The modern trends in alcohol, drugs and driving research

Research on alcohol, drugs and driving can be broadly separated into experimental and epidemiological studies. Every approach has its inherent advantages and disadvantages. Experimental studies can result in an interpretation by single cause, but can only identify potential risks, and the results can sometimes be of limited value because of the use of non-realistic doses or because of the drug use history or inter-individual differences of the volunteers. Recent studies have used higher, more realistic doses and paid more attention to the combination of alcohol and drugs and have shown that the chronic use of illicit drugs can be associated with some cognitive and/or psychomotor impairment, and can lead to a decrease in driving performance even when the subject is no longer intoxicated.Epidemiological studies include roadside surveys, studies in a subset of drivers, accident risk studies, responsibility analyses, surveys and pharmaco-epidemiological studies. Between studies, results may be incomparable due to testing different populations, different kinds of samples, etc. More large-scale roadside studies are conducted now.Advances in analytical toxicology have also contributed to a better understanding of the risks associated with driving under the influence. While older studies measured the inactive metabolite THC-COOH and did not show an increased risk in cannabis-positive drivers, more recent studies measured the active THC in blood and did show a concentration dependent increase in crash risk. The use of LC–MS/MS has allowed more broad-range screening as this technique can measure many different drugs in a small sample volume. While some older studies used saliva but had many analytical problems (including an insufficient sample volume in up to a third of the cases), newer methods of saliva sampling and analysis give better results. The use of saliva for roadside surveys allows non-invasive sampling, but the lack of correlation with the concentrations in blood makes interpretation of results difficult.The results of both epidemiological and experimental studies should be combined to obtain a good estimate of the impact of certain drugs on driving performance and accident risk. In 2006–07 a committee of international experts drafted guidelines for future research into drugs and driving. These have been taken on board by the DRUID project, a large-scale EU funded project on driving under the influence of drugs, alcohol and medicines.     

Role of drugs and alcohol in impaired drivers and fatally injured drivers in the Strathclyde police region of Scotland, 1995–1998

During the 4-year study period, 1995–1998, the Department of Forensic Medicine and Science, University of Glasgow received a total of 752 biological samples from drivers suspected of driving under the influence of drink and/or drugs in the Strathclyde region of Scotland. The majority of samples were blood and had been primarily obtained from males. Drugs were detected in 68 and 90% of blood and urine samples, respectively. Toxicological analyses revealed that cannabis was the most frequently encountered illegal drug which was detected in 39% of all drug positive blood samples. Benzodiazepines were detected in the majority of drug positive samples with 82% containing at least one member of this group. Polydrug use was prevalent, with the average number of drugs detected per sample increasing from 2.0 in 1995 to 3.1 in 1998. For comparison, the results of toxicological analyses from 151 fatally injured drivers are described. Although the majority of samples tested negative for the presence of drugs and alcohol, drugs were found to be present in 19% and alcohol was detected in 33%. As the majority of drugs had been prescribed or administered post-accident, this study shows that alcohol was the main causative factor conducive to fatal road traffic accidents.     

Drugged driving in the Nordic countries--a comparative study between five countries

The purpose of this study was to compare whether the high incidence of drugged driving in Norway was different to that in the other Nordic countries. All blood samples received by Nordic forensic institutes during one week in 1996, from drivers suspected by the police of driving under the influence (Denmark: n = 255, Finland: n = 270, Iceland: n = 40, Sweden: n = 86, Norway: n = 149), were analysed for alcohol and drugs (benzodiazepines, cannabinoids, amphetamines, cocaine, opiates and a number of antidepressant drugs) independent of the primary suspicion, and using the same analytical cut-off levels at the different institutes. The primary suspicion was directed towards drugs in more than 40% of the Norwegian cases, drugs were detected in more than 70% of these samples. In only 0-3% of the cases from Denmark, Finland and Iceland, were drugs suspected, while the corresponding frequency for Sweden was 17%. However, evidential breath analyses were used for about three-quarters of the Swedish drivers suspected to be influenced by alcohol. Blood alcohol concentrations (BAC's) below the legal limits were found in 32, 18 and 2% of the Norwegian, Icelandic and Finnish cases, respectively (BAC < 0.05%), in 10% of the Danish cases (BAC < 0.08%) and in 20% of the Swedish cases (BAC < 0.02%). Drugs were most frequently found in the Norwegian and Swedish cases with no alcohol (80-83%). Similar frequencies of drugs in samples with BAC's above the legal limits (19-22%), were obtained for all countries. Benzodiazepines, tetrahydrocannabinol and amphetamine represented the most commonly detected drugs. Our results show that differences between Norway and other Nordic countries with regard to drugs and driving, are connected to the selection criteria made by the police and with more focus on drugged driving in Norway.     

Psychoactive substances in seriously injured drivers in Denmark

This study assesses the presence of a number of psychoactive substances, including alcohol, based on blood samples from 840 seriously injured drivers admitted to five selected hospitals located in five different regions of Denmark. The study was a part of the EU 6th framework program DRUID (Driving Under the Influence of Drugs, Alcohol and Medicines). Blood samples were screened for 30 illegal and legal psychoactive substances and metabolites as well as ethanol. Danish legal limits were used to evaluate the frequency of drivers violating the Danish legislation while limit of quantification (LOQ) was used for monitoring positive drivers. Tramadol is not included in the Danish legislation therefore the general cut off, as decided in the DRUID project was used. Overall, ethanol (18%) was the most frequently identified compound (alone or in combination with other drugs) exceeding the legal limit, which is 0.53 g/l in Denmark. The percentage of seriously injured drivers testing positive for medicinal drugs at levels above the Danish legal limit was 6.8%. Benzodiazepines and Z-drugs (6.4%) comprised the majority of this group. One or more illegal drugs (primarily amphetamines and cannabis) were found to be above the Danish legal limit in 4.9% of injured drivers. Young men (median age 31 years) were over-represented among injured drivers who violated Danish law for alcohol and drugs.Diazepam (4.4%), tramadol (3.2%), and clonazepam (3.0%) were the medicinal drugs most frequently detected at levels above LOQ, whereas amphetamines (5.4%) (amphetamine [5.2%] and methamphetamine [1.5%]), tetrahydrocannabinol (3.7%), and cocaine (3.3%), including the metabolite benzoylecgonine, were the most frequently detected illegal drugs. A driver could be positive for more than one substance; therefore, percentages are not mutually exclusive. Poly-drug use was observed in 112 (13%) seriously injured drivers. Tramadol was detected above DRUID cutoffs in 2.1% of seriously injured drivers. This is 3.5 times that observed in a Danish survey of randomly selected drivers. Moreover, illegal and medicinal drug levels above the Danish legal limit were present more than 10 times as frequently as in injured drivers, whereas ethanol was present more than 30 times as frequently than in randomly selected drivers. The results indicate that there is an increased risk in traffic when driving under the influence of psychoactive drugs, especially alcohol in young male drivers.     

Screening for drug use among Norwegian drivers suspected of driving under influence of alcohol or drugs

Two hundred and seventy blood samples selected at random from Norwegian drivers apprehended on the suspicion of drunken or drugged driving were screened for the presence of amphetamine, benzodiazepines, cannabinoids, tetrahydrocannabinol (THC) and cocaine. Of the samples tested, 223 were from drivers suspected of driving under the influence of alcohol only (A-cases). In the rest (n = 47) of the cases, the police also suspected drugs as a possible reason for driving impairment (D-cases). In the A-cases, benzodiazepines were found in 17%, cannabinoids in 26%, THC in 13% and amphetamine in 2% of the blood samples. One or more drugs besides ethanol were found in 38% of the A-samples. In the D-cases, benzodiazepines were found in 53%, cannabinoids in 43%, THC in 43%, amphetamine in 13% and 77% of these samples contained one or more drugs. Cocaine was not detected in any sample. Blood alcohol concentrations (BAC) above the legal limit of 0.05% were found in 80% of the drug positive A-cases and in 28% of the drug positive D-cases. The frequency of drug detection in A-samples was similar (40%) in samples with BAC above and below 0.05%, while this frequency was much higher (above 90%) in D-samples with BAC below 0.05% than in D-samples with BAC above 0.05% (53%). Benzodiazepines were most frequently found among drivers above 25 years of age, while cannabinoids were most frequently found among drivers below 35 years. For about 15-20% of the A-cases with BAC below 0.05%, other drugs were detected at concentrations which may cause driving impairment. It was concluded that analysis of alcohol only might often be insufficient in A-cases to reveal driving impairment.     

Changing patterns of drug and alcohol use in fatally injured drivers in Washington State

We have previously reported on patterns of drug and alcohol use in fatally injured drivers in Washington State. Here we revisit that population to examine how drug use patterns have changed in the intervening 9 years. Blood and serum specimens from drivers who died within 4 h of a traffic accident between February 1, 2001, and January 31, 2002, were analyzed for illicit and therapeutic drugs and alcohol. Drugs when present were quantitated. Samples suitable for testing were obtained from 370 fatally injured drivers. Alcohol was detected above 0.01 g/100 mL in 41% of cases. The mean alcohol concentration for those cases was 0.17 g/100 mL (range 0.02-0.39 g/100 mL). Central nervous system (CNS) active drugs were detected in 144 (39%) cases. CNS depressants including carisoprodol, diazepam, hydrocodone, diphenhydramine, amitriptyline, and others were detected in 52 cases (14.1%), cannabinoids were detected in 47 cases (12.7%), CNS stimulants (cocaine and amphetamines) were detected in 36 cases (9.7%), and narcotic analgesics (excluding morphine which is often administered iatrogenically in trauma cases) were detected in 12 cases (3.2%). For those cases which tested positive for alcohol c. 40% had other drugs present which have the potential to cause or contribute to the driver's impairment. Our report also considers the blood drug concentrations in the context of their interpretability with respect to driving impairment. The data reveal that over the past decade, while alcohol use has declined, some drug use, notably methamphetamine, has increased significantly (from 1.89% to 4.86% of fatally injured drivers) between 1992 and 2002. Combined drug and alcohol use is a very significant pattern in this population and is probably overlooked in DUI enforcement programs.     

Drugged drivers in Norway with benzodiazepine detections

Norwegian drugged drivers with benzodiazepine (BZD) detections have been studied with regard to drug use pattern and rearrest rate. During 1995, 3343 drivers were apprehended by the police in Norway due to the suspicion of influence by drugs. Blood samples from all drivers were sent to the National Institute of Forensic Toxicology (NIFT). The samples were analysed using a standard program covering the most commonly abused drugs on the marked in Norway. BZDs, representing some of the most frequently detected drugs, were found in approximately 30% (n = 1051) of the cases, represented by 14% (n = 150) female and 86% (n = 901) male drivers. In 8% of the cases, one BZD only was detected, half of these cases with one BZD could reflect therapeutic use. One or more BZDs were combined with illegal drug(s) (73%), other prescribed drugs (10%), and/or alcohol (24%). 62% of the drivers with BZD detections, had earlier been arrested for the same offence, or six cases per rearrested driver. The frequency of earlier arrests were lower for female (34%) than for male (67%) drivers. Alcohol was most frequently found for those arrested for the first time before 1992, while BZD or illegal drugs were most frequently found for those with their first arrest during 1992-1995. Our study shows that apprehended drivers using BZD are mainly represented by drug abusers due to frequent multi-drug use, blood concentrations representing doses above therapeutic levels and high rearrest rate for the same offence. A treatment program or other reactions, are thus necessary in addition to fines, prison penalty and suspension of driving licence.     

Drugs and chronic alcohol abuse in drivers

Blood specimens from 210 drivers (179 male and 31 female) apprehended in Luxembourg from autumn 2001 to spring 2002 and requested for the determination of their blood alcohol concentration (BAC) were tested for medicinal drugs, illicit drugs, and chronic alcohol abuse (by quantification of the carbohydrate-deficient transferrin: CDT). These additional analyses were performed anonymously and with permission of state prosecutor. The 22.8% had consumed medicinal drugs, with benzodiazepines and antidepressants (10.9 and 7.6%, respectively) as main psychoactive classes. Cannabis was the most detected illicit drug (9.5%) but only one in three had THC detectable in their blood. Association of two or more psychoactive substances (poly-drug use) was observed in 27.6% of drivers (90.6% of drug consumers). On the basis of CDT values, 29.5% of drivers investigated were assumed to be chronic alcohol abusers. Statistical analysis revealed that chronic alcohol abuse and medicinal psychoactive drugs were associated with significantly higher BAC. Medicinal psychoactive drugs were clearly associated with poly-drug use, and were furthermore detected at supra-therapeutic levels in 34.9%.     

Driving under the influence of alcohol and/or drugs in the Netherlands 1995-1998 in view of the German and Belgian legislation

This study presents the test results of blood and urine samples of impaired drivers in the Netherlands between January 1995 and December 1998. In this period, the blood alcohol concentrations of 11,458 samples have been determined and 1665 blood or urine samples have been analysed for drugs. The median alcohol concentration was between 1.7 and 1.8 mg/ml blood. In 80% of the 1665 analysed samples drugs were detected. At least 42% (702/1665) of the impaired drivers were poly-drug users, with cocaine present in the most frequent combinations. In the Netherlands, the procedure to prove driving under the influence is complex. This procedure can be made more efficient and more effective by embedding the analytical test results, needed to prosecute an impaired driver, in the law. In Belgium and Germany, such laws already are in force. If we would apply the qualifications of the new Belgian law on our analytical data, 67% of the impaired drivers included in this comparison could have been prosecuted without discussion in court.     

Driving under the influence of alcohol and/or drugs in the Netherlands 1995–1998 in view of the German and Belgian legislation

This study presents the test results of blood and urine samples of impaired drivers in the Netherlands between January 1995 and December 1998. In this period, the blood alcohol concentrations of 11,458 samples have been determined and 1665 blood or urine samples have been analysed for drugs. The median alcohol concentration was between 1.7 and 1.8 mg/ml blood. In 80% of the 1665 analysed samples drugs were detected. At least 42% (702/1665) of the impaired drivers were poly-drug users, with cocaine present in the most frequent combinations. In the Netherlands, the procedure to prove driving under the influence is complex. This procedure can be made more efficient and more effective by embedding the analytical test results, needed to prosecute an impaired driver, in the law. In Belgium and Germany, such laws already are in force. If we would apply the qualifications of the new Belgian law on our analytical data, 67% of the impaired drivers included in this comparison could have been prosecuted without discussion in court.     

Driving under the influence of toluene

Toluene is the most common volatile used for sniffing among adolescents. During 1983-1987, 114 drivers were arrested in Norway with blood toluene concentrations (BTCs) greater than 10 microM. Only four of these drivers were women. The age range was 15-34 years, and the mean age was 21. The mean BTC was 109 microM. There was no simple relation between blood toluene concentration and degree of impairment, however, most drivers with BTCs greater than 100 microM were considered as impaired or probably impaired by toluene. In a five year prospective study of rearrests among drivers arrested for driving after toluene sniffing, 12 out of 15 drivers were rearrested. They were responsible for 40 cases of suspected driving under influence of toluene, alcohol, or other drugs. The blood levels of toluene determined in this study must be regarded as minimum concentrations, since the toluene concentration fell rapidly in samples stored at 4 degrees C or 23 degrees C. Blood samples from drivers suspected of driving under influence of toluene must therefore be kept frozen.     

Drugs and alcohol consumption amongst Spanish drivers.

We have analysed patterns of alcohol and regular drug consumption by Spanish drivers. Six hundred and seventy five properly completed questionnaires were received from drivers attending three medical traffic centres in Valladolid (Spain) for medical examination prior to obtaining or renewing their driving licence in 1990. Among those surveyed, 24% were 'daily' drinkers and 56.7% were 'weekly' drinkers, the majority (55.5%) being 'light' drinkers (1-39 g/day of pure alcohol). Of those surveyed 28.9% took drugs. The most commonly consumed drugs were analgesics (6.5%), anti-allergic drugs (5.2%) and oral contraceptives (4.6%). Of those drivers taking drugs 28.2% were 'daily' drinkers and 53.8% were 'weekly' drinkers. The study indicates widespread consumption of alcohol and drugs by Spanish drivers.     

Carisoprodol, meprobamate, and driving impairment

This paper considers the pharmacology of the centrally acting muscle relaxant carisoprodol, and its metabolite meprobamate, which is also administered as an anxiolytic in its own right. Literature implicating these drugs in impaired driving is also reviewed. A series of 104 incidents in which these drugs were detected in the blood of drivers involved in accidents or arrested for impaired driving was considered, with respect to the analytical toxicology results, patterns of drug use in these subjects, the driving behaviors exhibited, and the symptoms observed in the drivers. Symptomatology and driving impairment were consistent with other CNS depressants, most notably alcohol. Reported driving behaviors included erratic lane travel, weaving, driving slowly, swerving, stopping in traffic, and hitting parked cars and other stationary objects. Drivers on contact by the police displayed poor balance and coordination, horizontal gaze nystagmus, bloodshot eyes, unsteadiness, slurred speech, slow responses, tendency to doze off or fall asleep, difficulty standing, walking or exiting their vehicles, and disorientation. Many of these cases had alcohol or other centrally acting drugs present also, making difficult the attribution of the documented impairment specifically to carisoprodol and meprobamate. In 21 cases, however, no other drugs were detected, and similar symptoms were present. Impairment appeared to be possible at any concentration of these two drugs; however, the most severe driving impairment and most overt symptoms of intoxication were noted when the combined concentration exceeded 10 mg/L, a level still within the normal therapeutic range.     

Ethanol, marijuana, and other drug use in 600 drivers killed in single-vehicle crashes in North Carolina, 1978-1981

Although the use of ethanol, marijuana, and other drugs may be detrimental to driving safety, this has been established by direct epidemiological evidence only for ethanol. In this study, the incidences of detection of ethanol (and other volatile substances), delta-9-tetrahydrocannabinol (THC), barbiturates, cocaine and benzoylecgonine, opiates, and phencyclidine were determined in an inclusive population of 600 verified single-vehicle operator fatalities that occurred in North Carolina in 1978 to 1981. The incidence of detection of amphetamines and methaqualone were determined for drivers accepted for study during the first two years (n = 340) and the last year (n = 260), respectively. Blood concentrations of 11-nor-deta-9-tetrahydrocannabinol-9-carboxylic acid (9-carboxy-THC) were determined in THC positive drivers. EMIT cannabinoid assays were performed on blood specimens from all drivers accepted for study during the third year, and the feasibility of using the EMIT cannabinoid assay as a screening method for cannabinoids in forensic blood specimens was investigated. The incidence of detection of ethanol (79.3%) was far greater than the incidences determined for THC (7.8%), methaqualone (6.2%), and barbiturates (3.0%). Other drugs were detected rarely, or were not detected. Blood ethanol concentrations (BECs) were usually high; 85.5% of the drivers whose bloods contained ethanol and 67.8% of all drivers had BECs greater than or equal to 1.0 g/L. Drug concentrations were usually within or were below accepted therapeutic or active ranges. Only a small number of drivers could have been impaired by drugs, and most of them had high BECs. Multiple drug use (discounting ethanol) was comparatively rare. Ethanol was the only drug tested for that appears to have a significantly adverse effect on driving safety.     

Prevalence of drugs among drivers arrested for drinking and driving in Finland.

A combined thin layer and gas chromatography system was developed for qualitative and quantitative analysis of drugs in biological samples after extraction with heptane-isoamyl alcohol. Both acidic and basic extraction procedures were used. Special methods were used for the extraction and detection of salicylates, isoniazid, and morphine. Particular attention was given to the detection of psychostimulants; though these drugs have seldom been found in drinking drivers in Finland they are commonly found in Sweden. Two percent of all suspected drinking drivers were also suspected of concommitant drug use, which led to primary sampling of urine. Of 100 such drivers, 24 had blood alcohol levels (BALs) which were negative and 18 of that 24 had drugs in their sample. Seventy-six of the 100 had positive BALs and 25 of the 76 had drugs in their samples. Of the randomly chosen 100 suspected drinking drivers, 5 had drugs in their samples, and 4 of these 5 had positive BALs. The benzodiazeomes were the most commonly detected drugs. No stimulants were found in our subjects.     

Cannabis and driving: Results from a general population survey

The role of illicit drugs on driving, and particularly of cannabis and driving, is the object of increasing awareness. While there is increasing evidence of their effect on psychomotor performance and increased risk of involvement in traffic accidents, limited information is available concerning factors that can predict the likelihood of driving under the influence of cannabis. The present study aims to determine the past year prevalence of driving under the influence of cannabis, and of being a passenger in a vehicle driven by a person under the influence of cannabis, as well as to examine the correlations with a broad range of potential risk factors. A total of 2500 people, aged between 14 and 70 and living in Castille and Leon (Spain), were surveyed in 2004 with regard to their consumption of alcohol and illicit drugs. Among those who reported cannabis use in the previous year, further assessment was carried out. 15.7% of those surveyed reported cannabis consumption in the previous 12 months, of whom 9.7% reported driving a vehicle under the influence of cannabis during this period, on average eight times. One out of five (19.9%) reported being a passenger in a vehicle driven by a person under the influence of cannabis, on average five times in the previous 12 months. The predictors of driving under the influence of cannabis were the population size of community, the number of drugs consumed, reference to cannabis-related problems and to being a passenger in a vehicle driven by a person under the influence of alcohol. The data show that cannabis consumption and driving is common, and requires more attention from policy makers.     

Drugs and alcohol among suspected impaired drivers in Canton de Vaud (Switzerland)

Epidemiological and analytical laboratory records concerning living drivers suspected of driving under the influence of drug (DUID) during the 13 years period ranging from 1982 to 1994 were examined. This study included 641 records, 551 men (86%) and 90 women (14%). The average age of the drivers was 27±7 years (n=636, minimum 18 and maximum 74) and the 18–30 interval age range was overrepresented (80%) in this population sample. A traffic accident had occurred in 254 (40%) of the records, 273 (43%) drivers were suspected of DUID during police controls and 95 (15%) drivers were suspected of DUID because of their erratic driving. One or more psychoactive drugs were found in 92.8% of the samples. In these records, cannabinoids were found in 57%, opiates in 36%, ethanol in 36%, benzodiazepines in 15%, cocaine in 11%, methadone in 10% and amphetamines in 4%. The majority (58%) of cases presented two or more drugs in biological samples, thus indicating a high incidence of potential interactions between drugs. This observation was specially relevant for methadone and methaqualone. We conclude that police suspicion about drivers under influence highly correlated with positive results for drug analyses in biological samples.     

Occurrence of barbiturate, benzodiazepine, meprobamate, methaqualone and phenothiazine in car occupants killed in traffic accidents in the south of Sweden

An investigation of the following psychoactive drugs: barbiturate, benzodiazepine, meprobamate, methaqualone and phenothiazine, was performed on all automobile occupants killed in accidents in southern Sweden during 1977 and 1978. Of 122 drivers and 55 passengers analysed, low concentrations of these drugs were found in nine drivers and in five passengers. Thus, 7.3% of the drivers were driving under the influence of drugs and, of these, two drivers (1.6% of all analysed drivers) were also inebriated. Twenty-three per cent of the drivers were inebriated only. According to the circumstances in the accidents and the number of drivers whose analyses proved positive, drug influence seldom seems to be the cause of fatal traffic accidents.