The National Automobile Dealers Association (NADA) says it has received an advance copy of a new study commissioned by the Cato Institute which found that despite critics' claims, sport utility vehicles (SUVs) are lowering the incidences of roadway fatalities. Critics of SUVs have charged that the vehicle's size and weight endanger other drivers. But the study pointed out that despite a doubling of the percentage of light trucks on the nation's roadways over the past two decades, there has been a one-third decrease in traffic accident fatalities per capita, fatalities per licensed driver and fatalities per registered vehicle. The United States has also experienced a nearly 50 percent decline in fatalities per vehicle mile traveled, according to the report. This suggests that the large, stiff-framed light trucks may be lowering traffic fatalities instead of increasing them, according to NADA. The results of the study, conducted by economics professors Douglas Coate and James VanderHoff of Rutgers University, will be published in the spring issue of Regulation, the Cato Review of Business and Government.