Marijuana Safety Up in Smoke: How High Is Too High on the Road and on the Job?

The growing use of marijuana across the United States has cast a haze on a critical fact: Although states are rapidly legalizing the drug, we need to better understand impairment and its impact on driver and workplace safety. Congress, the administration, law enforcement and the private sector need to work together on more public awareness and research to develop an objective standard and a reliable methodology to test for impairment.

The dangers that marijuana use present in the workplace and on our roadways must become an essential part of the public conversation and public policy. All but 16 states now allow recreational and/or medicinal use of marijuana. 

As more states legalize marijuana, it’s inevitable there are more people driving or working under its influence. Yet the potential consequences are still broadly misunderstood.

Regardless of whether one supports or opposes legalizing marijuana, we can all agree on the importance of keeping our roads and workplaces safe. Marijuana use can slow reaction times and interfere with coordination, perception, judgment and other critical abilities necessary for safe driving or functioning in the workplace.  

The legalization of marijuana has created a particularly vexing problem for employers protecting the safety of their employees and customers. Employers must wrestle with the impact of drug use on worker safety and quality, the potential liability exposure for employing workers who legally use the drug in their off-time, and the burden and fairness to employees of drug screenings. 

But the lack of research on the effects of marijuana, including the impacts of different strains, potency and quantity on users, renders it difficult for users, employers and state law enforcement agencies to know when one is impaired.

It can be hard to know exactly how impaired someone is on marijuana because it is less predictable and less measurable than alcohol. When testing for alcohol impairment, there is a clear correlation between the amount of alcohol in the blood and a level of impairment.   

There are no standardized methods of measuring marijuana impairment, such as a Breathalyzer. And the impairment effects of use vary widely based on the potency and the person, and even whether it is smoked or consumed.  

Marijuana is metabolized by the body differently from alcohol. The level of tetrahydrocannabinol — the psychoactive ingredient in marijuana — may not accurately indicate the level of impairment. 

The level of THC in the body can vary based on several factors, including how marijuana is ingested and the potency of the product. The level of THC can drop before a user experiences impairment, and evidence of THC can still be found days or weeks after the impairment effects have passed. 

A positive test result for the presence of marijuana or THC in someone’s body suggests potential impairment but may not prove that the person is impaired at that exact time. Early studies suggest an approximate level of impairment could be measured through a blood test, but more needs to be done to develop clear impairment standards and practical roadside evaluation. Simply put, without more research, no one can say with any scientific precision, “how high is too high — to work or drive.” 

Without clear impairment standards and corresponding public education, studies have shown an ignorance of the dangers and costs of driving or working while high. A recent AAA Foundation for Traffic Safety survey found an estimated 14.8 million drivers reported driving within an hour of using marijuana in the past 30 days, though marijuana’s effects are generally felt at least one to four hours after use. Nearly 70 percent of Americans in the same survey think it’s unlikely a driver will be caught by police while high on marijuana. 

In the United States, the tragic costs and lessons of drunk and distracted driving have been hard-learned. We must apply the same level of public concern to the dangerous realities of driving and working while high.  

We need more public awareness and research to develop an objective standard of impairment and reliable methodology to determine impairment. Providing law enforcement with the necessary training and tools is also critical to enforcing highway safety laws and workplace safety regulations.   

Implementing better public policy and research on marijuana impairment will help protect drivers and workers and maintain a safer and more productive America. 


David A. Sampson is president and CEO of the American Property Casualty Insurance Association, and he also served as deputy U.S. secretary of commerce from 2005 to 2007 under President George W. Bush.

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