Drug and Driving: A Compendium of Research Studies

Annotated Sources (cont'd)

United Kingdom

57. Barbone, F., McMahon, A. D., Davey, P. G., Morris, A. D., Reid, I. C., McDevitt, D. G., and MacDonald, T. M. (1998)

Association of road-traffic accidents with benzodiazepine use. Lancet 352: 1331-6.

Overview

Within-person case-crossover study of crashes among psychoactive drug users

Type of study, population(s) and proportion tested

All drivers 18 years or older who experienced a road-traffic accident between August 1, 1992 – June 30, 1995, which was attended by Tayside (UK) police

Residents in Tayside and had been registered with a Tayside general practitioner between January 1992 and January 1995

Had been using a psychoactive drug at some time during the study period

Drugs examined
  • Benzodiazepines
  • Tricyclic and related antidepressants
  • Selective serotonin-reuptake inhibitors and related antidepressants
  • Other psychoactive drugs
Method of testing and medium used
  • Road-traffic accident data available from police
  • Drug data available from the Medicines Monitoring Unit (MEMO)
  • Linked by a unique patient identifier
Other dependent variables
Findings (including statistical methods)

Identified 1731 users of any study drug

  • 793 tricyclic antidepressants
  • 334 serotonin-reuptake inhibitors
  • 916 benzodiazepines
  • 138 other psychoactive drugs

Using logistic regression, the odds ratios for having a road-traffic accident on a day of drug use for different drugs were:

  • Benzodiazepines = 1.62
  • Tricyclic antidepressants = 0.93
  • Serotonin-reuptake inhibitors = 0.85
  • Too few cases for other psychoactive drugs

Risks associated with benzodiazepine use:

  • Greater among drivers younger than 30
  • Decreased with increasing age (not raised in people 65 and older)
  • Decreased as number of vehicles involved in accident increased
  • Higher with accidents where the driver was judged to be at fault

Was significant in drivers who failed a breath test for alcohol but was much stronger in those with a positive test (this difference in risk was significant)

Benzodiazepines with a long half-life were associated with an increased risk of accident

58. Buttress, S. C., Tunbridge, R. J., Oliver, J. S., Torrance, H., and Wylie, F. (2004)

The incidence of drink and drug driving in the UK – A roadside survey in Glasgow. In J. Oliver, P. Williams and A. Clayton (Eds), Proceedings of the 17th International Conference on Alcohol, Drugs and Traffic Safety (CD). Glasgow: Scottish Executive.

Overview

Roadside survey as part of a larger case-control study

Type of study, population(s) and proportion tested

Non-accident involved drivers at sites within the area of the hospitals from which they obtained their accident-involved sample

Collected at same times of day as the people in the accident sample had their accidents

Time period from July 2003 to June 2004

Drugs examined (threshold values for detection)
  • Benzodiazepines (100 ng/ml)
  • Opiates (300 ng/ml)
  • Methadone (300 ng/ml)
  • Amphetamines (500 ng/ml)
  • Ecstasy (500 ng/ml)
  • Cannabis (50 ng/ml)
  • Cocaine (150 ng/ml)
  • Alcohol
Method of testing and medium used

Drivers stopped at random and asked to offer a sample of saliva and complete a questionnaire about items such as alcohol consumption, driving habits, use of drugs and medicines

Other dependent variables

None

Findings (including statistical methods)

As of March 2004, chemical analysis completed on 386 saliva samples

Eighteen drugs detected (incidence of 4.7%)

Much lower than the 22.9% found previously in their road fatality study

Ecstasy was most common, followed by cocaine and cannabis

However, only 65 of the 386 cases had been tested for cannabis so researchers suggest that cannabis is likely to be the most common once all analyses are complete

No questionnaires analyzed at this point

Comments

Study is ongoing

59. Sexton, B.F., Tunbridge, R.J., Board, A., Jackson, P.G., Wright, K., Stark, M.M., and Englehart, K. (2002)

The Influence of Cannabis and Alcohol on Driving. TRL Report 543. Crowthorne, England: Transport Research Laboratory.

Overview

Study of the effects of cannabis in combination with alcohol

Type of study, population(s) and proportion tested

Male drivers

Simulator and laboratory tasks

Drugs examined (threshold values for detection)
  • Cannabis
  • Alcohol
Method of testing and medium used
Other dependent variables
Findings (including statistical methods)

Under the influence of cannabis subjects: reduced speed, increased headway, were aware of the effects, were less accurate in maintaining lane position, had poorer tracking, performed more poorly on sobriety tests

Subjects actively attempted to compensate for the effects

Alcohol and cannabis together produced an effect slightly greater than cannabis alone

60. Tunbridge, R. J., Keigan, M., and James, F. (2002)

A comparison of the incidence of drugs in drink drivers and fatal road casualties. In D. R. Mayhew and C. Dussault (Eds.) Proceedings of the 16th International Conference on Alcohol, Drugs and Traffic Safety. Quebec: Société de l’Assurance Automobile du Québec.

Overview

Comparison of drug use trends in drinking drivers and fatal road users

Type of study, population(s) and proportion tested

Random selection of drinking driver cases from TRL for England and Wales (n=2000)

Fatal road casualties (n=1184)

Time period of 1997

Drugs examined
  • Amphetamines
  • Cannabis
  • Cocaine
  • Benzodiazepines
  • Opiates
  • Methyl amphetamines
  • Methadone
  • Tricyclic antidepressants
  • Alcohol
Method of testing and medium used

Blood sample information from Forensic Science Service

Other dependent variables

Sex, and age

Findings (including statistical methods)
  • 27% of drinking drivers tested positive for drugs, with 23% testing positive for one drug and 4% testing positive for multiple drugs
  • Cannabis accounted for 18% of that 23%
  • 24% of fatally injured road users tested positive for drugs, with 18% testing positive for one drug and 6% testing positive for multiple drugs
  • Pattern of drug usage generally the same for these two populations
  • For drinking drivers, males and females did not differ in drug use
  • Illicit drug use in fatally injured drivers was predominantly (90%) in younger (under 40) individuals
  • Medicinal drug use in fatally injured drivers was largely (78%) in older (40 and over) individuals
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