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Updated 2:45 p.m. Friday, July 29

The BART board of directors approved a resolution Thursday night reinstating a mask requirement on the transit system effective immediately.

After a federal judge in Florida struck down an order from the Centers for Disease Control and Prevention requiring masks on public transit nationwide, BART broke ranks with most other operators in late April and adopted its own mask mandate. The agency allowed that requirement, which was incorporated into its customer code of conduct, to lapse on July 18.

• Skip to: What your local Bay Area transit agency says about masks

Board member Bevan Dufty proposed renewing the mandate because of the highly contagious nature of the currently dominant coronavirus variant.

"I think COVID is at its most transmissible right now, and I think our responsibility is to stay the course and to ensure our riders, many of whom are immunocompromised, are safe and feel welcome in our system," Dufty said.

Pushback came from board members Robert Raburn of Oakland and Debora Allen of Clayton. Raburn argued that mask mandates are not supported by current guidance from health authorities. Allen questioned the wisdom and effectiveness of having BART police enforce a mandate.

After hearing public comment, the board agreed to reinstate the mask requirement through Oct. 1 by a vote of 7-2. The board will consider extending the mandate further at its Sept. 22 meeting.

AC Transit is the only other major Bay Area transit agency currently requiring riders to wear masks.

Masks on transit: How we got here

Federal agencies imposed a mask mandate for passengers on most modes of transportation at the outset of the pandemic. And following guidance from the U.S. Centers for Disease Control and Prevention (CDC), the Transportation Security Administration (TSA) extended nationwide mask requirements on planes, buses, trains and ferries through May 3, 2022.

But on April 18, a federal judge in Florida struck down the CDC mask mandate. A few hours later, the TSA announced it would no longer enforce mask rules inside airports and airplanes and on public transportation.

This ruling meant private and public transportation agencies could drop their own mask mandates.

Most major airlines, along with the San Francisco, Oakland and San Jose international airports, now have made masks optional. Rideshare giants Uber and Lyft also have dropped their masking requirements for passengers and drivers. And private bus companies, like FlixBus and Megabus, have followed suit.

BART and AC Transit are the only Bay Area public transit agencies that currently require face masks

Several Bay Area transit agencies — including Caltrain and Muni — initially retained their mask rules after the TSA announcement.

But on April 20, the California Department of Public Health (CDPH) announced that the state's mask requirements for public transit — and transportation hubs, like stations — also were terminated "effective immediately." The statement nonetheless still "strongly" recommended that California residents keep wearing their masks in these settings.

Every Bay Area public transit agency subsequently dropped their mask requirements for riders following the state's announcement. However, AC Transit, which operates in both Alameda and Contra Costa counties, announced June 2 that its passengers would once again be required to wear face masks.

Could we see more agencies or regions reintroducing their own mask rules for public transit — regardless of the Justice Department's own appeal against the original decision by the Florida judge? Right now, it's unclear. CDC officials declined to comment on the status of that appeal, and The Associated Press reports that DOJ officials did not immediately respond to a request for information.

On April 22, Los Angeles County independently introduced a new health order that once again requires masks on all public transit within the county. LA County Public Health Director Dr. Barbara Ferrer cited the CDC's continued guidance that masking on public transit remains a key way of preventing the spread of COVID.

In the meantime, remember: Regardless of whether a transit agency has dropped its mask requirement, you can always choose to keep wearing your mask in whichever setting you please. NPR has tips on figuring out whether wearing a mask when others around you are not (aka "one-way masking") is the right call.

Face mask requirements of all Bay Area transit agencies

BART

Are masks required on BART? Yes.

The rapid transit system, which serves five Bay Area counties, now requires riders to wear masks in all its facilities beyond the fare gates. This includes any waiting areas, platforms and trains.

BART riders are required to wear face masks when waiting at a station and when riding a train. The rule is set to expire Oct. 1. The BART board of directors will review the mask requirement at a meeting on Sept. 22.

Caltrain

Are masks required on Caltrain? No.

Caltrain updated riders Wednesday afternoon that it will no longer require face masks on trains. The agency stated on Twitter that while its mandate has ended, "guests can and are strongly encouraged to continue wearing them."

AC Transit

Are masks required on AC Transit? Yes.

AC Transit, which serves both Alameda and Contra Costa counties, brought back its mandate in June. Wearing a face mask is required whenever riding an AC Transit bus.

Agency officials stressed that the return of the mandate is due to the recent spike in new COVID-19 cases in Alameda County.

Muni

Are masks required on Muni? No.

The San Francisco Municipal Transportation Agency, which operates Muni, is still "strongly recommending" that people who ride Muni continue to wear a mask. The agency emphasizes what it called "excellent air flow" on its vehicles, noting that "the Muni fleet HVAC systems turn the air over once every minute."

VTA (Santa Clara Valley Transportation Authority)

Are masks required on VTA? No.

Santa Clara County's public transit agency is still "strongly recommending" passengers wear masks.

SamTrans

Are masks required on SamTrans? No.

San Mateo County's public transit system says masks are not required but are still "strongly encouraged."

Golden Gate Transit

Are masks required on Golden Gate Transit? No.

A bank of BART turnstiles at 24th Street Station.

SMART

Are masks required on SMART? No.

Santa Cruz METRO

Are masks required on Santa Cruz METRO? No — but this only applies to vaccinated people.

Santa Cruz METRO — which serves both Santa Cruz and Santa Clara counties — announced on Tuesday it will no longer require individuals fully vaccinated for COVID-19 to wear face masks in agency vehicles and transit centers.

Unvaccinated passengers are still required to wear face masks on Santa Cruz METRO.

San Francisco Bay Ferry

Are masks required on the San Francisco Bay Ferry? No.

The Bay Area Water Emergency Transportation Authority, which oversees the Bay Ferry network, says masks are still "strongly recommended," though not required. The agency also urges patrons: "Be kind to fellow ferry passengers whether they choose to wear a mask or not."

This story contains reporting by KQED's Carly Severn and the Associated Press.