A lot has changed since cannabis was legalized, but certainly not everything. Even though cannabis has been legal in Germany under certain conditions since 2024, the following still applies in road traffic: anyone who smokes cannabis and drives a car risks penalties. But what does that mean in concrete terms? How do THC and cannabis affect your driving ability, and what is behind the new THC limit of 3.5 nanograms?
This article provides you with all the important information you need to know about cannabis and driving—explained in an easy-to-understand way.
What actually happens in the body when you smoke weed?
When you consume cannabis, the active ingredient tetrahydrocannabinol (THC) enters your bloodstream via your lungs or digestive system. THC binds to receptors in the brain, altering your perception, mood, and responsiveness. The effect can be relaxing, but also confusing or even frightening.
Many consumers experience euphoria and a feeling of calmness. At the same time, it can lead to concentration problems, dizziness, hallucinations, or reduced attention span. THC affects your brain more than many people think, especially if you consume it regularly.
Because THC is fat-soluble, it accumulates in the body and is broken down slowly. This means that even if you are no longer "high," the THC level in your blood serum may still be above the limit, and this could cost you your driver's license.
How does cannabis affect your driving ability?
THC slows down your reactions, impairs your concentration, and alters your perception of time. You react more slowly to dangerous situations, misjudge speeds, and are generally less attentive in traffic.
Studies show that cannabis users often drive more slowly, but at the same time make more driving errors. This is particularly the case when it comes to staying in lane or judging distances. In road traffic, this can have fatal consequences, especially when alcohol or other drugs are also involved.
So even if you feel fit, your body may still be under the influence of cannabis. This puts not only yourself at risk, but also other people on the road.
How does cannabis affect reaction times and attention?
Studies show that cannabis significantly reduces your reaction time and attention span, especially in the first few hours after consumption.
0D,0Your brain processes stimuli more slowly, so you react later to obstacles or other drivers' braking maneuvers. This significantly increases the risk of accidents. Combining cannabis with alcohol or other drugs is particularly dangerous because the effects reinforce each other.
Even if you are only slightly "stoned," your reaction time can be significantly impaired. That's why experts recommend waiting at least one day before getting back behind the wheel.
What is the new THC limit and how is it measured?
Since August 2024, a new THC limit of 3.5 nanograms per milliliter of blood serum has been in effect in Germany. Previously, the limit was only 1.0 nanograms, which many experts criticized as too low because it also affected regular users, even though they were not impaired at all.
The new THC limit is intended to more realistically reflect when driving ability is actually impaired. But the fact remains: if you exceed this limit, you are liable to prosecution under traffic law.
If the police suspect you of driving under the influence, they will conduct a blood test. If the test shows a value of 3.5 nanograms or more, you will face a fine, points on your license, and a driving ban.
The regulation is enshrined in the Road Traffic Act (StVG) and applies nationwide. For novice drivers and people under the age of 21, however, there is an absolute ban on cannabis, regardless of the THC level.
What are the penalties for driving under the influence of cannabis?
If you are caught with THC in your blood, the penalty depends on the measured value and your behavior:
- From 3.5 nanograms of THC in blood serum: €500 fine, 2 points in Flensburg, 1-month driving ban.
- Combined consumption of alcohol and cannabis: €1,000 fine, driving ban, points.
- Repeated consumption or accident under the influence: criminal proceedings, driver's license revocation, possible MPU.
If you are under 21 or still in your probationary period, there is also a strict ban on cannabis. Even a minimal THC level is enough to trigger sanctions.
The legal consequences can therefore be severe, even if you feel fit to drive. Although the laws have been amended with the legalization of cannabis, the legislator takes road safety very seriously.
When can you drive again after smoking weed?
This is one of the most frequently asked questions, and unfortunately there is no simple answer.
Unlike alcohol, the body does not break down THC linearly. It depends on many factors: how much you have consumed, how regularly you smoke weed, how your metabolism works, and what your body fat percentage is.
With occasional use, the THC level may fall below the limit again after a few hours. With regular use, however, it can take days for you to fall below 3.5 nanograms again.
If you want to be on the safe side: Do not drive for at least 24 hours after consumption. This is the only way to be sure that your condition is no longer impaired.
The ADAC also advises: If you smoke weed, don't drive. Even if the new limit allows more leeway.
What do the ADAC and experts say about the new limit?
The ADAC welcomes the introduction of the new THC limit of 3.5 nanograms, as it is fairer and more practical. However, the automobile club also warns that even with the new limit, cannabis remains a risk in road traffic.
The effects of THC vary greatly depending on the amount, method of consumption, and experience. Therefore, no one can say definitively when it is safe to drive.
Transport medicine experts are also calling for more education. Many people underestimate how long THC remains detectable in the blood and how much it impairs driving ability.
What applies to medical cannabis?
If you use cannabis for medical reasons, different regulations apply. But you still need to be careful.
With a doctor's prescription, you are generally allowed to drive a car, provided that you are not impaired. This means: no fatigue, no dizziness, no concentration problems.
You should always carry your prescription, a certificate from your doctor, and a patient ID card with you to avoid any misunderstandings during checks.
However, as soon as you feel any side effects, your ability to drive is impaired. Driving under the influence of THC remains dangerous and can have consequences for your driver's license.
How is an investigation conducted when drug use is suspected?
If the police suspect that you are driving under the influence of cannabis, they may send you for an examination or a blood test. The test shows the exact THC level in your blood serum.
If the value exceeds 3.5 nanograms, administrative proceedings will be initiated. If acute impairment is suspected, criminal proceedings may also follow.
In some cases, the authorities will require you to undergo a medical-psychological examination (MPU) to assess your fitness to drive. These procedures are expensive, time-consuming, and must be paid for by the individuals concerned.
How can false tests or problems be avoided?
Regular users often have the problem that THC remains in the body for a long time, even when they are not high. Because the active ingredient is stored in fatty tissue, THC levels can remain above the legal limit for days.
The only safe solution is to take breaks and consume consciously. If you consume regularly and still drive a car, there is a high risk that you will test positive. Even if you feel sober.
What does the legalization of cannabis mean for road traffic in the long term?
The legalization of cannabis has raised many questions. On the one hand, legislators want to decriminalize it and establish clear regulations. On the other hand, road safety is a priority.
The new limit is a compromise: it protects those who only consume occasionally from unfair penalties, but still ensures that no one drives under the influence.
In the future, new testing methods (such as saliva tests) could help to better assess the actual condition. However, it remains important that if you consume cannabis, you should avoid driving for at least one day.