Central to India’s lockdown to control the spread of COVID-19 was a complete shutdown of the transport system. Now, as the country emerges from the lockdown, a proper ramping up of the transport system is needed. This should not be done in haste, however.
Can COVID-19 spread through public transport systems? It is difficult to answer this question with numbers. A recent paper from the Massachusetts Institute of Technology argued that New York’s subways seeded the epidemic in the city. While the research fails to establish causation from the observed correlation, as the author had admitted, it cannot be discarded as implausible. It is commendable that India shut down public transport before it could contribute to the spread, with an early lockdown. We now need to consider what can ensue on a restart, especially of metro rail.
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COVID-19 and public transport
Fearing crowd infections, commuters prefer travelling in private modes like two-wheelers. Cities like Delhi, that resumed services nearly four weeks ago, observed less ridership than the allowed 20 passengers per bus, despite the limited frequencies on many routes. Although bus crowding is seen in some cities such as Mumbai, it is temporary and due to a lack of alternatives. A significant drop in public transport ridership can be expected for months after resumption, based on opinion surveys. That means measures are needed to gain the public’s confidence in mass transport modes, to avoid a significant modal shift to road traffic.
The Delhi Metro Rail Corporation has released guidelines to tackle several social distancing and sanitisation concerns, and to address the possibility of viral transmission through tokens, push buttons on lifts, and handrails at the station elevators. Other metro rail systems are also expected to follow similar guidelines. Are these measures enough to prevent serious viral transmission?
Unfortunately, public transit agencies around the world face the problem of a dearth of research by scientists on the specific modality of COVID-19 transmission during public transport commute. Confidentiality laws usually prevent the availability of contact-tracing data to extract the precise details of how any individual got infected. There have been some notable research efforts, currently under peer review, that did use detailed contact-tracing data from China and Korea. One study says that SARS-CoV-2 does not seem to get transmitted much outdoors. In fact, only a single cluster of two cases out of nearly a thousand was traced to an outdoor infection in China. Correlation to the effect of air conditioning airflow has also been established based on precise seating locations of those infected at a restaurant and at a call centre. Indian authorities who were already working under similar assumptions on the effects of AC will be proven justified by the conclusion of such research that there is clearly high risk in indoor areas under AC with focused air flow.
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From the above research we can conclude that a non-AC bus with open windows offers a much less risky outdoor-like environment. However, it would be wrong to conclude that an AC metro rail coach is risky – for a different reason, in that contact-time is also very important in viral transmission in indoor spaces. A majority of metro rail trips in Indian cities are no more than 20 minutes long, and there is research indicating that this may not be long enough for significant viral densities and inhalation of sufficient viral particles, even without social distancing. It is unlikely for any significant level of public transport infections to happen via inhalation or even crowding and clothed-body contact, though we cannot say it with certainty.
However, hand contact with common surfaces must be considered, as it is well-known to cause significant COVID-19 spread. The guidelines being developed in India address some of the related issues. However, they leave out certain key elements that should be taken very seriously – the handgrip rings and handrails from the ceilings, the stanchion poles, and any grabrails on the seatbacks. If an infected asymptomatic person deposits viral particles on such surfaces, and another person grabs the same spot even briefly, the viral particles could be picked up by their hand. The second person could later deposit the particles on his/her face.
Probabilities may help, and another person may not hold on to the exact 3-inch long area before the virus dissipates, in all cases but one – that of the handgrip rings. Their surface is potentially the most dangerous inside a coach. Every successive individual who hangs on to the handgrip where one infected person deposited the virus can pick up the virus at a high density from the same spot. Then the probability is quite high that, within an hour, two or three others could pick up the virus left by one person on a handgrip. There is also a high probability that those people will touch their faces soon after.
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Suggestions for more safety
Considering such possibilities, we offer a few safety suggestions that can be implemented immediately. The first is to employ staff to wipe the handgrips at frequent intervals, constantly moving from end to end in the train. Any handgrips in buses also need to be cleaned often. Another is to give wet sanitising wipes to every traveler entering a metro rail coach with a suggestion to have it in their palms before touching or gripping anything. Wipe disposal bins will be needed in the coaches.
The metro rail agencies’ focus may need to shift to the egressing passengers, as it is important to prevent them from transferring what is on their hands to their faces after egress. We should expect a lot of passengers to leave in a hurry and to not bother with cleaning their hands, even if hand sanitiser dispensers are available. Paid staff or volunteers dispensing hand sanitisers on platforms can be an option. Offering contact-less wash basins with soap dispensers at the platform level could be effective. Signs on hand hygiene vis-a-vis touching surfaces are needed.
There are possible options in metro trains to create external airflow to dissipate viral particles. Metro rail authorities are planning to leave the doors open at the terminal before the next run of each train. Since a majority of metro rail stretches in India are elevated, there are other creative options, if safety considerations will allow them. One would be to have staff onboard to direct passengers away from a certain coach to other coaches. The doors of the empty coach can be opened during a run for two or three minutes. We are not aware of such operations anywhere, so any attempt must only be after careful experimentation. Eventually, metro rail AC systems could be changed to High Efficiency Particulate Air filters with frequent circulation of fresh air.
Actions are needed from both authorities and the public to keep our public transport systems safe. If no such actions are taken and a serious level of viral transmission is later traced to public transit, the result will be a mode shift to private vehicles. As pollution and accidents kill more people in India than COVID-19 does now, a mode shift away from public transport will have long-term consequences. Our buses and trains must be perceived as safe, so it is vital to assure ourselves that public transport is for the public – not the virus.
R. Jayakrishnan is Professor, University of California, Irvine, U.S.; Ashish Verma is Associate Professor, Indian Institute of Science, Bengaluru; and S. Velmurugan is Chief Scientist, Central Road Research Institute, New Delhi
