It’s no secret that cannabis is more available and its use is increasing. With increasing use of cannabis, governments, police and anti-drunk driving organizations are calling for strictly enforced low limits on cannabis use while driving.

Numerous tech companies are rushing to develop roadside breathalyzer and testing technologies capable of identifying minute amounts of cannabis metabolites. The undeniable fact is that testing positive for THC is not the same as being impaired. Recent research has confirmed that specific drug levels cannot reliably indicate driver impairment.

Caught up in the effort to curb drugged driving are the legitimate patients using cannabis to improve their lives. These patients are being put at risk of being criminalized with little evidence of harm to road users or themselves. States such as Washington and Colorado have set legal limits for concentration of THC in blood while driving.

Many lives have been lost due to the impairment of alcohol while driving. Drinking and driving has been reduced in large part due to public-service efforts and strict enforcement of roadside alcohol testing. Perhaps that’s what makes roadside cannabis testing so appealing.

The easy reaction is to equate alcohol and cannabis. Driving under the influence of alcohol leads to deaths in a straightforward and predictable way; the effects of alcohol lead to impairments in both decision making and motor skills. Evidence shows that alcohol leads drivers to drive faster and with less control and reaction time leading to dangerous consequences. The same cannot be said for cannabis. Research conducted by the NHTSA has concluded that when adjusting for other factors such as age and gender, THC presence alone poses no statistical increase in crashes.

Breathalyzers work for alcohol because there is a consistent relationship between blood alcohol level, impairment and levels detected by the testing equipment. The relationship is so strong that these technologies have stood the test of litigation to prove to judges that beyond reasonable doubt, they are accurate. It’s easy to use the same logic of alcohol to apply to cannabis.

The profits from the company that successfully produces a breathalyzer technology could be immense; the potential market could be every police jurisdiction with a legal limit or a will to root out cannabis users. The consensus has been that is not a question of if but when we will introduce a roadside breathalyzer. As our society figures out how to deal with cannabis use on the roads, there is still a glaring question looming over this issue: are cannabis breathalyzers the only way to have safe roads?

Before the use of Breath Alcohol Content testers, there was the field sobriety test; a simple test to help law enforcement determine if an individual’s cognitive and spacial perceptions are so impaired that driving is dangerous and therefore illegal. There is no way to have perfect road safety with no crashes, so there may be an argument for using traditional methods to judge impairment rather than a catch all limit which will criminalize people unjustifiably.

The main issue with drug impairment testing is that it is a more complex chemical and neurological relationship than alcohol. Five nanograms of THC could have no effect or a strong effect depending on the user.

An experienced medical user may be unaffected by such an amount and be a safer driver because they are not in pain. States are trying to set a limit on cannabis use to discourage impaired driving but there is little scientific evidence to support the use of a strict limit for any drug. The most reliable way to ascertain impairment is the traditional method of a field sobriety test (with reasonable grounds to conduct the investigation).

The difficult yet logical conclusion is that a roadside breathalyzer may be an improper way to do policing. It may cost police forces too many resources, likely won’t improve public safety and would unnecessarily impact innocent drivers with legal costs and disruptions to life.