A Springfield woman was critically injured yesterday when her station wagon, which she had left idling in her driveway, ran over her. Fairfax County police said her 2-year-old son, left alone in the vehicle, apparently struck the automatic gearshift lever and shifted the car into "drive" as she walked in front of it.

Penny Hornberger, 27, was pinned beneath the car for an undetermined time until she was noticed by a neighbor, who at first thought the object under one of the front wheels was a shopping bag.

The Oldsmobile station wagon, which had been parked facing the street and in front of another car, moved several feet down the sloping driveway and stopped with its front end in the street.

Officer Judy Dailey, a county police spokeswoman, said investigators believe Hornberger left her son Christopher in the front seat while she went inside the one-story brick house at 5954 Atteentee Rd. for a moment. The child's father, John Hornberger, a D.C. police officer, was sleeping in the house at the time, Dailey said.

To get to the driver's side, Hornberger had to walk around the front of the car, Dailey said.

Hornberger was flown by helicopter to Fairfax Hospital about 8:30 a.m. and was listed in critical condition, hospital spokesman Lon Walls said.

"I think it's pretty unusual that someone would leave their 2-year-old in a car that's running," said Dailey. "But you wouldn't think a 2-year-old could slide over and put the car into gear."

The accident was discovered by George Sertzoglov. He summoned another neighbor, Sue Fimiani, for help.

Fimiani said she called the 911 emergency number for help, then rushed to the car. She said she found Christoper Hornberger dressed in pajamas inside, "crying, screaming.

"I don't know if he knew what was going on or he was frightened with all the people around," she said.

"I took him out of the car and tried to calm him down," said Fimiani, who then took him to her house. "I didn't want him to see his mom. He just said he wanted his mommy and his daddy."

Fimiani said she took Christopher back to his own home after he told her his father was asleep there.

Police and neighbors said they did not know where Penny Hornberger had planned to drive.