Cannabis use a recipe for road chaos

The decriminalisation of cannabis, which took effect on June 9, has triggered wide debate across Thai society. While the bold policy aims at promoting the controversial plant for medical purposes, there are growing concerns over misuse, including driving under the influence of cannabis as well as underage consumption.

Cannabis decriminalisation allows people to use all parts of the plant, except when the cannabis extract exceeds 0.2% of tetrahydrocannabinol, THC. This substance, which is the main psychoactive ingredient of cannabis, is still illegal in accordance with narcotics control and suppression laws.

As a bill on cannabis is currently being vetted in parliament, the country has lacked a law regulating the uses of this plant. One concern raised is the issue of cannabis-impaired driving. Will cannabis misuse make our roads even more dangerous than they already are and how will the authorities take precautions and handle this situation proactively?

There are a few studies in several countries which show that cannabis affects some abilities important to driving. Even though cannabis intoxication may last just a few hours, THC can be detected in the blood days or weeks after consumption.

One particular study “Cannabis and Driving” published in September last year shows the connection. The study was conducted by Godfrey D Pearlson and his team at the Department of Psychiatry, Olin Neuropsychiatry Research Center, Institute of Living, Hartford Healthcare Corporation in Connecticut. The research indicates that there is a relationship between driving impairment and the use of cannabis, even at small levels when compared to other intoxicants like alcohol.

Cannabis consumption may affect cognitive response as well as reduce concentration while driving, but there are no statistics that show a rise in traffic accidents in connection with the use of the substance.

Likewise, another study by the National Highway Traffic Safety Administration in the US found no significant connection between THC concentration and driving ability. As part of that, it found there is no major difference in the risk of a traffic accident between people with THC in the blood and those free of the substance.

This may be due to the fact that relevant studies have not yet been able to find a way to study and prove a correlation. As such, it could be said that THC concentration detected in the blood has no direct impact on traffic accidents.

Even so, in several countries like Uruguay and the US where cannabis is legalised, there have been attempts to curb cannabis DUIs due to road safety concerns. Uruguay considers drivers who have a blood test and are found to have THC in their blood system to be impaired. All 50 states of the US apply anti-alcohol measures to offences relating to cannabis and that means cannabis-intoxicated drivers will face action similar to that of an alcohol DUI. There are four levels of enforcement which can differ slightly in each state: drivers must be free of cannabis substance (a zero tolerance law); penalties relating to THC concentration (per se law); penalties on the impact of cannabis use on a case by case basis; a law that imposes control on THC level, does not exceed 5 nanograms per millilitre (ng/mL), (permissible inference law).

In the UK and Canada, the THC concentration threshold is set at 2ng/mL while Germany, tests only blood serum, accepts 1ng/mL levels.

Therefore, despite a lack of data relating to the impact of cannabis use on road accidents, we cannot overlook the problem. Mahidol University issued a warning that people who use cannabis should refrain from driving or operating machines for up to six hours since there is a chance of a serious accident.

However, it should be taken into consideration that the impact of cannabis consumption depends on the amount a person consumes while personal tolerances to the substance can also vary.

Given this, there is a need to be urgent and have more studies on the impact of cannabis use on driving impairment carried out, so traffic authorities can issue legal measures to help prevent road accidents relating to cannabis intoxication. Road carnage is already a problem in Thailand and there are concerns that having more cannabis users behind the wheel will only make roads less safe.

To prevent road accidents, the government should consider a zero-tolerance law that sends the message that the use of the substance while driving is not acceptable. Concerned agencies should start collecting data on accidents resulting from cannabis use in order to provide more information so that more appropriate laws and regulations can be issued accordingly.

Article by Sumet Ongkittikul, PhD, is a research director, Saliltorn Thongmeensuk, PhD, is a research fellow and Ratsameechan Saowakhon is a researcher at Transportation and Logistics Policy, Thailand Development Research Institute. Policy analyses from TDRI appear in the ‘Bangkok Post’ on alternate Wednesdays.

First Published: Bangkok Post on August 03, 2022

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