For  example, NHTSA’s 2007 National Roadside Survey of Alcohol and Drug  Use by Drivers (NRS) provides information on drivers testing positive for  illegal, prescription, and OTC drugs in a nationally representative sample  of weekend-nighttime and Friday daytime drivers. Based on the 2007  survey, NHTSA estimated that 16.3 percent of nighttime drivers  nationwide would have tested positive for at least one drug, with  marijuana being the most common drug found in test results (see table 1). While NRS survey data provides useful information on the estimated  prevalence of drugged driving, these results do not measure the extent to  which drivers are impaired by the drugs in their systems as the presence  of drugs or drug metabolites does not necessarily indicate impairment. Data on Impaired-Driving Arrests and Toxicology Results

Data on drug-impaired driving arrests and toxicology results in our seven  selected states provide some information on drug-impaired driving, but  are limited by a lack of separation of data from driving under the influence  (DUI) arrests, underreported instances of drug-impaired driving,  decentralized reporting, and a lack of standardization in drug testing. Difficulty of Defining Drug Impairment Exacerbates Challenges Related to Enforcement and Public Awareness

In addition to limited data on the extent of drugged and drug-impaired  driving, federal and state officials we spoke with cited difficulty in defining  drug impairment as a significant challenge to addressing drug-impaired  driving. Compared to alcohol, which is chemically simple and has  relatively predictable effects, defining and identifying impairment due to  drugs is much more complicated due to the large number of available  drugs and their unpredictable side effects. According to  toxicologists from two states and representatives from SOFT, it is more  expensive to test for drugs than alcohol. For example, officers may be trained to administer  the Standardized Field Sobriety Test, which focuses on detecting alcohol- impairment in drivers; however, officers may not be trained to recognize  drug impairment. The time between arrest and collection of a sample for drug testing can  affect the quality of biological evidence, such as blood samples, because  the concentration of drugs in the body is constantly changing. Currently, there is no validated roadside drug- testing device, such as the evidential breath-testing device for alcohol,  which would facilitate faster sample collection. Public Awareness about Dangers of Drugged Driving Is Limited

State prosecutors, toxicologists, law enforcement and highway-safety  office officials from all of the selected states, as well as NIDA, told us that  they believe that there is a lack of public awareness about the dangers of  driving after using prescription medications and marijuana. As a result of this perceived lack of awareness, members of the  public may risk unknowingly driving while impaired, potentially leading to  vehicle collisions, injuries, and fatalities. These actions  include improvements in the areas of research and data, education of law  enforcement and court personnel, evidence quality, legal remedies, and  public awareness. Furthermore, NHTSA, ONDCP, and states have  coordinated their efforts to address drug-impaired driving challenges. For example, NHTSA is  currently researching the crash risk of drug and alcohol use (including  illegal, prescription, and OTC drugs) by collecting samples from more  than 10,000 crash- and non crash-involved drivers in one city for 20  months. The  NTSB has recommended that NHTSA develop and disseminate similar  standards to state officials. NHTSA’s mission is to support state traffic safety efforts. These efforts to improve  public awareness are in the initial planning stages and could take several  years to implement. While NHTSA’s plans to improve public awareness of drug- impaired driving through a survey on public behaviors and attitudes and  training for medical professionals are promising, these initiatives will take  time to implement. Additional efforts, such as general messaging  reminding the public about the impairing effects of some drugs and the  dangers of driving after using drugs, could help improve public awareness  in the near term. Specifically, we analyzed (1) what is known about the extent  of drug-impaired driving in the United States; (2) what challenges, if any,  exist for federal, state, and local agencies in addressing drug-impaired  driving; and (3) what actions federal and state agencies have taken to  address drug-impaired driving and what gaps exist, if any, in the federal  response to drug-impaired driving. To describe what is known about the extent of drug-impaired driving in  the United States, to identify challenges to addressing drug-impaired  driving, and to identify actions federal and state agencies have taken to  mitigate those challenges, we conducted a literature search to identify  sources of data on the extent of drugged and drug-impaired driving in the  United States and studies on the issue of drug-impaired driving, including  challenges and strategies for addressing the problem. We interviewed  officials at relevant federal agencies including the National Highway  Traffic Safety Administration (NHTSA); the White House’s Office of  National Drug Control Policy (ONDCP); National Transportation Safety  Board (NTSB); and Department of Health and Human Services’ (HHS)  components including the Substance Abuse and Mental Health Services  Administration (SAMHSA), Centers for Disease Control and Prevention  (CDC), Food and Drug Administration (FDA), and National Institutes of   Additionally, we reviewed documentation obtained from  Health (NIH).and interviewed officials in seven states: Arizona, California, Colorado,  Kansas, Ohio, Vermont, and Washington.
Why GAO Did This Study

The issue of alcohol-impaired driving has received broad attention over the years, but drug-impaired driving also contributes to fatalities and injuries from traffic crashes. However, knowledge about the drug-impaired- driving problem is less advanced than for alcohol-impaired driving.
Through Senate Report No. 113-45 (2013), Congress required GAO to report on the strategies NHTSA, ONDCP, and states have taken to address drug-impaired driving and challenges they face in detecting and reducing such driving. This report discusses (1) what is known about the extent of drug-impaired driving in the United States; (2) challenges that exist for federal, state, and local agencies in addressing drug-impaired driving; and (3) actions federal and state agencies have taken to address drug-impaired driving and what gaps exist in the federal response. GAO reviewed literature to identify sources of data on drug-impaired driving; reviewed documentation and interviewed officials from NHTSA, ONDCP, and HHS; and interviewed officials from relevant advocacy and professional organizations and seven selected states. States were selected based on: legal status of marijuana, proximity to states with legalized marijuana, and drugged-driving laws.

What GAO Found

Various state and national-level data sources—including surveys, arrest data, drug-testing results, and crash data—provide limited information on the extent of drugged and drug-impaired driving in the United States. For example, based on preliminary results from a representative sample of weekend-nighttime and Friday daytime drivers, the National Highway Traffic Safety Administration's (NHTSA) 2013-2014 National Roadside Survey of Alcohol and Drug Use by Drivers ( NRS ) estimated that 20 percent of drivers would have tested positive for at least one drug, with marijuana being the most common drug. However, the survey does not capture the extent to which drivers were impaired by drugs. Arrest data and drug-testing results provide some information on drug-impaired driving, but these data are limited. For example, data for drug impairment may not be separated from that for alcohol impairment and drug testing is not standardized. According to NHTSA officials, currently available data on drug involvement in crashes are generally unreliable due to variances in reporting and testing.
The lack of a clear link between impairment and drug concentrations in the body makes it difficult to define drug impairment, which, in turn, exacerbates challenges related to enforcement and public awareness. Compared to alcohol, defining and identifying impairment due to drugs is more complicated due to the large number of available drugs and their unpredictable effects. For example, the NRS includes tests for 75 illegal prescriptions, and over-the-counter (OTC) drugs identified as potentially impairing. Additionally, law enforcement processes for obtaining samples for drug testing can be time consuming and result in a loss of evidence. For example, there is no validated device for roadside drug testing, and obtaining a search warrant to collect a blood sample to confirm the presence of drugs in a driver's system could take several hours, during which time the concentration of the drug in the driver's system could dissipate. Further, state officials identified limited public awareness about the dangers of drugged driving as a challenge. As a result, members of the public may drive while impaired without knowing the risks, potentially leading to collisions, injuries, and fatalities.
Federal and state agencies—including NHTSA, the White House Office of National Drug Control Policy (ONDCP), and the Department of Health and Human Services (HHS)—are taking actions to address drug-impaired driving, including improvements in the areas of research and data, education for police officers, evidence gathering, and legal changes. For example, NHTSA is currently conducting research to assess the crash risk associated with drug use (including illegal, prescription, and OTC drugs) by collecting samples from more than 10,000 drivers. However, public awareness of the dangers of drug-impaired driving is an area in which state officials told us that NHTSA could do more to support their efforts. As part of its mission to support state safety efforts, NHTSA has provided media and other materials to states for impaired-driving awareness programs, but these materials are focused on alcohol-impaired driving. While NHTSA plans to improve public awareness through initiatives to conduct surveys on drug-impaired-driving behaviors and attitudes as well as training for medical professionals, these plans could take several years to implement. Additional efforts, such as general messaging reminding the public about the impairing effects of drugs, could help improve public awareness in the near term.

What GAO Recommends

GAO recommends that NHTSA take additional actions to support states in emphasizing to the public the dangers of drug-impaired driving. DOT agreed with GAO's recommendation.