Effects of Drugs on Driving PerformanceAugust 11th, 2019
What drugs do – Illicit / Prescription
Different drugs impact driving performance in different ways.
For example, marijuana has the dual effect of reducing reaction time whilst also impairing time-distance judgment and reduced concentration. Other drugs, such as cocaine, result in more aggressive drivers – drivers who are otherwise far more likely to take greater risks. Methamphetamine has similar effects as cocaine.
In this regard, drugs can be divided into those that reduce reaction/performance time, and those that decrease inhibition that causes drivers to behave far more erratically than they otherwise would.
Of course, it’s not just illicit drugs that impair driving performance. Prescription drugs can have just as damaging an effect.
Take benzodiazepines, antipsychotic drugs, and opioids – all which cause effects such as drowsiness, dizziness and impaired reaction times. These drugs also impair judgment. Drivers are far more likely to make an ill-judged decision when taking these medicines compared to their standard driving performance. Some studies show that opioids can double the risk of a vehicular crash.
Of course, the drugs listed above are by no means exhaustive. There is an entire database of drugs that impair driving performance. These are just a few of the more common examples.
Let’s now turn our attention to marijuana.
Effects of Marijuana on Driving
Many falsely claim that marijuana use whilst driving is just as safe as driving without the drug.
This is simply not true. The evidence does not support that conclusion.
More specifically, marijuana has the following effects:
- Higher likelihood of lane weaving
- Reduced reaction times
- Poor judgment/ impaired coordination
Concurrent use of alcohol with marijuana only augments these effects.
According to a 2018 study on the effects of marijuana whilst driving, chronic users of marijuana had difficulty matching a lead vehicle’s speed compared to nonusers of the drug.
Taking marijuana when driving is, then, a major health concern; a problem that more police officers are having to handle than ever before. Given the widespread misuse and propagation of false and misleading information regarding marijuana use, it’s incumbent upon state and local authorities to improve education on the real, evidence-based impact of this drug.
Effects of Drugs on Driving Performance
Drug driving is more common than you might think. According to the 2017 National Survey on Drug Use and Health (NSDUH) report:
- In 2017, over 21 million drove after consuming alcohol.
- Just under 13 million drove after taking an illicit drug.
Among those killed in driving accidents:
- Almost 44% of those tested had positive test results.
- Almost half of those tested positive for 2 drugs.
- 40% tested positive for alcohol.
Those aged between 21-26 were more likely to have taken drugs compared to 16-21-year olds or 26-31-year olds. Furthermore, men are considerably more likely to take drugs whilst driving than women.
Drugs and Car Crash Statistics
Police officers must establish what drug the suspect has taken. The most commonly implicated drug is marijuana.
Law enforcement tests for delta-9-tetrahydrocannabinol (THC) to establish how much marijuana the suspect has taken. THC is the substance responsible for the cognitive effects linked to the drug. Of course, THC doesn’t need to be measured on the day. It remains in the body, often for many days/weeks ahead depending on how much was administered.
However, this alone comes with limitations:
- There is currently no one precise roadside test that measures how much THC a suspect has taken.
- Because the drug can be measured days, weeks or even months ahead, it can be difficult to establish how much drug was taken, if any, on the day that an accident has taken place.
- If a suspect has been found to have elevated blood alcohol levels, this alone is enough to charge them with a DUI. Further tests for other drugs may not be performed – skewing the statistics.
- Because more than one drug is often found in a suspect, it can be difficult to establish which drug had the greater / greatest effect compared to the other drug taken.
The risk of a car crash increases when THC is combined with alcohol, cocaine, or benzodiazepines compared to when any one of these drugs is taken in isolation.
Not all research conclusively links drug use with car crashes/risk of death. More studies are required to determine the degree of impact it has.
Police Test Study Guide is the leading online platform for aspiring police officers. Learn more about the police officer exam and why you need to have a comprehensive knowledge of the effects of drugs on driving performance.