The incidence of drugs in drivers killed in Australian road traffic crashes

The effects of dexamphetamine on simulated driving performance

RATIONALE

The number of road fatalities related to the presence of amphetamines in drivers has been relatively constant over the past 10 years. However, there remains uncertainty as to the extent that these drugs induce driving impairment, and whether any such impairments translate to an increase in road fatalities.

OBJECTIVES

To examine the acute effects of 0.42 mg/kg dexamphetamine on simulated driving performance, and to establish which, if any, simulated driving abilities become impaired following dexamphetamine administration.

METHODS

A repeated-measures, counter-balanced, double-blind, placebo-controlled design was employed. Twenty healthy volunteers completed two treatment conditions-0.42 mg/kg dexamphetamine and placebo. Performance was assessed using a driving simulator task. Blood and saliva samples were obtained prior to the driving tasks and immediately after task completion (120 min and 170 min post-drug administration, respectively).

RESULTS

Mean dexamphetamine blood concentrations were 83 ng/ml and 98 ng/ml at 120 min and 170 min, respectively. Results indicated a decrease in overall simulated driving ability following dexamphetamine administration during the day-time but not the night-time scenario tasks. Contributing to this performance reduction, "incorrect signalling", "failing to stop at a red traffic light" and "slow reaction times" were the behaviours most strongly affected by dexamphetamine.

CONCLUSIONS

The decrease in simulated driving ability observed during the day-time driving tasks are consistent with the perceptual narrowing or tunnel vision that is associated with dexamphetamine consumption.

A tale of two jurisdictions. Can Australia and Canada learn from each other's experience with cannabis control?

OBJECTIVE

To compare public health and legal policies to reduce the harm associated with cannabis use in Canada and Australia, given similarities between both countries.

METHOD

A review of the epidemiological and health policy literature.

RESULTS

Although both countries have adopted harm minimization, a continued heavy reliance on legislative and punitive approaches in both Canada and Australia has failed to arrest the increase in cannabis use, especially among young people. A Senate inquiry in Canada has recommended the liberalization of laws on the possession and use of cannabis, while tightening legislation against operating vehicles or machinery while intoxicated.

CONCLUSIONS

Existing policies are not evidence-based and lead to adverse outcomes such as criminalization of otherwise law-abiding citizens and diversion of resources from more effective policing or health service initiatives.

Drugs and driving

The authors present a global overview on the issue of drugs and driving covering four major areas: (1) Epidemiology and Prevalence--which reviews epidemiological research, summarizes available information, discusses the methodological shortcomings of extant studies, and makes recommendations for future research to better define prevalence and epidemiology; (2) Effects of Medicinal and Illegal Drugs on Driving Performance--focuses on the six classes of drugs most often found in impaired and injured drivers, draws conclusions regarding the risk of these drugs to traffic safety and discusses the need for additional research; (3) Toxicological Issues--discusses ways to identify drug users via behavioral testing and analytical techniques, reviews the approaches used by different countries, screening and confirmation techniques, alternative specimens (e.g., urine, oral fluid, sweat), and how rapid roadside testing could be coupled with behavioral and laboratory testing in an effective approach to identifying and prosecuting drugged drivers; (4) Driving Under the Influence of Drugs [DUID] Laws--provides an overview of DUID laws in the United States and Europe, discusses the basic tenets of these laws, the various types of DUID statutes, the reasons why many existing laws hinder the prosecution of drugged drivers and the rationale for developing per se legislation as a strategy to more effectively manage the drugged driver problem.

Dose related risk of motor vehicle crashes after cannabis use

The role of Delta(9)-tetrahydrocannabinol (THC) in driver impairment and motor vehicle crashes has traditionally been established in experimental and epidemiological studies. Experimental studies have repeatedly shown that THC impairs cognition, psychomotor function and actual driving performance in a dose related manner. The degree of performance impairment observed in experimental studies after doses up to 300 microg/kg THC were equivalent to the impairing effect of an alcohol dose producing a blood alcohol concentration (BAC) >/=0.05 g/dl, the legal limit for driving under the influence in most European countries. Higher doses of THC, i.e. >300 microg/kg THC have not been systematically studied but can be predicted to produce even larger impairment. Detrimental effects of THC were more prominent in certain driving tasks than others. Highly automated behaviors, such as road tracking control, were more affected by THC as compared to more complex driving tasks requiring conscious control. Epidemiological findings on the role of THC in vehicle crashes have sometimes contrasted findings from experimental research. Case-control studies generally confirmed experimental data, but culpability surveys showed little evidence that crashed drivers who only used cannabis are more likely to cause accidents than drug free drivers. However, most culpability surveys have established cannabis use among crashed drivers by determining the presence of an inactive metabolite of THC in blood or urine that can be detected for days after smoking and can only be taken as evidence for past use of cannabis. Surveys that established recent use of cannabis by directly measuring THC in blood showed that THC positives, particularly at higher doses, are about three to seven times more likely to be responsible for their crash as compared to drivers that had not used drugs or alcohol. Together these epidemiological data suggests that recent use of cannabis may increase crash risk, whereas past use of cannabis does not. Experimental and epidemiological research provided similar findings concerning the combined use of THC and alcohol in traffic. Combined use of THC and alcohol produced severe impairment of cognitive, psychomotor, and actual driving performance in experimental studies and sharply increased the crash risk in epidemiological analyses.