Stoned driving: a debate about safety and accuracy

Over the last few weeks, its been strange to see one aspect of the cannabis legalisation debate medicinal cannabis start to take a bit of a backseat (no pun intended) to another aspect drug driving testing. In honesty, it seemed near impossible for any drug-related issue, other than ice, to steal the headlines from the election promises, continuously discussed bills, and impassioned pleas that are associated with medicinal cannabis. But it appears court proceedings and protests mean the drug driving debate has quickly escalated and taken centre-stage.

Drug driving, particularly stoned driving, is a tricky subject. On the one hand, protestors say roadside drug tests punish people for the smallest trace of drugs in their system, regardless of effect on driving skills. On the other hand, cannabis does affect driving for up to around five hours, and none of us want our family to be on the other end of a serious bingle with a driver who has impaired coordination, depth perception, focus or reaction time.

It’s a difficult one because we have to consider whats right for everyone, and the wider effects of both arguments.

What does the evidence say?

While many stoned drivers will swear black and blue its not true, very credible research has shown those under the influence of cannabis will have impaired driving skills. Professor Marilyn Huestis, a highly respected leader in this area, notes two meta-analyses that provide evidence of the effect of cannabis on driving, indicating a two-fold risk of crashing after use. A study undertaken by her group also showed significant impairment of lateral driving control after cannabis use with and without low-dose alcohol.

Also of note, newer studies increasingly demonstrate that tolerance among regular cannabis users does not overcome impairments to driving skills, especially where complex decisions are required.

But this debate isn’t strictly about the effect of cannabis on driving skills. This debate is more about how long cannabis use affects driving skills, and what level of cannabis use can cause these negative effects.

Protestors argue there are clear rules around how much alcohol can be consumed before driving, but the blanket rule on drugs like cannabis means someone who used yesterday, may be pulled over, tested and fined, despite having comparable or better skills than a person legally driving after consuming alcohol.

So why not just dictate safe smoking and driving volumes?

Ultimately, the ideal for protestors is to either legalise stoned driving, or undertake the same studies as were undertaken for alcohol (and further studies) to determine safe consumption and driving volumes.

One big problem with the latter, is finding a standard measurement for cannabis when applied to road users. This is easily done in laboratory studies with known doses of THC but how do users translate the information on impairment levels when they don t know the potency of what they re using? Though grams might indicate a standard weight, potency changes from plant-to-plant, and depends on what part of the plant is used. People can also react vastly differently to use of cannabis. Without a standard measure, it s difficult to regulate consumption volumes. If this were possible, what would these limits be in Australia: 5ug/L of THC as in Colorado opr 0.5ug/L as in Italy?

In her paper, Cannabis impaired driving: a public health and safety campaign , Huestis points out the challenges of undertaking research similar in scale to alcohol by using databases of police, courts, hospitals and coroners. She notes producing accurate results is significantly challenged by various factors, including difficulty in obtaining relevant post-mortem data, combinations with other illicit drugs, and the lack of existing data. She also notes quantifying drugs in blood is expensive and time-consuming .

So with this in mind, it is likely we could be waiting quite a long time before there are standards around safe stoned driving . Unfortunately a long time is too long for many protestors, and they are seeking more immediate changes.

Are there other factors?

Something worthy of note, regardless of whether you agree with it or not, is that cannabis is still illegal in Australia. This means this debate could be seen as null and void, or at least before it s time there shouldn’t need to be a law that says don’t drive stoned, while getting stoned itself is still illegal. Lawyers for those charged with drug driving have argued that saying do not use drugs is absurd and ignores reality , but for what other illegal substances or practices do we make this same allowance?

And if we were to accommodate stoned drivers by no longer testing for cannabis or setting a safe consumption level, how far do the allowances go? Do we determine a safe level of consumption for heroin or crack when driving? And what message does this send? Does it contradict the laws that make these drugs illegal and confuse people into thinking they are legal? Or maybe they re just legal when you re driving?

This media has also driven this issue through medicinal cannabis stories, with outlets expressing concern about the poor medicinal users who get caught . Even for users of the pharmaceutical preparation nabiximols, the THC and CBD mouth spray, Australian research has shown users would fail roadside drug tests for up to three hours after dosing.

But this one should have an obvious answer if you want to treat cannabis as medicine (which it may be for some illnesses), treat it as medicine. You shouldn’t drive under the influence of medications (even legal ones) that impair driving skills. And though cannabis can be tested while other medications can’t, ultimately that shouldn’t matter your doctor or the pharmacist doesn’t tell you not to drive while using medication because they like the sound of their own voice, they say it because they care about your safety and that of others. So like all patients, those using medicinal cannabis will need to take this into consideration and make other plans.

The drug driving conversation is really part of the larger legalisation debate one that has strong support groups on both sides. Worth considering is if protestors are victorious, and THC isn t tested for and cannabis-related road incidents increase, could public opinion sway against legalisation and this small victory turn into a large thorn in the side for pro-cannabis advocates?

Where does that leave us?

And so we come full circle. Some cannabis users don’t feel they should be punished for impaired driving when they believe their driving is not indeed impaired. Other drivers don’t want to be hit, harmed or killed by drivers whose skills are impaired. But as with roadside alcohol breath testing, oral fluid testing can’t differentiate between drivers with some tolerance and those who do not.

It seems we are left with two options for the moment: to continue to fine and charge drivers who believe their driving is not impaired but still have THC in their system, or to legalise driving stoned and risk injury and death at the hands of drivers who are still impaired after use.

So what do we do?