OC260079
10 March 2026
Hayden
[FYI request #33252 email]
Tēnā koe Hayden,
I refer to your Official Information Act 1982 (the Act) request, partially transferred to the Ministry of
Transport (the Ministry) from the New Zealand Transport Agency (NZTA) on 11 February 2026:
“5. Policy Basis Question
Given that your own data shows THC alone contributes to approximately 8% of fatal crashes
(not 30%), please provide any analysis, briefings, or advice provided to Ministers or
decision-makers that:
(a) Distinguishes THC-specific crash risk from the broader "drugs" category
(b) Evaluates whether roadside oral fluid testing (which primarily detects recent cannabis
use) is an evidence-based response to the actual crash causation data”
Background context
The new roadside Oral Fluid Testing (OFT) regime was introduced in response to the significant
number of people who are kil ed in road crashes involving a driver who had consumed impairing
drugs. The data provided to you by NZTA in response to your earlier request shows that, over
2019 – 2023, approximately 8 percent of deaths involved a driver who had only THC in their
system, with an additional 18 percent of drivers having both THC and alcohol/another drug. This
means around 26 percent of people were kil ed in crashes that involved drivers with THC in their
system. A further 9 percent involved drivers with another drug in their system.
For context, there was an independent expert panel that provided advice on which impairing drugs
should be within scope of the new roadside testing regime. Each drug has different effects on
different people depending on factors like the dose, method of administering the drug, whether the
person regularly uses the drug, and biological factors that impact the way the drug is metabolised.
This advice is reflected in briefings and Cabinet papers provided to Ministers. The key documents
(including the panel’s report and relevant Cabinet papers) are available on our website
here:
https:/ www.transport.govt.nz/area-of-interest/safety/drug-driving-testing. Independent Expert Panel Report:
www.transport.govt.nz/assets/Uploads/Report/IndependentExpertPanelonDrugDrivingFinalReportA
pril2021.pdf.
transport.govt.nz | hei-arataki.nz
HEAD OFFICE: PO Box 3175, Wellington 6140, New Zealand. PH: +64 4 439 9000
AUCKLAND OFFICE: NZ Government Auckland Policy Office, PO Box 106483, Auckland 1143, New Zealand. PH: +64 4 439 9000
Response
Regarding point (a) of your request, the table attached as Annex 1 lists the key documents
provided to Ministers that include information about drug drivers (including data on drivers with
THC in their system). Some of the documents also discuss how cannabis/THC impacts on a
person’s brain functions, and the increased risk of driving after consuming cannabis. These
documents are publicly available on the Ministry’s website.
There is no analysis that distinguishes THC-specific crash risk from the broader drugs category, as
we don’t hold data or analysis on THC-specific crash risk or risk in relation to the other qualifying
drugs. There is little evidence to support crash risk factors for substances that, for most people, are
illegal. For example, there can be controlled studies on crash risk of drink driving as alcohol is a
legal substance, but this is not the case for il egal substances.
There are also many factors contributing to road deaths, as detailed in the data released to you in
NZTA’s response to your request on 4 March 2026. Because a crash may have multiple factors, it
is difficult to distinguish the THC-specific crash risk compared to the other factors involved.
I am therefore refusing this part of your request under section 18(g) of the Act, as the information
requested is not held by the Ministry and there is no reason to believe it is held by another
department.
Regarding point (b) of your request, the OFT regime is designed to target recent use of impairing
drugs to address the immediate road safety risk caused by drivers who have consumed and may
be affected by these drugs. Recent use is a proxy for impairment, in the same way that blood and
breath alcohol concentration levels are used as a proxy for impairment for drink driving.
You wil see from the key documents listed in Annex 1 that before the roadside oral fluid testing
was introduced, the only tool available to police of icers to detect drug driving was a compulsory
impairment test. A police officer can require a driver to undertake this behavioural test if the officer
has good cause to suspect the driver had taken a drug (or drugs). The time taken to complete the
test, and the requirement for suspicion of drug use, resulted in a small number of tests being
undertaken each year. A University of Waikato survey (referenced in the discussion document
listed as item 1 in the key documents table below) found that only 26 percent of New Zealand
drivers expected to be caught drug driving compared to 60 percent for drink driving.
Screening drivers for impairing drugs at the roadside means it is possible to improve the visibility of
drug driving enforcement and identify more drivers who have recently consumed impairing drugs.
This, in turn, creates a greater deterrent effect and improved road safety. This has been New
Zealand’s experience with roadside alcohol screening to detect and deter drink driving.
For these reasons, this part of your request is refused under section 18(g) of the Act as the
information requested is not held by the Ministry and there is no reason to believe it is held by
another department.
If you would like to discuss this response with us, please do not hesitate to contact us at
[email address].
You have the right to seek an investigation and review of this response by the Ombudsman, in
accordance with section 28(3) of the Act. The relevant details can be found on the Ombudsman’s
websit
e www.ombudsman.parliament.nz.
2
The Ministry publishes our Of icial Information Act responses and the information contained in our
reply to you may be published on the Ministry’s website. Before publishing we wil remove any
personal or identifiable information.
Nāku noa, nā
Joanna Heard
Manager, Safety
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Annex 1: Key Documents
Item
Date
Document and Description
1.
May 2019
Discussion Document Enhanced Drug Impaired Driver Testing
Cabinet approved the release of a discussion document and invited
feedback on dif erent approaches to drug impaired driving. The
discussion document included information on analysis of blood
samples of drivers that were kil ed in crashes between January 2013
and May 2018 [27 percent had used cannabis – see para 12].
2.
December 2019
Cabinet paper: Approval for an enhanced drug driver testing regime in
New Zealand
This paper sought Cabinet agreement to introduce a new compulsory
roadside oral fluid drug testing scheme. See p 3 – 4 for relevant
information.
3.
December 2019
Regulatory impact statement: Enhanced drug driver testing
This document provided to Cabinet includes information about the
prevalence of drug driving in New Zealand [see p 10] and research on
the increased crash risk after consuming certain drugs [see, for
example, p 8 and 25]
An updat
ed Regulatory Impact Statement includes similar information.
4.
April 2020
Cost-Benefit Analysis: Enhanced testing regime for drug-impaired
driving
Relevant information is found throughout this document. A summary
of this information was provided to Ministers in the Regulatory Impact
Statement.
5.
April 2021
Recommending statutory limits for drug concentrations relating to
impaired driving: final report of the Independent Panel on Drug Driving
This report includes data on drug use by New Zealand drivers,
including those kil ed or hospitalised after a motor vehicle crash. The
data lists cannabis (THC) alongside other drugs detected in blood
samples taken from the drivers (see pages 20 – 23]
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Document Outline
