Two teen-aged girls from Manassas were killed Saturday night when their pickup truck collided with a tractortrailer on Rte. 15 in Loudoun County, Virginia State Police said yesterday.

The driver of the pickup truck, Stacy Ann Simpson, 16, of 8721 Barnett St., and a passenger, Laura Ellen Mason, 17, of 8704 Fort Dr., were dead at the scene. Another passenger in the pickup truck, Becky Compliment, was listed in good condition at Prince William Hospital.

The girls, sutdents at Osbourn High School in Manassas, were going to a friend's house when the accident occurred at 9 p.m.

Police said the pickup truck and the tractor-trailer were traveling north on Rte. 15, with the pickup truck in the right line and the tractor-trailer in the left lane, trying to pass the pickup truck. The pickup truck collided with the larger truck when the pickup cut in fronttof the tractor-trailer in an attempt to turn left onto Rte. 600, police said.

The driver of the tractor-trailer, Harry Smith of Quarryville, Pa., was treated for minor injuries at Loudoun Memorial Hospital and released. He was not charged.

In another incident, a 29-year-old New York City woman was killed when her Volkswagen collided with a milk tanker truck in Comus yesterday, Montgomery County police said.

The woman, Iman Ibranyi-Kiss, was pulling out of a driveway on Rte. 109 around 10 a.m. when she collided with the truck, which was travelling southbound. Both vehicles skidded 128 feet and finally stopped against a tree 12 feet from the road.

A passenger in the Volkswagen, William Plumpe, 33, of Ann Arbor, Mich., was listed in fair condition at Suburban Hospial with neck, back and leg injuries. The driver of the truck, Gary Eugene Nicholson of Frederick, was taken to Frederick Hospital with a back injury.