Drugs Other Than Alcohol

What is a “drug?”

When using any drug, you should consider the risks and the effects it might have on your ability to perform routine and complex tasks. You should keep your level of risk low and avoid taking drugs that interfere with anything you might do. Remember that in addition to their intended purpose, many drugs have side effects. To complicate matters, drugs can affect various people in different ways, or a drug may affect a person differently each time it is used.


How Can a Drug Affect You?

When using any drug, you should consider the risks and the effects it might have on your ability to perform routine and complex tasks. You should keep your level of risk low and avoid taking drugs that interfere with anything you might do. Remember that in addition to their intended purpose, many drugs have side effects. To complicate matters, drugs can affect various people in different ways, or a drug may affect a person differently each time it is used.

Legal Drugs
Use of legal drugs is common in the U.S. Generally, they are designed to address causes or symptoms of problems by changing the body’s chemistry.

Prescription Drugs
A doctor’s prescription for these drugs includes directions for use. Always follow the label directions including those that say “Do Not Operate Heavy Equipment” while on the drug. Be sure to follow directions exactly, not only to accomplish the drug’s purpose, but also to limit dangerous and undesirable side effects. Prescription drugs can be helpful when used as prescribed. But they also can hinder your driving ability by reducing your level of alertness or ability to perform complex tasks. Do not use prescription drugs that are prescribed for other people.

Over the Counter/Non-Prescription Drugs
Available without a prescription, over-the-counter drugs can include anything from aspirin to cold pills, cough syrup and sleep aids. By law, these drugs must provide adequate directions for use in addition to information about possible side effects.

Ask Your Doctor
Whether a drug is prescribed by a doctor or obtained over the counter, always read the label carefully, especially if you intend to drive. Some may cause drowsiness or otherwise impair driving ability. If you have a question or concern about a drug’s effects, ask your doctor or pharmacist. Ask specifically how the drug could affect driving ability.

Illegal/Illicit Drugs
Illegal drugs, or street drugs, are sold without a prescription. Besides breaking the law, the risks of buying street drugs is not knowing what is in them. With street drugs, buyers also risk having one drug substituted for another without their knowledge.


Drugs and Their Effects

Drugs Vary by Type and Effect
Most drugs act on the central nervous system, which includes the brain and spinal cord. Stimulants—such as amphetamines—speed up the system, while depressants—such as tranquilizers—slow it down. Another drug family, hallucinogens, affects the way a user sees things.

Combining Drugs – Possible Synergistic Effect
What are the effects of taking two or more drugs at the same time? The result may be a synergistic effect: more than just one plus one. This means that the combined effect is 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. Anytime another drug is combined with alcohol, the effects may be different from those expected if either drug is taken alone. Combining drugs increases the risk of harmful and unexpected effects.


Drugs Other Than Alcohol and Driving

Driving under the influence of drugs has the potential to be just as unsafe as driving under the influence of alcohol. Driving is a complex task that involves the use of cognitive, perceptual and motor skills. While some drugs, specifically prescription and over the counter drugs, can improve medical conditions and abilities important to operating a vehicle, the use of illicit drugs or misuse of prescription drugs can impair functions critical to driving.


How Drugs Can Impact Driving

  • Coordination – Affects control of a vehicle, such as steering, braking and accelerating
  • Tracking Impacts a driver’s ability to stay in a lane or maintain a safe following distance
  • Reaction TimeInsufficient response and reactions times can lower a driver’s ability to avoid potential hazards and increase the risk of a collision or losing control of a vehicle
  • AttentionDecreases a driver’s alertness, ability to divide attention, and ability to simultaneously execute driving tasks that require visual, manual, and cognitive processing
  • PerceptionCan influence a driver’s ability to accurately process visual cues on the road
  • JudgementIncreases risk-taking behavior


The Challenges of Drugged Driving

Policymakers, the justice community, researchers, and safety advocates are working hard to address the growing prevalence of drugged driving, but face a complex challenge in establishing a baseline for legal drug impairment, educating motorists about safe use of drugs, and accurately detecting drug use among impaired drivers.

  • First, the impairment effects of alcohol at various concentrations in the blood have been well established.  In contrast, there is very little evidence to link concentrations of other drugs to driver performance.
  • Second, alcohol is just one drug; there are hundreds of drugs that can impair drivers in a number of different ways.
  • Lastly, drugs are often found in combination with other drugs, including alcohol. These combinations can enhance, subtract or make the impairing effects unpredictable.


Alcohol and Cannabis—What We Know

Cannabis is the most common drug linked to substance-impaired driving after alcohol. A number of states have legalized the drug for various purposes and many more are expected to do so in the near future. It is not yet clearly understood how cannabis impairs drivers at the roadside, but there is a large body of research that has demonstrated cannabis impairs psychomotor and physiological functions critical to driving. The table below outlines what we know about cannabis in comparison to alcohol, and where more research is needed.

Effects on driving-related functionsImpairs psychomotor functions, pursuit tracking, divided attention, signal detection, hazard perception, reaction time, attention, concentration, & hand-eye coordination.Recent use is known to diminish virtually every driving-related capacity: psychomotor functions, cognition, attention, vigilance, tracking, reaction time & coordination. The effects depend on dose, absorption, time since peak blood level, & skill/task.
Self-perceptionUsers tend to underestimate impairment and risk, even at low doses.Users tend to accurately estimate impairment.
Effects on driving behaviorDriver tends to increase variation in speed, average speed, lane positioning (weaving), passing attempts, and decrease following distance.Users tend to employ slower speed, less passing, larger following distance. The largest and most consistent effect is on lane position (weaving). Compensation may be less effective for responding to unexpected events (e.g., other driver behavior, or an animal running across the road).
ToleranceHeavy drinkers tend to be less sedated at a given BAC due to tolerance. This contributes to them being more likely to underestimate impairment and drive. Heavy drinkers show tolerance, particularly with respect to impairment of sensory and motor functions.There is inconsistent evidence on tolerance effects.
Other drug useUsers in social settings often only drink alcohol (or perhaps smoke tobacco). Use with other drugs with sedative effects (opiates, barbiturates, etc.) may increase risk of crashes, but may be more likely to have taken place at home. Some research suggests chronic (but not concurrent) marijuana use decreases effects of alcohol.Users often drink alcohol while ingesting alcohol. While research generally suggests additive or even multiplicative effects with alcohol, some studies suggest effects are no different than alcohol alone. Alcohol likely reduces compensation skills marijuana users otherwise may employ. There little research on marijuana use with other drugs other than alcohol.

How Various Types of Drugs Impact Driving

Drugs share similar patterns of effect and are classified by how they influence driver behavior. The following seven categories represent hundreds of drugs but each category is distinct in terms of the signs and symptoms exhibited by a driver.

  • Central Nervous System (CNS) Depressants slow down the operations of the brain and the body. Drivers can experience relaxation, drowsiness and/or loss of coordination. The effects can last 1 – 16 hours, depending on the substance. Examples include alcohol, barbiturates, anti-depressants, anti-anxiety tranquilizers, and GHB.
  • CNS Stimulants speed up the operations of the brain and the body. Drivers can experience exaggerated reflexes, aggression, and/or irritability. The effects can last anywhere from 5 minutes to 12 hours, depending on the substance. Examples include cocaine, amphetamines and methamphetamines.
  • Inhalants create a wide range of mind-altering and physical effects. Drivers can experience disorientation, confusion, and/or lack of muscle control. The effects can last for 5 minutes to 8 hours, depending on the substance. Examples include volatile solvents, aerosols, and anesthetic gases.
  • Hallucinogens cause users to perceive reality differently. Drivers can experience distorted sensory perceptions, nausea, disorientation, and/or poor perception of time and distance. The effects can last 5 minutes to 12 hours, depending on the substance. Examples include LSD and ecstasy.
  • Narcotic Analgesics relieve pain, induce euphoria and create mood changes. Drivers can experience drowsiness, nausea, and/or depressed reflexes. The effects can last 4- 24 hours, depending on the substance. Examples include opium, codeine, heroin, morphine and Vicodin.
  • Dissociative Anesthetics inhibit pain by cutting off or dissociating the brain’s perception of the pain.Drivers can become confused and agitated, aggressive, and/or disoriented. The effects can last 4-6 hours. Examples include PCP and its analogs.
  • Cannabis is the botanical name for marijuana. Drivers can experience impaired perception of time and distance, possible paranoia, and/or disorientation, impaired balance and coordination. The effects can last 2-3 hours depending on the method of administration. THC is the active ingredient in cannabis. Other forms of cannabis include the synthetic drug dronabinol, hash, and hash oil.

Source: (National Highway Traffic Safety Administration)


Prevalence of Drugged Driving

A recent nationwide survey of drivers revealed that drugged driving is increasing at the roadside. Since 2007, drivers with measurable levels of illegal drugs, prescription drugs and over-the-counter drugs have risen. Cannabis, the second most common drug linked to drugged driving after alcohol, increased from 8.6 percent to 12.6 percent. The percent of drivers who tested positive for illicit drugs rose from 12 percent to 15 percent. The percent of drivers who tested positive for at least one drug rose form 16.3 percent to 20 percent.

Another study revealed that an increasing number fatally injured drivers are testing positive for drugs other than alcohol. Of drivers tested for drug use, 46.5 percent tested positive for prescription drugs. The most common Rx drugs found in drivers were: Xanax, Vicodin, OxyContin, and Valium. Cannabis was the second drug most commonly found in fatally injured drivers, with 36.9 percent of drivers testing positive. The third most common drug found in fatally injured drivers was cocaine (9.8 percent).

Please note: These studies only measured the presence of drugs in drivers. It does not necessarily mean the driver was impaired by the drug or was at fault for the crash.    

Source: National Highway Traffic Safety Administration, Wilson FA (Fatal Crashes from Drivers Testing Positive for Drugs)


Countermeasures that Work

  • Drug recognition enforcement: The best tools available to law enforcement to combat drugged driving (cannabis and other classes of drugs) are Advanced Roadside Impaired Driving Enforcement (ARIDE) training and Drug Evaluation & Classification (DEC) training, which certifies officers as Drug Recognition Experts or DREs. DREs objectively assess a subject’s impairment at the time of driving with a standardized, research-based 12-step procedure. DRE testimony can lead to the conviction of impaired drivers and does not depend on the driver’s THC blood concentration.
  • Better data collection: Require mandatory drug and alcohol testing for drivers involved in all fatal and serious injury crashes. 
  • Improved laws: Establish separate and distinct sanctions for alcohol- and drug-impaired driving.  Seek graduated or enhanced sanctions for poly-drug use or combined drug and alcohol use while driving impaired. 
  • Education and training for criminal justice practitioners: Law enforcement, prosecutors, and judges would benefit from specialized training on the complexities of drug-impaired driving.  Suggest that your highway safety office expand the Traffic Safety Resource Prosecutor program. Judges would also benefit from the drugged driving course at the National Judicial College.