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

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Abstract

The incidence of alcohol and drugs in fatally injured drivers were determined in three Australian states; Victoria (VIC), New South Wales (NSW) and Western Australia (WA) for the period of 1990–1999. A total of 3398 driver fatalities were investigated which included 2609 car drivers, 650 motorcyclists and 139 truck drivers. Alcohol at or over 0.05 g/100 ml (%) was present in 29.1% of all drivers. The highest prevalence was in car drivers (30.3%) and the lowest in truckers (8.6%). WA had the highest rate of alcohol presence of the three states (35.8%). Almost 10% of the cases involved both alcohol and drugs. Drugs (other than alcohol) were present in 26.7% of cases and psychotropic drugs in 23.5%. These drugs comprised cannabis (13.5%), opioids (4.9%), stimulants (4.1%), benzodiazepines (4.1%) and other psychotropic drugs (2.7%). 8.5% of all drivers tested positive for Δ9-tetrahydrocannabinol (THC) and the balance of cannabis positive drivers were positive to only the 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid (carboxy-THC) metabolite. The range of THC blood concentrations in drivers was 0.1–228 ng/ml, with a median of 9 ng/ml. Opioids consisted mainly of morphine (n=84), codeine (n=89) and methadone (n=33), while stimulants consisted mainly of methamphetamine (n=51), MDMA (n=6), cocaine (n=5), and the ephedrines (n=61). The prevalence of drugs increased over the decade, particularly cannabis and opioids, while alcohol decreased. Cannabis had a larger prevalence in motorcyclists (22.2%), whereas stimulants had a much larger presence in truckers (23%).

Introduction

There is increasing interest throughout the world concerning the incidence of drugs in driving and in their contribution to road trauma specifically. The most common drugs (other than alcohol) found in fatally injured drivers have been cannabis, benzodiazepines, amphetamine-like stimulants and opioids. A number of reports have detailed the incidence of drugs in fatally injured drivers around the world [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14]. A number of jurisdictions have reported increase in the proportion of drivers using drugs [15], [16], [17], [18]. Preliminary data has also suggested similar trends in Australia [19], [20].

Injured drivers also show a high prevalence of drugs. Cannabinoids were found in 13.9% of French injured drivers, while opioids, cocaine and amphetamines were found in 10.5, 1.0 and 1.4%, respectively [21]. Impairing drugs were found in 32% of injured drivers presented to an urban emergency center in Colorado in which cannabis was the most frequent detected drug (17%), followed by alcohol (14%) [22]. In a South Australian study on injured drivers, cannabis was found in 10.8%, benzodiazepines in 2.7% and stimulants in 1.0% [23].

There are significant variations in the type and frequency of detected drugs between jurisdictions. In New York, 20% of drivers killed in traffic crashes were positive to cocaine amongst drivers in the 16–45-year group [24]. A high incidence of cocaine use in impaired drivers was also observed in The Netherlands (33%). Benzodiazepines (33%) and opioids (19%) were also commonly seen [25]. In France, cannabinoids (13.9%) and opioids (10.5%) were most frequently drugs in drivers admitted to hospital as a result of their injuries [26]. Cocaine (1.0%) and amphetamines (1.4%) were infrequently detected. In contrast, Norwegian drugged drivers show a high incidence of benzodiazepines use of about 31% followed by THC (30%) and amphetamine (28%) [27]. In Scotland, benzodiazepines tend to be even more dominant with over 85% of fatally injured drivers testing positive to benzodiazepines [17].

The most controversial aspect of the involvement of drugs in accident causation is that of cannabis. Previous reports of Australian drivers have relied on coroners’ records in which forensic laboratories only measured the inactive form of cannabis (carboxy-Δ9-THC). Following the use of cannabis, this species is present in blood for up to several days and therefore its presence cannot be used to imply recent use of cannabis, and therefore likely impairment. Since 1998, the Australian forensic laboratories used in the study have measured THC routinely in fatal road crashes.

Australia is a modern community with a large and evolved network of roads in both urban and rural settings, and with a long history of a focus on road safety. The national legal limit for blood alcohol concentration (BAC) is 0.05%. The blood alcohol limit for commercial drivers and non-full license holders is zero. The population of Australia approaches 20 million and the states of Victoria (VIC), New South Wales (NSW) and Western Australia (WA) represent some 69% of Australian drivers.

The purpose of this study was to establish the incidence and extent to which drugs contributed to fatal motor vehicle accidents. This study presents the results of a 10-year research project involving a number of collaborating centers over three Australian states. In total 3398 drivers were included in this study. Due to the large amount of data, the results of the culpability analyses of alcohol and the various drug types have been described elsewhere [28].

Section snippets

Study population

The study population consisted of drivers killed in motor vehicle accidents in the three Australian states of VIC, NSW and WA. In VIC these data were obtained from records kept at the Victorian Institute of Forensic Medicine and the State Coroner’s Office at Southbank. Drivers were identified on the basis of records obtained from the Victorian Institute of Forensic Medicine. These cases included Victorian drivers killed in road crashes from 1990 to 1999.

In NSW, Coroner’s case numbers and names

Characteristics of drivers

The total number of drivers included in the study was 3398. On average this represented over 85% of all drivers killed in this period. This included Victorian drivers (47.4% of study population), NSW (30.3%) and WA (22.3%). The breakdown of crash types (single and multiple vehicle crashes) and type of vehicle is shown in Table 1. Car drivers, motorcyclists and truckers represented 76.7, 19.1, and 4.1% of the study group, respectively. Single vehicle crashes represented 50.7% of the cases.

The

Discussion

This 10-year multi-center study of drug-involved driving has shown a substantial incidence of drugs other than alcohol. In the last 3 years, over one-quarter of all drivers had used an impairing drug, an overall increase of 6.7% compared to the 1990–1993. The increasing prevalence of drug presence in fatally injured drivers was associated with a decline in the involvement of alcohol. Overall, the proportion of drivers with a BAC of 0.05% or higher fell over 8% between 1990 and 1999, and was

Acknowledgements

We thank the staff of the Victorian Institute of Forensic Medicine for their assistance in these investigations. We also thank the toxicologists in each state for their support and assistance, particularly Mr. Robert Hansson (WA) and Mr. Allan Hodda (NSW), as well as coroners, registrars and clerical assistants at the respective coroners’ courts. We acknowledge the financial assistance of VicRoads for financing many of these studies, as well as AustRoads and the NSW roads and traffic authority.

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