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We all want our roads to be safer. A Bill has proceeded through select committee and is due to be discussed by Parliament for the second time soon aims to do just that, by using saliva testing to detect and deter drug drivers.

The Drug Foundation supports the intention behind the Land Transport (Drug Driving) Amendment Bill, which will establish a new roadside oral fluid testing regime to test for drug driving. However, it’s based on imperfect science.

Executive Director Sarah Helm and Policy & Advocacy Manager Kali Mercier presented an oral submission to the Select Committee debating the Bill in May. [Download Drug Driving submission]

It’s a complex issue, says Sarah. “We support the government’s efforts to make our roads safer, but this regime is not going to provide the results they are after.”

The proposed method could lead to both false negatives and false positives. As many as 13% of tests will return a false negative test. This means that a person may be sent on their way even though they had consumed one of the drugs tested for, at a level that was impairing. Others may be fined when they haven’t consumed drugs.

Neither saliva nor blood tests can accurately show impairment, she says. “Unlike breath alcohol tests, saliva testing can only detect the presence of a drug. It won’t tell how much that person has consumed. More importantly, there’s no way of knowing if they were impaired from that use at all, let alone how significantly.”

“Worse still, some drugs can stay in a person’s system for days so they could get an infringement offence even though they haven’t recently used.”

It’s clear the Government has gone to significant effort to make the regime fairer. For example, a double test will go some way towards reducing the chance of a false negative or false positive, and the infringement fee is not excessive - though for some it equates to a week’s income which makes it a significant penalty. 

The Bill also provides a referral path to drug education or rehabilitation, for those who require it. Government will need to make a meaningful increase in funding for AOD sector providers to ensure they are geared up for any extra referrals.

Why not improve on the methods we already have, asks Sarah. Police already have access to an impairment test – they’re just not using it, because it’s expensive and time-consuming. The test involves tasks such as balancing on one leg, walking a straight line or accurately estimating when 30 seconds have elapsed.

“We think a shorter, streamlined version of that test could be developed,” she says. “This could be carried out at roadside checkpoints alongside alcohol breath tests - with a failed test leading to the full (more time consuming) test.”

The Drug Foundation is asking for investment in better technology that could accurately test for impairment, instead of just identifying the presence of a substance. “Such a test would be the gold standard for improving road safety, and could also be used in workplaces.”

Regardless of whether this Bill is passed, the Government should invest into developing such a test as quickly as possible.

Should the select committee and Government decide to implement saliva testing, we ask that a positive test be followed by some form of compulsory impairment testing.

We think this would be a much fairer process, says Kali. “It would combine the ease of a saliva test, with the rigour of an impairment test. Saliva checkpoints would still give that deterrent effect, while also ensuring that all those who are caught are in fact impaired.”

Download the Drug Foundation's submission to the Land Transport (Drug Driving) Amendment Bill:

NZDF drug driving amendment submission FINAL ( PDF 298kb )

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