Anxieties take all shapes and forms during a pandemic--could I contract the virus in a cab, why do the police insist on masks inside cabs? Is it safe to travel in a car? Can we carpool or use Uber Pool in the near future? Where do I sit to cut the risk of transmission in a cab?
A new study, 'Airflows inside passenger cars and implications for airborne disease transmission', published on 1 January in Science Advances might have answers to some of these questions. Four scientists recreated a variety of situations in a passenger car--windows open, windows closed, partially open, and more--and mapped how airborne particles, such as aerosols that help spread the covid-19 virus, move through the cabin of a car. How the air flows through the cabin of a car essentially is responsible for whether the passengers are at risk of contracting the virus or not. The speed at which the car is travelling when the windows are open also matters.
"An airflow pattern that travels across the cabin, farthest from the occupants, can potentially reduce the transmission risk," the authors write. The findings reveal the complex fluid dynamics at play during everyday commutes and the ways in which open windows can either increase or suppress airborne transmission.
This is research that's relevant at the moment because the covid-19 virus has changed every human interaction and how we commute, and travel in passenger cars, has implications for everything from road congestion to urban air pollution.
"For maximum social isolation, driving alone is clearly ideal, but this is not widely practical or environmentally sustainable, and there are many situations in which two or more people need to drive together, the authors note. Wearing face masks and using barrier shields (think Uber's plastic sheets around the driver's seat) to separate occupants are an effective first step toward reducing infection rates. "However, aerosols can pass through all but the most high-performance filters, and virus emissions via micrometer-sized aerosols associated with breathing and talking, let alone coughing and sneezing, are practically unavoidable," they write.
As expected, it's best to have all windows open, which allows for good cross-ventilation, but that's a bit hard when it's 3 degrees Celsius or the other extreme, 45 degrees Celsius.
With all windows open, "establishes two distinct airflow paths within the car cabin, which help to isolate the left and right sides, and maximizes the (air flow) in the passenger cabin"
So what's the best place to sit in a cab? If it's just you and the driver, most likely diagonally from the driver with the two windows farthrest from each occupant cranked open enough to let the air circulate "appears to give better protection to the passenger. The particular airflow patterns that the pressure distributions establish—channeling fresh air across the rear seat and out the far right window—help to minimize the interaction with the driver in the front left position."
Think you already knew that? Maybe but here's the science to back it, and as the authors say "these results will have a strong bearing on infection mitigation measures for the hundreds of millions of people driving in passenger cars and taxis worldwide and potentially yield safer and lower-risk approaches to personal transportation."