The investigation of Grammy nominee Luther Vandross' traffic accident has been referred to the Los Angeles city attorney for possible misdemeanor vehicular manslaughter charges "because there was insufficient evidence to prove beyond a reasonable doubt that (Vandross) was driving with gross negligence," district attorney spokesman Al Albergate said. Vandross, 34, allegedly was driving his car at 48 m.p.h. in a 35 m.p.h. zone Sunday, when he crossed the center divider on Laurel Canyon Boulevard in North Hollywood and collided with two cars, police said. One of his passengers, Lawrence Salvemini, 27, died. Police said there was no indication that the singer was driving under the influence of alcohol or drugs.