Why Steer Clear?

According to the National Institute on Drug Abuse:

Use of illicit drugs or misuse of prescription drugs can make driving a car unsafe—just like driving after drinking alcohol. Drugged driving puts the driver, passengers, and others who share the road at risk.
Along with marijuana, prescription drugs are also commonly linked to drugged driving crashes.
A 2010 nationwide study of deadly crashes found that about 47 percent of drivers who tested positive for drugs had used a prescription drug. The most common prescription drugs found were pain relievers. However, the study didn't distinguish between medically-supervised and illicit use of the prescription drugs.

The US Food and Drug Administration Reports:

While most medications don't affect driving ability, some prescription and over-the-counter (OTC) medicines can cause reactions that may make it unsafe to drive. Products that could make it dangerous to drive include:
- prescription drugs for anxiety
- some antidepressants
- products containing codeine
- some cold remedies and allergy products
- tranquilizers
- sleeping pills
- pain relievers
- diet pills, "stay awake" drugs, and other medications with stimulants (e.g. caffeine, ephedrine, pseudoephedrine)
Products that contain stimulants may cause excitability or drowsiness.
Never combine medication and alcohol while driving.

In 2015, the most recent year for which data are available, NHTSA’s Fatality Analysis Reporting System (FARS) reported that drugs were present in 43% of the fatally-injured drivers with a known test result, more frequently than alcohol was present.