Kia ora Nigel

This email acknowledges your below request for information made under the Official Information Act 1982.

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-----Original Message-----
From: Nigel Gray <[FOI #34772 email]>
Sent: Saturday, 23 May 2026 3:45 pm
To: Official Correspondence <[email address]>
Subject: Official Information request - Official Information Act Request – Crash Classification Logic and Causation Determination

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To: Dear New Zealand Transport Agency,
From: Nigel Gray
Date:23 May 2026
Official Information Act 1982 Request
I am requesting the following information regarding the classification of road crashes as “drug‑related”, “alcohol‑related”, “medical‑event‑related”, or any similar causal category used in official reporting, dashboards, or public statements.

This request arises from the contradiction between:

Agency statements that no single factor can be confidently identified as the primary cause of a crash, and

The agency’s practice of classifying crashes into specific causal categories such as “drug‑related”.

To resolve this contradiction, I request the following information:

1. The decision rules used to classify a crash as “drug‑related”
Please provide:

The criteria, thresholds, decision rules, or tests used to determine that a crash is “drug‑related”.

Whether toxicology detection alone is sufficient to classify a crash as “drug‑related”.

Whether impairment must be established, and if so, how impairment is determined.

Whether causation must be established, and if so, how causation is determined.

2. The process for moving a crash from “pending toxicology” to “drug‑related”
Please provide:

The workflow, internal guidance, or standard operating procedures governing this change.

The roles or units responsible for making the classification decision.

Any quality‑assurance or review processes applied before the classification is finalised.

3. The evidential standard required to classify a crash as “drug‑related”
Please provide:

The evidential threshold required (e.g., presence, impairment, contribution, causation).

Any scientific, legal, or policy basis for this threshold.

Any documents that define or describe the difference between:

presence of a substance

impairment

causation

contribution

4. Reconciliation of the contradiction
Please provide:

How the agency reconciles the statement that “no single factor can be confidently identified as the primary cause of a crash” with the practice of assigning crashes to specific causal categories such as “drug‑related”.

Any internal documents, emails, memos, or guidance that address this issue.

5. Classification audit or accuracy checks Please provide:

Any audits, reviews, or assessments of the accuracy, consistency, or validity of crash‑cause classifications.

Any documents discussing limitations, uncertainties, or risks associated with assigning causal labels based on toxicology results.

6. Historical or current definitions
Please provide:

All definitions of “drug‑related crash” used by the agency in the last 10 years.

Any changes to these definitions, including the dates and reasons for the changes.

Format
I request that all information be provided in electronic form.

If any part of this request is refused, please provide the grounds for refusal under the OIA and identify the person responsible for the decision.

Purpose (not part of the request, but for clarity) This request seeks to understand the methodology and evidential basis for assigning causal labels to crashes, particularly where the agency has stated that causation cannot be confidently determined.

Yours faithfully,

Nigel Gray

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