A 14-year-old girl died yesterday evening at Maryland Shock Trauma Center after being struck by a police car as she and two other teen-agers ran across an unlighted section of the Baltimore-Washington Parkway, a short distance south of the city-Baltimore County line, authorities said.

The accident scene was about 200 yards north of a pedestrian walkway across the highway, built so people could cross safely, state police said.

Killed was Ashley D. Dean of the first block of Birdnest Court in the county's Baltimore Highlands neighborhood.

About 6:15 p.m., Ashley, along with her brother and another youth, both 17, left their homes in the Highland Village Apartments on the east side of the parkway and were heading to apartments on the west side by running across the road about 1 1/2 miles north of the Baltimore Beltway, police said.

The brother had gotten across when the girl, wearing dark jeans and a dark jacket, and the other boy darted from a center median strip.

Police said Ashley ran into the path of a marked city police Ford Crown Victoria assigned to the traffic investigation unit. The 37-year-old officer at the wheel, who was not named last night, was going to Baltimore-Washington International Airport on a traffic assignment, police said.

The officer tried to avoid hitting the girl, state police said.

Ashley was pronounced dead at Shock Trauma shortly before 7 p.m.