Are you likely to catch COVID while riding the subway? Study after study has concluded that you aren’t. And a new one published last week by researchers at NYU’s Rudin Center for Transportation Policy and Management argues that transit is not a vector for outbreaks of respiratory disease; moreover, it may even be safer than other activities conducted in public, in part because of the way people behave when they’re on the subway.
Although several studies conducted in other countries have examined the relationship between COVID transmission and transit ridership, efforts to understand whether the virus is spreading this way in U.S. systems have been more limited. No city uses a contact-tracing method robust enough to tackle such a complex task with case numbers still so high. So instead of looking specifically at COVID-19 data, the NYU team used a well-documented proxy for respiratory-infection prevalence: the CDC’s data set for influenza, one of the most meticulously studied diseases in the U.S. In 121 cities over a nine-year period, there was no correlation between transit ridership and the number of influenza deaths — and New York City, with the highest transit ridership rates, had the lowest flu mortality rates of all the cities. “We now have a great body of evidence on flu transmission,” says Mitchell Moss, NYU urban policy and planning professor and one of the study’s co-authors. “There is no relationship between the use of transit and flu deaths.”
Moss notes that the study is not an epidemiological survey in that it does not assess if influenza rates are higher for people who ride public transit compared to people who don’t. Indeed, that’s exactly the kind of information you’d need to rule out transit-based disease transmission, says Dr. David W. Dowdy, associate professor of infectious disease epidemiology at the Johns Hopkins Bloomberg School of Public Health. “You’d want to look at individual people and see if the ones who are riding public transport are getting the flu more often,” says Dowdy. “I would not take this study as strong evidence that public transport is not associated with disease transmission.” However, he’s quick to add, there have been plenty of other studies done on just that, and “in general the weight of evidence suggests that ridership on public transport is not an overwhelming driver.” Paris’s health department could trace only four clusters out of nearly 400 outbreaks to any form of transportation; Japan has had no clusters linked to transit at all.
That may be, in part, because a train or bus ride is a different experience from other indoor situations. Even though you’re in close quarters with other people, the filtration system in a subway car completely refreshes the air every three minutes (remember those gross animations of people sneezing?). And most transit trips are too short for the sustained exposure required for transmission. “People don’t spend a tremendously long time on transit, for the most part,” says Dowdy. “They hop on the subway, and for that ten minutes a lot of people have their antennae up about possible transmission.” And here’s where years of engrained subway-riding behavior — looking down at books or screens, being hyperaware of your body positioning — can help protect New Yorkers even more, argues Moss. “The typical New York subway rider doesn’t interact with other riders,” he says. “There’s a culture of avoiding eye contact. This is not where people are scheming to meet.” The masks help a lot, too. A study of bus riders in China looked at passengers who traveled with a COVID-19 positive man on two longer bus trips on the same day, one when he wore a mask and one where he didn’t: 5 out of 39 passengers were infected on the unmasked ride, but none of the 14 passengers were infected when he was masked. In Moss’s anecdotal observations, mask compliance has been near universal on subways; MTA data say 90 percent.
Now that surface transmission is not seen as a major factor for spreading COVID, making transit safe is really about avoiding overcrowding. “For something like transit where the risk is on the lower side, I’m not going to say that you shouldn’t do it,” Dowdy says. “But to the extent that people could avoid crowded buses and trains, I think they should.” That’s the advice most riders will likely be following until they feel more comfortable climbing into an enclosed space with a few dozen of their fellow New Yorkers. It’s also what’s clobbering the system’s finances. Ridership is currently 70 percent below pre-pandemic levels, and the MTA is facing budget cuts that would slash service by 40 percent, partially due to the loss in fare revenue. While Dowdy suggests running more train cars to give passengers more space to distance, that’s not a possibility for the MTA since stations aren’t long enough to accommodate longer trains. But running more frequent buses above ground could definitely help. Mayor Bill de Blasio promised 20 miles of dedicated busways at the beginning of the pandemic, but as of this week, only 0.8 miles have been built. Moss suggests another change to further reduce interaction that could make subway cars safer, and might even be popular long after the pandemic: ban talking.