More than 20 rush-hour commuters were injured yesterday morning when a Metrobus collided with a truck and then crashed through a guard rail, plunging down a 20-foot embankment and landing on its side near the entrance to Bolling Air Force Base in far Southeast Washington.

The A-9 bus, bound for L'Enfant Plaza and carrying about 30 passengers, fell off an access ramp that leads from Portland Street to South Capitol Street, sending passengers sprawling in a heap of bodies, metal and broken glass.

"People fell all over each other; all you could see were bodies flying," said passenger Dorothy Hankerson, 38, who was on her way to work as a researcher at the Department of Education. "I saw the driver get up and crawl out the front windshield, which was all broken. Then he fell down on his face. I came out after him. All I thought about was getting out."

Emergency personnel from the air base reached the scene within minutes of the 8:35 a. m. collision and began helping passengers out of the bus and treating the injured.

By the time the first of more than a dozen ambulances and helicopters arrived to take the victims to five area hospitals, the injured were lined up on the median strip, many of them covered with blankets to ward off the chilly winter air.

"It looked like a bomb hit," said Melvin Neil, a city ambulance supervisor who described the scene as the worst he had seen during his seven years on the job. "There were bodies all over the place. Only two were unconscious. One was unconscious from the beginning -- that was the driver -- and one went unconscious after about 15 minutes."

"It looked like a battle scene, it really did," Neil said. "There were just bodies all over the place."

The driver of the bus, 24-year-old Ronald W. Arrington of Capitol Hill, was taken to Washington Hospital Center, where he was reported in serious condition with chest and abdominal injuries.

Passenger Robert Abney, 19, of 4016 Martin Luther King Jr. Avenue, suffered a head injury and was also reported in serious condition. No other passengers were reported to have life-threatening injuries.

The driver of the truck apparently was not injured, according to the proprietor of the firm that owned the truck, Crow's Hauling Service Inc. of Washington.

Police said late yesterday they were still trying to sort out details of the accident. They indicated it might be Monday before the investigation is completed.

Metro operations chief Theodore Weigle said, "as far as we know now, we don't think that there was any excessive speed or faulty equipment involved."

He said the bus, a 1977 or 1978 Grumman Flxible "new look bus," was a very reliable model and had withstood the impact of the accident relatively well. "I was amazed that a bus could roll down a 25-foot embankment and be as undistorted as it appears to be," Weigle said.

The accident occurred at a point where Portland Street crosses South Capitol Street on an overpass. The truck, on the way to the Air force base where it was to pick up a load of debris, was westbound on Portland. The bus was heading north, about to enter an access ramp that leads down to South Capitol.

The truck had been standing at a red light, preparing to cross the overpass. First, however, it had to pass through an intersection with the access ramp. The truck and the bus were both trying to cross that intersection when the collision occurred.

Several passengers said the bus entered the intersection after the yellow caution light came on. None interviewed by The Washington Post recalled seeing the light turn red, however.

Two of the passengers said they believed the bus driver had increased speed to try to make it through the light before it turned red, and one recalled that passengers at the rear of the bus had complained in the instant before the crash that the driver was going too fast.

"The light was long since yellow," said passenger Floyd Powell, a 48-year-old security guard at the Smithsonian Institution, as he was being released yesterday afternoon from D. C. General Hospital with minor injuries. "How fast was he going? Too damn fast."

An Air Force communications specialist whose vehicle was stopped at the traffic light alongside the hauling truck said the light facing him was still red when the truck pulled out and struck the bus.

The specialist, Sgt. Walter Zumbrennen, said that the driver of the truck began to move when a traffic light across the overpass turned green. But the light that he and the truck were supposed to obey was still red, he said.

"I guess he thought we had the light," Zumbrennen said of the truck driver. "I heard the horn of the bus , they hit and the bus was shooting up . . . the overpass. It rode the guard rail 10 or 15 feet and then tipped over it."

Sgt. David Givans of the public affairs office at the air base said that at least four accidents have occurred at the intersection since September. The unusual sequence of traffic light changes is such a concern, Givans said, that mention of them is a routine part of the safety briefings given to new base personnel.

Robert L. Wright, an engineer for the General Services Administration, said he was driving south on South Capitol when the crash occurred. " . . . I looked up and this bus was coming over the cliff," he said. "When the bus came down I pulled over. I stopped and jumped out and people were hollering 'Help me, help me, please.' "

Wright said that rescue personnel from Bolling arrived within minutes. "They worked a beautiful operation," he said. "If they hadn't moved the way they did, there might have been people dead. It wasn't as bad as it could have been."

"It was very dramatic, the bus on its side, windows broken out," said Maj. Anthony Fasano, a physician at Bolling's Malcolm Grow Clinic, who was one of the doctors to treat the injured. "I fully expected to see mangled bodies, but it was not as bad as I expected."

Fasano, who worked along with six Bolling medical technicians, said that most of the injuries were facial cuts and brusies. But despite the fact that few of the injuries were serious, the scene was nonetheless a brutal one. A pool of blood had gathered at the bottom of the bus.

D. C. Police Sgt. William Aleshire, among the first to arrive on the scene, went through the property on the bus and turned the passengers' belongings over to administrators of the Metro transit system.

"There were wallets, purses, umbrellas, lunches scattered all over the bus," he said. "There was also a Christmas cake that somebody was bringing to the office, which was lying flattened on the floor of the bus."

Callestine Graham, a 27-year-old clerk typist who said she rides the A-9 every morning, said she was reading a "love novel" when she looked up and heard passengers screaming.

"The bus was going too fast and I saw we were in the middle of the intersection and the light was yellow," said Graham. "The driver tried to stop -- I heard him slam on the brakes and they screeched, but the bus was just rolling over, falling off the embankment. I felt like we were in a dream, we kept falling and I didn't want to hit bottom."

Graham said she was very glad she was sitting in the middle of the bus, not in the front, with those who were injured most seriously. "Usually I sit in the front and that's where I sat first today when I got on but I had this big heavy coat and a shopping bag of novels for my friend from the office so I switched seats."

Yvette Jackson, a 29-year-old secretary with the governmnent agency ACTION, said she had boarded the bus at the corner of Sixth and Forrester streets SE on her way to work.

In her room at Washington Hospital Center, where she was treated for neck injuries, she said her husband offered to drive her to work yesterday, but she declined the offer because he had just worked an all-night shift.

As the bus approached the intersection, she recalled, passengers at the rear began to grumble that the driver was going too fast. "You know how when the bus starts bouncing and you feel the engine in your seat?" she said. "People were swaying in their seats, and then I felt my neck snap back."

Other passengers said they watched as the truck pulled out of the intersection, and knew that there would be a collision. But Jackson said she had no idea anything was about to happen until the impact.

Response by emergency teams was "spontaneous," she said. Within minutes she was in a helicopter bound for Washington Hospital Center.

As she sat later in her hospital room, wearing a neck brace and with a bruise on her forehead, she looked solemnly at her husband, Isaac Jackson. "He's mad at me. I should have let him take me to work," she said.

"I'm not mad, baby." Isaac Jackson replied. "I'm lucky."Picture 1, Aerial view shows bus lying on its side near South Capital Street after plunge down embankment. By James M. Thresher -- The Washington Post; Picture 2, Injured passengers lie wrapped in blankets awaiting ambulances; Picture 3, a victim is loaded on a medevac helicopter. Photo by Larry Morris -- The Washington Post; Map, no caption, by Dave Cook