Exploring Cannabis-Impaired Driving: A Growing Concern

By Eugene Bruno on January 13, 2025

In Colorado, where America’s experiment with legal recreational marijuana began over a decade ago, a unique line of research has started to unfold. Federal scientists are paying regular cannabis users to get stoned in the name of road safety. As marijuana use grows nationwide, the studies—conducted in vans adorned with hippie tapestries and featuring high-tech car simulators—aim to address a critical gap in understanding cannabis-impaired driving.

The Problem: Detecting Cannabis Impairment

Unlike alcohol-impaired driving, law enforcement lacks reliable tools to detect cannabis impairment. While blood-alcohol levels can be easily measured, determining if a driver is impaired by cannabis remains far more challenging. It doesn’t help that few states routinely test the blood of drivers involved in serious accidents for marijuana, leaving researchers with limited data on how cannabis affects road safety. And even when blood samples are collected, they cannot reliably indicate whether cannabis was consumed hours or days before the test.

State laws on cannabis-impaired driving vary widely, which further complicates matters, as this makes enforcement inconsistent and confusing for both police and motorists. “We’re kind of painting the plane as we fly it when it comes to cannabis liberalization,” said Jake Nelson, Director Of Traffic Safety Advocacy & Research for AAA. Public health and safety, noted Nelson, have often been treated as afterthoughts.

How Cannabis Affects Driving

While national data on the impact of marijuana on road safety is spotty, existing studies suggest cannabis impairs a driver’s ability to respond quickly and judge distances accurately. Unlike alcohol, which impairs people in predictable ways, the effects of cannabis vary based on how it’s consumed.

For example, smoking marijuana produces a high within minutes, with effects wearing off relatively quickly. On the other hand, edibles take longer to kick in and can have more prolonged effects. Additionally, habitual users may develop some tolerance, further complicating efforts to establish universal impairment standards.

Colorado’s Groundbreaking Research

In Colorado, federal scientists are conducting two major studies to help shape cannabis-impaired driving policies. One study focuses on developing portable breathalyzers to determine how recently a driver consumed cannabis. The other uses car simulators to observe stoned drivers and understand how cannabis affects motor skills and reflexes in both habitual and occasional users.

“Policymakers need data on which to base their policies,” said Tara M. Lovestead, a chemical engineer at the National Institute of Standards and Technology, “and there isn’t much data here.”

A Nationwide Issue

As of 2024, 39 states have legalized medical marijuana, and 24 have approved recreational use. According to recent surveys, around 15 percent of American adults reported using marijuana, compared to 7 percent in 2013. Many admit to driving after using cannabis. In fact, AAA found that an estimated 14.8 million motorists drove within an hour of consuming marijuana in 2019. Further, one Virginia survey showed that 22 percent of drivers admitted to driving stoned a few times or more a year.

The Challenges of Regulation

Some states, like Nevada, have adopted THC limits for drivers, which are similar to blood-alcohol concentration laws. However, experts argue these laws are ineffective because THC affects individuals differently, depending on factors like tolerance and method of consumption. For example, drivers who regularly use cannabis may not feel impaired even with high THC levels in their system.

Dr. Ashley Brooks-Russell, a public health professor leading Colorado’s federally funded simulator study, emphasized that cannabis policies shouldn’t mimic drunk-driving laws. “There’s a wishful thinking that it should be like alcohol,” Says Brooks-Russell, “but it’s not.”

Real-Life Consequences

The lack of clear standards has led to heartbreaking cases. In California, Krystal Kazmark died in a 2020 crash caused by her boyfriend, who had smoked marijuana eight hours earlier. Her mother, Mary Kazmark, lamented the lack of reliable tools to measure cannabis intoxication, which might have prevented the tragedy.

Meanwhile, in Nevada, Navy veteran Jeff Krajnak faced felony charges after a fatal accident. Though he passed a field sobriety test and hadn’t used cannabis for 19 hours, his blood contained THC levels exceeding the state’s limit. The case highlights the inadequacies of current laws, which often fail to distinguish between impairment and residual THC presence.

The Road Ahead

As marijuana becomes more accessible, states must balance the benefits of legalization with the potential risks to road safety. Colorado and Washington, the first states to legalize recreational marijuana, have seen increases in fatal accidents involving drivers with THC in their blood. However, it remains unclear how many of these drivers were impaired at the time.

Pam Fischer of the Governors Highway Safety Association called for more research and thoughtful policies. “There was a lot of emphasis on the tax revenue,” Fischer says, “but we need to think about the societal harm that can happen if we aren’t careful.”

With cannabis use on the rise, the need for comprehensive research and sensible policies is urgent. While states like Colorado are taking steps to understand and address cannabis-impaired driving, the nation as a whole must prioritize road safety alongside the economic and social benefits of legalization. Only then can we navigate this new era of cannabis use responsibly and safely.

Eugene Bruno & Associates Can Help You Understand the Law

At Eugene Bruno & Associates, our lawyers are skilled at interpreting the law. If you’ve been involved in a car accident involving a cannabis-impaired driver, navigating the law can be tricky. Let Eugene Bruno & Associates help. Our law firm has been recognized by Expertise as one of the Best Car Accident Lawyers in San Diego and El Cajon. Our attorneys have recovered tens of millions of dollars for our clients, and we can help you. Reach out to our San Diego car accident law firm by calling 1-888-BRUNO-88 (1-888-278-6688).