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Roadside testing for intoxication just around the corner

Similar to many current prescription pain medications such as tramadol and codeine, psychoactive forms of medical cannabis can reduce reaction times and diminish alertness making them unsafe to drive while under the influence. Unlike alcohol, there is currently no method available in New Zealand to test for accurate intoxication levels on the roadside. The main reasons for this is the psychoactive compound in cannabis (THC) is very difficult to measure for current levels of intoxication. Preliminary studies suggest that anywhere above one nanogram of THC per milligram of blood can be considered as impairment.

The current test method for cannabis involves a urine test that can return a positive result anywhere up to 30 days after use depending on the frequency of use and the test subjects body fat percentage. It does not provide any information on current intoxication levels or give accurate information on when cannabis was last used. With medical cannabis now legal in New Zealand and recreational legalisation on the horizon, it is imperative that a simple, quick and accurate method for testing intoxication is found.

A study (1) by researchers from the American Chemical Society are investigating a new saliva test that can quickly and accurately determine a driver’s level of intoxication on the roadside. The researchers have engineered THC sensor strips and an electronic reader that is simple to use and easy to integrate into law enforcement. The sensor strips are coated with antibodies that bind to the THC in a saliva sample. A specific voltage is then applied to the strip, which will give different current readings depending on the amount of THC bound to the antibodies. The device then quickly converts this data to accurate and current THC concentration.

One of the biggest worries for people who intend to vote against legalisation here in New Zealand is the potential increase of intoxicated drivers on our roads. While there is absolutely no doubt that cannabis impairs driving ability, research (2) completed by surgeons in The United States suggest that legalisation does not lead to an increase in motor vehicle accidents. The logical explanation for this is that people who are willing to wait for legalisation to use cannabis tend not to be the type of people that will drive while intoxicated. Either way, an accurate, fast and easy method to test for roadside intoxication levels could be just around the corner, and this can only be viewed as a positive.

1) American Chemical Society. (2020, March 30). Saliva test for cannabis could someday help identify impaired drivers. ScienceDaily. Retrieved September 23, 2020 from

2) Keric, N., Hofmann, L. J., Babbitt-Jonas, R., Michalek, J., Dolich, M., Khoury, L., Perez, J. M., & Cohn, S. M. (2018). The Impact of Marijuana Legalization on Vehicular Trauma. Cureus, 10(12), e3671.

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