THE DEFENSIVE DRIVING COURSE (DDC), LIKE OTHER POST-LICENSURE DRIVER TRAINING PROGRAMS, IS INTENDED TO REDUCE THE RATE OF MOTOR VEHICLE CRASHES AMONG THOSE WHO TAKE THE COURSE. A REVIEW OF THE LITERATURE REVEALED 14 CONTROLLED STUDIES OF THE EFFECTS OF DDC. ABOUT A THIRD OF THESE STUDIES PROVIDED METHODOLOGICALLY STRONG TESTS OF DDC, BUT THE REMAINDER HAD DESIGN FLAWS THAT MADE THEIR FINDINGS QUESTIONABLE OR INADEQUATE AS TESTS OF DDC. ONLY AMONG THE FLAWED TESTS WERE THERE LARGE, POSITIVE EFFECTS OF DDC. IN THE METHODOLOGICALLY STRONG TESTS, DDC HAD NO CONSISTENT EFFECT ON CRASHES BUT DID DECREASE THE FREQUENCY OF TRAFFIC VIOLATIONS BY ABOUT 10%. THE FAILURE OF VIOLATION REDUCTIONS TO BE TRANSLATED INTO CRASH REDUCTIONS MAY INDICATE THAT THE VIOLATION REDUCTION IS AN ARTIFACT OF TRAFFIC RECORD PROCEDURES OR THAT THE CHANGES IN DRIVER BEHAVIOR, IF REAL, WERE INSUFFICIENT TO MODIFY INDIVIDUAL CRASH LIKELIHOODS. IN EITHER EVENT, THE BEST AVAILABLE EVIDENCE DOES NOT SUPPORT THE HYPOTHESIS THAT DDC DECREASES THE LIKELIHOOD OF MOTOR VEHICLE CRASHES.(Author/publisher).
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