FRESNO, Calif. (KSEE/KGPE) — A team of researchers and transit industry professionals led by Fresno State’s Transportation Institute released its findings Wednesday on ways to reduce the spread of COVID-19 and other airborne viruses on modes of public transit.
The team used five buses to study airflow, including diesel, compressed natural gas, and electric-powered vehicles, and tested different virus mitigation technologies in the lab and on the buses, said Rebecca Wass, from the Lyles College of Engineering. They found several efficient and economically viable solutions that can enhance passenger safety and help public transit rebound from the challenges presented by a global pandemic.
Virus mitigation solutions for public transit include:
- Photocatalytic oxidation inserts: This air purification technology has the ability to destroy very small particles, and it eliminated more than 99% of all viruses that entered the HVAC system during testing.
- UV-C light: This form of ultraviolet light eliminated almost 98% of all viruses that entered the HVAC system during testing.
- Positive pressure environment: Maintaining a higher pressure within the bus than exists outside the bus eliminated 100% of viruses found on surfaces during testing.
- Copper tape and fabric: Copper foil tape, as well as fabrics with higher copper percentages, eliminated one virus found on surfaces by 99.7%. However, the results were inconclusive with the other two viruses tested.
Researchers found that the technologies would not only protect passengers and drivers from the coronavirus, but also other airborne viruses like the flu.
The study also found that social distancing on its own may not be effective in buses as a virus can spread throughout the entire bus within seconds of being released.
While retrofitting buses with accessible and affordable materials can be efficient, the Transportation Institute’s director said face masks are still the first line of defense against the spread of COVID-19.
“Face masks are extremely important because these technologies will only clear the air after the virus reaches the HVAC,” said Dr. Aly Tawfik. “These technologies will not only help protect passengers and drivers from the coronavirus, but also from other airborne viruses, such as the flu. So, they would be valuable even in post-corona times.”
At the beginning of the coronavirus pandemic, ridership fell significantly across the country’s public transit systems, according to a Congressional report published in March.
Even when transit runs at full capacity, it doesn’t make a profit.
“Transit is sometimes 80% or 90% subsidized, and if you cut this by another half, transit agencies cannot continue to operate with such huge losses,” Tawfik said.
Tawfik added despite falling ridership, many people — including essential workers — rely on public transit but many chose not to ride, fearing for their safety and health. Because of this, the team wanted to do something to help passengers and drivers.
To get their results, the research team used non-toxic colored candles, steam and computer models to simulate the movement of airflow and airborne contamination.
Tawfik and the team found that under normal cooling conditions, viruses are reduced up to 85% and that public transportation may be safer in the winter since higher HVAC heating temperatures alone mitigate a large percentage of viruses. They found this possible due to two factors: heat mitigating the virus, and by drying out the aerosol particles to which the viruses can attach.
The full published peer-reviewed report will be available in January. Tawfik said the team is also pursuing additional research grant opportunities to test the long-term efficiency of virus mitigation.