Roadside Drug Testing Proves Inconsistent for Cannabis Consumers

By Oliver Bennett, Special Contributor, New Frontier Data

In the U.K., as part of the Conservative Party’s London mayoral candidate Shaun Bailey’s campaign, businesses are being encouraged to subject their employees to random drug testing, with results published during his 2021 bid to run the city. Under Bailey’s plan, businesses with more than 250 employees would sign up to a drug-testing charter to routinely test staff members – the goal aiming to dent the cocaine market and impact drug gangs.

The plan drew minor controversy, revisiting a vexing issue of drug testing, and its impact on cannabis consumers. Indeed, a general rise has been reported in positive test results among U.K. workers. Whereas more than one in four workers tested positive in 2019, the rate climbed to 30.5% this year, across sectors including construction, transport, utilities, aviation, and healthcare. In the U.K., cannabis was the most highly detected drug at 39.7%, followed by cocaine at 17.2% (the rise reflected a 2019 North American study in which was found a 16-year-high in workplace positive rates).

Meantime, public awareness about “drug driving” has given rise to various roadside saliva tests such as DrugWipe (the brand most commonly used by U.K. police). Attention has commonly been paid since the EU Council’s road safety action programme in 2003-2010, proposing “taking any appropriate measures (which may include sanctions) in respect of vehicle drivers who are under the influence of psychoactive substances, which reduce their capacity to drive”.  Since then, testing has increased – along with convictions.

Recent  figures from the Irish Road Safety Authority (RSA)  indicate that cannabis use nearly rivals that for alcohol, with 68% of drivers found positive for cannabis during 2017-2019 roadside tests. Drug-driving prosecutions in the U.K. have risen exponentially, with a record 10,215 cases cited in England and Wales in 2018, up 90.3% from 5,368 recorded in 2017. Some police forces have asserted that a trend towards cannabis and cocaine has become more prevalent than alcohol in roadside tests. More police data shows the numbers of arrests for drug-driving surpassing drink-drive arrests for the first time in England, with 672 drug-driving arrests in 2018-2019 versus 652 drink-driving arrests. In Greater Manchester, police carried out 640 breath tests, with some 90 proving positive for alcohol as compared with 114 roadside drug tests revealing 50 samples showing positive for cannabis or cocaine.

A 2015 change in the law, helped by the advent of saliva testing, lets the police need only prove the presence of drugs in a DrugWipe roadside test to effect an arrest. A positive saliva test is subsequently corroborated (or disproved) by a blood test to serve as evidence for prosecution. Refusal to participate in the saliva test, too, is an arrestable offence.

Similar laws exist across Europe, if with particular differences between countries. For example, driving under the influence of cannabis in Germany carries a €500 penalty for THC over 1 ng/ml in blood serum, with a driver losing their licence for three months. In Belgium, a €1600-€16,000 fine is levied for those found driving over a THC limit of 1 ng/ml, and in the U.K. (with a slightly higher THC limit at 2 ng/ml) those testing positive face losing their driving licence for a year, and a fine up to £5,000. France maintains zero tolerance for THC, with fines reaching €4,500 and potential loss of a licence for three years. In Spain, a fine for a positive test is €1,000, while in Italy the punishment for driving under the influence of cannabis carries a fine between €1500-€6000, with a potential sentence of a year in jail.

Roadside testing is complicated by a tendency for drivers to consume several intoxicants. Research by the Finnish Crash Data Institute (OTI) of fatal collisions in Finland during 2014–2018 found that 65% of those driving under the influence of drugs had mixed intoxicants. In the Netherlands, where a drug-driver is subject to a €850 fine, the THC limit is calibrated at 3 ng/ml on its own, but drops to 1 ng/ml if used in conjunction with alcohol or another drug.

Still, issues remain with cannabis and drug testing, most notably that frequent cannabis users are known to have THC in their systems for over a week or longer, and therefore may arguably test positive without being recently intoxicated. In the U.K., the British army last year saw 660 personnel dismissed after failing drug tests (if more likely due to cocaine use rather than cannabis). It has been suggested that the popularity of cannabis has declined since it remains traceable for a longer time.

Tests for drug driving also potentially sweep up legitimate medical cannabis patients. In Pittsburgh, Pennsylvania (U.S.), a medical cannabis patient last year crashed her car after suffering an epileptic seizure. Though charged with driving under the influence after minor traces of THC were found, the woman is contesting the charge.

There are also questions about the accuracy of the saliva tests. Some believe that unmonitored CBD may trigger false positives. The success rate of popular  saliva tests have also been called into question in Australia, where University of Sydney studies have found both Securetec’s DrugWipe and the Draeger DrugTest 5000 returning significant numbers both of false positives and false negatives.

There are also individual differences to consider, with a U.K. legal advocacy group warning of a prevalent “huge range of tolerance variations” in the population, and noting that the  “bearing of population-variable doses on the ability of the individual to drive” can be “extremely complex”. Testing is underway for further research into effects of cannabis on driving impairment, with the objective to clarify discrepancies.