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Background and aim: In Uruguay, residents age 18 and older seeking legal cannabis must register with the government and choose one of three supply mechanisms: self‐cultivation, non‐profit cannabis clubs or pharmacies. This is the first paper to measure the association between type of legal cannabis supply mechanism and traffic crashes involving injuries. Design Ecological study using ordinary least squares regression to examine how department‐level variation in registrations (overall and by type) is associated with traffic crashes involving injuries. Setting: Uruguay. Cases 532 department‐quarters. Measurements Quarterly cannabis registration counts at the department level and incident‐level traffic crash data were obtained from government agencies. The analyses controlled for department‐level economic and demographic characteristics and, as a robustness check, we included traffic violations involving alcohol for departments reporting this information. Department‐level data on crashes, registrations and alcohol violations were denominated by the number of residents ages 18 and older. Findings From 2013 to 2019, the average number of registrations at the department‐quarter level per 10 000 residents age 18 and older for self‐cultivation, club membership and pharmacy purchasing were 17.7 (SD = 16.8), 3.6 (SD = 8.6), and 25.1 (SD = 50.4), respectively. In our multivariate regression analyses, we did not find a statistically significant association between the total number of registrations and traffic crashes with injuries (β = −0.007; P = 0.398; 95% CI = −0.023, 0.01). Analyses focused on the specific supply mechanisms found a consistent, positive and statistically significant association between the number of individuals registered as self‐cultivators and the number of traffic crashes with injuries (β = 0.194; P = 0.008; 95% CI = 0.058, 0.329). Associations for other supply mechanisms were inconsistent across the various model specifications. Conclusions: In Uruguay, the number of people allowed to self‐cultivate cannabis is positively associated with traffic crashes involving injuries. Individual‐level analyses are needed to assess better the factors underlying this association. [ABSTRACT FROM AUTHOR]

Background and aims: Cannabis and alcohol are frequently detected in fatal and injury motor vehicle crashes. While epidemiological meta‐analyses of cannabis and alcohol have found associations with an increase in crash risk, convergent evidence from driving performance measures is insufficiently quantitatively characterized. Our objectives were to quantify the magnitude of the effect of cannabis and alcohol—alone and in combination—on driving performance and behaviour. Methods: Systematic review and meta‐analysis. We systematically searched Academic Search Complete, CINAHL, Embase, Scopus, Google Scholar, MEDLINE, PsycINFO, SPORTDiscus and TRID. Of the 616 studies that underwent full‐text review, this meta‐analysis represents 57 studies and 1725 participants. We extracted data for hazard response time, lateral position variability, lane deviations or excursions, time out of lane, driving speed, driving speed variability, speed violations, time speeding, headway, headway variability and crashes from experimental driving studies (i.e. driving simulator, closed‐course, on‐road) involving cannabis and/or alcohol administration. We reported meta‐analyses of effect sizes using Hedges' g and r. Results: Cannabis alone was associated with impaired lateral control [e.g. g = 0.331, 95% confidence interval (CI) = 0.212–0.451 for lateral position variability; g = 0.198, 95% CI = 0.001–0.395 for lane excursions) and decreased driving speed (g = –0.176, 95% CI = –0.298 to –0.053]. The combination of cannabis and alcohol was associated with greater driving performance decrements than either drug in isolation [e.g. g = 0.480, 95% CI = 0.096–0.865 for lateral position variability (combination versus alcohol); g = 0.525, 95% CI = 0.049–1.002 for time out of lane (versus alcohol); g = 0.336, 95% CI = 0.036–0.636 for lateral position variability (combination versus cannabis; g = 0.475, 95% CI = 0.002–0.949 for time out of lane (combination versus cannabis)]. Subgroup analyses indicated that the effects of cannabis on driving performance measures were similar to low blood alcohol concentrations. A scarcity of data and study heterogeneity limited the interpretation of some measures. Conclusions: This meta‐analysis indicates that cannabis, like alcohol, impairs driving, and the combination of the two drugs is more detrimental to driving performance than either in isolation. [ABSTRACT FROM AUTHOR]

Aims To evaluate a new method being used by some states for motivating interlock installation by requiring it as a prerequisite to reinstatement of the driver's license. Design The driving records of Florida DWI offenders convicted between July 2002 and June 2008 were analyzed to determine the proportion of offenders subject to the interlock requirement who installed interlocks. Setting Most driving-while-impaired (DWI) offenders succeed in avoiding state laws requiring the installation of a vehicle alcohol interlock. Participants A total of 82 318 Florida DWI offenders. Findings Due to long periods of complete suspension when no driving was permitted and the failure to complete all the requirements imposed by the court, only 21 377 of the 82 318 offenders studied qualified for reinstatement, but 93% of those who qualified did install interlocks to be reinstated. Conclusions Because of the lengthy license suspensions and other barriers that the offenders face in qualifying for reinstatement, it is not clear that requiring a period on the interlock as a prerequisite to reinstating will greatly increase the current installment rate. [ABSTRACT FROM AUTHOR]

Aims This study, conducted within a driving under the influence (DUI) court intervention, evaluated the degree to which removing electronic monitoring (EM) and/or mandatory vehicle sales requirements increased rates of post-sentence traffic violations among repeat DUI offenders. Design Randomized trial. Setting and participants A total of 477 repeat DUI offenders entering the Driving under the Influence of Intoxicants (DUII) Intensive Supervision Program (DISP), Multnomah County, Oregon. Intervention Subjects were randomized into four intervention groups. Group 1: standard DISP with EM and vehicle sales requirements; group 2: standard DISP with mandatory vehicle sale, but without EM; group 3: standard DISP with EM, but without mandatory vehicle sale; and group 4: standard DISP without EM or mandated vehicle sale. Standard DISP includes treatment for alcohol abuse and dependence, polygraph testing, regular court appearances, and probation or court-based monitoring. Measurements The risk of re-arrest for traffic violations was compared among the four groups using hazard ratio estimates from complementary log–log regression models. Findings Compared with group 1, subjects in group 2 initially had increased re-arrest risks, but this effect dissipated within 3 years of entering DISP. Group 3 subjects had a 96% increase in re-arrest rates. Group 4 subjects had smaller increased risks than predicted, with re-arrest rates similar to those of group 1 at the end of the follow-up period. Conclusions Although some of the findings suggest that mandatory vehicle sales may deter future traffic violations, inconsistent results across groups make this finding equivocal. Positive effects of EM, while large in the short term, appear to have a relatively small long-term value in reducing traffic arrest rates. [ABSTRACT FROM AUTHOR]

Background New legislation aimed at combating driving under the influence of drugs (DUID) in Sweden stipulated zero-concentrations in blood for scheduled substances. DUID suspects ( n = 300), with amphetamine as the only psychoactive drug identified in blood, were investigated in relation to age and gender. In a smaller retrospective sample ( n = 70) the relationship between clinical tests of impairment were compared with the concentration of amphetamine in blood. Measurements All forensic blood samples were subjected to a broad toxicological screening analysis by immunoassay methods [enzyme multiplied immunoassay technique/cloned enzyme donor immunoassay (EMIT/CEDIA)] and positive results were verified by gas chromatography-mass spectrometry (GC-MS). The limit of quantitation (LOQ) for determination of amphetamine in blood was 0.03 mg/l. People suspected of being under the influence of drugs were examined by a physician who asked various questions about state of health and use of drugs and also administered simple psychomotor and cognitive tests of impairment. After conducting these tests the physician concluded whether the suspects were not impaired, slightly, moderately or highly impaired by drugs other than alcohol. Findings Among 300 DUID suspects with amphetamine in blood there were 246 men (82%) and 54 women (18%). Mean age (± SD) of the men was 37.1 ± 8.7 years compared with 35.5 ± 7.1 years for the women ( P > 0.05). The frequency distribution of blood amphetamine concentration was positively skewed with mean, median and highest values of 1.0 mg/l, 0.9 mg/l and 7.1 mg/l, respectively. The mean concentrations were slightly higher in the women 1.11 mg/l (median 1.0 mg/l) compared with 0.97 mg/l (median 0.8 mg/l) in the men ( P > 0.05). There was a weak but statistically significant correlation between the person's age and the concentration of amphetamine in blood ( r = 0.18, P < 0.05). The results of clinical tests of impairment showed no relationship with the concentration of amphetamine in blood according to analysis of variance ( P > 0.05). Conclusions The lack of association between degree of drug influence and the concentration of amphetamine in blood speaks against the notion of introducing concentration per se limits or graded penalties depending on the blood-concentration of this stimulant. Zero-concentration limits or LOQ-limits are a much more pragmatic way to enforce DUID legislation. [ABSTRACT FROM AUTHOR]

The author argues that high-visibility law enforcement methods requiring substantial public support are required in order for law enforcement to have a significant impact on alcohol-impaired driving fatalities. Topics include the impact of Mothers Against Drunk Driving (MADD) on U.S. attitudes towards drunk driving 1980, and a study by Yao et al. showing a decline in the percentage of fatal crashes involving an alcohol-impaired driver in states with higher DWI arrest rates per capita.

The author comments on the article "Minimum legal drinking age (MLDA) laws protect high school students from both crashes and alcohol abuse," by R. Callaghan and colleagues. The author states that it focuses on health benefits outside traffic safety and because the MLDA's in Canadian provinces are set at either age 18 or 19 years. He mentions that if the U.S. MLDA laws were lowered to 18-19-year age range, it would fall back its protective value for 19- and 20-year-olds.