Simply Explained: Why Cannabis Roadside Tests Are a Problem in Germany

Since August 2024, Germany has a new THC limit for driving. But: The cannabis tests police use don't work properly with this new limit. Police now demand new tests. We explain the problem – simply and clearly.

🚗 What Changed?

The New Limit: 3.5 Instead of 1.0

Previously in Germany: If you consumed cannabis, you practically couldn't drive at all. The limit was very low (1.0 ng/ml THC in blood). Even if you consumed days ago and were completely sober, you were often still above this limit.

Since August 2024, there's a new limit: 3.5 ng/ml THC in blood (Federal Ministry of Transport).

This means: If you consumed a while ago and only have trace amounts of cannabis in your blood (below 3.5 ng/ml), you can now legally drive.

Why 3.5 ng/ml?

Experts studied how much THC in blood impairs driving ability. They found: 3.5 ng/ml THC has similar effects to 0.2‰ alcohol (Science Media Center Germany). At 0.2‰ alcohol, you're still allowed to drive (but not above that).

So 3.5 ng/ml THC was set as the new limit.

🇩🇪 Context for Non-Germans: How German Drug Testing Works

Germany's approach is different from many countries:

• Fixed limits, not impairment tests: Unlike the UK or USA where police test if you seem impaired (walk straight, follow a pen), Germany uses blood concentration levels. If you're above the limit, it's automatic – doesn't matter if you seem fine.
• Roadside tests first: Police can't take blood on the spot. They use quick saliva/urine tests. If positive → then blood test at hospital.
• THC stays in blood for days: Even when you're sober, traces remain. Old limit (1.0 ng/ml) meant you could be legal but still test positive days later.

❌ What's the Problem?

Old Tests Are Too Sensitive

At traffic stops, police use rapid tests – small devices that immediately show if cannabis is in saliva or urine. But these tests were developed for the old limit (1.0 ng/ml).

The problem: These tests show "positive" as soon as they detect more than 1.0 ng/ml. But now the limit is 3.5 ng/ml. This means:

• Test shows "positive"
• But you might only have 2.0 ng/ml (legally below 3.5)
• Police don't know this and order a blood test
• Blood test shows: You were legally below 3.5 ng/ml
• But you still had stress, lost time, maybe temporarily lost your license

🆕 What Do Police Demand?

"Cannabis Breathalyzer" for the Right Limit

The German Police Union (GdP) says: We need new tests. Tests that only show "positive" when the 3.5 ng/ml limit is likely exceeded (GdP).

They compare it to alcohol breathalyzers. With alcohol tests, you immediately see: Red = too much alcohol. Green = all OK. Police need something like that for cannabis too.

Think of it like this: Imagine if UK police still used old breathalyzers calibrated to the pre-2014 limit (0.08%), even though the law changed to 0.05%. Thousands of people legally under 0.05% would fail the test. That's exactly what's happening in Germany with cannabis.

🧪 Are There New Tests Already?

Rhineland-Palatinate Tests Them

Yes! In Rhineland-Palatinate (Trier region, western Germany near Luxembourg), police have been testing new cannabis roadside tests since May 2025 (1730live).

These new tests are calibrated differently. They only trigger at higher values (closer to 3.5 ng/ml). This should reduce "false alarms."

How Do the New Tests Work?

• Fast: One test takes only 3 minutes.
• Fewer false alarms: Test only triggers when you're likely above 3.5 ng/ml.
• Scientifically verified: University of Mainz checks if tests are reliable.

If the tests work well, Rhineland-Palatinate could use them everywhere. Other German states could then adopt these tests too.

⚠️ What Happens If No Solution Comes?

If Germany doesn't get new tests, there are two possible problems:

Problem 1: Police Do Fewer Checks

Police might say: The tests don't work properly. We'll do fewer cannabis checks. This means: Less road safety. People who actually have too much cannabis in blood won't get caught.

Problem 2: Many Unfair Blood Tests

Police continue as before. They order a blood test for every positive roadside test. Many of these blood tests then show: The driver was legally below 3.5 ng/ml. That's unfair. And it costs a lot of time and money (one blood test costs about €200-300).

💡 Summary

What?	Details
Old limit	1.0 ng/ml THC (until August 2024)
New limit	3.5 ng/ml THC (since August 2024)
Problem	Old tests can't detect the new limit
Solution?	New tests being tested in Rhineland-Palatinate
Status	Pilot project running since May 2025

🔮 What Happens Next?

It now depends on whether the new tests in Rhineland-Palatinate work. If yes, they can be used across all of Germany. Then police would finally have a tool that matches the new law.

If not, the problem remains. Then either new tests need to be developed, or the limit might be changed again.

📌 What Does This Mean for You?

If you consume cannabis and drive in Germany, you should know:

• The limit is now 3.5 ng/ml. Below this value, you're legally allowed to drive.
• But: Police roadside tests can't measure this properly yet. They might show "positive" even when you're driving legally.
• If the test is positive: You have the right to a blood test. The blood test shows the exact value. If you're below 3.5 ng/ml, the case will be dismissed.
• Safest way: Don't drive if you've consumed cannabis – not even after hours. THC levels in blood remain detectable for a long time.

💡 For International Readers: How This Compares
🇬🇧 UK: Even stricter – 2 ng/ml limit (almost zero tolerance).
🇺🇸 USA: Varies by state. Colorado: 5 ng/ml. California: No fixed limit, police judge impairment.
🇨🇦 Canada: 2-5 ng/ml = fine. Over 5 ng/ml = criminal offense.
🇩🇪 Germany's challenge: Trying to balance science (3.5 ng/ml is safe) with practice (need tests that measure it). Most countries either go ultra-strict (UK) or leave it to police discretion (California). Germany wants the middle path – but only works if technology exists.