Earlier in the pandemic, 16-year Regional Rail rider Annie Craig found enough room on Lansdale/Doylestown Line trains to be able to sit far from passengers without masks.

But in recent weeks, ridership on many of the trains she takes from Fort Washington to Center City has increased. The buffer of space has shrunk.

“It’s putting the rest of us at risk,” said Craig, a nurse at a home-care agency.

President Joe Biden’s executive order mandating masks on public transit nationally took effect last week, but enforcement is a bit of a gray area, with regulators so far allowing local agencies flexibility.

Unlike some other agencies, SEPTA is reminding the barefaced of the requirement — educating them and offering free masks — instead of fining violators or removing them from their ride. The agency says its continuous audits show an average systemwide compliance rate north of 90%.

But customers say they see plenty of fellow riders, and even some SEPTA employees, without face coverings — and as the pandemic has dragged on, subway and train cars and buses on some routes are more crowded, making it more difficult for passengers to follow social distancing guidelines.

“There needs to be enough cars so people can maintain at least a 6-foot distance,” Craig said.

“We don’t have enough [extra] vehicles to put in service, so as ridership starts to return, sometimes the opportunity for social distancing is going to be reduced,” SEPTA spokesperson Andrew Busch said. “That makes the mask mandate all the more important.”

» READ MORE: Face masks are required on SEPTA. Now if only more riders would comply.

Riders are pretty good about wearing masks now, but overcrowding is a problem, the Philly Transit Riders Union says. It has urged SEPTA to run additional buses and to reduce Regional Rail fares in the city to spread ridership more evenly.

“They should be trying anything and everything right now to make transit safer in the pandemic, but management is meekly hoping nobody notices all the opportunities they’ve missed,” said Nat Lownes, a spokesperson for the riders union.

On Friday, the Transportation Safety Administration announced it is stepping up enforcement of Biden’s order with fines ranging from $250 for a first offense to $1,500 for repeat violators. Still, on the local level, it will be up to the agencies and companies carrying passengers to identify scofflaws and report them to TSA.

The federal rules mandate that travelers and transit operators wear masks when in airports; at bus, ferry, and rail stations; and when flying commercially or riding buses and trains. TSA has enforcement authority in airports.

SEPTA is putting up signs around the systems reminding people that not wearing a mask is a violation of “federal law.” But it has no plans for an enforcement crackdown.

» READ MORE: SEPTA’s ‘social-distancing coaches’ are the newest part of your commute

“We don’t want to confront customers — we want to continue to reach out in a positive way,” Busch said.

More aggressive measures, such as removing maskless people from a bus or train car, could get employees or riders injured, he said. And verbal combat might increase the chance of spreading COVID-19.

In April, SEPTA quickly backed off mask enforcement after a widely shared video showed a man being dragged off a bus, allegedly for not wearing one. The video captured several Philadelphia police officers forcibly removing the man, who was later heard saying he was taken off the bus for not wearing a mask.

Besides, SEPTA says its speak-softly-and-carry-a-box-of-masks strategy is working.

In a January audit, SEPTA found an average of 93% of bus and trolley riders were wearing masks correctly, compared with 81% of passengers on the subway and El, and 96% of those on Regional Rail. The agency sampled 3,906 customers.

» READ MORE: SEPTA’s ridership won’t rebound for a long time. Fear of contracting COVID-19 is partially to blame.

Mike Bee of South Philadelphia said SEPTA drivers on the No. 17 and No. 7 bus lines refused to let him board twice this summer when he forgot his mask — rightfully so, he added.

But lately, on several different routes, he’s noticed bus drivers, who are behind plastic-glass barriers, not wearing masks, and even uniformed SEPTA employees riding the El without them.

“There needs to be a consistent message both for the people who run SEPTA and those who ride it,” said Bee, 32, a waiter.

Busch said SEPTA instructs its employees to “keep up their vigilance” on using protective masks, “the same thing we are stressing to our customers.”

» READ MORE: Without commuters, what will happen to SEPTA Regional Rail?

Some other agencies stepped up their mask-scofflaw enforcement even before the federal mandate. The New York Metropolitan Transit Authority began hitting refuseniks on the system’s buses, subways, and railroads with a $50 fine in September, a step ordered by Democratic Gov. Andrew Cuomo to increase compliance with the state mask mandate.

NJ Transit police ran 2,000 mask enforcement details in the last four months of 2020. It said most people complied when asked, but officers issued a $500 summons to at least one repeat offender.