Drivers on Pot - Issues and Options

This archived article is from October 2003. Although every effort has been made to make sure the information presented is accurate, please note that it may contain information that is out-of-date.

The UK government is reclassifying cannabis this year. While the drug remains illegal, it is now classed with amphetamines and barbiturates, rather than heroin. The advisory council which recommended the change stressed that cannabis is unquestionably harmful and was anxious that the public be informed of the dangers associated with its use. A public education campaign is being implemented as part of that country's drug strategy.

Canada's federal government is moving in a somewhat similar direction. In response to recommendations from a Senate special committee on illegal drugs, it wants to decriminalize possession of small amounts of cannabis. Although the substance would still be illegal, this proposal has raised concerns about increased use, which may lead to more drivers impaired by marijuana.

Under the Criminal Code of Canada, drivers can be charged if impaired by alcohol or drugs. However, there is no per se offense for substances other than alcohol. Criminal charges can be laid if a driver's blood alcohol concentration (BAC) is 0.08 or higher. Above that level, the likelihood of a crash is known to increase substantially. Most Canadian jurisdictions impose administrative licence suspensions at BACs of 0.05 or lower.

Breathalyzers provide an easy, effective and convenient way for police to detect and measure the presence of alcohol. However, at present there is no reliable and non-intrusive rapid roadside method to test for pot. Even if a "potalyzer" were available, a defensible per se limit must be set, at which a pot-using driver is criminally impaired.

In Canada, some police services have officers trained specifically as drug recognition experts, who can determine if a driver is impaired by drugs. The Senate special committee felt this visual recognition method has yielded satisfactory results.

Who's using pot?

The Traffic Injury Research Foundation (TIRF) found that 1.5 per cent of drivers surveyed in its 2002 Road Safety Monitor had used marijuana within two hours of taking the wheel. The survey found that young men are most likely to drive after using marijuana or other illegal drugs. One-third of those who drove after using marijuana also drove after drinking.

An Ontario study released in March 2003 showed 15 per cent of students in grades 10 to 13 who had a driver's licence reported driving within an hour after consuming two or more drinks. Even more, 20 per cent, reported driving within an hour after using cannabis.

The Canadian Centre on Substance Abuse (CCSA) says cannabis use by Canadian teens is among the highest in the world. In Canada (as well as Australia, France, Ireland, UK and the US) more than 25 per cent of all high school students report past-year use.

In its September 2002 report, the Senate special committee concluded that between five and 12 per cent of drivers may driver under the influence of cannabis; this percentage increases to over 20 per cent for young men under 25 years of age.

How does pot affect drivers?

The psychoactive chemical in marijuana is tetrahydrocannabinol (THC). THC has a very different effect from alcohol. Pot users are acutely aware of their impairment - that is, they feel "high" - and some try to compensate by driving more cautiously.

THC diminishes psychomotor skills and attention span. It reduces the ability to perform tracking tasks; at high doses, users drive less accurately and show difficulty with steering. Alcohol additionally impairs cognitive function, including risk perception, decision-making and planning. It can also trigger aggressive driving behaviour such as speeding and following too closely.

For alcohol, levels of impairment have been correlated with specific concentrations in the blood. No such correlation is available for THC. Complicating the issue, THC can be detected in the body for up to four weeks, although its impairing effects do not last.

Studies indicate that the effect of cannabis use on driving is related to the dose. Some claim that a single glass of wine will impair driving more than smoking a joint. However, the potency of a joint can vary considerably. Driver use of cannabis is of particular concern when combined with alcohol. The combination increases a drinking driver's risk of being responsible for a crash.

Further research is needed in order to establish a THC level at which the substance criminally impairs driving ability, and how to assess drivers.

In January 2002, the European Commission initiated a three-year project with the acronym IMMORTAL (Impaired Motorists, Methods of Roadside Testing and Assessment for Licensing). The results of this study will provide a much-needed scientific base for legislation.

Cannabis and Crashes

  • A significant number of drivers killed in road crashes have a combination of drugs and alcohol. "Drugs" include cannabis and other illicit substances as well as prescription and over-the-counter medications.)
  • A TIRF study of Ontario driver fatalities in the early 1980s determined that over half of all the deceased who tested positive for drugs had also been drinking.
  • A similar 1990 study found alcohol in 57 per cent and cannabis in 11 per cent of driver fatalities. Of the cases that were positive for cannabis in the blood, 84 per cent also tested positive for alcohol and 70 per cent were males under age 25.
  • In a British Columbia study of drivers killed in 1990 and 1991, 48 per cent tested positive for alcohol. Drugs were found in 20 per cent of all cases; cannabis alone accounted for 13 per cent. Over half of drivers who tested positive for any drugs had also been drinking.
  • A 2002 Quebec study showed drugs are implicated in a substantial number of fatal crashes. Cannabis was detected in 19.5 per cent of driver fatalities. Alcohol was found in 41 per cent of all drug-positive cases. In the roadside sample, drugs were found in 11.8 per cent of drivers, including 6.7 per cent who had cannabis. Alcohol was detected in 5.1 per cent. Alcohol and drugs were found together in 5.9 per cent of drug-positive cases.
  • A UK Department for Transport study published in 2000 revealed that traces of illicit drugs were present in 18 per cent of road fatalities in that country, a six-fold increase from the mid-1980s. Cannabis was found in two-thirds of these cases.

Legal Options

France has passed a law making it a crime to drive under the influence of drugs. The law foresees a two-year prison sentence and a € 4,500 fine for anyone driving or accompanying someone driving "under the influence of plants or substances classified as narcotics." These measures are above and beyond those for drunk driving. Critics say it will be very hard to implement the new law. Police officers may have a hard time getting suspected drug users to a medical clinic or hospital for blood or urine tests.

This zero tolerance approach would not likely work in Canada. French law, unlike Canadian law, assumes the accused is guilty and is not as open to court challenges.

Other EU countries take varying approaches to drug-impaired driving. In Germany and Spain, detection of any trace of a drug gives rise to an administrative offence, but there must be proof of impaired driving skills for a criminal charge to be applied.

In January 2003, a judge in Pembroke, Ontario acquitted a man charged with driving while impaired by marijuana. The accused man had a medical exemption to smoke marijuana as a treatment for his multiple sclerosis. The judge could not tell what caused the accused to swerve over the centre line when driving, and to slur his speech and lose his balance when police pulled him over. It could have been the pot smoke, the illness or some other factor.

Conviction under the Criminal Code of Canada requires proof 'beyond a reasonable doubt,' so Canadian legislators must weigh their alternatives carefully. In the absence of definitive research on how cannabis use relates to road crashes, court challenges may hinder conviction in criminal cases. Until sufficient evidence is available, sanctions outside the Criminal Code should be seriously considered.

Administrative licence suspensions have proven to be an effective tool in the fight against impaired driving. Most provinces impose 12-to 24- hour suspensions under their traffic codes on drivers whose BAC is below the 0.08 criminal limit. These suspensions remove potentially dangerous drivers from the road. They provide a stern and effective warning without the punitive lifetime consequences of a criminal record and a costly criminal court case.

The Canada Safety Council urges provincial and territorial governments to consider imposing administrative licence suspensions on drivers who have been using cannabis. Police with reason to believe a driver has been smoking pot should be able to suspend that driver's licence without a criminal charge. If alcohol is also involved, appropriate action would be taken depending on the BAC.

The prevalence of cannabis use among younger, mostly male, drivers raises cause for concern. Precautionary action is needed - but the research to date does not support zero tolerance with automatic criminal sanctions.