Marijuana Impairment and Driving : Challenges for Education and Enforcement

1. Marijuana Impairment and Driving: Challenges for Education and Enforcement Carol Flannagan, Ph.D. University of Michigan Transportation Research Institute March 20, 2019

2. Marijuana in Michigan • Medical marijuana was legalized in 2008 (Michigan Medical Marihuana Act, or MMMA) • Recreational marijuana was legalized in 2018 (Michigan Regulation and Taxation of Marihuana Act, or MRTMA; took effect Dec. 6, 2018)

3. Marijuana in Michigan • Current law requires demonstration of impairment due to marijuana ingestion to charge a driver with drugged driving • Zero tolerance policy for non-medical-marijuana users means any marijuana equals drugged driving, but this may change

4. Vocabulary • Marijuana = Marihuana -> common term for parts of the cannabis sativa plant • Cannabis -> technical term for marijuana • ∆9-tetrahydrocannabinol (∆9-THC) -> The primary psychoactive compound in marijuana & the primary compound measured in blood (but not the only one)

5. Does cannabis impair driving? In controlled laboratory, simulator and driving studies*, ∆9-THC: • Affects areas of the brain that control movement, balance, coordination, memory, and judgment • Impairscritical driving-related skills including reaction time, tracking ability, target detection, judgment, anticipation, divided attention, route planning and risk taking *Hartman, R. L., & Huestis, M. A. (2013). Cannabis effects on driving skills. Clinical chemistry, 59(3), 478-492

6. Does cannabis impair driving? • Cannabis-impaired subjects typically drive slower, keep greater following distances, and take fewer risks* • Alcohol-impaired subjects generally drive faster and take more risks when drunk • However, cannabis-impaired drivers do not fully mitigate the effects of the drug on driving skills, and acute cannabis intoxication can result in more risk taking rather than risk compensation. *Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

7. Does cannabis cause crashes? • National Academy of Sciences concluded that “there is substantial evidence of a statistical association between cannabis use and increased risk of motor vehicle crashes”* • Estimated the increased risk at 22% - 36% • A case-control study found that when concurrent alcohol and driver demographics were taken into account, the cannabis-specific risk goes away* • This may result from the low-severity crashes in the sample and not considering THC level in the analysis *Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

8. Does cannabis cause crashes? • Yes, but the specific risk increase isn’t nailed down • The risk for cannabis is less than alcohol • But drivers positive for ∆9-THC are often also positive for alcohol • This is called “polydrug impairment” and is a growing problem (more on this later)

9. Per se limits • Per se limits for Blood Alcohol Content (BAC) have been very successful in creating a clear definition of drunk driving and BAC-based laws have helped to reduce drunk driving worldwide • This is the “0.08” level, above which the driver is impaired per se • This approach is desirable for cannabis • Several states have set limits ranging from 1 ng/ml-5 ng/ml

10. Per se limits • Per se limits for Blood Alcohol Content (BAC) have been very successful in creating a clear definition of drunk driving and BAC-based laws have helped to reduce drunk driving worldwide • This is the “0.08” level, above which the driver is impaired per se • This approach is desirable for cannabis • Several states have set limits ranging from 1 ng/ml-5 ng/ml Remember these numbers

11. Blood levels of ∆9-THC Graph from: Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

12. Blood levels of ∆9-THC Initial rapid elimination phase—blood levels peak very quickly Graph from: Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

13. Blood levels of ∆9-THC Long terminal elimination phase—blood levels fade away very slowly Graph from: Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

14. Blood levels of ∆9-THC In chronic users, this tail can last for weeks even after quitting Graph from: Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

15. Blood levels of ∆9-THC It often takes 2 hours to get to drawing a blood sample after a traffic stop Graph from: Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

16. Blood levels of ∆9-THC 100 80 Blood ∆9-THC (ng/ml) 60 Percent of Baseline 40 20 Graph from: Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

17. Blood levels of ∆9-THC 100 80 Blood ∆9-THC (ng/ml) 60 Percent of Baseline 40 Worst performance at 90 mins 20 Graph from: Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

18. Blood levels of ∆9-THC Peak blood levels at 15-30 mins 100 80 Blood ∆9-THC (ng/ml) 60 Percent of Baseline 40 20 Graph from: Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

19. Blood levels of ∆9-THC 100 80 Blood ∆9-THC (ng/ml) 60 Percent of Baseline ~5 ng/ml (Did you remember the numbers???) 40 20 Graph from: Compton, R. P. (2017). Marijuana-impaired driving-a report to congress (No. DOT HS 812 440). United States. National Highway Traffic Safety Administration.

20. What does this mean? • Lack of correspondence between blood ∆9-THC and impairment • This requires particular emphasis on detecting (and documenting) impairment • Enter: Standardized Field Sobriety Tests (SFSTs)…

21. Role of SFSTs Standardized Field Sobriety Tests (SFSTs): • Many field tests have been studied for relationship to impairment • Three specific tests are scientifically validated on alcohol impairment and are generally admissible in court: • Horizontal gaze nystagmus (HGN): The subject is instructed to follow the movement of a light (or finger or other object) with only the eyes and no head movement; impaired subjects cannot follow the movement smoothly and a distinct jerk will appear prior to 45º. • Walk-and-turn test (WAT): The subject must walk nine heel-to-toe steps on a line, turn, and return along the line with nine heel-to-toe steps. • One-leg stand (OLS): The subject must raise one leg and hold it ~6 inches up while counting slowly until told to stop (at 30 sec.).

22. Role of SFSTs • More recent studies have looked at SFSTs and marijuana impairment Papafotiou, K., Carter, J. D., & Stough, C. (2005). An evaluation of the sensitivity of the Standardised Field Sobriety Tests (SFSTs) to detect impairment due to marijuana intoxication. Psychopharmacology, 180(1), 107-114

23. Role of SFSTs • SFSTs do correspond to cannabis-impaired driving, but not as well as for alcohol • In the field, SFSTs are only administered when other evidence of impaired driving is observed • The study authors note that in combination with observations of impaired driving behavior, the SFSTs also identify cannabis impairment well enough • Alcohol is often present in cannabis-impaired drivers, making SFSTs more likely to be effective tools for determining impairment Papafotiou, K., Carter, J. D., & Stough, C. (2005). An evaluation of the sensitivity of the Standardised Field Sobriety Tests (SFSTs) to detect impairment due to marijuana intoxication. Psychopharmacology, 180(1), 107-114

24. Role of SFSTs • But more research is needed! • Need to consider additional SFSTs to be validated specifically for cannabis impairment

25. Polydrug Impairment • Drivers who test positive for ∆9-THC are more often also positive for alcohol or other drugs than ∆9-THC-negative drivers • In a 2013 roadside survey, during the day, drug-positive drivers were over three times as likely to have BAC≥0.08 compared to the average driver (1.4% vs. 0.4%) • At night, drug positive drivers were slightly more likely to have BAC≥0.08 than the average driver (1.7% vs. 1.5%)

26. Trends in Michigan: Drug-Involved Crashes • Graph shows all drug-involved crashes • Cannabinoids are 70% of drug-positive tests

27. Trends in Michigan • Of the 540 drivers who tested positive for cannabinoids and also had alcohol tests, 44% had been drinking before driving (i.e., had non-zero BAC) and 11% were over the 0.08 BAC limit • In Michigan (and many other states), drug tests are typically not done if BAC≥0.10 • This makes it difficult to get an accurate estimate of polydrug use • Polydrug use is likely higher than estimated

28. What can we do? Enforcement • Oral fluids study conducted in four counties showed promising results with correspondence between oral and blood results • Oral fluids have the advantage of being sensitive to recent use (even of edibles) • Oral fluid testing can be done at roadside, avoiding delays when blood levels drop • Report available at: https://www.michigan.gov/documents/msp/Oral_Fluid_Report_646833_7.pdf

29. What can we do? Enforcement • Greater training for officers in recognizing signs of cannabis-impairment • Broader Advanced Roadside Impaired Driving Enforcement (ARIDE) training • Expansion of the Drug Recognition Expert (DRE) program

30. ARIDE • ARIDE training is intended to bridge the gap between the SFST and DEC/DRE programs by providing officers with general knowledge related to drug impairment • 16-hour training course taught by DRE instructors • Sessions include: • Introduction and Overview of Drugs and Highway Safety • SFST Update, Review and Proficiency Examination • Observations of Eyes and other Sobriety Tests to Detect Alcohol and Drug Impairment • Seven Drug Categories • Effects of Drug Combinations • Pre- and Post-Arrest Procedures

31. Drug Recognition Experts (DRE) • DREs undergo substantial training (2-3 weeks of intensive classroom and practical work) • A DRE conducts a detailed, diagnostic examination of persons arrested or suspected of drug-impaired driving or similar offenses. Based on the results of the drug evaluation, the DRE forms an expert opinion on the following: • Is the person impaired? If so, is the person able to operate a vehicle safely? If the DRE concludes that the person is impaired… • Is the impairment due to an injury, illness or other medical complication, or is it drug-related? If the impairment is due to drugs… • Which category or combination of categories of drugs is the most likely source of the impairment?

32. Drug Recognition Experts (DRE) • While ARIDE training is meant for all officers, DREs are a small subset • Ideally, DREs are deployed around the state and can be called in to evaluate as needed

33. What can we do? Education • Public misconceptions about the safety of cannabis-impaired driving are common • According to a GHSA report: • In surveys and focus groups with regular marijuana users in Colorado and Washington, almost all believed that marijuana doesn’t impair their driving, and some believed that marijuana improves their driving • Most regular marijuana users surveyed in Colorado and Washington drove “high” on a regular basis. They believe it is safer to drive after using marijuana than after drinking alcohol. They believe that they have developed a tolerance for marijuana effects and can compensate for any effects, for instance by driving more slowly or by allowing greater headways.

34. What can we do? Education • Educational campaigns are being developed in many states, especially those with recreational marijuana • Campaigns that engage the dispensary industry in helping get the message out are thought to be more effective

35. What can we do? Education • According to GHSA, drivers need to understand: • That marijuana can impair driving • That driving while impaired by marijuana is illegal

36. What can we do? Research • Research is needed in several areas: • Oral fluids and other biological tests of the presence and impairing levels of ∆9-THC in the body • SFSTs (i.e., behavioral tests) that are most diagnostic of ∆9-THC impairment • Effects of polydrug impairment, especially involving alcohol and cannabis (or other drugs), on driving

37. Thank you! (Questions?)