According to a report commissioned by the American Public Transportation Association (APTA) and published September 2020, no outbreaks of COVID-19 cases clearly linked to intracity public transit such as city buses and subways were found. 

This means that there is minimal risk to using public transportation as long as specific preventive measures are enforced. These measures include but are not limited to social distancing, wearing face coverings, cleaning and disinfecting, proper ventilation, and encouraging minimal talk among passengers.

Even though studies show that there is a low probability of COVID-19 transmission through public transportation, public transit agencies should continue reviewing their policies and procedures in response to the COVID-19 health crisis.

You can also help reduce the spread of COVID-19 by practicing good personal hygiene as the first defense against contracting COVID-19, staying home as much as possible, and minimizing your travel and participation in social gatherings.

Source: American Public Transportation Association