Asking a driver to walk in a straight line would be a more accurate test for impairment than the government’s roadside drug tests, according to an internationally-recognised expert on drugs and road safety.
Dr Michael White, Adjunct Senior Fellow at the School of Psychology, University of Adelaide, South Australia, who specialises in research on the effects of drugs on road safety, describes roadside drug testing as: “close-to worthless.”
“Drugs like alcohol can be reliably detected during roadside testing. Most other drugs, however, can’t be reliability tested. Cannabis is the most obvious example.”
“Roadside tests can show the presence of cannabis, but these tests cannot reliability say a person was affected significantly, even if the recorded drug concentration is very high. That’s quite different to tests for alcohol, which can reliably say a person was drunk and that their driving would have been affected.”
According to Dr White, the crash risk associated with cannabis (THC) is relatively low compared to alcohol and is often overstated in policy discussions.
Dr White believes roadside saliva drug tests offer false hope for improved road safety because the testing devices have significant limitations in accuracy and often detect the mere presence of a drug rather than actual impairment.
“Asking drivers to walk in a straight line is generally an accurate test of impairment. A driver who fails this test is probably unfit to drive. By comparison, a roadside drug test may fail a person who’s safe to drive. The same test may miss that a driver is actually blotto, because some drugs are harder to detect.”
“The government’s roadside tests will only screen for a small panel of common substances: cannabis (THC), cocaine, methamphetamine, and MDMA. This means that many other psychoactive substances, such as LSD, psilocybin, most synthetic cannabinoids, together with many prescription opioids and benzodiazepines won’t be detected by roadside drug tests.”
Dr White’s conclusions are shared by the NZ Drug Foundation:
“[Roadside] saliva tests can detect drugs long after they’ve been used and long after someone is impaired by them.”
Dogandlemon.com editor Clive Matthew-Wilson, whose road safety research was awarded by the Australian Police Journal, believes the police should give up drug testing and instead test motorists for general impairment: anything that affects their ability to drive safely.
“There are already scientifically proven apps that can detect any form of impairment. These tests work well in laboratories but most are not currently suitable for roadside testing. But these apps are improving all the time and they point to the future of roadside testing, because they can reliably detect impairment caused by drugs, but also fatigue, jetlag or even concussion."
“That’s the sort of roadside test that would make a difference, because it’s targeting dangerous behavior rather than lifestyle."
Matthew-Wilson also points out that alcohol is still the worst drug on our roads.
“We live in a strange time in history where meth dealers get jailed for life, legal highs are banned, but liquor stores are overflowing with alcoholic drinks, many of them aimed squarely at young adults. If the government was serious about saving lives, it would urgently restrict the sale and promotion of alcohol, especially to vulnerable groups like teenagers. Although cannabis is frequently implicated in fatal road accidents, it’s generally most dangerous when combined with the world’s worst legal drug: alcohol.”
