How to Make Car Trips Safer During the Pandemic

Research offers tips to reduce COVID-19 exposure risk for drivers and passengers

AVDEEV ALEKSEI/GETTY IMAGES

By:

Peter Urban,

AARP

En español

Published January 29, 2021

To protect yourself and slow the spread of COVID-19, the Centers for Disease Control and Prevention (CDC) advises that whenever possible, avoid car trips with anyone outside your immediate household. But when it can't be avoided, you can reduce your potential exposure to coronavirus, according to scientists.

The coronavirus is thought to spread mainly through respiratory droplets when infected people exhale, cough or sneeze — this includes the estimated 40 percent of those who are asymptomatic, meaning they are infectious but never develop symptoms of the illness. Avoiding those respiratory droplets is the key to stopping the virus's spread. That's why the CDC and Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases, recommend that you mask up, maintain a social distance from others and avoid crowded indoor spaces.

Not surprisingly, traveling by car can be risky. The confined space inside a typical four-door sedan doesn't allow for proper social distancing, and the ventilation system is inadequate. Researchers have found that a viral load capable of infecting others can build up within a 15-minute drive and that respiratory droplets can remain for up to three hours.

Roll down the windows

The simplest solution is to roll down all the windows, which the CDC advises. But that's not always an option in bad weather.

However, a group of researchers in New England have published a new study in Science Advances that explores ways to strategically open car windows to remove infectious droplets. With a Toyota Prius exterior and Kia Forte cabin as models, the researchers used computer simulations to study air flow inside a car driven at 50 miles per hour with windows open or closed.

They found that keeping all the windows up did the poorest job of refreshing the air — providing the lowest rate of air change per hour (ACH): 62. Having all the windows open provided the highest rate: approximately 250 ACH.

The researchers also observed how the air moves through the cabin of a moving vehicle when various windows are open or closed and, more important, how that airflow may affect passengers’ exposure to virus-laden droplets.

"One might imagine that people instinctively open windows right beside them while riding with a co-passenger during the pandemic. That may not be optimal,” Varghese Mathai, an assistant professor of physics at the University of Massachusetts Amherst, said in a statement.

Diagram showing airflow in a car with windows open

Air flows in a car when the front right and rear left windows are open.

American Association for the Advancement of Science

In that configuration, with the passenger sitting in the rear seat farthest from the driver, air flows from the open rear passenger window to the open front driver's-side window, creating a clockwise recirculating flow of air within the cabin that could increase the transport of droplets from driver to passenger.

Or go on the diagonal

The better option is to do the opposite: Open the window directly behind the driver and the front passenger's-side window. In that configuration the counterclockwise airflow separates the driver and passenger, limiting the chance for droplets to move between them. See the graphic of air flows above at right.

"To our surprise, the simulations showed an air current that acts like a barrier between the driver and the passenger,” Mathai said. “While these measures are no substitute for wearing a face mask while inside a car, they can help reduce the pathogen load inside the very confined space of a car cabin."

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