The Need to Treat Driving Under the Influence of Drugs as Seriously as Driving Under the Influence of Alcohol

Report Public Health

The Need to Treat Driving Under the Influence of Drugs as Seriously as Driving Under the Influence of Alcohol

May 16, 2018 33 min read Download Report

Authors: Paul Larkin, Robert DuPont and Bertha Madras


After 40 years of education, prevention, and intervention by law enforcement authorities, American society has seen a significant decline in alcohol-related crashes and fatalities. But various drugs can also severely impair the brain, and drugged driving can be as deadly as drunk driving. It is time to address the complex problem of drugged driving and commit ourselves to keeping that preventable behavior from offsetting the reduction in morbidity and mortality that our efforts against drunk driving have produced. Reasonable steps can be taken to keep someone from maiming or killing innocent people by using drugs and driving. We should not let the perfect be the enemy of the good—certainly not where what is good and doable will save lives.

Key Takeaways

For 40 years, American society has addressed the problem of drunk driving through education, prevention, and intervention by law enforcement authorities.

Physicians, scientists, and others also agree that driving while drugged is likewise a danger to drivers, passengers, pedestrians, and their families.

We should now commit ourselves to keeping that preventable behavior from offsetting the gains that we have seen from our efforts against drunk driving.

Driving Under the Influence of Alcohol (DUI or DUIA)

Ever since Noah became the first vintner,REF Western society has known that alcohol impairs one’s judgment. In the first century A.D., Flavius Josephus expresses the need to teach one’s children to drink wine in moderation.

The disabling effect of alcohol is particularly evident and especially dangerous when a person gets behind the wheel of a multi-ton steel vehicle while under its influence.REF Alcohol-impaired driving is dangerous to the driver, any passengers travelling with him or her, anyone else on the roadway, and pedestrians. Alcohol hampers attention, signal detection, reaction time, hazard perception, object-tracking skills, concentration, and hand-eye coordination.REF Aggravating the impairing effects of alcohol are its abilities to reduce the perceived negative consequences of risk-taking and to “sneak up” on a driver by degrading his driving skills before he becomes aware of its effect.REF

Drunk driving imposes severe costs on the parties injured or killed in an alcohol-induced motor vehicle collision, as well as on the nation as a whole. Approximately 29 people die every day in alcohol-impaired vehicle crashes: one every 50 minutes or more than 10,000 per year.REF Using the most recent cost data, alcohol-induced morbidity and mortality costs the nation $44 billion per year,REF which dwarfs the revenue earned from alcohol taxes.REF

To address that problem, states long ago prohibited “driving under the influence” of alcohol or “driving while intoxicated,” better known by their acronyms DUI or DWI.REF Based on compendia of research on alcohol-impaired driving, the U.S. Department of Transportation arrived at two seminal conclusions:

  • Evidence of impairment at blood alcohol concentrations (BACs) of 0.05 grams per deciliter (g/dL) and higher was found with respect to reaction time, tracking, concentrated attention, divided attention, information processing, vision, perception, and psychomotor performance and on various driver performance measures;REF and
  • Every state should consider adopting illegal per se laws at the 0.08 level for drivers aged 21 and older.REF

In response, all 50 states and the District of Columbia have made it a crime to drive with a specific blood-alcohol concentration level of 0.08 g/dL.REF Those laws deem a person intoxicated as a matter of law, regardless of whether he was impaired as a matter of fact, if his BAC level equals or exceeds that concentration.

The state and federal governments are not the only ones that have fought alcohol-impaired driving. The aggressive efforts of private organizations such as Mothers Against Drunk Driving have changed the societal attitude toward drunk driving.REF What was once treated as an anodyne peccadillo or an occasion for humorREF is now properly seen as a serious crime.REF

Driving Under the Influence of Drugs (DUID)

Numerous substances aside from alcohol can also impair a person’s driving skills, including a variety of illicit drugs as well as lawfully prescribed tranquilizers and soporifics (sleep-inducing drugs).REF For that reason, states have made it a crime to drive under their influence.REF

The problem of “drugged driving” or DUID is not a trivial matter. The National Highway Traffic Safety Administration conducted a roadside survey in 2013 and 2014 and discovered that 20 percent of drivers surveyed tested positive for potentially impairing drugs.REF It is quite troubling to find that one out of every five drivers has used a drug that could adversely affect his ability to drive safely.

Three of the drugs that are particularly troublesome are benzodiazepines (minor tranquilizers); opiates (or opioids);REF and marijuana. The following sections discuss the available evidence regarding their role in drug-impaired driving.REF

Benzodiazepines. Two meta-analyses showed that benzodiazepines are associated with an elevated risk of traffic crashes and an increase in “accident driver-responsibility.” Co-ingestion of benzodiazepines and alcohol was associated with a 7.7-fold increase in the accident risk.REF

Opioids. Opioids, even when lawfully prescribed by a physician, can impair the skills and judgment necessary to handle a motor vehicle safely.REF Given the rise in the nonmedical use of prescription drugs and use of illegal opioids and related analogues (for example, heroin and fentanyl) over the past decade, it should come as no surprise that over the past year, there have been numerous media reports of drivers being involved in wrecks where opiates or opioid drugs were involved.REF As proof, a 2017 study published in the American Journal of Public Health found a sevenfold increase from 1975 to 2015 in the prevalence of opioids in the blood of drivers involved in fatal crashes in several states.REF The reports also stated that hydrocodone, oxycodone, and morphine were the most commonly detected prescription opioids.REF

Marijuana. Marijuana can also impair a driver’s ability to handle a vehicle safely.REF Given the decisions by various states over the past 20 years to authorize the medical or recreational use of marijuana, most of the discussion of driving under the influence of drugs (DUID) has focused on the impairing effect of its active ingredient, ∆REF-tetrahydrocannabinol or THC.REF THC hampers the ability of drivers to process and respond to unexpected or rapidly changing driving scenarios quickly and effectively.REF

Polydrug Use. The evidence also shows that people who use drugs, whether illicit or legal, often do not limit their intake to one particular drug.REF Polydrug use is common, perhaps particularly in the case of alcohol and marijuana.REF Alcohol and marijuana are the two most frequently used substances that degrade a driver’s ability to operate a vehicle. Their combination can have an additive (if not synergistic) effect on a driver, leaving him incapable of driving safely even though neither drug alone might impair his ability to handle a vehicle.REF A person can be incapable of driving safely even though his BAC level is only 0.05 g/dL if he has also recently consumed marijuana and there is THC in his brain.

The result is this: Studies indicate that the combination of alcohol and THC can be impairing even though the amount of either drug consumed by itself might not cause the same degree of deterioration in an average driver’s skills.REF The extent of current polysubstance use, especially with a rising tide of marijuana and opioid use, is unknown. The last well-designed roadside tests for polysubstance use were performed in 2007.

Contemporary Problems: Opioid Abuse and State Marijuana Legalization Initiatives

State marijuana legalization measures have exacerbated the DUID problem.REF In May 2016, the American Automobile Association Foundation for Traffic Safety concluded that after Washington State legalized marijuana, the proportion of fatal crashes involving drivers who had used that drug doubled.REF A recent study by Smart Approaches to Marijuana (SAM) concluded that state marijuana legalization initiatives have contributed to increased risk of morbidity and mortality on their roadways.REF “Drugged driving and motor vehicle fatalities have increased in states that have legalized recreational marijuana,”REF SAM concluded. Relying on the data collected from the Fatality Analysis Reporting System, SAM further reported that approximately 50 percent of fatal crashes nationwide involved drivers who tested positive for THC.REF

According to SAM, the numbers in Colorado were particularly troublesome. From 2013 to 2015, there was an increase of 88 percent in the number of Colorado drivers testing positive for marijuana.REF The four-year averages before and after Colorado legalized marijuana in 2012 saw a 66 percent increase in marijuana-related traffic deaths.REF Drivers, passengers, and other motorists were not the only parties at risk. Other states that legalized recreational marijuana also saw an increase in pedestrian fatalities.REF

Admittedly, the evidence is not dispositive that recent drug use inevitably and invariably causes motor vehicle collisions; there is disagreement on that score.REF For example, a recent study for the National Bureau of Economic Research concluded that there was no material difference between the marijuana-related, alcohol-related, and overall traffic fatality rates before and after the Colorado and Washington marijuana legalization initiatives went into effect.REF Advocates of marijuana legalization use that study and others to argue that there is no proven causal relationship between the new state medical and recreational marijuana laws and an increase in highway morbidity or mortality. Inconsistencies of testing for other drugs if alcohol is found above the legal limit may confound attribution of crashes to other drugs in the system. Also, THC concentrations are rising rapidly; levels of cannabidiol, which can attenuate the florid pharmacological actions of THC,REF are declining steeply, and traffic morbidity and mortality records of five to 10 years ago may not reflect this growing trend.REF

But there are two other factors to consider. The first one is that different states are entitled to hold different opinions regarding their willingness to expose innocent parties to the risk of being injured or killed by a driver whose ability to operate a vehicle safely has been impaired by a lawful or illicit drug.REF The second factor is that there is unanimity regarding a crucial moral judgment: No one should drive under the influence of any substance that could impair a motorist’s ability to operate his vehicle safely. Numerous government authoritiesREF and private expertsREF have recommended against anyone driving while under the influence of any impairing drug, illicit or legal. Even parties who advocate the liberalization of current federal and state marijuana laws recognize that no one should drive while impaired by marijuana.REF

The Need to Treat DUID and DUIA as Posing Equally Serious Public Safety Risks

Unfortunately, there is no easy solution to the DUID problem. Nonetheless, some reasonable steps can be taken to reduce the risk of drug-involved collisions. Below is a list of proposals that should occasion a consensus among the parties interested in addressing this problem, as well as bipartisan support in the legislatures and elsewhere in government. Each one will take a step toward improving roadway safety. Each one deserves serious consideration at all levels of government.

There is a particular need for Congress to address this problem. Interstate highways have that name for a reason. People who drive while under the influence of marijuana do not limit their trips to states that have legalized that drug, nor do people who use potentially impairing prescription medications drive only within their home states. They cross state lines, sometimes several, sometimes far from home. The result is to put at risk residents of states who had no say over whether marijuana should be legalized or whether a person should have let someone else drive while he was using an impairing prescription drug. No one state or group of states can adequately address this problem. While any one state can adopt the proposals mentioned below, only Congress can address the matter nationally.

Interstate roadways are arteries of national commerce, and Congress can regulate the safety of travel along those roads under the Commerce Clause.REF Congress therefore could direct the states to adopt these proposals.REF But there is another option available to Congress: It can condition the receipt of at least a portion of federal highway funds on every state’s compliance with these proposed safety measures.

Precedent exists for that approach. In the 1980s, Congress enacted legislation establishing a national minimum drinking age of 21 and penalizing states that decline to comply with that mandate by directing the withholding of a small portion of the highway funds that the state otherwise would receive.REF The states argued that the statute interfered with their prerogative, granted by the Twenty-First Amendment,REF to decide how to regulate the in-state consumption of alcohol and also imposed an “unconstitutional condition” on their receipt of federal funds, in violation of the Tenth Amendment.REF In South Dakota v. Dole,REF however, the Supreme Court of the United States upheld the constitutionality of that law. The Court ruled both that Congress has the authority to condition the receipt of a portion of federal highway funds on a state’s compliance with a federal minimum drinking age requirement and that Congress’s decision to impose that mandate did not violate the Tenth Amendment because it was a reasonable condition on the receipt of federal funds.REF

The South Dakota v. Dole rationale would apply here. States that legalize the recreational or medical use of marijuana place at risk drivers, passengers, and pedestrians in other states. It is also reasonable to demand that states comply with the conditions noted below as a prerequisite to receipt of all federal highway funds for much the same grounds that the Court found persuasive in South Dakota v. Dole. Finally, such a condition would not trespass on the rights of drivers because driving under the influence of a drug is already unlawful in all 50 states and, in the case of drugs such as marijuana or heroin, the drug is contraband under federal law.

To be sure, the pharmacokinetics and pharmacodynamics of alcohol differ from opioids, marijuana, and other drugs. The result is that we cannot automatically apply to drugs other than alcohol the same countermeasures that we have adopted for alcohol itself. What we can do is treat impaired driving as a serious public safety problem regardless of the chemical structure of the compound that keeps someone from handling his vehicle safely. By so doing, we will demonstrate our commitment to lowering highway morbidity and mortality whatever the chemical agent might be that impairs safe driving.

How to Respond to the Public Safety Risks of DUID

What follows is a set of six proposals to address DUID. The common denominator is treating DUID in the same manner as DUI or DUIA. Although the procedures used in the case of alcohol-impaired driving cannot be transferred automatically to drug-impaired driving because of the different pharmacokinetics and pharmacodynamics of the two types of substances, these proposals can and should be used to address drug-impaired driving because they do not raise the problems posed by uncritical application to the very different context of DUIA protocols.

  • Proposal 1: Apply to every driver under 21 years old who tests positive for any illicit or impairing drug, including marijuana and impairing prescription drugs, the same zero-tolerance standard specified for alcohol, the use of which in this age group is illegal.
  • Proposal 2: Apply to every driver found to have been impaired by drugs, including marijuana, the same remedies and penalties that are specified for alcohol-impaired drivers, including administrative or judicial license revocation.
  • Proposal 3: Test every driver involved in a crash that results in a fatality or a major traffic accident (including injury to pedestrians) for alcohol and impairing drugs, including marijuana, a panel of opioids, and prescription drugs.
  • Proposal 4: Test every driver arrested for driving while impaired for alcohol and impairing drugs, including marijuana.
  • Proposal 5: Use reliable oral fluid testing technology at the roadside for every driver arrested for impaired driving.
  • Proposal 6: Develop national standardized testing, synchronize the testing with drug overdose testing, and develop a national database that collects the information for program and policy decisions.

States, as required by federal law, must have age 21 as the minimum drinking age. It is illogical to treat differently someone under that age who tests positive for heroin, other opioids, cocaine, methamphetamine, LSD, THC, or benzodiazepines, since they can impair a driver’s ability to operate a vehicle and are illegal under federal law. If a state automatically suspends a driver’s license for 30, 60, 90, or 180 days (or longer) if he is convicted of driving under the influence of alcohol, the state should use the same penalty for someone convicted of DUID. Polydrug use is sufficiently common that an arresting officer should test every driver involved in a crash resulting in a fatality or arrested for impaired driving not only for alcohol, but also for impairing drugs. The principal objection to testing for a wider range of drugs is financial, not legal, and the states can use federal highway funds for that purpose. Finally, the development of technology to perform roadside oral fluid testing (for example, with a buccal swab) would enable an arresting officer to obtain supportive (or nonsupportive) evidence of the presence of an impairing substance in an expeditious and relatively nonintrusive manner.REF Together, those proposals would help address the problem that DUID poses for society.REF

Obviously, drugs differ in important ways from alcohol and differ from each other. The pharmacodynamics (what drugs do to the body) and pharmacokinetics (how the body processes drugs) of drugs are not the same, and they also differ from the corresponding pharmacology of alcohol. That makes it difficult to apply standardized protocols and procedures to all problems attributable to psychoactive substances.REF But the above proposals do not make that attempt. Instead, they seek to treat substances that impair brain function—alcohol and other drugs—alike for purposes of the law of impaired driving, not for medical or scientific purposes, and focus this effort insofar as they can on how these substances endanger highway safety.


The paterfamilias of television’s Simpson family, Homer Simpson, once said, while holding a bottle of beer in his hand, “To alcohol! The cause of, and solution to, all of life’s problems.”REF He was almost half-right. Alcohol is not the solution to any of life’s problems, and while it does not cause all of them, it does cause many. One of them happens far too often on our roads. We have known for more than a century that combining alcohol and motor vehicles is always highly problematic and far too often fatal. For the past 40 years, however, American society has dedicated itself to addressing that problem through education, prevention, and, when necessary, intervention by law enforcement authorities. As a result, we have witnessed a considerable decline in alcohol-related crashes and fatalities.

With regret, we have learned that various drugs can also severely impair the brain and that drugged driving can be as deadly as drunk driving. Physicians, scientists, policymakers, and government officials agree that DUID is a danger to drivers, passengers, pedestrians, and their families regardless of their views about drug legalization and regardless of where they live. There is also a societal consensus that reasonable steps to reduce that danger do exist and can be effective.

Accordingly, it is time to address the complex problem of drugged driving. We should commit ourselves to an effort to keep that preventable behavior from offsetting the reduction in morbidity and mortality that we have seen from our efforts to stop drinking and driving. Each problem deserves the same commitment. No one action could altogether eliminate drinking and driving, and American society took what steps were available to reduce its incidence where possible. We should pursue the same course for DUID. Reasonable steps can be taken to keep someone from maiming or killing innocent people by using drugs and driving. We should not let the perfect be the enemy of the good—certainly not where what is good and doable will save lives.

—Paul J. Larkin, Jr., is the John, Barbara, and Victoria Rumpel Senior Legal Research Fellow in the Edwin Meese III Center for Legal and Judicial Studies, of the Institute for Constitutional Government, at The Heritage Foundation. Robert L. DuPont, MD, is President of the Institute for Behavior and Health, Inc., and former Director of the National Institute on Drug Abuse. Bertha K. Madras, PhD, is a Professor of Psychobiology in the Department of Psychiatry at the Harvard Medical School. Dylan Brandt, An Administrative Assistant at The Heritage Foundation, and Peter Newman, a Summer Intern in the Meese Center, provided valuable research assistance for this paper.


Paul Larkin
Paul Larkin

Rumpel Senior Legal Research Fellow

Robert DuPont

Clinical Professor of Psychiatry, Georgetown University School of Medicine

Bertha Madras