Apart from the obvious precautions, what can you do to reduce your risk of catching or spreading the coronavirus on public transport?

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On the London Underground, the smartest commuters know hidden tricks to get from A to B. In the walking tunnels between station platforms, for example, non-signposted routes can offer shortcuts. And if you pick certain carriages, they’ll deposit you exactly by the platform exit at your destination so you can zip ahead of the crowds.

Navigating public transport during the pandemic, however, is something that even the most experienced commuter has never faced before. Getting around quickly now feels much less important than getting around safely.

During the pandemic, public transport usage has plummeted. In London, buses in late ypical for this time of year, and the Tube carried only a third. But as lockdowns lift and offices reopen for many nations, many commuters are tentatively returning to trains, buses and subways.

So, how might a savvy passenger reduce their risk? There are of course essential things you should do – wear a mask, avoid rush hours if you can, and follow physical distancing guidance in stations and onboard. Following local public health advice is the most important thing, and will reduce your risk significantly. 

But there are also less obvious measures that are worth knowing. Insights from transport research and passenger psychology can provide clues – as well as pointing to changes in how we will get around in the months ahead.

Ventilation and airflow matters

With a respiratory disease like Covid-19, the more people breathing, coughing and talking into the same air as you in a confined space, the more chance there is of being infected by the virus.

If you can cycle, walk or ride a scooter outside to get to work, that’s your best option as there is more space to keep your distance from others.

Cars are obviously personally safer too, provided you stick to travelling with those in your own household. But if everyone drives it will lead to a “tragedy of the commons” effect of more traffic, and greater environmental cost, so it’s difficult to recommend as a socially responsible choice. “Cars are very inefficient in using the urban infrastructure. If we all move in a car, nobody moves,” says Carlo Ratti, director of the Senseable City Lab at MIT in Cambridge, Massachusetts.

If travelling by train, bus and subway, one factor to consider when plotting your route is how well your method of transport is ventilated, according to Nick Tyler, a transport researcher at University College London, who has modelled the way that the virus propagates through buses. “Outside, in the open air, droplets are dissipated in the air and the wind,” he explains. “Once we're inside, you get much less movement.”

Designs differ, but the more windows the better. For this reason, a deep subway is more difficult to ventilate than a train or bus at the surface. According to a 2018 study by Lara Gosce at University College London, people who used the London underground regularly were more likely to suffer flu-like symptoms than those that didn’t.

Generally, public transport ventilation systems are less effective than those on aeroplanes. The air in planes is recirculated through sophisticated HEPA (High Efficiency Particulate Air) filters every few minutes, which should screen out most viral particles. “Aircraft ventilation gets a very bad press in many ways. It’s actually one of the best systems you can find,” says Tyler. And unlike many trains and buses, the air flow travels directly from the ceiling to the floor. This means that droplets will be pushed to the ground, away from hands and faces, more rapidly.

A New York subway car, by contrast, pushes air horizontally, and uses filters with a lower performance than planes, rated seven out of a scale of 20 in terms of screening efficiency. (You can dive deeper into the technical specs of filters in this interactive guide to the ventilation system on the NYC subway, which also shows the path of viral particles through the carriage.)

Silence is golden

When assessing your chosen form of transport, it is worth considering how much talking goes on inside – and how loudly.

Noisy environments, where people must lean in and shout to be heard, are higher risk than quieter spaces. It’s thought to be one of the reasons why nightclubs, bars or meat-packing plants have experienced high levels of contagion.

So, a cacophonous train carriage with singing sports fans would therefore pose more risk than a bus of silent commuters reading their phones.

This diagram, recently published by researchers in the BMJ, captures these relative risks: