This February 2015 report from the U.S. Government Accountability Office (GAO) was conducted because although drug-impaired driving contributes to fatalities and injuries from traffic crashes, knowledge about the drug-impaired- driving problem is less advanced than for alcohol-impaired driving. GAO recommends that NHTSA take additional actions to support states in emphasizing to the public the dangers of drug-impaired driving, and the U.S. Department of Transportation is in agreement with this recommendation.
Access the report through the link below.
http://www.gao.gov/products/GAO-15-293