A new federal order requiring masks at airports and aboard trains and buses creates a layer of protection for federal safety screeners while putting added pressure on transit drivers and operators on the front lines to enforce the mandate, transit officials say.

Across the Washington region, airports and transportation agencies have required passengers to wear face coverings for months, enforcing those rules to varying degrees. The new Centers for Disease Control and Prevention order, effective at 11:59 p.m. Monday, requires a new level of enforcement, telling drivers and operators to act as gatekeepers, denying entry to riders who try to board without their faces shielded.

The order states passengers must wear masks “while boarding, disembarking, and traveling on any conveyance into or within the United States,” as well as “at any transportation hub that provides transportation within the United States.” People with disabilities who cannot wear masks are exempt, and face coverings can be removed while eating, drinking, taking medication and going through security screenings.

It’s an increased responsibility that will fall on the shoulders of transit operators who already have reported increasing verbal and occasional physical attacks as they fear for their own health and well-being.

The Amalgamated Transit Union, North America’s largest transportation workers guild, said while officials welcomed the public health order, enforcing it cannot be left solely to operators.

“Public transportation providers need to immediately begin working with front line workers and their unions in order to develop practical and effective protocols for dealing with passengers who refuse to wear masks as mandated by the directive,” ATU International President John Costa said in a statement.

At airports, warnings and reprimands to passengers who refuse to comply with federal security screeners gained teeth with the order.

The Transportation Security Administration has asked travelers to wear masks when moving through security checkpoints, but President Biden’s order will give the agency new authority. TSA officers can bar people who refuse to wear a mask from entering secure areas of the airport. Those who refuse to comply could also face civil fines.

Before the order, enforcement of mask policies was largely left to individual airports and airlines. The TSA began requiring front-line workers to wear masks in May, shortly after airlines put mask policies in place for passengers and crew members. While the TSA recommended that travelers wear masks as they moved through checkpoints, the agency did not mandate it.

Washington Dulles International, Reagan National and Baltimore-Washington International Marshall airports have required people to wear masks since summer. Enforcement measures, however, vary.

Travelers at New York’s LaGuardia, John F. Kennedy International and Newark Liberty airports who refuse to wear a mask could face a $50 fine. But the Port Authority of New York and New Jersey, which manages the airports, has issued only eight tickets. Most airports, including Dulles and National, have relied on voluntary compliance.

On the rails, Metro said it has been successful in getting riders to comply with a mask order approved in May. Still, officials often field calls from upset passengers who see rule-breakers.

The transit agency’s board last week heard comments from riders who urged Metro to do more to enforce its policy.

“I know that you share a lot of information about using face masks in an effort to prevent covid-19,” rider Kevin Gonzalez said to the board. “But I do see many people get in the system without a face mask. And the driver says nothing.”

Metro’s face-covering policy came soon after high-profile incidents in Philadelphia and New York that involved physical confrontations between maskless passengers and transit officers. Metro General Manager Paul J. Wiedefeld had said he hoped to avoid such clashes when he decided Metro’s rule would not be strictly enforced.

Metro counts on riders to feel obligated to wear masks for themselves and the “community.” Metro Transit Police can intervene, although officers have been given masks to carry to defuse tense situations. Masks also are available at stations.

Metro Chief Safety Officer Theresa M. Impastato said last week that Metro is working with federal and local leaders “to ensure that our existing efforts to require masks throughout the system are aligned with this new order.” She said Metro looked forward to “enhanced compliance of our passengers and occupants of the system.”

Asked to clarify Metro’s stance on enforcement, Wiedefield told board members the transit agency’s policy on enforcement remains largely unchanged.

“We do not have our operators confront customers,” he said. “If they feel that they’re unsafe, they can stop the bus. They don’t need to have people board if they’re not wearing masks. They basically can call the police to deal with specific issues, but similar to fare evasion issues, our experience has been that that elevates to other issues very quickly.”

The federal order states that operators “must use best efforts” to make sure riders are wearing masks. The order also notes that enforcement ultimately falls to “federal authorities” and “cooperating state and local authorities.”

“We welcome any policy that further promotes compliance on Metro and in all public spaces to combat the spread of the virus and welcome the ability of TSA and other federal authorities to enforce this mandate when appropriate,” Metro spokeswoman Sherri Ly said in an email Monday.

Transit advocates welcomed the backing of a presidential order to push mask usage. Some systems already have stepped up outreach in the form of announcements to get the message across to riders that the policy is a federal mandate.

The American Public Transportation Association said the order will help re-instill “confidence in our shared public spaces.”

In Montgomery County, Ride On drivers are being encouraged to use the public announcement system aboard buses to remind riders of the face-covering policy and to ensure passengers are familiar and compliant with the rule.

Hannah Henn, a county transportation department spokeswoman, said drivers are reminded that “they are empowered and expected to observe mask-wearing and take action to promote compliance, including providing masks to passengers and suspending service if passengers refuse to comply.”

In Virginia, under an executive order from Gov. Ralph Northam (D), facial coverings already are required aboard buses and Virginia Railway Express stations and rail cars. VRE said the agency does not expect changes to enforcement, in which conductors request compliance from any passenger not wearing a facial covering.

VRE spokeswoman Karen Finucan Clarkson said the system has close to 100 percent compliance.

The only penalty for noncompliance is denying a ride to the noncompliant passenger, Maryland and Virginia officials said. In D.C., a mask requirement on public transit allows for violators to be fined as much as $1,000.

In Arlington, ART bus passengers are offered a face mask if they do not have one.

“The operator will notify the passenger they must board the bus with a face mask and will contact dispatch if issues arise,” county spokesman Eric Balliet said. “These procedures will continue once the new CDC mask mandate is in place.”

Maryland Gov. Larry Hogan (R) issued a statewide order requiring face coverings on public transportation on April 18. The Maryland Transit Administration already has enforcement measures similar to those required in the federal order.

“If a rider is not wearing a face covering, the rider will not be allowed to board the bus or train,” said Veronica Battisti, an MTA spokeswoman. “If a rider is not wearing a face covering while on a MARC train, a conductor requests them to put on a face covering. If they do not comply, the rider is then asked to exit the train at the next station.”

Amtrak, which in May began requiring passengers to wear masks, updated its messaging to indicate that the requirement is now federal law. Passengers are told about the mask policy when they purchase a ticket, in reminders before arriving, when they are at the station and onboard.

“Onboard personnel, including conductors, are the first line of enforcement,” Amtrak spokeswoman Christina Leeds said. “Should assistance be needed in gaining compliance, Amtrak Police and local authorities may be contacted to assist.”

The new directive gives Amtrak a mechanism for identifying those who violate the rule, Leeds said. She said the railroad can report security issues, including mask policy violators, to the TSA for further investigation and potential civil fines.