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Impaired Driving: How Marijuana, Alcohol, and Prescription Drugs Can Affect You

alcohol drinking and driving drugged driving drunk driving dui impaired driving resources weedui Apr 27, 2022

What is Impaired Driving?

Impaired driving is operating a vehicle while under the influence of alcohol, legal or illegal drugs.

Alcohol-impaired driving

Alcohol has a significant effect on driving skills due to its depressant effects. While under the influence of alcohol, drivers can misjudge their capabilities and experience the following:

  • Decreased reaction time due to slower reflexes
  • Feelings of drowsiness
  • Poor coordination affecting the mechanics of driving (steering, working, braking, etc.)
  • Inattention to driving tasks
  • Decreased rational decision making
  • Depressed eye movement and perception affecting night vision and color perception
  • Inability to judge car’s potion on the road, road signs and location of other vehicles

(Taibbi, R. How Alcohol Affects You. Current Health, Vol. 2, p. 16-19 (1994).)

Drug-impaired driving

Drug-impaired driving refers to driving after taking any prescription or over the counter drugs, or illegal substances. Like alcohol, drugs can decrease your reaction time, affect your coordination, make you fall asleep at the wheel or lead to inattention while driving.

From Ventura County Limits, “We all know the dangers of drunk driving, however drugged driving is on the rise around the nation, in California, as well as in Ventura County. Drugged Driving is defined as being under the influence of any drug that impairs motor skills, reaction time, and judgment while operating an automobile. Ventura County is taking the lead in California by starting conversations about driving under the influence of marijuana, prescription drugs, and illicit drugs. With funding from the California Office of Traffic Safety, the Ventura County Drugged Driving Risks and Realities Campaign is working in the community to prevent arrests, injuries, and deaths due to drugged driving.

WEEDUI (Pronounced WEED-YOU-EYE) is driving under the influence of marijuana also known as weed. The Ventura County’s Risks and Realities Campaign aims to change social norms associated with driving under the influence of drugs. Impairment due to marijuana or in combination with alcohol can seriously hinder a person’s ability to drive a car, and we are attempting to change social norms, to get people to put down their keys and only drive sober. Perceptions about the safety of marijuana and rules pertaining to its use are currently changing around the nation. However, the California Vehicle Code is clear, that driving under the influence of impairing drugs can lead to a DUI arrest.”

“A lot of people just don’t understand how marijuana affects your driving,” Deputy Justin Doering, a drug-recognition expert for the Ventura County Sheriff’s Office said. “Even just a couple of hits can have you impaired.”

  • 10.3 million people reported driving under the influence of illicit drugs at least once during the past year.
  • The rate was the highest among young adults ages 18-25 (NSDUH 2012)
  • 1 in 12 of all fatally injured drivers tested positive for marijuana.
  • 1 in 7 fatally injured drivers under age 25 tested positive for marijuana.

Collision data reported by Ventura County DUI Program participants shows that 10% had been using drugs, other than alcohol, on the day of their DUI arrest.

In Ventura County:

  • 1 in 8 high school seniors reported that within the past two weeks, they had driven after using marijuana.
  • 1 in 4 had recently ridden in a car with such a driver. (NIH)

Motor vehicle crashes are the leading cause of death among young people aged 16 to 19. Teen drivers are more likely than older drivers to underestimate or not recognize dangerous situations. According to the National Institute on Drug Abuse, a 2011 survey of middle and high school students showed that the number of 12th-grade students who had driven after using marijuana was 12.4 percent, other illicit drugs was 2.4 percent, and alcohol was 8.7 percent. After alcohol, marijuana is the drug most often linked to drugged driving. And the reality is, teens get in twice as many crashes after using marijuana.

How Marijuana Impairs Driving Ability

  • Impairs motor skills, alters perception of speed and slows reaction time.
  • Risk of an accident doubles when a person drives soon after using marijuana.
  • After alcohol, marijuana is the most frequently found substance in the blood of impaired drivers, fatally injured drivers and crash victims.

Prescription Drugs & Driving 

You can get a DUI for driving under the influence of prescription drugs.

In 2014, $374 billion was spent on prescription drugs in the United States, over $1,100 per person. 2/3 of adults age 65 and over take five or more prescription medications that can affect their ability to drive (AAA). Prescription drug-impaired driving can diminish an individual’s performance behind the wheel and pose the risks of harm to a driver or an innocent bystander. 

Points to Remember

  • Use of illicit drugs or misuse of prescription drugs can make driving a car unsafe – just like driving after drinking alcohol.
  • In 2014, 10 million people aged 12 or older reported driving under the influence of illicit drugs in the past year.
  • It’s hard to measure how many crashes drugged driving causes.
  • After alcohol, marijuana is the drug most often linked to drugged driving.
  • In 2010, more than one-quarter of drugged drivers in fatal crashes were aged 50 years or older.
  • When lack of driving experience is combined with drug use, the results can be tragic.
  • People who use drugs and alcohol should develop social strategies to prevent them from getting behind the wheel of a car while impaired.

Source: NIDA (2016). Drugged Driving

Fatigue-impaired driving

Fatigue-impaired driving can be just as dangerous as alcohol or drug-impaired driving. Driving when you’re too tired can have the following affects:

  • Impair reaction time, judgment, and vision
  • Create problems with information processing and short-term memory
  • Decrease performance, vigilance, and motivation
  • Increase moodiness and aggressive behaviors

Just like drugs or alcohol, sleepiness slows reaction time, decreases awareness, and impairs judgment. Just like alcohol, sleepiness can be fatal when driving. Groups who are especially at risk for fatigue-impaired driving are drivers under 25 years of age, shift workers, commercial truck drivers and business travelers.

For more information about impaired driving prevention, including statistics for Ventura County and local resources, visit Ventura County Limits.