimize crowding during all parts of the passengers’
journey: walking, waiting, traveling onboard, and transferring. Crowding management measures at stations
such as one-way entrances, passages, and staircases can help isolate flows and reduce the physical interaction
between passengers. Similarly, designated vehicle doors might be used for boarding and alighting, although this
measure will likely increase dwell time at stops where boarding from all doors was previously allowed (Jara-Díaz
and Tirachini 2013; West and Cats 2017).
Public transportation priority and control measures can also play a critical role in mitigating passenger
crowding. In the post-lockdown period, congestion may increase if not properly managed because of the
migration of travelers from public transportation to cars. As congestion increases, operational measures to
support public transportation will be more necessary than ever. Dedicated bus lanes would not only reduce
operator costs and travel time for public transportation users, but also reduce crowding on vehicles and at
bus stops and stations. If the bus fleet is kept constant, a reduction in travel time will be translated into a
proportional reduction in average occupancy levels per vehicle, due to the increase in service frequency. At the
same time, as the irregularity of headways between buses induces unnecessary overcrowding (a half-empty bus
followed by a full bus), even if the aggregate capacity of the system is sufficient to satisfy the demand for public
transportation trips, measures to control bus headway to mitigate bunching will become more relevant than
ever during the COVID-19 pandemic. Strategies to deal with bus bunching include holding, station skipping, and
speed control (Muñoz et al. 2013; Hickman 2001).
Opportunities for Spreading Passenger Demand
Public transportation demand is usually derived demand, meaning people travel because of the activities
they need to perform at the destination. erefore, reducing occupancy levels at stations and in vehicles is
not achievable only by means of supply-oriented measures, but requires also the deployment of demand
management measures. Effectively, all measures are aimed at reducing the size and connectivity of the contact
14 Journal of Public Transportation, Vol. 22, No. 1, 2020
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
networks resulting from public transportation journeys. Encouraging working from home and refraining from
nonessential travel are among the most important measures. With the gradual opening in the post-lockdown
phase, it is inevitable that demand will exceed supply in the peak hours on the high-demand services given the
greatly reduced capacity of public transportation services under physical distancing requirements. It is therefore
key to try and distribute services over time and space as much as possible. Here it is important to coordinate
exit strategy plans of different sectors in the economy and society to try and schedule working, studying, and
shopping patterns to spread the demand over a longer period. is requires coordination among stakeholders
and should continue to be beneficial when the COVID-19 crisis has passed. Notwithstanding, it is expected that
capacity of certain public transportation services during certain time periods will remain a resource for which
there is more demand than the supply can offer.
The Potential Role of Travel Information on Mitigating Crowding
Information on onboard crowding conditions is becoming increasingly available. Several travel apps (e.g., Google
Maps Transit service, Moovit) provide crowding information based on historical user feedback on crowding
experience. Moreover, apps developed by individual service providers such as the Dutch railways, Tokyo
railways, and Singapore buses distribute crowding information based on real-time data of vehicle occupancy
loads (e.g., from weight sensors) (Hänseler et al. 2020). In contrast, implementations of at-stop crowding
information displays regarding upcoming departures have been hitherto limited. Passenger reluctance to ride
a crowded vehicle is likely to be much higher due to the pandemic, reflected in larger crowding penalties than
previously reported (Hörcher, Graham, and Anderson 2017; Tirachini et al. 2017; Yap, Cats, and van Arem
2020). Consequently, more passengers are expected to seek crowding information and adjust their travel plans
accordingly. is can prove to be an effective means of distributing travel demand over the available supply.
A key challenge will be to ensure that the reliability of the provisioned information is not hampered by an
over-response, defeating its purpose. is calls for the development of demand-anticipatory travel information
schemes inspired by developments in the car traffic context, where this has been a subject of considerable
research (Dong, Mahmassani, and Lu 2006).
Behavioral Responses and Adaptation Exercised by Passengers
Passengers may exercise a variety of behavioral adaptations in response to COVID-19 pandemic conditions and
related lockdown and exit strategies. e main motivation is to avoid exposure to the virus. In the absence
of better information, this often implies following the principle of avoiding crowds. is can impact all travel
choices, from altering routes to less congested ones, changing departure time to avoid the peaks, mode shift
to privately used (and preferably owned) modes, changing trip destination (e.g., to less crowded stores),
or refraining from traveling altogether (e.g., e-shopping). All these decisions have significant consequences
for travel patterns and ridership. e population’s willingness and ability to exercise such adaption varies
considerably, depending on personal preferences as well as household income and composition, logistics,
working hours flexibility, working from home, digital proficiency, and vehicle availability. All of this means
there is considerable inequality in people’s ability to avoid the crowds if they so desire, as supported by some
preliminary evidence.
Concluding Remarks
e COVID-19 pandemic poses great challenges for public transportation systems worldwide. is paper has
reviewed the available evidence as it pertains to the influence of several factors on reducing or increasing the
Journal of Public Transportation, Vol. 22, No. 1, 2020 15
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
COVID-19 contagion risk in public transportation, including the occupancy levels of vehicles and stations,
the exposure time (trip length), the enforcement of face mask use, and the application of enhanced hygiene
standards (including sanitization and ventilation). e ongoing pandemic forces policy makers to make
decisions in the context of uncertainty.
e absolute risk of contagion is highly dependent on the disease prevalence in the community at any
specific time, therefore any restrictions or regulations on public transportation use should be tailored
differently depending on the phase of an outbreak. A detailed analysis on this issue is required, identifying
levels of contagion that make public transportation use increasingly risky from a public health perspective.
Notwithstanding, some promising evidence is emerging as to how to make public transportation safe or at
least significantly decrease the contagion risk, with implications particularly for the post-lockdown phase. It
is still too early to arrive at definitive conclusions; more research is needed to assess the true level of safety in
public transportation when proper virus containment measures are taken at different stages of the pandemic.
is is a matter of uttermost relevance because if public transportation is perceived as unsafe and unhealthy
by large segments of the population, it will not be able to fulfill the societal roles that it is set to serve, including
accessibility, sustainability, and equity. Certain developments such as finding a vaccine or lifting lockdown
measures lie outside the control of the public transportation sector, but many of the measures discussed above
are within the principal responsibility of public transportation service providers. is will also help assure the
public that adequate measures are taken. Communication, public relations, and enforcement of safety measures
are especially important during this period.
ere is a risk that if the public transportation sector is viewed as poorly transitioning to two-meter distancing
conditions, that perceptions of public transportation as unhealthy will gain ground and might be sustained
even in the aftermath, resulting in the formation of new habits. Our societies need public transportation
services to prosper and to address key societal challenges that are paramount and persistent. It is therefore
critical to avoid contributing to stereotyping the use of public transportation as unhealthy, which may outlive
the pandemic itself and hinder the long-term prospects of public transportation services.
Acknowledgements
Support from ANID Chile (Grant PIA/BASAL AFB180003) is acknowledged. e authors are indebted to
Cristobal Cuadrado (School of Public Health, Universidad de Chile) and three anonymous referees for
comments that helped to improve the paper. All views and any errors are the authors’ responsibility alone.
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About the Authors
Alejandro Tirachini (Alejandro.tirachini@ing.uchile.cl) is an associate professor of civil engineering at the
Universidad de Chile. He holds an MS in Transport Engineering from the Universidad de Chile and a PhD from
the Institute of Transport and Logistics Studies, the University of Sydney. His main research interests include the
optimal design and operation of public transport systems and the study of emerging mobility technologies with
a focus on sustainable mobility. He has served in the Experts Panel of Chile’s Ministry of Social Development
for the examination of improvements to the methodology of cost-benefit analysis for transport projects, in the
Experts Panel of the Ministry of Transport to improve the understanding of fare evasion in public transport,
and in the Experts Panel of the government’s MAPS Initiative (Mitigation of Climate Change and Low Carbon
Transportation Development).
Oded Cats (O.Cats@tudelft.nl) is an associate professor at the Department of Transport and Planning at Delft
University of Technology, the Netherlands. Dr. Cats’ research is devoted to developing theories and models of
multimodal passenger transport networks by combining advancements simulation and operations research,
behavioural sciences, and complex network theory and modeling. Most of his work is in metropolitan public
transport systems where he focuses on network dynamics and robustness, service operations and control, and
passenger demand and flow distributions. Dr. Cats is the recipient of a European Research Council Starting
Journal of Public Transportation, Vol. 22, No. 1, 2020 21
COVID-19 and Public Transportation: Current Assessment, Prospects, and Research Needs
Grant entitled "CriticalMaaS" and he co-directs the Smart Public Transport Lab at TU Delft, leading a research
group that works closely with public transport authorities and operators. He is also editor-in-chief of the
European Journal of Transport and Infrastructure Research.
