Metro volunteer Melissa Pollak gives directions to tourists at the Rosslyn station. (Kery Murakami/Kery Murakami/Express)

Even as she talked about the Holocaust with a reporter at the Rosslyn station last Wednesday, the woman in the blue “Metro Volunteer Person” vest kept scanning the fare machines nearby.

Suddenly, Melissa Pollak darted off toward a man at one of the machines. To the untrained eye, he showed no obvious sign of distress.

“When you’ve been doing this for as long as I have, you can tell the signs,” she said after helping the tourist load his SmarTrip card.

The machine had been asking the man if he wanted a receipt, she said. It only does that when someone is using a credit card. But the man had cash in his hand.

It was hot at the station. For an hour, she’d been helping people figure out the wonky machines or explaining other quirks of the system, like how going to D.C. involves getting on a train headed for places called New Carrollton and Largo Town Center.

Beads of sweat were forming on her forehead. It looked like there’d be better places to spend a retirement.

For more than three years, Pollak has been coming to the station three times a month for two hours at a time, one of 25 people who volunteer for Metro.

“I could do two times a month for three hours, but I’m old, so it’s hard to be on my feet so long,” said Pollak, who declined to give her age.

As she hurried around, most of the people around her were rushing to get on a train — or out of the station, trying to leave.

The unlikely subject of the Holocaust came up when she was asked why she does this — why she, literally, volunteers to stand in a Metro station.

In 1938, as the Nazis were invading Vienna, Pollak said, 13-year-old Eva Susanne Tschelnitz and her family fled to England.

Pollak’s father, Theodore, then 19 and still years from meeting Eva, also fled Vienna. But he and has family went to Memphis, Tenn., where Theodore was drafted into the Army.

The war took him to England, where he met a woman from his hometown. They fell in love, married and moved back to Memphis.

“Can you imagine the culture shock of moving to Memphis?” Pollack said of her mother.

Eva Pollak liked to take the bus around Memphis, bringing her daughter along with her.

“I think having moved to new countries at a very young age, she had to be very independent,” Pollack said.

Melissa continued to ride buses and trains when she moved to Washington to attend American University, and then throughout her career as a senior analyst at the National Science Foundation.

“I inherited this gene from my mother where I’ve always been pro public transportation,” she said as an explanation for why she was there.

After she retired, she heard Metro was looking for volunteers. Hanging around a Metro station seemed fun, she said.

She likes helping people, too. And during her couple of hours at the station, a lot of people needed help.

Metro is promising to upgrade its fare machines and gates and introduce the ability to pay fares with a smartphone app sometime this year. But for now, the tourists and regulars are mainly relying on the fare machines.

“Each one can do odd things,” Pollack said. “You have some that don’t accept bills, and others that don’t accept credit cards.” And there are some whose prompts skip steps, leaving even veterans like her befuddled.

But the occasional odd request keeps things entertaining. “I had a couple of tourists who told me the escalator [at Rosslyn] was the second-tallest in the world under some kind of escalator standard,” she said. (It’s actually only the fifth-longest in the Metro system, according to the civic group Greater Greater Washington.)

“They begged me: ‘We just want to ride down and come back up.’” She let them through the emergency gate.

“The station manager got really mad at me. The last time somebody wanted to do that, they fell. She said there was ‘blood everywhere,’” Pollack said, laughing at how irate the manager was.

“Fortunately,” she said, “my people came back up and they were fine.”