What is Roadside Drug Testing?
Police can now randomly stop drivers and check if they have drugs in their system. A driver will usually be tested for alcohol first. These laws are being rolled out nationwide to improve road safety and reduce drug-impaired driving.
There are four drugs that will be tested roadside: cannabis, cocaine, methamphetamine and MDMA.
We’ve pulled together information to keep you informed on this rollout, your rights and how to look after yourself and your whānau.
Contents
How does the test work?
A small swab is rubbed inside your mouth/along your tongue. It will check for cannabis (THC), cocaine, MDMA and meth.
Click on the tiles below to find out more about each substance (credit: The Level).
Taking prescription/medicinal cannabis?
Roadside drug testing applies to all drivers, including those prescribed medicinal cannabis. If you are a medicinal cannabis patient, you could still test positive for THC – however, a medical defense may apply if you are following your doctor’s instructions.
Even if you feel well, THC may still be detectable for a period after use. Other medicines can affect your driving. If you’re taking any kind of medication, even medicinal cannabis, plan ahead:
- Follow your doctor’s advice
- Check if it affects alertness or coordination
- Don’t drive if you feel unsafe
- Store medication in a labelled pharmacy container
For more information on medicinal cannabis and roadside drug testing, see below.
Yes, if you are using a legally prescribed medicinal cannabis product that contains THC, then you may test positive on a roadside saliva test.
No. You can test positive for THC even if you are not impaired. Saliva tests detect the presence of substances, not real-time impairment.
It varies from person to person. If you use THC often, it can show up in saliva tests for up to 72 hours. If you use it less often, it is usually closer to 4-12 hours. Even when you feel clear and not impaired, small amounts can still be present and trigger a positive saliva test.
What happens if I test positive?
If the first test is positive, you’ll be asked to provide a saliva sample and take another roadside test.
If the second test is also positive:
- You cannot drive for the next 12 hours
- Further testing (at a lab) may be required
- Can result in further infringements (fines/demerits)
If the second test is negative, you are free to go but your saliva sample will still be sent to the lab [1].
Can I refuse?
You can be fined or face penalties if you refuse a roadside drug test.
Police do not need good cause to suspect a driver has consumed drugs for roadside drug driving testing. Any driver at any time could be stopped and be required to undergo a random roadside drug screening test.
| Two positive roadside drug screening tests | 12-hour driving ban |
| One listed qualifying drug detected (at or above the threshold) | $200 and 50 demerit points |
| Two or more listed qualifying drugs detected (at or above the threshold) | $400 and 75 demerit points |
Refusing to comply with roadside drug testing procedures will result in an infringement notice issued at the roadside that includes a $400 fine, 75 licence demerit points, as well as being forbidden to drive for 12 hours [2].
If you get 100 or more demerit points within 2 years [3]:
- you’ll get a 3-month suspension on your licence
- you won’t be allowed to drive
According to the NZ Drug Foundation, police say roadside testing devices are calibrated to pick up signs of recent drug use. However, how long a drug can be detected can vary widely depending on factors like your body, the amount used, and how often you take it.
The studies available so far show a broad range of possible detection times for saliva testing:
- THC (cannabis) around 12 hours for people who use cannabis infrequently, up to 72 hours for people who use cannabis frequently.
- MDMA 2-4 days
- Methamphetamine 1-4 days
- Cocaine 12-48 hours
| Drug | Positive screening threshold (ng/mL) |
| Cocaine | 50 |
| MDMA | 50 |
| Methamphetamine | 50 |
| THC (cannabis) | 15 |
Testing positive for drug driving from saliva will primarily result in an infringement notice (fines & demerit points).
However, a blood test may be required in some circumstances. A blood test could result in an infringement or criminal charge.
A blood test may be required following roadside drug driving testing when a driver:
- is unable to provide enough saliva for a drug screening test or sample for laboratory testing
- has been involved in a crash involving death or injury of another person, and the driver has two positive drug screening tests
The outcome of a blood test depends on the concentration of drug(s) found in the blood by laboratory analysis. It is an infringement offence if the drug concentration is within the tolerance level, and a criminal offence if the drug concentration is at a high-risk level. You can find these in Schedule 5 of the Land Transport Act 1998.
Looking after yourself & your whānau
If you or your whānau have used drugs and need to travel, find an alternative way to travel. Impaired driving can put you, your passengers, and others on the road at risk. Have a quick kōrero and make a plan.
- Don’t drive if you feel impaired or have recently used drugs
- Think ahead – plan how you’ll get home safely
- Have a drop off/pick up plan from school for the tamariki
- Sort another way home – whānau, friends, or public transport
Understanding your responsibilities before driving can help reduce unnecessary stress and risk. A little planning goes a long way in keeping you and others safe.
You don’t have to give the police your name, date of birth or address unless:
- You’re driving
- They think you’re breaking alcohol laws
- You’re arrested
Giving false information to the police is a crime! You can exercise your right to silence (beyond giving compulsory information). You can also stop answering questions at any time.
The police can search you, your belongings, your home or car if:
- You are under arrest
- You consent (staying silent counts as consent for searches – say Yes or No)
- They have a warrant (from the District Court)
- There are reasonable ground to suspect you have drugs or an offensive weapon on you
- You are in a liquor ban area and they are searching for alcohol
- You are in transit (i.e. in an airport, railway station etc) and they have reasonable gorund to believe that you have property that has been stolen or unlawfully obtained
Police must let you know why they are searching you, and what the legal authority they have to search you. The police should not generally strip search you and they cannot do an internal search.
The police have to tell you, at the time they make the arrest, the reason for it.
- You must go with the police if you have been arrested.
- You should contact a lawyer as soon as possible.
- Free lawyer on the police lawyer list
- Apart from having to tell them your name, date of birth and address, you have the right to remain silent.
If you’re under 18:
- You can ask the police to explain your rights to you.
- You should have a lawyer with you when you’re questioned/the police take a statement.
- You can have an “Independent Nominated Person” (someone at least 20 years old, unconnected with the crime and readily available) to support you
You can make a complaint about a police officer to the Independent Police Conduct Authority.
Community Law and YouthLaw may be able to help you make a complaint.
Helpful Resources
Disclaimer
This information is provided for general educational purposes only and does not constitute legal advice. While every effort has been made to ensure accuracy, laws and enforcement practices may change over time. You should seek independent legal advice from a qualified professional for guidance specific to your situation.
This page was last updated in June 2026.
