There’s online dating, but then, on the subways, there’s dating on the line.
The odds are solid in New York City, which attracts the most beautiful among us, that a subway car will be filled with attractive people from all backgrounds and cultures.

But, of course, the subway is no single’s bar, so the risk of failure is high when trying to pick up a date. Riders will instead read and reread advertisements around the person who had caught their eye.

Kay Mittal, 32, works in finance and lives in the Financial District. He is still haunted by a would-be love he exchanged glances with on the No. 6 train. She got off the train at Canal Street, before Mittal had a chance to give her his number. “I took too much time,” he said. He calls the incident “My biggest regret ever.”

Adam Hartke, 28, of Park Slope, recounted a time he was on the R train and started a conversation with a girl about movie posters. “You're walking a fine line,” Hartke said, explaining it's not always easy to predict who will want to chat. “You just gotta say hello and see where it goes.”

Erin Gell, 32, a freelance writer who lives in Astoria, said coming across attractive straphangers makes for a better train ride

“It’s exciting, it makes the commute a little better,” she said.

There are a couple of cons to finding love however. “It's hard to judge right away whether a person is a creep or not,” Gell added. Another hindrance? “Unfortunately, we're all on our phones these days.”

Riders for years have tried Craigslist’s infamous Missed Connections page when stolen glances and sly smiles can’t break the ice.

Ashley Laber, 26, of Hoboken, works at a non-profit and once posted on the Craigslist “Missed Connections” page, after an encounter on a World Trade Center-bound PATH train. It was early morning, and a handsome man (tall, blond, nice shoes, apparently) compliment Laber on her yellow gloves. It was an early morning start for Laber, who regrets that she wasn't in the mind frame to start a conversation with a stranger.

“I was so upset because I would be the person to keep talking,” she said. She still hopes to find that handsome stranger again. As to chatting with strangers on the train, “you have to be ballsy,” she said.

In the run up to Valentine’s Day, more than 100 lovelorn subway riders between Feb. 4 and 12 posted ads in hopes those who got away will be reading.

Erika Christensen, a fan of perusing Missed Connections ads, knows it is possible to land a date from the subway — she did it herself, during her single days. Carrying a guitar on the train, she said, would be an icebreaker.

Now, Christensen, who has since married, runs Train Spottings, which has recruiters go on “fishing trips” in the “streams of the subway” to find eligible daters to hook up with paying clients (“Right now, we’re hunting men pretty hardcore. We’re a little lady heavy,” she said). The matchmaking firm also goes to subway platforms to hold events like free love advice clinics; tomorrow, Train Spotting out 200 love notes from riders at the Atlantic Ave-Barclays station

Her team hits large transit hubs and key stations, like York Street in DUMBO for guys in tech, or around 23rd Street near the city’s fashion firms, according to Christensen, the “Head Love Conductor” at Train Spottings.

“The beauty of New York is everyone is riding every line,” she said. “You’re getting all kinds.”

Her advice for subway flirting: stick to the platforms so the whole train car won’t be involved and be cool, not creepy.

But there are riders who finds themselves on a train, avoiding eye contact with an attractive passenger, having read every advertisement in view.

“I worry with online dating we’re losing that, we’re losing that potential for wonder and nervousness,” she said. “At a certain point, you got to swallow the nerves and muster a little, ‘Hi how you doing?’ and it can go a long way. I’ve heard so many success stories.”