Exposure Risk On Different Modes of Transportation-01

Travel During Covid-19: Exposure Risk On Different Modes of Transportation

Many of us are itching to get back to traveling. It’s been a long year of canceled, postponed, or never-planned vacations, family visits, get-togethers, and other occasions that normally would’ve called for socialization and celebration but had to be reconsidered to help curb the number of infections during the pandemic.

While most of us have been doing everything in our power to continue to help curb the spread of Covid-19, many have been gradually shifting from sheltering in place to adapting to life with the virus still around us, even as we all anxiously await our turn in line for the vaccine shot(s). While current travel rates are still at less than half of their pre-pandemic levels, people are certainly traveling, or thinking about travel. A recent study conducted by the home rental company Vrbo found that 82% of families have travel plans in mind for 2021 (based on 8,000+ people surveyed from 8 countries).

Keep in mind, the CDC warns that “travel can increase your chance of both spreading and getting Covid-19.” However, if you still choose to or need to travel, read on to better understand the risk profiles of different modes of transportation.


1. Planes

  • As noted by the CDC, “most viruses and other germs do not spread easily on flights because of how air is circulated and filtered on planes,” making them among the safest options when it comes to infection risk. That’s because they’re equipped with HEPA filters, which remove over 99% of airborne particles, and also because they have a high ventilation rate of 20-30 air changes per hour, which mixes outdoor and recirculated air at a 50/50 ratio. That said, you should still absolutely wear a mask for the duration of your flight – only taking it off to eat or drink – and if you’re sitting next to someone you don’t know, you may want to stagger your eating breaks so that your masks aren’t off at the same time.
  • Other things to take into consideration when planning to travel by plane are whether masks are mandatory (and enforced) by the airline of your choice, how close you’ll be sitting to others (some airlines block the middle seat, some don’t), the duration of the flight, the mode of transportation you’ll be using to get to the airport, and how crowded your departure and arrival airports might be at the time of travel. Maintain distance as much as possible at check-in, security and boarding lines, as those usually are the most crowded areas of the airport.
  • According to preliminary research, the risk of infection based on a simulation of a 2-hour full flight in coach is about 1 in 3,900, and about 1 in 6,400 when the middle seats are kept empty (based on data from late September 2020).

2. Trains and Subways

  • Depending on trip duration, trains and subways might be riskier options than planes, as they usually only use MERV (minimum efficiency reporting value), and not HEPA filters. Lower-rated MERV filters are often used, typically less than 13, which is the minimum recommended MERV filter rating for filtering particles the size of viruses; however, even lower-rated MERV filters can help to reduce the number of viral particles in the air.
  • In addition, air on trains is replaced less frequently than on planes, at a rate of about 12-15 air changes per hour, and is also replaced less frequently on subways, at about 18 air changes per hour. Some trains might also have windows that open, although that is rare.
  • Outdoor train stations that allow people to socially distance also help reduce the risk of transmission.
  • Other considerations when traveling by train or subway: Similar to the considerations on planes, it is important to note whether masks are mandatory (and enforced), how close you might be sitting to others (some trains don’t have middle seats, leaving more room between people), and the duration of the trip. A subway ride is likely to be shorter than a train or plane ride – however, while risk generally increases the longer you are around a potentially infected person within 6 feet, there is no hard and fast rule about this, so it’s important you take every precaution available, and choose shorter travel durations whenever possible.

3. Buses

  • Similar to trains and subways, buses rely on MERV filters to clean their recirculated air. However, the filters used on buses are often lower-rated than MERV 13 (the minimum recommended MERV filter rating for filtering particles the size of viruses).
  • In addition, ventilation is poorer on buses compared to planes and trains; some buses have ceiling vents or operable windows, but not all. One advantage of city buses that make frequent stops on their route is that fresh air comes in every time the doors open, thus helping dilute the concentration of potentially infectious particles.
  • Other considerations when traveling by bus: similar to when traveling by plane or train, it is important to note whether masks are mandatory (and enforced), how close you’re sitting to others, and the duration of the ride – which may or may not be shorter than a plane or train ride, especially for routes outside of a city. If possible, choose a seat near a window that opens, and sit further away from other passengers.

4. Cars

  • Cars are not usually equipped with air filters that filter particles as small as viruses. However, all cars have operable windows that can be used for ventilation, and most have air circulation systems that can be set to primarily take in outside air. Traveling by car as a single family can be a relatively safe option, assuming that all necessary precautions are taken when stopping at gas stations and rest stops, which may be crowded both indoors and outside.
  • However, when using ride-share services, additional precautions such as mask use, social distancing (e.g., sitting in the back seat instead of the front seat – now mandatory on both Uber and Lyft), opening windows, and plastic shields between the driver and passengers can offer some additional safety. Limiting talking can also help reduce risk, as talking (especially if talking loudly) emits more particles than simply breathing. These rideshare precautions also apply if you’re traveling in a car with people outside your household. One key advantage of rideshare programs is the duration of the trip, which usually tends to be relatively short compared to other modes of transit, especially in cities.

5. All Modes of Transportation

  • If possible, try to book a trip that is direct; avoid switching between different modes of transportation and/or reduce the number of transfers, as they might increase your likelihood of coming into contact with more individuals in crowded environments.
  • Choose an off-peak time to travel, if feasible, to travel with fewer passengers around and to help reduce the chance of crowded waiting areas and long lines.

This article is the second in a three-part series on travel during the Covid-19 pandemic, and we hope the information will help you decide which mode of transportation is best suited for you, and what precautions to follow while en route. Our third installment in this series will provide helpful tips on how to stay healthy while you travel.


Edited by: Bing Bing Guo, MPH and Radhika Singh