Definition: drinking, smoking and driving

At present, we rarely hear about drivers "under the influence of hashish" who endanger traffic. Drivers under the influence of alcohol are still in the clear majority. However, the normalisation of cannabis use, which is slowly but surely taking hold in Switzerland, leaves this question unanswered: what would happen if all consumers, beginners, occasional users and addicts of marijuana and hashish got behind the wheel or handlebars and invaded our cantonal roads?Around a quarter of young people between the ages of 18 and 25 use cannabis, and almost all of them are road users. It can be assumed that around 90,000 people in Switzerland smoke cannabis on a daily basis.

Cannabis impairs driving

No reliable statistics on cannabis in relation to road traffic have been compiled to date. And if there were, cannabis would be classified in the "other drugs" category when defining accident factors. Road safety experts have no precise data, but they are predicting the worst, and probably not without reason! More is known abroad. American studies report that four to twelve per cent of drivers who died in road accidents had THC in their bodies, and in most cases, in combination with alcohol. Cannabis users claim that the drug has no influence on driving ability, or even a positive influence. What is embarrassing is that, according to another survey conducted last year by the Swiss Institute for the Prevention of Alcoholism and Other Addictions (ISPA), eighty per cent of cannabis users admit that they feel their driving ability is impaired. Is this admission merely a figment of their imagination? Very shortly after smoking cannabis, there is already a noticeable decrease in driving ability, but it takes an hour for the drug to reach its full effect. Drivers experience a loss of reflexes and are more likely to react inappropriately in stressful situations. Joint smokers are therefore at high risk of accidents. In this context, there is no fundamental difference between smoking a joint and drinking alcohol.

Cannabis and alcohol consumption

After taking a dose of THC of 40 to 300 µg/kg, concentration, reaction time and short-term memory are impaired. This leads to drowsiness, slower reactions and an inability to judge distances and speed correctly, which increases risk-taking behaviour. Cannabis smokers are rarely just smokers. They are often also dependent on alcohol. Anyone who drives a vehicle after consuming cannabis and alcohol is venturing into dangerous territory. Research shows that the risk of an accident increases threefold, or even ninefold, in this scenario. Whereas previously the choice was between "drinking and driving", today the trio of "drinking, smoking a joint and driving" must be clearly separated. It must be assumed that the combined effects of these three elements can have fatal repercussions on a person's ability to control a vehicle.

Assessment of driving ability

Unlike alcohol, there are no clear limits for cannabis consumption. For this reason, it is much more difficult and laborious to assess drivers' fitness to drive. In general, establishing a case of unfitness to drive due to drug use requires three steps: a police investigation, a medical diagnosis and the results of toxicological blood and urine tests. As described above, cannabis consumption leads to a decrease in the ability to react quickly and appropriately to traffic conditions, even the most critical ones. Therefore, the inability to drive due to cannabis consumption is a possible and provable fact.*THC = Tetrahydrocannabinol