Mitigating Exposure to Airborne Diseases for Public Transportation Passengers and Employees: Executive Summary (2024)
Chapter: Research Methodology
Introduction
The COVID-19 pandemic increased awareness of airborne contagions and the importance of advanced air control systems and measures, which can lower the risk of transmission of airborne diseases. Public transportation vehicles, particularly buses, can be high-risk environments for (1) passengers who cannot socially distance themselves and are contained within a volume of air that may carry infectious diseases, and (2) transportation employees who are vulnerable to airborne contagion in their work environment inside a bus, putting both groups at an increased risk of infection. This research was conducted to increase awareness of effective measures to reduce airborne infections to help transportation agencies, especially transit agencies, safeguard the health and welfare of their employees and the public who use their services.
This research was a joint project of the Transit Cooperative Research Program (TCRP) and the National Cooperative Highway Research Program (NCHRP). The research team developed a guide for public transportation agencies and departments of transportation on how to mitigate exposure to airborne diseases to protect the health and well-being of transportation system employees while at work and the traveling public. The primary audience for this research includes public transportation agencies (i.e., agencies that provide bus, rail, ferry, and paratransit services), departments of transportation, and practitioners.
Research Methodology
This project included the following research methods: a literature review, bus experiments computational models, and closed box modeling.
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Literature review. A literature review was conducted to examine strategies for reducing contagion on public transportation vehicles. The review focused on the following mitigation measures:
- dilution by ventilation,
- use of personal protective equipment (PPE) and masks,
- surface cleaning,
- cabin air filtration, and
- installation of Plexiglas® barriers.
The literature review also considered exposure and infection rates in buses, trains, and airplanes, as well as aircraft ventilation systems, which are known to provide a highly protected cabin environment. The synthesized results present mitigation strategies to improve current practices and provide suggestions for implementation.
- Bus experiments. Two public transit buses were obtained for experimentation. The buses were chosen based on their availability and not by their specifications. Bus A was a 2002 40-foot vehicle used to conduct stationary tests and Bus B was a 2008 45-foot vehicle used for stationary and on-road tests. To create COVID-like particles, a modified humidifying device called an aerosol generator was designed and manufactured to
