The Center for Disease Control and Prevention (CDC) in the U.S. has issued a mandatory mask order on public transportation systems including, rail, and van, bus and motorcoach service providers, but the Order exempts commercial motor vehicles if a truck driver is the sole occupant of the vehicle.
The Order also clarifies that the mask requirement becomes mandatory for a truck driver once they enter a transportation hub such as a port.
More information about this Order can be found on the CDC’s website, which also includes CDC’s FAQ’s for conveyances and transportation hubs which can be found here.