One person was killed and several others were injured yesterday in three traffic accidents that left morning commuters idling for hours on the Capital Beltway in Maryland.

Part of the outer loop west of Interstate 270 in Montgomery County was closed for nearly nine hours as crews dealt with a tractor-trailer that flipped onto a car about 5 a.m. The driver of the car was killed, and his wife and son were injured, police said.

At midmorning, sections of the Beltway in Prince George's County were closed after a four-vehicle pileup on the outer loop near New Hampshire Avenue and a collision involving a tractor-trailer and a car on the inner loop near Branch Avenue. Four people were hurt in those accidents, police said.

"It was just terrible," said Rita Gaines, 51, whose normal 30-minute commute from New Carrollton to her Energy Department office in Germantown grew to 90 minutes. If not for a quick decision to avoid the Beltway and drive through the District, Gaines said, "I might still be sitting there."

The tie-ups began when a tractor-trailer driven by Shannon Wade Furrow, 29, of Ferrum, Va., went out of control and flipped onto a 2000 Mercury Sable driven by Juan Gallegos, 49, of Stamford, Conn., police said. Gallegos was killed, and his wife, Isabel Gallegos, and their son, Joao Pablo Gallegos, 14, suffered minor injuries, according to police.

Maryland State Police closed the outer loop west of I-270 for an hour and had two lanes open by midmorning, said Capt. Suzanne Jordan, commander of the state police Rockville barracks. All lanes were open by about 2 p.m., she said.

The cause of the crash was under investigation yesterday and no charges have been filed against Furrow, who was not injured. The truck he was driving, owned by Mabe Trucking of Eden, N.C., was carrying lumber and construction supplies, Jordan said.

Just after 9 a.m., a car and tractor-trailer collided near Branch Avenue on the inner loop. The driver of the car, whose name was not released, was ejected from his car. He was taken to a hospital with what appeared to be non-life-threatening injuries, said Chauncey Bowers, a Prince George's County fire department spokesman. The truck driver was unhurt, Bowers said.

At 10:13 a.m., a four-vehicle pileup halted traffic on the Beltway's outer loop just east of New Hampshire Avenue. The accident involved a box truck, two cars and a pickup truck towing a trailer filled with roofing tar, and it trapped three women in vehicles.

Two women were trapped inside a Nissan Maxima after the collision, Bowers said. Another woman was trapped in a BMW that had flipped over, Bowers said. All three were taken to hospitals with what appeared to be non-life-threatening injuries, Bowers said.

All lanes of the Beltway near the New Hampshire Avenue exit were closed briefly but were open by 12:30 p.m., said Maryland State Police Sgt. Ernie Ford.

In the aftermath of the crashes, Michael Reilly, 21, got on the Beltway at New Hampshire Avenue about 10:30 a.m. and encountered a bizarre scene for a Friday morning in the Washington area: no cars in sight on the Beltway.

Reilly was entering just after police had closed off all lanes of the outer loop, so he was alone -- at least until he hit the wall of traffic remaining from the 5 a.m. tractor-trailer accident a few miles ahead.

"It was surreal," he said.

His 30-minute commute from Bethesda to Gaithersburg stretched into an hour. "I was stuck for a good 20, 25 minutes before I bailed out on Connecticut," he said.

Police investigate a four-vehicle accident on the outer loop, one of three serious crashes yesterday morning on the Capital Beltway in Maryland.