There is a perfectly reasonable explanation why William Heaser unknowingly jumped off a 115-foot bridge. But it is a long story.

And it begins with Donald Knight, who sat in Prince William County General District Court Friday with no memory of a December accident he was involved in that triggered a sequence of events that left one man nearly dead and Virginia state troopers rubbing their foreheads.

Knight, 30, of Stafford County was convicted Friday of reckless driving and fined $200 plus court costs by Judge Joseph A. Gallagher, who also suspended Knight's license for six months.

The charges stem from a Dec. 10 one-car accident about two miles south of Potomac Mills Mall on I-95, that began a night Heaser, a modern day Good Samaritan, will never forget.

At 1:15 a.m., a man was driving on I-95 south when he lost control of his car, which struck a concrete barrier bordering the highway and came to rest in the middle of the road facing traffic, police said.

Heaser, who was traveling home with his wife and grandson, saw that the man, identified by police as Knight, needed help. He parked his car on the road's shoulder and ran to the victim's car. But before he could help Knight, Heaser saw another car heading right for him. So he ran to jump over a concrete railing to safe ground.

There was no ground. Heaser had unknowingly jumped off a bridge.

"The first impression I had was of this wonderful feeling," said Heaser, a 42-year-old postal worker from Stafford County. "Then I realized . . . I'm in trouble. So I let the air out of myself and went limp. I think I hit some trees. The next thing I realized I was on the ground. I was hurting so bad. Then the pain gave way to the fear that no one knew that I was there."

Heaser's wife was sitting in the car with 3-year-old Allen. She, too, thought Heaser had just jumped to safety.

But a short while later, Trooper A.S. Foster arrived on the scene and asked Marilyn Heaser where the driver of her car was.

"She said he jumped over that guard rail," Foster said. " . . . I had a horrified look on my face. I was horrified because I knew that was a more than 100-foot drop."

Looking over the side of the bridge, Foster could see nothing. Heaser was found only after rescue companies arrived on the scene with night lights.

"It was an incredible night," Foster recalled. And one that was just beginning.

Traffic had to be stopped so that a Medivac helicopter could land. At 3:07 a.m., after the traffic was cleared, a driver who had been waiting in the tie-up was asleep, Foster said. The driver was rudely awakened by another motorist who ran his car into the back of the first driver's vehicle, Foster said. Police wound up charging both men with driving under the influence. And during the period, another trooper, who had helped reroute traffic, was nearly run down by another driver, who was also charged with drunken driving.

"We don't normally catch that many drunks at one time," said Foster, acknowledging that night was unusual.

For Heaser, who suffered broken bones too numerous to list, that night has become surreal: "I can't believe that it happened . . . . I travel over that stupid thing {bridge} every day. There is no lighting, the terrain is such that there is nothing to indicate that it is a bridge," he said. Neabsco Creek runs quietly below the bridge.

"I'm afraid of heights," Heaser said. "I get sick just going on the roof."

No matter how painful, said Heaser, who spent nearly a month in Fairfax Hospital, the incident will not stop him from helping others in distress, like Knight.

"All I remember is that I hit my head and there was blood," Knight said in an interview Friday outside of court. "I lost a lot of blood. I heard a man tried to help me. I don't remember seeing him. I don't even remember the helicopter."

Heaser said he saw only a man's figure in the vehicle. He never even saw the face of the man he tried to help.