As lockdowns start to ease, trains, buses and planes are becoming an even greater focus of anxiety, with larger numbers of people considering when and how to resume travel. Larger crowds could pose a greater risk to both essential workers who may have been using transit all along, and the others who may start to join them. What factors most affect your risk of catching Covid-19 while using mass transit? CityLab talked to several experts about both the dangers and necessary precautions.
Keep your distance – and watch your mouth
When it comes to staying safe on mass transit, one piece of advice outweighs any other: Do whatever you can to stay at a safe distance from other people. The same six-feet rule applies as elsewhere, and the safest form of transit is always the one that makes this easiest. Dr. Simon Clark, associate professor of microbiology at the University of Reading, cautions against focusing too narrowly on balancing one mode against another.
“Let’s face it,” he says. “With public transport, it’s an aluminum can that people are packed into, whatever the mode. The key question is: How densely are people packed in together? That’s basically it. The longer they are exposed to one another, the greater the risk. The more densely packed in they are, the greater the risk. It doesn’t particularly matter if you are in a bus or a train.”
These are also the key considerations for airplanes, says Dr. Julian Tang, a professor in the Department of Respiratory Sciences at the University of Leicester, where it is distance rather than air cleaning that is the key issue:
“Airplanes have good ventilation systems but if you’re sitting side-by-side next to a stranger within talking distance, then that may not leave time for the ventilation in the roof and the walls of the plane to change the air between you. That means local airborne transmission will not necessarily be prevented.”
In keeping your distance, it isn’t just evidently ill-looking people you need to be wary of. The contagion risk from sitting or standing too close to people goes beyond the simple danger of being coughed on, says Tang. “If you talk, you produce aerosol. If you talk louder, you produce more, so the loud-talking guys on the train are possibly the worst spreaders of the virus. Because when you cough or sneeze you usually look away or cough into your sleeve.”
Wearing masks can do much to mitigate the risk of this kind of proximity, says Tang. “Masks are better at containing virus exhaled by the wearer. If everyone wears masks, protection is two-way, containing your own virus and protecting you from others’ exhaled virus. If there is little or no ventilation present, the masks are even more effective, as virus will start to build up in the air, so distancing alone is not effective if the virus is distributed throughout the carriage.”
Ventilation could matter — but maybe not how you think
If proximity is still the overwhelming issue, how much does the ventilation on a train or bus matter? It depends on the type of ventilation you’re taking about: Being in a vehicle with poor ventilation that doesn’t adequately circulate infected air probably makes a difference. But the idea that a ventilation system could play a perverse role by spreading the virus has far less support.
Worries about spread through ventilation systems were sparked by a study tracing an outbreak of Covid-19 in a restaurant in Guangzhou, China, that suggested that air conditioning could have played a role in spreading contagion. While the study concluded that infection in the restaurant did indeed follow the direction of the air conditioning’s flow, experts have suggested that this single reported case is a freak outlier and that the actual cause was more likely the proximity of the people in the room.
“This virus is not like TB, where people could get ill in two separate places if they have a ventilation link,” says Dr. Lena Ciric, a microbiologist at University College London. “Hospitals, which are the places most on top of this at the moment, are not so worried about ventilation systems.” Ciric notes that while there have been traces of the virus found in hospital ventilation systems, they are not necessarily able to cause infection.
But while the likelihood of a vehicle’s ventilation system actively spreading the virus seems low-to-nonexistent, the risk of poor ventilation is considered higher. This is the reason why the outdoors is considered safer than indoors, and why confined spaces are considered higher-risk areas.
“Basically, the packed subways of Tokyo, London and New York are in the worst possible situation for both aerosol and close contact transmission,” Tang says. “The London Underground is old, the trains are very narrow and the carriages are closed at each end so that you can’t walk through. That reduces the volume [of air in the space] in there that can reduce the concentration of airborne contaminants.” Other transit systems, however, perform better.
“If you look at the Hong Kong and Singapore systems, they have fantastic air conditioning,” adds Tang. “They have vents going to the outside so they have fresh air coming in cool, and inside air filtered, hopefully allowing greater removal of contaminants, including viruses.”
While these comments might alarm transit users, Tang nonetheless underlines that being in close proximity with someone is the key risk, a risk that no ventilation system can eradicate.
“[Fully preventative] ventilation would need to be so powerful, that it pulls away the air straight away when it comes out of your mouth. You might get these conditions outside on a very windy day when you’re trying to talk to your neighbor, and you’ll feel it because you can’t hear anything. There’s no ventilation system like that in an indoor area. You can’t maintain it because it’s too powerful and impractical.”
Clark agrees, conceding an advantage for vehicles that are partially open air.
“Certainly, if you’re in a tightly packed trolley that is fully open, there would be a lower risk — concern about ventilation is not a red herring — but otherwise it is difficult to make broad statements about a particular mode of transport because there are so many different systems at play.”
In other words, while good ventilation, and larger, more open carriages might moderate the risk of becoming infected by someone standing close to you, no indoor air conditioning can ever be as effective at protecting you as taking a step or two back.
It’s prudent to be careful of surfaces, too
What you touch during travel may also be important, although exactly how important is not a matter of consensus among the experts CityLab talked to. Tang notes that there is a lack of evidence proving coronavirus transmission from people touching their faces with virus-contaminated hands, while Clark and Ciric emphasized that it is nonetheless a very good idea to take precautions given the high-exposure surfaces like turnstiles and subway poles in transit systems. They advise regularly using hand sanitizer, considering wearing gloves and avoiding unnecessary contact with surfaces.
The best precautions
The potential areas of risk outlined here are by no means limited to mass transit. People occupying any kind of crowded, or ill-ventilated spaces, especially for longer periods of time, would be just as vulnerable to infection — meaning that trains or buses are not inherently less safe than, say, offices or stores.
The primary difference with mass transit is that you may face a greater challenge maintaining enough distance from others. Even if you get on a relatively empty train, you may find that a crowd enters at a subsequent stop. So what can you do if you still have to ride? The advice here will sound familiar: Wear a mask, keep your distance and don’t touch your face.
Tang recommends staying in a place that offers good air flow: “If I have to take a train,” he says, “I personally choose to sit in a place close to the door, as there is a more regular exchange of air there.” Ciric, meanwhile, advises wearing some protective gear, and avoiding unnecessary trips altogether. And if there is a portion of your trip that you can take outside by walking or biking, Ciric suggests doing that rather than getting on multiple trains or buses in the course of your journey.
“If I had to get into London by public transport right now, I’d probably avoid getting the bus [the short distance] to my local station. Once there, I’d definitely wait for a train that’s less busy, and I’d think about changing hours to miss the rush. I’d wear a mask and maybe wear gloves while on the train, and when I got to my destination, I’d give my hands a really good clean.”
Depending where you live, some of these precautions may be partially baked into city policies. Milan, for example, plans to stagger the times of some functions like schools and stores in the hope of reducing rush-hour crowds. Many places are adding more bike lanes and closing streets to cars so more people have the option to walk. And New York has ordered rider capacity limits on trains to reduce crowding. Many transit authorities are also giving passengers visual guidelines to maintain social distancing, requiring masks, and reducing contact between passengers and drivers by making public transit free.
And while only a few airlines — notably Air India for repatriation flights — have gone as far as leaving middle seats empty to facilitate social distancing, Airbus is now recommending that airplanes start their ventilation systems before passengers board, so that air exchange is already up and running by the time they enter the craft.
It’s sensible to make yourself as aware as possible of the safety measures adopted by your transit provider — safety measures that may still change in the near future, as transit authorities introduce new measures. And if you can avoid traveling at peak times, you’ll not only be helping yourself. You could be making more space for essential workers, who don’t have the luxury of opting for a less-crowded time.