There is a growing body of scientific evidence which demonstrates drugged driving to be a leading cause of traffic crashes, injuries, and fatalities. IBH shares its collection of drugged driving research information from various experts, articles, and national health and drug prevention organizations. In 2011, IBH developed a Drugged Driving White Paper that summarizes current drugged driving research and provides perspective regarding future research needs.
a. Scientific Studies and Policy Articles
Whitehill, J. M., Rivara, F. P., & Moreno, M. A. (2014). Marijuana-using drivers, alcohol-using drivers, and their passengers. JAMA Pediatrics. doi:10.1001/jamapediatrics.2013.5300
Importance. Driving after marijuana use increases the risk of a motor vehicle crash. Understanding this behavior among young drivers and how it may differ from alcohol-related driving behaviors could inform prevention efforts. Objective. To describe the prevalence, sex differences, and risk factors associated with underage college students' driving after using marijuana, driving after drinking alcohol, or riding with a driver using these substances. Design, Setting, and Participants. Cross-sectional telephone survey of a random sample of 315 first-year college students (aged 18-20 years) from 2 large public universities, who were participating in an ongoing longitudinal study. At recruitment, 52.8% of eligible individuals consented to participate; retention was 93.2% one year later when data for this report were collected. Main Outcomes and Measures. Self-reported past-28-day driving after marijuana use, riding with a marijuana-using driver, driving after alcohol use, and riding with an alcohol-using driver. Results. In the prior month, 20.3% of students had used marijuana. Among marijuana-using students, 43.9% of male and 8.7% of female students drove after using marijuana (P < .001), and 51.2% of male and 34.8% of female students rode as a passenger with a marijuana-using driver (P = .21). Most students (65.1%) drank alcohol, and among this group 12.0% of male students and 2.7% of female students drove after drinking (P = .01), with 20.7% and 11.5% (P = .07), respectively, reporting riding with an alcohol-using driver. Controlling for demographics and substance use behaviors, driving after substance use was associated with at least a 2-fold increase in risk of being a passenger with another user; the reverse was also true. A 1% increase in the reported percentage of friends using marijuana was associated with a 2% increased risk of riding with a marijuana-using driver (95% CI,?1.01-1.03). Among students using any substances, past-28-day use of only marijuana was associated with a 6.24-fold increased risk of driving after substance use compared with using only alcohol (95% CI, 1.89-21.17). Conclusions and Relevance. Driving and riding after marijuana use is common among underage, marijuana-using college students. This is concerning given recent legislation that may increase marijuana availability.
Patterns of Alcohol and Marijuana Use and Unsafe Driving Among High School Seniors
Terry, McElrath, Y. M., O'Malley, P. M., & Johnston, L. D. (2014). Alcohol and marijuana use patterns associated with unsafe driving among U.S. high school seniors: high use frequency, concurrent use, and simultaneous use. Journal of Studies on Alcohol and Drugs, 75, 378-389.
Objective. This article examines noncausal associations between high school seniors' alcohol and marijuana use status and rates of self-reported unsafe driving in the past 12 months. Method. Analyses used data from 72,053 students collected through annual surveys of nationally representative cross-sectional samples of U.S. 12th-grade students from 1976 to 2011. Two aspects of past-12-month alcohol and marijuana use were examined: (a) use frequency and (b) status as a nonuser, single substance user, concurrent user, or simultaneous user. Measures of past-12-month unsafe driving included any tickets/warnings or accidents, as well as tickets/warnings or accidents following alcohol or marijuana use. Analyses explored whether an individual's substance use frequency and simultaneous use status had differential associations with their rate of unsafe driving. Results. Higher substance use frequency (primarily alcohol use frequency) was significantly and positively associated with unsafe driving. The rate of engaging in any unsafe driving was also significantly and positively associated with simultaneous use status, with the highest rate associated with simultaneous use, followed by concurrent use, followed by use of alcohol alone. Individuals who reported simultaneous use most or every time they used marijuana had the highest likelihood of reporting unsafe driving following either alcohol or marijuana use. Conclusions. This article expands the knowledge on individual risk factors associated with unsafe driving among teens. Efforts to educate U.S. high school students (especially substance users), parents, and individuals involved in prevention programming and driver's education about the increased risks associated with various forms of drug use status may be useful.
Association Between Riding With an Impaired Driver and Driving While Impaired
Li, K., Simons-Morton, B. G., Vaca, F. E., & Hingson, R. (2014). Association between riding with an impaired driver and driving while impaired. Pediatrics. doi: 10.1542/peds.2013-2786
Objective. To examine the association between driving while alcohol/drug impaired (DWI) and the timing and amount of exposure to others' alcohol/drug-impaired driving (riding while impaired [RWI]) and driving licensure timing among teenage drivers. Methods. The data were from waves 1, 2, and 3 (W1, W2, and W3, respectively) of the NEXT Generation Study, with longitudinal assessment of a nationally representative sample of 10th graders starting in 2009-2010. Multivariate logistic regression was used for the analyses. Results. Teenagers exposed to RWI at W1 (adjusted odds ratio [AOR] = 21.12, P < .001), w2 (aor = 19.97, P < .001), and W3 (AOR = 30.52, P < .001) were substantially more likely to DWI compared with those reporting never RWI. Those who reported RWI at 1 wave (AOR = 10.89, P < .001), 2 waves (AOR = 34.34, P < .001), and all 3 waves (AOR = 127.43, P < .001) were more likely to DWI compared with those who never RWI. Teenagers who reported driving licensure at W1 were more likely to DWI compared with those who were licensed at W3 (AOR = 1.83, P < .05). Conclusions. The experience of riding in a vehicle with an impaired driver increased the likelihood of future DWI among teenagers after licensure. There was a strong, positive dose-response association between RWI and DWI. Early licensure was an independent risk factor for DWI. The findings suggest that RWI and early licensure could be important prevention targets.
Recommendations for Toxicological Investigation of Impaired Driving and Motor Vehicle Fatalities
Logan BK1, Lowrie KJ, Turri JL, Yeakel JK, Limoges JF, Miles AK, Scarneo CE, Kerrigan S, Farrell LJ. Recommendations for toxicological investigation of drug-impaired driving and motor vehicle fatalities. J Anal Toxicol. 2013 Oct;37(8):552-8.
This report describes the review and update of a set of minimum recommendations for the toxicological investigation of suspected alcohol and drug-impaired driving cases and motor vehicle fatalities involving drugs or alcohol. The recommendations have the goal of ensuring that a consistent set of data regarding the most frequently encountered drugs linked to driving impairment is collected for practical application in the investigation of these cases and to allow epidemiological monitoring and the development of evidence-based public policy on this important public safety issue. The recommendations are based on a survey of practices in US laboratories performing this kind of analysis, consideration of existing epidemiological crash and arrest data and practical considerations of widely available technology platforms in laboratories performing this work. The final recommendations were derived from a consensus meeting of experts recruited from survey respondents and the membership of the National Safety Council's Alcohol, Drug and Impairment Division (formerly known as the Committee on Alcohol and Other Drugs, CAOD).
Recent Increases in the Prevalence of Drugs Among Fatally Injured Drivers
Brady, J. E., & Li, G. (2013). Trends in alcohol and other drugs detected in fatally injured drivers in the United States, 1999-2010. American Journal of Epidemiology. doi: 10.1093/aje/kwt327
Drugged driving is a safety issue of increasing public concern. Using data from the Fatality Analysis Reporting System for 1999-2010, we assessed trends in alcohol and other drugs detected in drivers who were killed within 1 hour of a motor vehicle crash in 6 US states (California, Hawaii, Illinois, New Hampshire, Rhode Island, and West Virginia) that routinely performed toxicological testing on drivers involved in such crashes. Of the 23,591 drivers studied, 39.7% tested positive for alcohol and 24.8% for other drugs. During the study period, the prevalence of positive results for nonalcohol drugs rose from 16.6% in 1999 to 28.3% in 2010 (Z = -10.19, P < 0.0001), whereas the prevalence of positive results for alcohol remained stable. the most commonly detected nonalcohol drug was cannabinol, the prevalence of which increased from 4.2% in 1999 to 12.2% in 2010 (z = -13.63, P < 0.0001). The increase in the prevalence of nonalcohol drugs was observed in all age groups and both sexes. These results indicate that nonalcohol drugs, particularly marijuana, are increasingly detected in fatally injured drivers.
Drug-Positive Drivers Have Triple the Risk of Fatal Crash
Li G, Brady, JE, Chen Q. Drug use and fatal motor vehicle crashes: a case-control study. Accident Anal Prev. 2013 Nov; 60:205-210.
Drugged driving is a serious safety concern, but its role in motor vehicle crashes has not been adequately studied. Using a case-control design, the authors assessed the association between drug use and fatal crash risk. Cases (n = 737) were drivers who were involved in fatal motor vehicle crashes in the continental United States during specific time periods in 2007, and controls (n = 7719) were participants of the 2007 National Roadside Survey of Alcohol and Drug Use by Drivers. Overall, 31.9% of the cases and 13.7% of the controls tested positive for at least one non-alcohol drug. The estimated odds ratios of fatal crash involvement associated with specific drug categories were 1.83 [95% confidence interval (CI): 1.39, 2.39] for marijuana, 3.03 (95% CI: 2.00, 4.48) for narcotics, 3.57 (95% CI: 2.63, 4.76) for stimulants, and 4.83 (95% CI: 3.18, 7.21) for depressants. Drivers who tested positive for both alcohol and drugs were at substantially heightened risk relative to those using neither alcohol nor drugs (Odds Ratio = 23.24; 95% CI: 17.79, 30.28). These results indicate that drug use is associated with a significantly increased risk of fatal crash involvement, particularly when used in combination with alcohol. Health Day article.
Driving After Drug or Alcohol Use by US High School Seniors
O'Malley, P. M., & Johnston, L. D. (2013). Driving after drug or alcohol use by US high school seniors, 2001-2011. American Journal of Public Health, 103(11), 2027-2034.
Objectives. We examined prevalence, trends, and correlates of driving or riding after use of drugs or alcohol among US high school seniors from 2001 to 2011. Methods. Data come from Monitoring the Future, an annual survey of nationally representative samples of high school seniors. We used logistic regressions with data from more than 22,000 respondents to examine multivariate associations with demographic and lifestyle factors. Results. Large numbers of US high school seniors put themselves and others at great risk of harm by driving after using marijuana or other illicit drugs or drinking alcohol or by riding in a vehicle whose driver had used marijuana, other illicit drugs, or alcohol. Driving after drinking has declined in recent years, but driving after use of marijuana has increased. A higher percentage of students reported driving after using marijuana than after having 5 or more alcoholic drinks. Risky driving and riding behaviors differed little between demographic subgroups but considerably according to lifestyle factors. Conclusions. Stronger efforts are needed to combat adolescent driving under the influence of illicit drugs.
Patterns of Drug Use in Fatal Crashes
The following abstract is from the article: Romano E, Pollini RA. Patterns of drug use in fatal crashes. Addiction. 2013, 108(8): 1428-1438.
Aims. To characterize drug prevalence among fatally injured drivers, identify significant associations (i.e. day of week, time of day, age, gender), and compare findings with those for alcohol. Design. Descriptive and logistic mixed-model regression analyses of Fatality Analysis Reporting System data. Setting. US states with drug test results for >80% of fatally injured drivers, 1998-2010. Participants. Drivers killed in single-vehicle crashes on public roads who died at the scene of the crash (n = 16 942). Measurements. Drug test results, blood alcohol concentration (BAC), gender, age and day and time of crash. Findings. Overall, 45.1% of fatally injured drivers tested positive for alcohol (39.9% BAC ≥ 0.08) and 25.9% for drugs. The most common drugs present were stimulants (7.2%) and cannabinols (7.1%), followed by 'other' drugs (4.1%), multiple drugs (4.1%), narcotics (2.1%) and depressants (1.5%). Drug-involved crashes occurred with relative uniformity throughout the day while alcohol-involved crashes were more common at night (P < 0.01). the odds of testing positive for drugs varied depending upon drug class, driver characteristics, time of day and the presence of alcohol. Conclusions. Fatal single-vehicle crashes involving drugs are less common than those involving alcohol and the characteristics of drug-involved crashes differ, depending upon drug class and whether alcohol is present. Concerns about drug-impaired driving should not detract from the current law enforcement focus on alcohol-impaired driving.
Commentary: DuPont RL, Talpins SK, Shea CL. Commentary on Romano & Pollini (2013): Stopping drug-impaired driving and alcohol-impaired driving - synergy, not competition. Addiction. 2013, 108(8), 1439-1440.
Effects of Marijuana on Driving Skills
The following abstract is from the article: Hartman RL, Huestis MA. Cannabis effects on driving skills. Clin Chem. 2013 Mar;59(3):478-92. doi: 10.1373/clinchem.2012.194381.
Background. Cannabis is the most prevalent illicit drug identified in impaired drivers. The effects of cannabis on driving continue to be debated, making prosecution and legislation difficult. Historically, delays in sample collection, evaluating the inactive 9-tetrahydrocannabinol (THC) metabolite 11-nor-9-carboxy-THC, and polydrug use have complicated epidemiologic evaluations of driver impairment after cannabis use. Content. We review and evaluate the current literature on cannabis' effects on driving, highlighting the epidemiologic and experimental data. Epidemiologic data show that the risk of involvement in a motor vehicle accident (MVA) increases approximately 2-fold after cannabis smoking. The adjusted risk of driver culpability also increases substantially, particularly with increased blood THC concentrations. Studies that have used urine as the biological matrix have not shown an association between cannabis and crash risk. Experimental data show that drivers attempt to compensate by driving more slowly after smoking cannabis, but control deteriorates with increasing task complexity. Cannabis smoking increases lane weaving and impaired cognitive function. Critical-tracking tests, reaction times, divided-attention tasks, and lane-position variability all show cannabis-induced impairment. Despite purported tolerance in frequent smokers, complex tasks still show impairment. Combining cannabis with alcohol enhances impairment, especially lane weaving. Summary. Differences in study designs frequently account for inconsistencies in results between studies. Participant-selection bias and confounding factors attenuate ostensible cannabis effects, but the association with MVA often retains significance. Evidence suggests recent smoking and/or blood THC concentrations 2-5 ng/mL are associated with substantial driving impairment, particularly in occasional smokers. Future cannabis-and-driving research should emphasize challenging tasks, such as divided attention, and include occasional and chronic daily cannabis smokers.
Detection of Cannabinioids Among Daily Marijuana Smokers During Abstinence
The following abstract is from the article: Bergamaschi MM, Karschner EL, Goodwin RS, Scheidweiler KB, Hirvonen J, Queiroz RH, Huestis MA. Impact of prolonged cannabinoid excretion in chronic daily cannabis smokers' blood on per se drugged driving laws. Clin Chem. 2013 Mar;59(3):519-26. doi: 10.1373/clinchem.2012.195503.
Background. Cannabis is the illicit drug most frequently reported with impaired driving and motor vehicle accidents. Some "per se" laws make it illegal to drive with any amount of drug in the body, while others establish blood, saliva, or urine concentrations above which it is illegal to drive. The persistence of -tetrahydrocannabinol (THC) in chronic daily cannabis smokers' blood is unknown. Methods. Thirty male chronic daily cannabis smokers resided on a secure research unit for up to 33 days, with daily blood collection. Samples were processed in an ice bath during sample preparation to minimize cannabinoid adsorption onto precipitant material. We quantified THC by 2-dimensional GC-MS. Results. Of the 30 participants, 27 were THC-positive on admission, with a median (range) concentration of 1.4 μg/L (0.3-6.3). THC decreased gradually; only 1 of 11 participants was negative at 26 days, 2 of 5 remained THC-positive (0.3 μg/L) for 30 days, and 5.0% of participants had THC ≥1.0 μg/L for 12 days. Median 11-hydroxy-THC concentrations were 1.1 μg/L on admission, with no results ≥1.0 μg/L 24 h later. 11-Nor-9-carboxy-THC (THCCOOH) detection rates were 96.7% on admission, decreasing slowly to 95.7% and 85.7% on days 8 and 22, respectively; 4 of 5 participants remained THCCOOH positive (0.6-2.7 μg/L) after 30 days, and 1 remained positive on discharge at 33 days. Conclusions. Cannabinoids can be detected in blood of chronic daily cannabis smokers during a month of sustained abstinence. This is consistent with the time course of persisting neurocognitive impairment reported in recent studies.
Quantifying THC Concentrations in Chronic Marijuana Users During Continuous Monitored Abstinence
The following abstract is from the article: Karschner EL, Schwilke EW, Lowe RH, Darwin WD, Pope HG, Herning R, Cadet JL, Huestis MA. Do Delta9-tetrahydrocannabinol concentrations indicate recent use in chronic cannabis users Addiction. 2009 Dec;104(12):2041-8. doi: 10.1111/j.1360-0443.2009.02705.x. Epub 2009 Oct 5.
Aims. To quantify blood Delta(9)-tetrahydrocannabinol (THC) concentrations in chronic cannabis users over 7 days of continuous monitored abstinence. Participants. Twenty-five frequent, long-term cannabis users resided on a secure clinical research unit at the US National Institute on Drug Abuse under continuous medical surveillance to prevent cannabis self-administration. Measurements. Whole blood cannabinoid concentrations were determined by two-dimensional gas chromatography-mass spectrometry. Findings. Nine chronic users (36%) had no measurable THC during 7 days of cannabis abstinence; 16 had at least one positive THC > or =0.25 ng/ml, but not necessarily on the first day. On day 7, 6 full days after entering the unit, six participants still displayed detectable THC concentrations [mean +/- standard deviation (SD), 0.3 +/- 0.7 ng/ml] and all 25 had measurable carboxy-metabolite (6.2 +/- 8.8 ng/ml). The highest observed THC concentrations on admission (day 1) and day 7 were 7.0 and 3.0 ng/ml, respectively. Interestingly, five participants, all female, had THC-positive whole blood specimens over all 7 days. Body mass index did not correlate with time until the last THC-positive specimen (n = 16; r = -0.2; P = 0.445). Conclusions. Substantial whole blood THC concentrations persist multiple days after drug discontinuation in heavy chronic cannabis users. It is currently unknown whether neurocognitive impairment occurs with low blood THC concentrations, and whether return to normal performance, as documented previously following extended cannabis abstinence, is accompanied by the removal of residual THC in brain. These findings also may impact on the implementation of per se limits in driving under the influence of drugs legislation.
Downregulation of Brain Cannabinoid CB1 Receptors in Chronic Daily Marijuana Users
The following abstract is from the article: Hirvonen J, Goodwin RS, Li CT, Terry GE, Zoghbi SS, Morse C, Pike VW, Volkow ND, Huestis MA, Innis RB. Reversible and regionally selective downregulation of brain cannabinoid CB1 receptors in chronic daily cannabis smokers. Mol Psychiatry. 2012 Jun;17(6):642-9. doi: 10.1038/mp.2011.82. Epub 2011 Jul 12.
Chronic cannabis (marijuana, hashish) smoking can result in dependence. Rodent studies show reversible downregulation of brain cannabinoid CB(1) (cannabinoid receptor type 1) receptors after chronic exposure to cannabis. However, whether downregulation occurs in humans who chronically smoke cannabis is unknown. Here we show, using positron emission tomography imaging, reversible and regionally selective downregulation of brain cannabinoid CB(1) receptors in human subjects who chronically smoke cannabis. Downregulation correlated with years of cannabis smoking and was selective to cortical brain regions. After 4 weeks of continuously monitored abstinence from cannabis on a secure research unit, CB(1) receptor density returned to normal levels. This is the first direct demonstration of cortical cannabinoid CB(1) receptor downregulation as a neuroadaptation that may promote cannabis dependence in human brain.
The Mirage of Impairing Drug Concentration Thresholds
The following abstract is from the article: Reisfield GM, Goldberger BA, Gold MS, DuPont RL. The mirage of impairing drug concentration thresholds: a rationale for zero tolerance per se driving under the influence of drugs laws. J Anal Toxicol. 2012 Jun;36(5):353-6.
Motor vehicle crashes are a leading cause of morbidity and mortality in
the United States. Drivers with measurable quantities of potentially
impairing illicit or prescription drugs in their body fluids are multiple
times more likely to be involved in motor vehicle crashes than those
without such drugs in their bodies. Drug-related impairment, however,
cannot be inferred solely on the basis of the presence of drugs in
biological fluids. Thus, for more than a quarter century, there has been a
search for drug blood concentrations that are the equivalent of the 0.08
g/dL threshold for alcohol-impaired driving in the United States. We
suggest that such equivalents are a mirage, and cannot be determined due
to variable drug tolerance, lack of consistent relationships between drug
blood concentrations and impairment, innumerable drug combinations and
multiple other factors. Thus, while the idea of determining impairing drug
concentrations is attractive, it is ultimately unattainable, and
withholding drugged driving legislation pending the acquisition of such
data is tantamount to a plan for inaction with regard to an important and
growing public health and safety problem. We propose specific legislation
to address alcohol- and drug-impaired driving in the United States.
The Need for Per Se Laws
The following abstract is from the article: DuPont RL, Voas RB, Walsh JM, Shea C, Talpins SK, Neil MM. The need for drugged driving per se laws: a commentary. Traffic Inj Prev. 2012;13(1):31-42.
Objective: Triggered by the new federal commitment announced by the Office
of National Drug Control Policy (ONCDP) to encourage states to enact
drugged driving per se laws, this article reviews the reasons to establish
such laws and the issues that may arise when trying to enforce them.
Methods: A review of the state of drunk driving per se laws and their
implications for drugged driving is presented, with a review of impaired
driving enforcement procedures and drug testing technology. Results:
Currently, enforcement of drugged driving laws is an adjunct to the
enforcement of laws regarding alcohol impairment. Drivers are apprehended
when showing signs of alcohol intoxication and only in the relatively few
cases where the blood alcohol concentration of the arrested driver does
not account for the observed behavior is the possibility of drug
impairment pursued. In most states, the term impaired driving covers both
alcohol and drug impairment; thus, driver conviction records may not
distinguish between the two different sources of impairment. As a result,
enforcement statistics do not reflect the prevalence of drugged driving.
Conclusions: Based on the analysis presented, this article recommends a
number of steps that can be taken to evaluate current drugged driving
enforcement procedures and to move toward the enactment of drug per se
Marijuana and Alcohol, a Dangerous Driving Combination
The following abstract is from the article: Sewell RA, Poling J, Sofuoglu M. The effect of cannabis compared with alcohol on driving. Am J Addict. 2009;18(3):185-93.
The prevalence of both alcohol and cannabis use and the high morbidity associated with motor vehicle crashes has lead to a plethora of research on the link between the two. Drunk drivers are involved in 25% of motor vehicle fatalities, and many accidents involve drivers who test positive for cannabis. Cannabis and alcohol acutely impair several driving-related skills in a dose-related fashion, but the effects of cannabis vary more between individuals than they do with alcohol because of tolerance, differences in smoking technique, and different absorptions of Delta(9)-tetrahydrocannabinol (THC), the active ingredient in marijuana. Detrimental effects of cannabis use vary in a dose-related fashion, and are more pronounced with highly automatic driving functions than with more complex tasks that require conscious control, whereas alcohol produces an opposite pattern of impairment. Because of both this and an increased awareness that they are impaired, marijuana smokers tend to compensate effectively while driving by utilizing a variety of behavioral strategies. Combining marijuana with alcohol eliminates the ability to use such strategies effectively, however, and results in impairment even at doses which would be insignificant were they of either drug alone. Epidemiological studies have been inconclusive regarding whether cannabis use causes an increased risk of accidents; in contrast, unanimity exists that alcohol use increases crash risk. Furthermore, the risk from driving under the influence of both alcohol and cannabis is greater than the risk of driving under the influence of either alone. Future research should focus on resolving contradictions posed by previous studies, and patients who smoke cannabis should be counseled to wait several hours before driving, and avoid combining the two drugs.
Risk of Injury by Driving with Alcohol and Other Drugs
The DRUID (Driving Under the Influence of Drugs, Alcohol and Medicines) Project released a report assessing the risk of driving with alcohol, illicit drugs, and medicines in various European countries. Researchers calculated the risk of serious or fatal injury in a crash while positive for a substance. The highest risk of injury is associated with high alcohol concentrations and alcohol combined with other psychoactive drugs, followed by medium alcohol concentrations, multiple drug use, and amphetamines. Overall, driving with alcohol and drugs produced higher risk of serious of fatal injury -- between 2 and 200 times that of sober drivers. Full Report.
Marijuana Use and Car Crash Injury
The following abstract is from the article: Blows S, Ivers RQ, Connor J, Ameratunga S, Woodward M, Norton R. Marijuana Use and Car Crash Injury. Addiction. 2005 ;100(5):605-11.
Aims: To investigate the relationship between marijuana use prior to driving, habitual marijuana use and car crash injury. Design and Setting: Population based case-control study in Auckland, New Zealand. Participants: Case vehicles were all cars involved in crashes in which at least one occupant was hospitalized or killed anywhere in the Auckland region, and control vehicles were a random sample of cars driving on Auckland roads. The drivers of 571 case and 588 control vehicles completed a structured interview. Measurements: Self reported marijuana use in the 3 hours prior to the crash/survey and habitual marijuana use over the previous 12 months were recorded, along with a range of other variables potentially related to crash risk. The main outcome measure was hospitalization or death of a vehicle occupant due to car crash injury. Findings: Acute marijuana use was significantly associated with car crash injury, after controlling for the confounders age, gender, ethnicity, education level, passenger carriage, driving exposure and time of day (OR 3.9, 95% CI 1.2-12.9). However, after adjustment for these confounders plus other risky driving at the time of the crash (blood alcohol concentration, seat-belt use, travelling speed and sleepiness score), the effect of acute marijuana intake was no longer significant (OR 0.8, 95% CI 0.2-3.3). There was a strong significant association between habitual use and car crash injury after adjustment for all the above confounders plus acute use prior to driving (OR 9.5, 95% CI 2.8-32.3). Conclusions: This population-based case-control study indicates that habitual use of marijuana is strongly associated with car crash injury. The nature of the relationship between marijuana use and risk-taking is unclear and needs further research. The prevalence of marijuana use in this driving population was low, and acute use was associated with habitual marijuana use, suggesting that intervention strategies may be more effective if they are targeted towards high use groups.
One Third of Fatally Injured Drivers Recently Used Drugs
A new report released by the National Highway Transportation Safety Administration (NHTSA) shows that one third of all drug tests on drivers killed in motor vehicle accidents were positive for drugs in 2009. Although drug involvement does not imply driver impairment or indicate that drug use was the cause of the crash, the large presence of drugs among drivers is of great concern. Reducing drugged driving has been named a national priority for the United States and this data reflects the immense presence of both illegal and prescription drugs which can have impairing effects. Full Report.
2007 National Roadside Survey Shows Drugged Driving is as Widespread as Drunk Driving
The recently released NHTSA 2007 National Roadside Survey (NRS) was the first US national random-stop roadside survey to collect oral fluid and/or blood samples from drivers for laboratory testing of illegal drugs as well as for alcohol. Of all weekend nighttime drivers sampled who were willing to provide specimens, 12.4% were positive for alcohol while 16.3% were positive for illegal, prescription, or over-the-counter drugs which could possibly cause impairment. Only 2.2% of drivers had blood alcohol concentrations at or above the legal limit of 0.08 g/dL. Of the 16.3% of drivers positive for drugs, 11.3% were positive for illegal drugs, 3.9% for medications and 1.1% for both illegal drugs and medications. The most common illegal drugs were cannabis (8.6%), cocaine (3.9%) and methamphetamine (1.3%). Read the IBH Commentary and NHTSA Research Note.
Marijuana May Double the Risk of Motor Vehicle Crashes
The following abstract is from the article: Li M, Brady JE, DiMaggio CJ, Lusardi AR, Tzong KY, Li G. Marijuana use and motor vehicle crashes. Epidemiol Rev 2011 [Epub ahead of print].
Since 1996, 16 states and the District of Columbia in the United States have enacted legislation to decriminalize marijuana for medical use. Although marijuana is the most commonly detected nonalcohol drug in drivers, its role in crash causation remains unsettled. To assess the association between marijuana use and crash risk, the authors performed a meta-analysis of 9 epidemiologic studies published in English in the past 2 decades identified through a systematic search of bibliographic databases. Estimated odds ratios relating marijuana use to crash risk reported in these studies ranged from 0.85 to 7.16. Pooled analysis based on the random-effects model yielded a summary odds ratio of 2.66 (95% confidence interval: 2.07, 3.41). Analysis of individual studies indicated that the heightened risk of crash involvement associated with marijuana use persisted after adjustment for confounding variables and that the risk of crash involvement increased in a dose-response fashion with the concentration of 11-nor-9-carboxy-delta-9-tetrahydrocannabinol detected in the urine and the frequency of self-reported marijuana use. The results of this meta-analysis suggest that marijuana use by drivers is associated with a significantly increased risk of being involved in motor vehicle crashes.
The following abstract is from the article: Ashbridge, M., Hayden, J. A., & Cartwright, J. L. (2012). Acute cannabis consumption and motor vehicle collision risk: Systematic review of observational studies and meta-analysis. British Medical Journal, 344:e536 doi: 10.1136/bmj.e536
Abstract: Objective To determine whether the acute consumption of cannabis (cannabinoids) by drivers increases the risk of a motor vehicle collision. Design. Systematic review of observational studies, with meta-analysis. Data sources. We did electronic searches in 19 databases, unrestricted by year or language of publication. We also did manual searches of reference lists, conducted a search for unpublished studies, and reviewed the personal libraries of the research team. Review methods. We included observational epidemiology studies of motor vehicle collisions with an appropriate control group, and selected studies that measured recent cannabis use in drivers by toxicological analysis of whole blood or self report. We excluded experimental or simulator studies. Two independent reviewers assessed risk of bias in each selected study, with consensus, using the Newcastle-Ottawa scale. Risk estimates were combined using random effects models. Results. We selected nine studies in the review and meta-analysis. Driving under the influence of cannabis was associated with a significantly increased risk of motor vehicle collisions compared with unimpaired driving (odds ratio 1.92 (95% confidence interval 1.35 to 2.73); P=0.0003); we noted heterogeneity among the individual study effects (I2=81). Collision risk estimates were higher in case-control studies (2.79 (1.23 to 6.33); P=0.01) and studies of fatal collisions (2.10 (1.31 to 3.36); P=0.002) than in culpability studies (1.65 (1.11 to 2.46); P=0.07) and studies of non-fatal collisions (1.74 (0.88 to 3.46); P=0.11). Conclusions. Acute cannabis consumption is associated with an increased risk of a motor vehicle crash, especially for fatal collisions. This information could be used as the basis for campaigns against drug impaired driving, developing regional or national policies to control acute drug use while driving, and raising public awareness.
New Study Shows Tough Laws and Treatment are Top Deterrents Against DUI Offenders
A University of Montana study that targeted repeat DUI offenders shows that tougher laws and chemical dependency treatment are the strongest deterrents to chronic drunken driving. In Montana where a DUI becomes a felony after the fourth offense, felony DUI offenders say that penalties for initial DUIs are not tough enough. Full report.
Large Majority of Drivers Ages 55 and Older Are Unaware of Potentially Dangerous Combination of Medications and Driving
The AAA Foundation for Traffic Safety released a report in August 2009 of a survey of community dwelling drivers 55 years and older to assess knowledge regarding prescription and over the counter (OTC) medication use and driving. Ninety-five percent of respondents 55 and older had one or more medical conditions and 78% used one or more medications, yet only 28% indicated some awareness of the potential impact on driving performance associated with those medications. Full Report.
More Than Half of Motor Vehicle Crash Drivers Tested Positive for Drugs Other Than Alcohol in a Level-1 Trauma Center
The following abstract is from the article: Walsh JM, Flegel R, Cangianelli LA, Atkins R, Soderstrom CA, Kerns TJ. Epidemiology of alcohol and other drug use among motor vehicle crash victims admitted to a Level-1 trauma center. Traffic Inj Prev 2004;5:254 - 60.
The purpose of this research was to determine the incidence and prevalence of drug use, alcohol use, and the combination of drug and alcohol use among motor vehicle crash (MVC) victims admitted to a Level-1 trauma center. In a 90-day study, nearly two-thirds of trauma center admissions were victims of motor vehicle crashes. Blood and urine was collected from 168 MVC victims of whom 108 were identified as the driver in the crash. Toxicology results indicated that 65.7% of drivers tested positive for either commonly abused drugs or alcohol. More than half of the drivers tested positive for drugs (50.9%) other than alcohol, with one in four drivers testing positive for marijuana use. About one-third of those using drugs had also been drinking, but alcohol was detected in only 30.6% of all injured drivers. Within the total MVC patient pool, passenger drug/alcohol use was equivalent to the driver population; however, injured pedestrians had higher rates of alcohol only than other MVC victims. There were no significant differences in drug and alcohol use between MVCs and trauma admissions of other causes. Of the patients with positive toxicology results, less than half (42%) were referred for evaluation for substance abuse disorders.
Drug & Alcohol Use Among Victims of Motor Vehicle Crashes in West Virginia
An issue of the Center for Disease Control's Morbidity and Mortality Weekly Report examines the number of motor vehicle fatalities in West Virginia where the Office of the Chief Medical Examiner routinely screens all victims for alcohol and drugs. Of the 784 motor vehicle fatalities that took place in WV in the years 2004-2005, over 80% were tested for the presence of drugs and/or alcohol. Almost half (47.3%) of all decedents tested positive for alcohol or drugs and 11.1% tested positive for both. Over one quarter (25.8%) of decedents tested positive for drug use which is similar to the 27.7% of decedents who had a blood alcohol concentration (BAC) >0.08 g/dL.
High Rates of Drug Use Found Among Injured Motorists at Adult Australian Trauma Centre
The following abstract is from the article: Drug Use in Motor Vehicle Drivers Presenting to an Australian, Adult Major Trauma Centre, C W Ch'ng, M Fitzgerald, J Gerostamoulos, P Cameron, D Bui, P McCaffrey, O Drummer, J Potter, M Odell. Emerg Med Australas. 2007 Aug;19 (4):359-65).
Objectives: To determine the drug use in injured Victorian drivers involved in motor vehicle collisions and subsequently transported to a major adult trauma centre in Victoria. Methods: A blood sample was obtained from patients who had been taken to The Alfred Emergency & Trauma Centre (Prahran, Vic., Australia) following a motor vehicle collision. This was performed at the same time and under the same law as compulsory blood screening in Victoria (Section 56 of the Road Safety Act). Four hundred and thirty-six specimens were analysed. Blood stored in vacutainer tubes containing preservative were screened for drugs using enzyme-linked immunosorbent assay and gas chromatography-mass spectometry analysis. Medically administered drugs were excluded from the results. Results: Four hundred and thirty-six specimens were analysed. Metabolites of cannabis were the most commonly found drug (46.7%), the active form of cannabis (Delta9-tetrahydrocannabinol) was found in 33 specimens (7.6%). The next most prevalent drugs were benzodiazepines (15.6%), opiates (11%), amphetamines (4.1%) and methadone (3%). Cocaine was detected in 1.4% of cases. Of the motor vehicle collisions 66% involved males and females of 15-44 years old and Delta9-tetrahydrocannabinol was almost exclusively found in this age group. In motor vehicle collisions involving older drivers there was an increasing use of benzodiazepines. In women >65 years old 30% were positive for benzodiazepines. Conclusions: Drug usage found in this group of injured drivers was disturbingly high. The introduction of further initiatives to decrease the prevalence of drug use in motor vehicle drivers is required.
Australia Report on Impaired Driving Shows Drugged Driving Great Concern for Country
Drugs and Driving in Australia: A Survey of Community Attitudes, Experience and Understanding is an extensive report which discusses various concerns and issues when considering policies to address drugged driving from impairment to public perception of risks, etc. The report confirms the fact that drugged driving is on the same scale as drunk driving in Australia and while the data on rates of impaired driving shared in the report are useful to that end, the Institute for Behavior and Health, Inc. (IBH) disagrees with the harm-minimization or harm reduction approach taken in this report, focusing primarily on education only. IBH believes that law enforcement must play a critical role in making an impact to reduce drugged driving, the way it has impacted rates of drunk driving, in addition to national education campaign. Report summary.
British Columbia Roadside Survey Examines High Rates of Impaired Driving in Canada
The Canadian Centre on Substance Abuse (CCSA) completed the British Columbia Roadside Survey in 2008 which revealed higher rates of drugged driving than drunk driving. Over 10% of tested drivers were positive for drug use compared to only 8% who tested positive for alcohol. While alcohol-impaired drivers tended to be younger in age, with more positive test results occurring during weekends and later nighttime hours, drug-impaired drivers were more evenly distributed across all age groups and survey times.
Repeat DUI Offenders Diagnosed with Drug Use Disorders Show Increased Risk of Negative Traffic Outcomes
The following abstract is from the article: C'de Baca, J., McMillan, G.P., & Lapham, S.C. (2009). Repeat DUI Offenders Who Have Had a Drug Diagnosis: Are They More Prone to Traffic Crashes and Violations . Traffic Injury Prevention,10(2),134-140.
Objective: Study objectives are to test for differences (1) in rates of negative traffic outcomes between DUI offenders who have lifetime drug use disorders (DUD) and those with no lifetime DUD; and (2) by drug class for those with a DUD. Methods: The study sample of 379 male and 74 female repeat DUI offenders was interviewed using the Composite International Diagnostic Interview. Results: Compared to those with an alcohol use disorder (AUD) only, the relative risk of being involved in a vehicular crash was greater for those with a central nervous system (CNS) depressant use disorder. The risk of being convicted of a traffic offense was higher for those with any DUD and for those with a CNS stimulant use disorder. Differences by class of drug used, after adjusting for demographics, were a 47 percent (confidence interval: 6 - 103%) greater risk of being in a crash with a CNS depressant use disorder and 28 percent (confidence interval: 11 - 48%) greater risk of a traffic conviction with a stimulant use disorder. Conclusions: Results underscore the increased risk of negative traffic outcomes among repeat DUI offenders diagnosed with DUD, particularly CNS depressant disorders, supporting the call to establish policies that include comprehensive evaluation and treatment for this population.
30% of High School Seniors Reported Driving After Using Alcohol or Other Illicit Drugs or Riding With a Driver Who Had
The following abstract is from the article: O'Malley, P.M., and Johnston, L.D. (2007). Drugs and driving by American high school seniors, 2001-2006. Journal of Studies on Alcohol and Drugs 68(6):834-842.
Objective: The aim of this study was to report trends from 2001 to 2006 in the percentage of all high school seniors who drive after using marijuana, other illicit drugs, or alcohol or who are exposed as passengers to such behaviors. A second objective is to examine demographic and psychosocial correlates of these behaviors. Method: The data were obtained from the Monitoring the Future study, in which nationally representative samples of high school seniors have been surveyed annually since 1975. Results: In 2006, 30% of high school seniors reported exposure to a drugged or drinking driver in the past 2 weeks, down from 35% in 2001. Exposure was demonstrated to be widespread as defined by demographic characteristics (population density, region of the country, socioeconomic status, race/ethnicity, and family structure). Individual lifestyle factors (religiosity, grade point average, truancy, frequency of evenings out for fun, and hours of work) showed considerable association with the outcome behaviors. Conclusions: Impaired driving by youth remains a problem needing serious attention despite some progress in recent years. (J. Stud. Alcohol Drugs 68: 834-842, 2007)
Research Abstracts from the International Association of Forensic Toxicologists & International Council on Alcohol, Drugs and Traffic Safety International Conference
The TIAFT & ICADTS 2007 International Conference was held in August 2007 in Seattle, Washington, USA. This conference of international experts, hosted by former McGovern Award winner, Barry Logan, Ph.D., had a strong emphasis on drugged driving, its effects and ways countries can start to reduce it. This conference highlighted how much valuable research is being conducted on drugged driving and how great the outcry is around the world for it to stop. Review the research abstracts from this conference.
Driving Under the Influence of Cannabis Increases Risk of Car Crash in France
The following abstract is from the article: Laumon, B., Gadegbeku, B., Martin, JL., Biecheler, MB. -- Cannabis intoxication and fatal crashes in: population based case-control study BMJ. 2005 Dec 10;331(7529):1371.
Objectives: To evaluate the relative risk of being responsible for a fatal crash while driving under the influence of cannabis, the prevalence of such drivers within the driving population, and the corresponding share of fatal crashes. Design: Population based case-control study. Participants: 10,748 drivers, with known drug and alcohol concentrations, who were involved in fatal crashes in France from October 2001 to September 2003. Main outcome measures: The cases were the 6,766 drivers considered at fault in their crash; the controls were 3,006 drivers selected from the 3,982 other drivers. Positive detection of cannabis was defined as a blood concentration of delta-9 tetrahydrocannabinol of over 1 ng/ml. The prevalence of positive drivers in the driving population was estimated by standardising controls on drivers not at fault who were involved in crashes resulting in slight injuries. Results: 681 drivers were positive for cannabis (cases 8.8%, controls 2.8%), including 285 with an illegal blood alcohol concentration ( ≥ 0.5 g/l). Positive cannabis detection was associated with increased risk of responsibility (odds ratio 3.32, 95% confidence interval 2.63 to 4.18). A significant dose effect was identified; the odds ratio increased from 2.18 (1.22 to 3.89) if 0 < detla-9 tetrahydrocannabinol < 1 ng/ml to 4.72 (3.04 to 7.33) if detla-9 tetrahydrocannabinol ≥ 5 ng/ml. the effect of cannabis remains significant after adjustment for different cofactors, including alcohol, with which no statistical interaction was observed. the prevalence of cannabis (2.9%) estimated for the driving population is similar to that for alcohol (2.7%). at least 2.5% (1.5% to 3.5%) of fatal crashes were estimated as being attributable to cannabis, compared with 28.6% for alcohol (26.8% to 30.5%). Conclusions: Driving under the influence of cannabis increases the risk of involvement in a crash. However, in France its share in fatal crashes is significantly lower than that associated with positive blood alcohol concentration.
Full article available: http://www.pubmedcentral.nih.gov/articlerender.fcgi artid=1309644
b. Drugged Driving Expert Presentations
Drugged Driving Webinar for Drug Court Professionals
As part of its Tune-In on Tuesday Webinar Series, the National Drug Court Resource Center of the National Association of Drug Court Professionals invited IBH President Robert L. DuPont, MD to present on the topic of Drugged Driving. This March 2014 webinar discusses the current knowledge about drugged driving and what can be done to reduce this serious problem focusing on the important role of Drug Courts and the criminal justice system linked to substance abuse treatment. Watch the webinar.
IBH President Presents Drugged Driving to the American Society of Forensic Sciences
In February 2013, Robert L. DuPont, M.D. presented the problem of drugged driving to toxicologists of the American Society of Forensic Sciences (AAFS). He focused specifically on the need for per se drug laws and the fact that setting impairment thresholds based on tissue levels of drugs or metabolites for illegal drugs is not a viable enforcement option. There is no 0.08 BAC equivalent for drugs, including marijuana. He also discussed the use of administrative license revocation (ALR) to bring drug testing to the police station in a way parallel to current alcohol testing. View the presentation.
IBH President Discusses Drugged Driving at the 2011 CADCA Leadership Forum
IBH President Robert L. DuPont, M.D. was part of a joint presentation entitled Drugged Driving: Confronting An Epidemic. Dr. DuPont explored why the problem of drugged driving has previously been overlooked and why it is a national priority now. He documented the prevalence of drugged driving among different driving populations including seriously injured, fatally injured and randomly stopped drivers. He explained why there cannot be an impairment standard for illegal drugs as there is for alcohol and what ideas and programs organizations like CADCA among other can promote to address this public health and safety problem. View the presentation.
Barry Logan, Ph.D., DABFT Director of the Forensic Laboratory Services Bureau, Washington State Patrol and State Toxicologist
An expert in the field of forensic toxicology and drug analysis, Dr. Logan has made drug-impaired driving a focus of his research activities since 1994, with more than 25 publications on this topic, and frequent testimony as an expert in drug impaired driving cases. Dr. Logan serves on the board of the International Association of Forensic Toxicologists from which he received in 2003 the Mid-Career Achievement Award for Excellence in Forensic Toxicology for his work in postmortem and impaired driving toxicology. He was the recipient of the John P. McGovern Award for innovation in drug abuse prevention on June 1, 2006 by the Institute for Behavior and Health, Inc. View the presentation.
Bruce Goldberger, Ph.D., Professor, Director of Toxicology, University of Florida College of Medicine
In November, 2007 Dr. Goldberger participated in the John P. McGovern lecture series on drugged driving hosted by the Institute for Behavior and Health, Inc. Dr. Goldberger reviewed currently available technology, including breath, urine, saliva and sweat tests. He discussed the uses and limitations of these methodologies, and suggested new avenues of research and development that are in the pipeline. View the presentation.
c. Reports & Factsheets
2014 State-by-State Analysis of Laws Dealing with Driving Under the Influence of Drugs
NMS Labs and StopDUID.org released an updated report on the current statutory language concerning driving under the influence of drugs in the United States. View report. Visit www.StopDUID.org.
2012 California Roadside Survey of Nighttime Weekend Drivers' Alcohol and Drug Use
The California Office of Traffic Safety released results of a 2012 roadside survey of nighttime weekend drivers. The study is modeled on data collection procedures used in the "2007 National Roadside Survey of Alcohol and Drug Use by Drivers," sponsored by the National Highway Traffic Safety Administration. One in seven (14%) drivers tested positive for drugs that may impair driving while 7.3% tested positive for alcohol. Slightly more drivers, 7.4%, tested positive for marijuana. More than one quarter of all marijuana-positive drivers also tested positive for another drug. This survey provides a baseline California prevalence estimate for alcohol and drug use among nighttime weekend drivers and can be compared with results of future surveys to examine patterns of change in drug and alcohol use in that population. View report. Press Release.
Drug Testing and Drug-Involved Driving of Fatally Injured Drivers in the United States: 2005-2009
In October 2011, the White House Office of National Drug Control Policy (ONDCP) released a report using data from the Fatality Analysis Reporting System (FARS) to provide a description of drug-involved driving and its correlates. This report examines drug test results of fatally injured drivers killed between 2005 and 2009 and presents findings related to occurrence of drug testing, testing positive for any drug, and testing positive for specific drug classes, noting state-to-state variation. View report.
European Monitoring Centre for Drugs and Drug Addiction: Drug Use, Impaired Driving and Traffic Accidents
This literature review provides a comprehensive report on the relationship between drug use, impaired driving and traffic accidents. It covers methodological issues, presents results of prevalence surveys among drivers and provides an overview of findings from major international epidemiological surveys published since 1999. The report also gathers evidence from experimental and field studies of the relationship between drug use, driving impairment and traffic accidents. View report.
Priorities and Strategies for Improving the Investigation, Use of Toxicology Results, and Prosecution of Drug-Impaired Driving Cases
The National Safety Council's Committee on Alcohol and Other Drugs organized a group of toxicologists, drug recognition experts (DREs), and prosecutors active in the area of drugged driving, in May 2004. The panel was charged with identifying problems with the current system of prosecuting drug-impaired driving cases. This report focuses on the recurrent themes and major issues identified. Among the issues addressed were:
Issue #1: What are the major problems encountered in processing a drug-impaired driving case through the criminal justice system
Issue #2: Are current laws optimally structured to deter drugged driving
Issue #3: What resources currently exist to promote informed and effective drugged driving prosecution, and how can they be used more effectively
Issue #4: What should be the priority activities of stakeholders in advancing the enforcement and prosecution of drug-impaired driving
NIDA InfoFacts: Drugged Driving
The National Institute on Drug Abuse (NIDA) fact sheet on drugged driving addresses the following questions and issues:
- What is drugged driving
- How many people take drugs and drive
- Teens and drugged driving
- Why is drugged driving hazardous
New South Wales Government Drugs and Driving Frequently Asked Question
The government of New South Wales, Australia's most populous state, provides answers to frequently asked questions about roadside drug testing, laws and consequences relating to drugged driving.
NHTSA Drugs and Human Performance Fact Sheets
A panel of international experts on drug-related driving issues met to review developments in the field of drugs and human performance over the last 10 years to identify the specific effects that both illicit and prescription drugs have on driving and to develop guidance for others when dealing with drug-impaired driving problems.
NTHSTA Fact Sheets By Drug
d. Drug Abuse Research
National Survey on Drug Use and Health
Substance Abuse and Mental Health Services Administration's National Survey on Drug Use & Health (NSDUH) is the primary source of information on the prevalence, patterns, and consequences of alcohol, tobacco, and illegal drug use and abuse in the general U.S. civilian non institutionalized population, age 12 and older. It is currently conducted by SAMHSA's Office of Applied Studies (OAS). Correlates in OAS reports include the following: age, gender, pregnancy status, race/ethnicity, education, employment, geographic area, frequency of use, and association with alcohol, tobacco, & illegal drug use. View report.
Monitoring the Future
Monitoring the Future is an ongoing study of the behaviors, attitudes, and values of American secondary school students, college students, and young adults. Each year, a total of approximately 50,000 8th, 10th and 12th grade students are surveyed (12th graders since 1975, and 8th and 10th graders since 1991). In addition, annual follow-up questionnaires are mailed to a sample of each graduating class for a number of years after their initial participation. View study.
National Drug Threat Assessment from National Drug Intelligence Center
The National Drug Threat Assessment is an interagency report that provides a strategic overview and predictive outlook of the threat to the United States from the illicit trafficking and use of cocaine, methamphetamine, marijuana, heroin, pharmaceutical drugs, and other dangerous drugs. Read the full National Threat Assessment.