The countdown has begun toward U.S. rules that will require workers at businesses with more than 100 employees to be vaccinated against Covid-19 or be tested on a weekly basis.

The mandate, scheduled to be published in the U.S. Federal Register on Friday, will take effect Jan. 4.

Despite intense lobbying efforts, and predictions that many truck drivers will quit if facing such a mandate, trucking operations are not explicitly exempt.

But the American Trucking Associations (ATA) sees one exemption that could apply.

“The rule does exempt employees who work 100% alone or outdoors, so long as their indoor contact with other employees or customers is minimal,” ATA CEO Chris Spear said in a related update. “In our view, that exemption covers much of the commercial driver population — but as with any complex new rule, it is impossible to be certain how OSHA [Occupational Safety and Health Administration] will apply it until they issue guidance or begin enforcement.”

The group is asking regulators whether that exemption could apply to commercial drivers.

The ATA previously warned that affected carriers could lose 74% of their unvaccinated employees or 34% of their driving workforces as unvaccinated truckers opt to leave for smaller carriers, retire, or resign.

The association has also referred to Canadian rules in arguing against the mandate. Here in Canada, federally regulated trucking companies are not included in a mandate that requires air, rail, and marine employers to establish vaccination policies.

Unvaccinated workers at the affected businesses in the U.S. will need to begin wearing masks Dec. 4 and provide a negative Covid test on weekly basis after the January deadline. But companies will not need to pay for tests unless required by state laws. They’ll have until Dec. 5 to offer paid time off for employees to receive the vaccine and recover from any side effects.

The Truckload Carriers Associations (TCA) has already expressed its “dismay” about the ruling.

“TCA repeatedly called on the administration to heed our warnings regarding this mandate’s impact on the already constrained supply chain, yet they chose to proceed with a disastrous mandate which will undoubtedly ensure the trucking industry loses a substantial number of drivers,” the association said in a statement released Wednesday morning.

“President [Joe] Biden cannot call on trucking to ‘work harder’ when his policies are cutting us off at the knees and depriving us of the workforce we need.”

The TCA referred to efforts by businesses, non-profit groups, and a dozen state governors to file lawsuits against the mandate.

It isn’t the only U.S. mandate that will affect truckers. Border-bound truck drivers will need to prove they’re double-vaccinated by this January. Assuming that Canadian border officials would respond with a similar mandate, the Canadian Trucking Alliance estimates that 38,000 truck drivers could walk away from border-crossing work because of it.

About 120,000 Canadian truck drivers are involved in cross-border work, while 40,000 U.S.-licensed truck drivers do the same.

• This article has been updated to include ATA commentary on exemptions for employees who work 100% alone or outdoors.