Air Quality Inside Buses

The COVID-19 pandemic brought air quality to the forefront of the transit industry. In the summer of 2022, due to the immediate need to understand the issue, the Transit Cooperative Research Program (TCRP) conducted its first Insight Event. TCRP Insight Event--Air Quality in Transit Buses explored how air quality inside transit vehicles, especially buses, may contribute to the spread of infections. During that event, presentations and conversations about dispersion, ventilation, circulation, and filtration issues were held. Presentations from the event and the literature search results are available on the TCRP Insight Event web page at Since that event and the end of the pandemic’s restrictions, the public transit industry has learned that air quality inside transit buses matters to bus operators and passengers. There is an increased focus on reducing the concentration of pathogens containing respiratory aerosols and other harmful pollutants in the air inside a bus cabin. Transit agencies are working to increase operators and passenger confidence in air quality. With increased confidence, riders will return, and it will be easier to hire bus operators. Transit systems are analyzing the current air quality inside their buses to better understand current airflows and possible risks. Measuring and controlling air quality inside the bus cabin has proven difficult. Buses idle, constantly open their doors to embark or disembark passengers, and are exposed to traffic-related air pollutants, such as exhaust. This reality has not hampered the desire to improve air quality inside cabins. Transit agencies are employing the following solutions to mitigate poor air quality: dilution, which consists of bringing more fresh air inside the bus while sending indoor air out; filtration with the use of better-quality filters; and cleaning, including the use of ultraviolet light and photocatalytic oxidation. Research is needed to find clear solutions to improve air quality on buses for operators and passengers. Transit systems are doing the best that they can to protect their employees and passengers. However, research can provide information to improve air quality and standardization of practice. The objective of this research is to create a research document that helps transit agencies understand air circulation inside a typical 40-foot heavy-duty transit bus and finds solutions to protect employees and passengers without decreasing passenger comfort, safety, and reliability of the system. The research should help guide the development of future design and performance criteria to support better transit rolling stock procurement and heating, ventilation, and air conditioning (HVAC) operations in emergency conditions (e.g., airborne diseases and wildfires).


  • English


  • Status: Active
  • Funding: $150000
  • Contract Numbers:

    Project E-15

  • Sponsor Organizations:

    Transit Cooperative Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC    20001

    Federal Transit Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Garcia-Colberg, Mariela

  • Performing Organizations:

    University of Maryland, College Park

    College Park, MD  United States  20742
  • Principal Investigators:

    Srebric, Jelena

  • Start Date: 20240528
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01879056
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project E-15
  • Files: TRB, RIP
  • Created Date: Apr 10 2023 5:08PM