The growing consumption of drugs and psychoactive substances represents another challenge for road safety, putting at risk not only those who decide to drive under their influence, but also all road users. According to the National Survey on Drug, Alcohol and Tobacco Use 2016-2017, in relation to the use of any drug, illegal drugs and medical drugs ever in life, in the population aged 12 to 65 years old, there is an increase between 2008, 2011 and 2016, going in the case of any drug from 5.7%, to 7.2% and 10.3% respectively; and in the case of illegal drugs from 5.2% to 7.2% and 9.9% respectively, being a considerable increase for both in 2016. In the case of medical drugs, there is an increase between 2008 and 2011, going from 1% to 1.4% and a slight decrease in 2016, registering with 1.3% (Centros de Integración Juvenil A.C).
Every time a driver chooses to get behind the wheel while under the influence of mind-altering substances, he or she is making a decision that could have fatal consequences, although further research into their effects is essential: Several studies indicate that drug use significantly impairs the skills necessary for safe driving. Several studies have shown that drivers with THC in their blood (delta-9-tetrahydrocannabinol -THC, the mind-altering ingredient in marijuana) were approximately twice as likely to cause a fatal accident or die in a car crash as those who had not used drugs or alcohol. However, a large NHTSA study controlling for the presence of alcohol and the age, sex, and race of the driver found no significant increase in the risk of traffic crashes attributable to marijuana. (National Institute on Drug Abuse. Advancing Addiction Science)
According to PAHO, alcohol-impaired road users are at a significantly increased risk of being involved in a crash. Studies conducted in low- and middle-income countries revealed the presence of alcohol in the blood of between 4% and 69% of drivers, between 18% and 90% of pedestrians, and between 10% and 28% of motorcyclists injured in traffic accidents (International Center for Alcohol Policies).
In this blog we address how different drugs and psychoactive substances affect driving ability, with the aim of promoting greater awareness of the importance of making responsible decisions regarding driving and drug use.
Drugs and their effects on driving ability
To understand the effects of drugs on the ability to drive, it is convenient to begin by briefly explaining how drugs are classified and the effects they generate.
Psychoactive drugs are substances that, when consumed, alter a person’s perception, mood or behavior. For purposes of analysis in the context of driving, they are classified according to their primary effect on the central nervous system (CNS):
- Stimulants: Increase CNS activity, resulting in increased alertness, arousal, and energy. Common examples include cocaine, amphetamines, and methamphetamine. Stimulants act by increasing the release of neurotransmitters such as dopamine and norepinephrine, resulting in a temporary increase in energy, attention, and self-confidence. However, they can lead to risk-taking behavior, overestimation of driving skills, and decreased ability to critically evaluate situations.
- Depressants: They reduce CNS activity, decreasing alertness and coordination, and slowing bodily functions. Alcohol, benzodiazepines and barbiturates are typical examples. These types of narcotics affect the brain by increasing the activity of GABA, a neurotransmitter that produces sedative effects. This leads to a decrease in motor coordination, reaction time and ability to make quick and accurate decisions, critical components for safe driving.
- Hallucinogens: Alter perception and can cause hallucinations, distortions of reality, and significant emotional changes. LSD, psilocybin (magic mushrooms) and MDMA (ecstasy) are substances in this category. They interfere with serotonin, a neurotransmitter involved in mood control and perception. The use of hallucinogens can lead to severe perceptual distortions, loss of sense of direction and time, which is extremely dangerous when driving.
Why is it dangerous to drive under the influence of drugs?
Driving under the influence of drugs means driving a vehicle when one’s abilities are impaired by intoxicating effects.
The effects of each drug are different. For example, marijuana can decrease coordination, reaction time, and the ability to judge time and distance. Drivers who have used cocaine or methamphetamine may drive aggressively or recklessly. Certain types of prescription drugs-including opioids and benzodiazepines-can cause dizziness and lethargy and impair cognitive functioning (judgment and thinking ability). All of these impairments can cause traffic crashes.
Research has shown that marijuana has negative effects on drivers, including slower reaction times, increased weaving between lanes, and inattention on the road. The combination of alcohol and marijuana further decreases a driver’s ability and causes them to drift out of their lane more frequently. Other studies indicate that opioids can cause lethargy or drowsiness and impair judgment and thinking ability and that driving under the influence of opioids can double the likelihood of being involved in an accident.
What is the population most affected by drug-impaired driving?
The groups most affected are teenagers and older adults. Teenagers are less experienced and are more likely than other drivers to underestimate or fail to recognize dangerous situations. They are also more likely to drive at excessive speeds and keep less distance from other vehicles. When inexperienced driving is combined with drug use, the results can be tragic.
On the other hand, mental impairment in older adults may lead them to take prescription drugs more or less often than necessary or in the wrong amount. Older adults may also not metabolize medication as quickly as younger people. These factors can cause unintentional intoxication while driving a vehicle.
What drugs are commonly found in people who drive high?
After alcohol, marijuana is the drug most frequently found in the blood of drivers who have been involved in a traffic crash. Similarly, the risk of a crash or rollover associated with the combination of marijuana with alcohol, cocaine, or benzodiazepines appears to be greater than the risk of each drug alone. Along with marijuana, prescription drugs are also commonly associated with crashes caused by drugged drivers.
A survey of college students who had access to an automobile revealed that one in six had driven under the influence of some drug (other than alcohol) at least once in the year prior to the survey. Marijuana was the most common drug, followed by cocaine and prescription painkillers.
Mental decline in older adults may lead them to take prescription drugs more or less often than necessary or in the wrong amount. Older adults may also not metabolize medication as quickly as younger people. These factors can cause unintentional intoxication while driving a vehicle.
How often do accidents occur because the driver is drugged?
It is difficult to measure how many accidents occur because of a drugged driver. This is mainly because:
- There is not yet a good test to measure drug levels in the driver’s system at the roadside.
- Some drugs can remain in the body for days or weeks after consumption, which makes it difficult to determine when the consumption took place and therefore how and to what extent the consumption impaired the ability to drive.
- Generally, if the driver has an illegal blood alcohol level (blood alcohol cannot exceed 0.8 grams per liter and exhaled air 0.4 milligrams per liter), the police do not look for the presence of drugs in the body because they already have enough evidence to file a substance impaired driving charge.
- Many drivers who cause traffic crashes have both drugs and alcohol in their system, or have more than one drug, making it difficult to determine which substance has had the greater effect.
Road safety begins with recognizing our responsibilities as drivers and understanding that our decisions have the power to change lives, including our own. Road Safety is everyone. Get informed and take action.
