Virus Transmission Aboard a Transit Bus

Abstract Unsteady numerical simulations of virus transport released from an infectious passenger aboard a transit bus have been investigated. The goal of the investigation was to explore methods for controlling the spread of a virus or any contaminants aboard a public transportation system for improving public health. The virus was modeled as a 2.5 μm round solid particle released from the mouth of the infectious passenger at a rate of 21 particles per second at a mouth velocity of 0.278 m/sec. The air delivery to the cabin was two linear ceiling slots spanning the length of the bus delivering 59.38 m3/min (2,097 CFM) of air at a mean velocity of 1 m/sec. Axial linear exhaust slots placed on the side walls have been investigated to contain and prevent the spread of the virus to the other parts of the cabin. Simulations were performed for both cases of the bus in transit and at the bus stop when the drop-off door was opened. Results indicate during the transit, virus spread was contained to passengers sitting in immediate front and behind the infectious passenger and the level of virus concentration could merit an increased risk of infection with increased virus residence time. However, augmented air mixing was observed between inside and outside air during the passenger drop-off with viruses spread to the front and back of the bus with reduced concentration and risk of infection. Analytical analyses of the risk of infection using the Wells-Riley equation have shown that with axial slots, the viruses are contained around the infectious but with the increased concentration, the risk of infection for these passengers is increased.