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Impaired Driving

Impaired driving is responsible for over 10,000 fatalities every year. Whether the impairment is caused by prescription medication, illicit drugs, alcohol or cognitive impairment, the results are the same. These injuries and deaths were preventable with education, planning and responsible driver behavior.

The Issue

  • Alcohol-impaired drivers are involved in at least one-third of all motor vehicle deaths, according to the Fatality Analysis Reporting System (FARS), National Highway Traffic Safety Administration (NHTSA).
  • In the U.S., one alcohol-impaired driving death occurs every 45 minutes and impaired-driving crashes cost more than $50 billion.
  • Most alcohol-impaired driving crashes occur during the evening hours and on weekends. In fact, the rate of alcohol impairment among drivers involved in fatal crashes is four times higher at night than during the day. The rate is twice as high for drivers involved in crashes on the weekends as compared to during the week (NHTSA 2015). 
  • Drivers with a blood alcohol concentration (BAC) of 0.08 or higher involved in fatal crashes are six times more likely to have a prior conviction for driving impaired than were drivers with no alcohol. 

Recognizing the drunk driver 

Motorists should never take the law into their own hands or engage with those driving erratically. If a fellow motorist exhibits these signs, impaired driving may be occurring. To seek law enforcement assistance, make mental notes of the location of the vehicle, model and color and, if possible, license plate number. Pull to a safe place and call 911 to alert officers. Here are a few signs that a fellow motorist may be driving while impaired:

  • Quick acceleration or deceleration 
  • Tailgating 
  • Weaving or zig-zagging across the road 
  • Driving anywhere other than on a road designated for vehicles 
  • Almost striking an object, curb, or vehicle 
  • Stopping without cause or erratic braking
  • Signaling that is inconsistent with driving actions 
  • Slow response to traffic signals (e.g. sudden stop or delayed start)
  • Straddling the center lane marker 
  • Driving with headlights off at night 
  • Driving slower than 10 mph below the speed limit 
  • Turning abruptly or illegally 
  • Driving into opposing traffic on the wrong side of the road

A Word About Ignition Interlock Devices

  • An ignition interlock is a device about the size of a cell phone that is wired into the ignition system of a vehicle.  A driver who has been previously convicted for drunk driving may be court-ordered to blow into the device in order to start their vehicle. Acting much like a roadside breathalyzer test, the device will not allow the vehicle to start if the driver has a measurable amount of alcohol in their system.  The use of Ignition Interlock Devices have been shown to reduce repeat offenses for driving while intoxicated by about 70% when used properly.
  • Motorists should never take the law into their own hands or engage with those driving erratically. If a fellow motorist exhibits these signs, impaired driving may be occurring. To seek law enforcement assistance, make mental notes of the location of the vehicle, model and color and, if possible, license plate number. Pull to a safe place and call 911 to alert officers.

Over the Counter (OTC) & Rx Drugs

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The Issue

  • Prescription drugs are the most prevalent of all drugs found in drugged drivers involved in fatal crashes (46.5%), and the percentage has continually increased since 2005.
  • Nearly half of Americans reported taking one or more prescription drugs in the past 30 days, 31% reported taking two or more prescription medications and 11% reported taking three or more prescription medications. 
  • Only 28% of drivers consider driving under the influence of prescription drugs a very serious threat. In comparison, 66% of people consider driving under the influence of alcohol a very serious threat and 56% of people consider driving under the influence of illegal drugs a very serious threat.
  • Benzodiazepines (prescribed for anxiety or sleep disorders) and opiates (prescribed for pain relief) are the two prescription drugs most commonly found in fatal and seriously injured drivers.
  • 35% of drivers reported self‐regulating their driving in the past when they believed their medication would affect their ability to drive safely, according to a national roadside survey
  • Some types of antidepressants have been shown to increase crash risk by up to 41%.
  • Diphenhydramine is an ingredient commonly found in over-the-counter cold and allergy medications. This drug has been shown to severely impair the ability to follow at a safe and constant distance, maintain speed  and maintain lane position.

What you need to know about medication and driving

If you’re taking a medication, is it safe to drive?  While most medications do not impact your ability to operate a vehicle safely, it’s important to understand how a medication you take could impact your ability to operate a vehicle safely, including a car, boat, bus, plane or watercraft.

Some prescription and non-prescription medications (also called over-the-counter or OTC) can have side effects and cause reactions that may make it unsafe to drive. Side effects can include: 

  • sleepiness/drowsiness
  • blurred vision
  • dizziness
  • slowed movement 
  • fainting
  • inability to focus or pay attention
  • nausea
  • excitability

Some medications can affect your driving for a short time after you take them. For others, the effects can last for several hours, and even the next day. If a medication has a warning to not operate heavy machinery, this includes driving a car.

Medications That May Affect Driving

  • Some medications—including many popular painkillers and cough, cold, and allergy remedies—contain more than one ingredient that can react with alcohol.  Other medications contain alcohol, some up to 10% alcohol. Cough syrup and laxatives may have some of the highest alcohol concentrations. 
  • Alcohol affects women differently. Women , in general, have a higher risk for problems than men. When a woman drinks, the alcohol in her bloodstream typically reaches a higher level than a man’s even if both are drinking the same amount. This is because women’s bodies generally have less water than men’s bodies. Because alcohol mixes with body water, a given amount of alcohol is more concentrated in a woman’s body than in men’s.

Older people face greater risk 

  • Older people are at particularly high risk for harmful alcohol–medication interactions. Aging slows the body’s ability to break down alcohol, so alcohol remains in a person’s system longer. Older people also are more likely to take a medication that interacts with alcohol—in fact, they often need to take more than one of these medications. 

Timing is important

  • Alcohol and medicines can interact harmfully even if they are not taken at the same time.
  • Remember...Mixing alcohol and medicines puts you at risk for dangerous reactions. Protect yourself by avoiding alcohol if you are taking a medication and don’t know its effect. To learn more about a medicine and whether it will interact with alcohol, talk to your pharmacist or other health care provider.  (Source: National Institute on Alcohol Abuse and Alcoholism)

Knowing how your medications—or any combination of them—affect your ability to drive is a safety measure. Read the Drug Facts label of your prescription or OTC medication and ask your pharmacist or doctor about side effects. Understand the warnings before operating any vehicle.

Some drugs that could make it dangerous to drive include:

  • opioid pain relievers
  • prescription drugs for anxiety (for example, benzodiazepines)
  • anti-seizure drugs (antiepileptic drugs)
  • antipsychotic drugs
  • certain antidepressants
  • products containing codeine
  • certain cold remedies and allergy products, such as antihistamines (both prescription and OTC)
  • sleeping pills (including zolpidem, commonly found in Ambien and Ambien CR, Edluar, Intermezzo and Zolpimist)
  • muscle relaxants
  • medicines that treat or control symptoms of diarrhea
  • medicines that treat or prevent symptoms of motion sickness
  • diet pills, “stay awake” drugs, and other medications with stimulants (e.g., caffeine, ephedrine, pseudoephedrine)

Also, taking cannabidiol (CBD) products and driving can be dangerous. CBD can cause sleepiness, sedation  and lethargy. Because of these side effects, consumers should use caution if planning on operating a motor vehicle after consuming any CBD products.

A Word of Warning About Combining Medications

Combining two or more drugs, including alcohol, may result in a synergistic effect. This means that the combined effect is even greater than the sum of the two effects separately.

Synergism is not a rare occurrence.  For example, a beer and another depressant may amplify sedative effects. Drinking alcohol or taking sleep medications while using certain antihistamines can increase the sedative effects. Anytime another drug is combined with alcohol, the effects may be different from those expected if either drug is taken alone.

Illicit Drugs

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The Problem

How many people take drugs and drive?

According to a 2018 National Survey on Drug Use and Health (NSDUH), 20.5 million people aged 16 or older drove under the influence of alcohol within the past year and 12.6 million drove under the influence of illicit drugs.  The survey also showed that men are more likely than women to drive under the influence of drugs or alcohol.

Which drugs are linked to drugged driving?

After alcohol, cannabis is the drug most often found in the blood of drivers involved in crashes.  Moreover, the vehicle crash risk associated with cannabis is greater when it is used in combination with alcohol, cocaine or benzodiazepines than when it is used alone.

Along with cannabis, prescription drugs are also commonly linked to drugged driving crashes. In 2016, 19.7 percent of drivers who drove while under the influence tested positive for some type of opioid.

How often does drugged driving cause crashes?

The number of crashes that can be attributed to the use of either illicit or prescription drugs is difficult to measure. Unlike roadside tests for alcohol impairment, there are no reliable roadside tests for drug levels that are able to measure impairment. However, according to the Governors Highway Safety Association, 43.6 percent of fatally injured drivers in 2016 tested positive for drugs and over half of those drivers were positive for two or more drugs.

Because of the lack of reliable roadside testing for drug impairment, it’s more common for law enforcement to test for blood alcohol level if it is suspected that there’s sufficient evidence for a DUI charge without consideration of drug-induced impairment. Many drivers who cause crashes are using combinations of drugs and alcohol.



Drug Recognition Expert

A drug recognition expert or drug recognition evaluator (DRE) is a police officer specially trained to recognize impairment in drivers under the influence of drugs other than, or in addition to, alcohol. The International Association of Chiefs of Police (IACP) coordinates the International Drug Evaluation and Classification (DEC) Program with support from the National Highway Traffic Safety Administration (NHTSA) of the U.S. Department of Transportation. In addition to officers who are certified as DREs, the DEC Program educates prosecutors and toxicologists on the DRE process and the drug categories.

A DRE conducts a detailed, diagnostic examination of persons arrested or suspected of drug-impaired driving or similar offenses. The DRE drug evaluation takes approximately one hour to complete and is conducted in a controlled environment, rather than roadside. The evaluation is typically conducted post-arrest. Based on the results of the drug evaluation, the DRE forms an expert opinion on the level and cause of the impairment.


The Problem

The use of cannabis / marijuana affects psychomotor skills and cognitive functions critical to driving, including vigilance, drowsiness, time and distance perception, reaction time, divided attention, lane tracking, coordination and balance.

There are many misconceptions about cannabis use, including rumors that cannabis can’t impair you or that cannabis use can actually make you a safer driver. However, several scientific studies have shown this to be false. Cannabis impairs motor skills, lane tracking and cognitive functions (Robbe et al., 1993; Moskowitz, 1995; Hartman & Huestis, 2013. The THC in cannabis also hurts a driver’s ability to multitask, a critical skill needed behind the wheel.

There is no device in existence to measure a person’s impairment due to cannabis.  Additionally, even if there were, cannabis does not leave the body at a predictable rate nor does it do so in direct correlation with the degree of impairment.  Some states that have legalized recreational cannabis use have established a per se limit similar to the one for alcohol , but those limits have been found to have no correlation to determining impairment.  In other states, a person can be found guilty of DUI if there are traces of cannabis present, even days or weeks after the impairment has ended.

NHTSA continues to conduct research to better understand the relationship between cannabis impairment and increased crash risk. NHTSA’s Drug and Alcohol Crash Risk Study found that cannabis users are more likely to be involved in crashes. However, the increased risk may be due in part because cannabis users are more likely to be young men, who are generally at a higher risk of crashes.


Learn more about the studies on cannabis and driving conducted by the AAA Foundation for Traffic Safety:

Additional Resources:

Prevention of Impaired driving

What steps can you take to prevent impaired driving due to drugs or alcohol?

Bottom line? Driving impaired by any substance—alcohol or other drugs, whether legal or illegal—is against the law in all 50 states and the District of Columbia. Law enforcement officers are trained to observe drivers’ behavior and to identify impaired drivers.

NHTSA’s National Roadside Survey conducted in 2013-2014 (PDF, 173 KB) found that 20 percent of surveyed drivers tested positive for potentially impairing drugs.

We can all save lives by making smarter choices.

  • Plan ahead for a designated sober driver, if you plan to use an impairing drug.
  • Don’t let friends get behind the wheel if they’re under the influence of drugs.
  • If you’re hosting a party where alcohol or other substances will be used, it’s your job to make sure all guests leave with a sober driver.
  • Always wear your seat belt—it’s your best defense against impaired drivers.
  • Offer to be a designated driver.
  • Use a rideshare service.
  • Discuss the risks of impaired driving with friends in advance.
  • Tell your health care provider about all the medications you are taking, including prescription, OTC  and herbal products. Also, let them know about any reactions you experience.
  • Always follow directions for use and read warnings on medication packaging, or handouts provided by the pharmacy and your healthcare provider.
  • Ask your pharmacist and/or healthcare provider how the medication could impact your ability to operate a motor vehicle safely.
  • Follow the advice of your healthcare provider before stopping any medication.

Drowsy Driving

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The Problem

Feeling sleepy is especially dangerous when you are driving. Sleepiness slows your reaction time, decreases awareness and impairs your judgment, just like drugs or alcohol. People who are very sleepy behave in similar ways to people who are drunk. The impact that this has on traffic safety should not be underestimated.

Symptoms of sleepiness include but are not limited to:

  • Having trouble keeping your eyes open and focused
  • The inability to keep your head up
  • Daydreaming or having wandering, disconnected thoughts
  • Drifting from your lane or off the road, or tailgating
  • Yawning frequently or rubbing your eyes repeatedly
  • Missing signs or driving past your intended exit
  • Feeling irritable and restless
  • Being unable to remember how far you have traveled or what you have recently passed.

Daylight Saving Time Increase Risk

  • Fatal car crashes in the United States spike by 6% during the workweek following the "spring forward" to daylight saving time, resulting in about 28 additional deaths each year, according to new University of Colorado Boulder research.
  • The study, published in the journal Current Biology, also found the farther west a person lives in his or her time zone, the higher their risk of a deadly crash that week.


To remain alert and avoid drowsiness, AAA suggests:

  • Getting plenty of sleep (at least six hours) the night before a long trip
  • Traveling at times when you are normally awake, and staying overnight rather than driving straight through
  • Scheduling a break every two hours or every 100 miles
  • Stop driving if you become sleepy; someone who is tired could fall asleep at any time – fatigue impacts reaction time, judgment and vision, causing people who are very sleepy to behave in similar ways to those who are drunk
  • Not planning to work all day and then drive all night
  • Drink a caffeinated beverage. Since it takes about 30 minutes for caffeine to enter the bloodstream, find a safe place to take a 20-30 minute nap while you’re waiting for the caffeine to take effect
  • Avoid sleepy times of day. Take a mid-afternoon nap and find a place to sleep between midnight and 6 a.m.
  • Traveling with an awake passenger.