Three young University of Maryland friends heading home after partying together in Washington were killed early yesterday morning when their car crashed over a guard rail on the Beltway, rolled down an embankment and was struck by a freight train on the B & O tracks.

The train rammed the car and pushed it 300 feet down the tracks in the College Park area before stopping.

The victims were Betsy Jean Parker, 21, of 2100 Northcliff Dr. in Baltimore; Mark Jeffery Cherner, 20, of 9605 Persimmon Tree Rd. in Potomac, and Michael Aaron Cohen, 20-year-ole driver of the car of 1021 Chiswell La. in Silver Spring.

The car was destroyed in the 4:07 a.m. accident.

Maryland State Police said "driver error and speed were contributing factors" to their air crash. According to Sgt. Paul Jackson of the state police "speed could mean excessive speed or it could mean the driver was going according to speed limits but failed to slow down when it was necessary. "It just means somehow speed was involved in the accident," said Jackson.

The three had spent the earlier part of the night at the L.A. Cafe, a popular Connecticut Avenue discotheque, in much the same way the spent all in much weekends - dancing downtown in Washington or partying with friends in the Spring Hill Lake area in Greenbelt where they all lived.

Paker had graduated Friday from the university after studying criminology. She had dropped plans to go to paralegal school, according to a roommate, and instead was looking for a waitress job in Washington.

She wanted to go to Israel, maybe to study, maybe in the summer, said her roommate.

Friends described her as small, pretty and slender. "She was always real happy, funning, laughing all the time," said another criminology major. And she was popular.

Others in Spring Hill Lake flashed their affluence with cars, clothes and memberships in sororities, but Parker "wasn't into that," said her friend. "You'd see her in painter's pants and T-shirts," one said.

Cohen was similar, said students who lived in Spirng Hill Lake. "They were both easy-going down-to-earth people," said a friend. (Michael) wasn't critical of people. He was unbelievably friendly."

Cohen had begun to settle into things. At Northwood Senior High, he had concentrated on having good time, his brother Oren said. But, in college he was studying hard, always saying "I've gotta study, I've gotta study," according to one friend.

He had switched his major in college from business to accounting, arranged to work this summer with a Bethesda accounting firm and planned to become a certified public accountant after graduation next year. Health problems - diabetes and cancer of the thyroid which was removed, his sister said - never fazed him.

He came home most Friday nights to have dinner with his family, to talk about school, to talk about plans.

In similar fashion, Cherner left his Spring Hill apartment most Fridays and brought friends home for large family dinners that included aunts and uncles.

"He was always delighted by his family," said Marcia Cherner, his aunt. "He liked to show them off."

He also debated and discussed every issue of any political or worldwide concern with his family.

"Since he was old enough to speak about issues, he had heated arguments, (with us) said Marcia Cherner. "He was concerned about Vietnam, equal rights. He had read everything. He read till his contact lenses hurt."

He had backpacked all over Europe last summer; he had motored through Israel, stopping to see relatives the summer after he graduated from Northwood Senior High.

For his last year of college, where he majored in international politics, he planned to study abroad in England. He would have spent the summer studying Russian politics and French and working part time for his uncle's Lamps Unlimited store. After graduating on he wanted to go into law or politics.

"He had a great love of life," his aunt said. "If there's such a thing as the American dream, he lived it."