"This report has summarized available research on cannabis and driving. Evidence of impairment from the consumption of cannabis has been reported by studies using laboratory tests, driving simulators and on-road observation. ... Both simulation and road trials generally find that driving behavior shortly after consumption of larger doses of cannabis results in (i) a more cautious driving style; (ii) increased variability in lane position (and headway); and (iii) longer decision times. Whereas these results indicate a 'change' from normal conditions, they do not necessarily reflect 'impairment' in terms of performance effectiveness since few studies report increased accident risk. – Senate Special Committee on Illegal Drugs, 2002
Injured drivers taken to B.C. hospitals over the next five years will help answer the question: Do those who are high on marijuana cause more crashes than sober drivers?
The ultimate goal of the $1-million study, funded by the federal Canadian Institutes of Health Research, is to help traffic-safety experts develop safer driving policies. It is possible, for example, that the study might show whether there should be a legal cutoff level for THC blood concentration, just as there is for alcohol. The study results should also help inform the debate around whether marijuana possession should be decriminalized.
This study should have taken place before Bill C-2, the controversial drugged-driving legislation, was passed in 2008.]
Watch a video-taped experiment with cannabis and driving.
"Driving under the influence of marijuana"
TV Channel: Speed TV (U.K.)
Program: Fifth Gear
A summary of the Conservative government's proposed "drugged-driving" legislation
In order to allow extra time for police, prosecutors, defence counsel, judges and other criminal justice system personnel to prepare to implement the important changes being introduced through the Tackling Violent Crime Act, the two remaining sections of the Act -- impaired driving and dangerous offenders -- will come into force on July 2, 2008.
These provisions of the Act will provide for:
* More effective sentencing and monitoring to prevent dangerous, high-risk offenders from offending again; and
* New ways to detect and investigate drug-impaired driving as well as stronger penalties for impaired driving.
Justice Minister Vic Toews introduced a new law in Parliament [November 21,2006] that will make Canada’s streets safer by cracking down on drug-impaired driving.
Drug impaired drivers are involved in an estimated one out of every eight fatal collisions in Canada.
[Where is the data to back up this claim? What is implied here by the term "involved?" Does it simply mean that cannabis was detected in a person's system? If so, cannabis can be detected long after consumption, for weeks or months.]
The new legislation introduced today will get tough on drug impaired driving by:
Making it an offence to refuse a test for driving a car while drug-impaired;
Making it a criminal offence to be in care or control of a vehicle while in possession of an illegal drug;
Providing for a driver to face the same penalties as the person who is in possession of such drug and to receive a mandatory driving prohibition;
No longer accepting witness testimony which challenges test results, and limit the “evidence to the contrary” defense against the result of approved screening devices to evidence based on science;
Extending the “impaired driving causing death/bodily harm” penalties to include refusal to take a breathalyzer test;
Increasing the minimum fine to $1,000, and triple the maximum penalty for a summary conviction to 18 months; and
Enabling police to test someone they have reasonable grounds to suspect has been in care or control of a vehicle in the previous two hours.
For repeat offenders, the new law will increase the prison term to 30 days from 14 days for a second offence, and to 120 days from 90 for a third offence. The new law will also impose the same minimum penalties and driving prohibitions currently given to repeat impaired drivers to those found driving in violation of their prohibition.
Andrew Murie, chief Executive officer of Mothers Against Drunk Driving (MADD), welcomed the new government’s commitment to crack down on drug impaired driving and urged MPs to pass the new law in this Sitting of Parliament.
Canada’s New Government encourages Parliamentarians of all political stripes to support the new law because it will help police get drug-impaired drivers off Canadian streets.
to create an offence of operating a motor vehicle while in possession of a controlled substance as defined in subsection 2(1) of the Controlled Drugs and Substances Act;
to authorize specially trained peace officers to conduct tests to determine whether a person is impaired by a drug or a combination of alcohol and a drug;
to authorize the taking of bodily fluids to test for the presence of alcohol or a drug;
to create an offence of operating a motor vehicle with a concentration of alcohol in the blood that exceeds 80 mg of alcohol in 100 mL of blood and causing bodily harm or death to another person;
to clarify what evidence a person accused of driving with a concentration of alcohol in the blood that exceeds 80 mg of alcohol in 100 mL of blood can introduce to raise a doubt that they were not committing the offence;
to create an offence of refusing to provide a breath sample when the accused knows or ought to know that the accused’s operation of a motor vehicle caused an accident resulting in bodily harm to another person or death; and
to increase the penalties for impaired driving.
The enactment also makes consequential amendments to other Acts.
… The results to date of crash culpability studies have failed to demonstrate that drivers with cannabinoids in the blood are significantly more likely than drug-free drivers to be culpable in road crashes. …
G. Chesher and M. Longo, 2002. Cannabis and alcohol in motor vehicle accidents,
Cannabis and Cannabinoids: Pharmacology, Toxicology, and Therapeutic Potential.
The THC-only drivers had a responsibility rate below that of the drugfree drivers. … While the difference was not statistically significant, there was no indication that cannabis by itself was a cause of fatal crashes.”
K. Terhune. 1992. The incidence and role of drugs in fatally injured drivers.
Washington, DC: US Department of Transportation National Highway Traffic Safety Administration,
Report No. DOT HS 808 065.
Drivers under the influence of cannabis seem aware that they are impaired, and attempt to compensate for this impairment by reducing the difficulty of the driving task, for example by driving more slowly.
In terms of road safety, it cannot be concluded that driving under the influence is not a hazard, as the effects on various aspects of driver performance are unpredictable. In comparison with alcohol however, the severe effects of alcohol on the higher cognitive processes of driving are likely to make this more of a hazard, particularly at higher blood alcohol levels.
B. Sexton et al. 2000. The influence of cannabis on driving:
A report prepared for the UK Department of the Environment, Transport and the Regions (Road Safety Division)
"Drivers under the influence of marijuana retain insight in their performance and will compensate, where they can, for example, by slowing down or increasing effort. As a consequence, THC's adverse effects on driving performance appear relatively small."
The report concluded, "there was no indication that marijuana by itself was a cause of fatal accidents."
Evidence from the present and previous studies strongly suggests that alcohol encourages risky driving whereas THC encourages greater caution, at least in experiments. Another way THC seems to differ qualitatively from many other drugs is that the former's users seem better able to compensate for its adverse effects while driving under the influence. Still one can easily imagine situations where the influence of marijuana smoking might have an exceedingly dangerous effect; i.e., emergency situations which put high demands on the driver's information processing capacity, prolonged monotonous driving, and after THC has been taken with other drugs, especially alcohol. http://druglibrary.org/schaffer/misc/driving/driving.htm
1992 National Highway Transportation Safety Administration study (Report # DOT-HS-808-065) The Incidence and Role of Drugs in Fatally Injured Drivers,
by K.W. Terhune, et al. of the Calspan Corp. Accident Research Group in Buffalo, NY
2005 Developing Science-Based Per Se Limits
for Driving under the Influence of Cannabis http://www.canorml.org/healthfacts/DUICreport.2005.pdf (PDF)
"Even frequent users of cannabis do not seem to have a higher accident risk than nonusers, as long
as they are not under the acute influence of the drug, i.e., there appear to be no extended effects
of cannabis use on traffic safety beyond the period of acute impairment."
Marijuana and actual driving performance. Washington, DC: National Highway Traffic Safety Administration. 1993.
Effects of Cannabis on Psychomotor Skills and Driving Performance - a Metaanalysis of Experimental Studies
Institute of Forensic Medicine, University of Cologne, Melatengürtel 60, 50832 Cologne, Germany http://casr.adelaide.edu.au/T95/paper/s1p2.html
Ottawa Public Health and Carlington Community and Health Services have received funding from Health Canada’s Drug Strategy to design and promote a public awareness campaign which educates teens and parents about the driving-related risks of marijuana use, called “Why Drive High?”
A 2002 Centre for Addiction and Mental Health Monitor survey indicates that:
2.9 per cent of drivers have driven a vehicle within 1 hour of smoking marijuana.
This estimate represents over 200,000 drivers in Ontario or (1 in every 34 drivers).
Of student drivers, the 2005 Ontario Student Drug Use Survey reports:
20 per cent drove within 1 hour after smoking marijuana.
Ottawa Public Health and Carlington Community and Health Services, on behalf of twenty-five community partners, developed a new interactive game called “Why Drive High?”
Comment: The “Why Drive High?” campaign provides results from two surveys conducted in 2002 and 2005 on cannabis use and driving but there is no declaration of accident statistics that verify to what extent cannabis use is a cause of automobile accidents.
Despite the increase in the prevalence of driving under the influence of cannabis, it is not clear what impact this is having on crash-related death and injury.
"Controlled studies that have attempted to determine the risk of crash involvement associated with driving after cannabis use have shown mixed results," said Rita Notarandrea, CCSA's Director of Research and Policy. "The CAS data provide us with a more accurate understanding of the prevalence of driving after cannabis use in Canada, but points to a gap in understanding how much of a factor this is in causing or contributing to harms such as motor vehicle crashes."