For once, there was no traffic on Montauk Highway — only former Long Islander Mark Maggi, 32, moving his feet toward a sub three-hour finish in the Suffolk County Marathon Sunday morning. Maggi, who crossed the finish line in 2 hours, 48 minutes, 8.43 seconds, grew up in West Sayville and is a federal government economist who lives in Cohasset, Massachusetts.

Pam O’Sullivan, 29, who is from Bay Shore and a school psychologist in Nashua, New Hampshire, won the women’s marathon in 2:58:45.93. O’Sullivan won the women’s Suffolk half marathon last year, she said.

“It’s pretty cool to win a race that runs right through my hometown,” Maggi said of the course that began and ended in downtown Patchogue and touched in Sayville, Blue Point, Bayport, Oakdale and Great River.

“It’s a great course,” O’Sullivan said. “Nothing stood out as super hard to me.”

The victories qualified Maggi and O’Sullivan for the 2018 Boston Marathon.

It was Maggi’s first marathon win in eight tries and first in 21⁄2 years after having surgery to replace torn tendons in his lower stomach in 2014.

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Maggi said he was in second place for the majority of the first half of the 26.2-mile race, taking the lead in the Bayard Cutting Arboretum in Great River and running by himself for the second half of the race.

The arboretum, Maggi said, provided a much-needed respite from the heat that persisted throughout the race. After a week of colder temperatures on Long Island, yesterday morning’s race was run primarily under a hazy sun with temperatures in the high 60s, making prime real estate out of places where runners can move into shade.

The relief started for full marathoners at the halfway turn in Heckscher State Park.

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“Heckscher was great,” Maggi said. “It was nice and cool by the bay. That was the best part of the race. There was a light breeze and a lot of shade — same with the arboretum and St. John’s [University in Oakdale].”

Maggi said the temperatures got hotter “by the minute” in the race’s final hour. But that didn’t bother O’Sullivan at all.

“To me, it’s the perfect weather,” she said. “I like it a little bit warm and I like it quiet. There are parts [to the course] that are nice and scenic and quiet . . . I’m one of those people who are always cold. You know, one of those people who are always in sweatpants and long sleeves. So for me, this keeps me temperate. I don’t have to wear gloves or have to heat myself throughout the race. I acclimate well to the heat.”

O’Sullivan will run the Philadelphia Marathon on Nov. 20. She said she used the Suffolk Marathon as a “buildup” race.

“Although I won and am honored to win, it wasn’t my best effort,” she said. “I’m saving that for Philly.”

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O’Sullivan said she ran alone for most of the course, first realizing that she was in the lead when the marathon and half- marathon courses split.

“The bikers who were with the lead pack said, ‘You’re winning,’ ” she said with a laugh. “And I thought, ‘Oh, I have a long way to go.’ ”

Ben Jacobs, 27, of Minnetonka, Minnesota, won the men’s half-marathon in 1:12:37.32 and Leonora Petrina, 34, who is from New Zealand but lives in Bayport, won the women’s half-marathon in 1:17:23.28.

“Being alone out there was tough,” Petrina said. “I was able to chase down one of the guys, but it’s hard to work by yourself.”