Traffic safety - ADAC advises against driving after one-day abstinence from cannabis consumption
The ADAC advises people who occasionally consume Cannabis to abstain from driving a car for a full day. The automobile club stated that one cannot be certain if one can safely sit at the wheel after consuming Cannabis. The results came from their own tests, but only with three Cannabis consumers.
Since April 1st, Cannabis is partly legal in Germany. For participation in road traffic, the limit is three and a half nanograms of the intoxicating substance THC per milliliter of blood serum. For novice drivers, the limit is one nanogram per milliliter.
Cannabis-Test Subjects Couldn't Find the Right Path
Three subjects were tested to see how Cannabis consumption affects driving ability. For this purpose, their condition was assessed an hour, four hours, and 20 hours after consumption. Blood samples were also taken to determine the THC concentration.
One hour after consuming Cannabis, the self-assessment and performance of the test subjects in the car and in cognitive tests were significantly below the level in the sober state. There were clear signs of failure.
The test subjects, for example, forgot to adjust the seat or mirrors correctly, could not find the gears, drove unsafely or parked incorrectly. In cognitive tests, experts noticed significant limitations in memory performance and concentration. Therefore, the ADAC assumes that the accident risk is significantly higher. The THC value in the blood of the test subjects was between seven and twelve nanograms per milliliter and significantly above the permitted limits.
Differences between Occasional and Regular Consumers
Four hours after consumption, the THC concentration in the blood was already below the future limit of three and a half nanograms per milliliter. However, the driving ability was not fully restored for the subjects. The Automobile Club states that both the participants and the experts noticed that they could not safely operate in road traffic.
Only after approximately 20 hours were the subjects fit for the road again, as both blood tests and expert assessments showed. Therefore, the ADAC advises all Cannabis consumers not to drive within 24 hours of consumption. Since it is often unclear how much of the substance one has ingested and for how long it continues to act, the ADAC recommends this precaution.
Only occasional consumption was investigated. However, if someone consumes Cannabis regularly – for example, several days a week – the THC is stored in the body. Due to a slow elimination into the blood, it takes several days until it falls below the limit. Experts from the German Society for Transport Medicine (DGVM) and the German Society for Transport Psychology (DGVP) point out that "regular or frequent high consumption excludes traffic participation." Only after a several-week abstinence can driving be considered again.
Even if Cannabis is consumed orally – for example, as a cake or cookie – the periods of effect and detection are significantly longer. In this case, a waiting period of more than 24 hours before driving should be observed.
The ADAC suggests that individuals who partake in Cannabis on a regular basis should renounce driving for several weeks due to its long-term effects and slow elimination from the body. The 24-hour traffic rule is also applicable to those who consume Cannabis orally, as the periods of effect and detection are significantly extended. The results from the ADAC's tests showed that even after 24 hours, the driving ability of Cannabis consumers was not fully restored, highlighting the need for caution. Despite the legal limit of 3.5 nanograms of THC per milliliter for occasional users, the test subjects' THC levels were significantly higher, which significantly impacted their driving ability and cognitive functions.
