Dusty Stimpson, a jockey who last month rode the winner in one of the richest stakes in Quarter Horse racing, was killed in a traffic accident. He was 29.Stimpson died early Tuesday after being ejected from a car that struck a guard rail at a motorway interchange, said Scott Carrier, a spokesman for the Los Angeles County coroner. Stimpson and his girlfriend, Jody Behunin, were returning home from a concert when the accident occurred.Behunin, who was driving the car, was taken to County-USC Medical Center, where she was in the intensive care unit. Her condition was not immediately available.Stimpson had been riding at Los Alamitos Race Course since 1994. He had 44 career stakes victories, 15th on the track's career list.He won the last two runnings of the Los Alamitos Million, the most recent aboard Your First Moon on Dec. 15. Stimpson was the second-leading rider in earnings with more than $1.7 million in 2001 at Los Alamitos."We are all in complete shock," said Rick Henson, Los Alamitos' president and general manager. "Dusty was a gentleman on and off the track and we will miss the class and talent that he brought to this sport."