How does marijuana affect driving?
Marijuana has adverse effects on many of the skills needed for driving a car. These effects may include difficulty in judging distances and delayed reactions to sights and sounds that drivers need to notice. There are data showing that marijuana plays a role in crashes. When users combine marijuana with alcohol, as they often do, the hazards of driving can be more severe than with either drug alone. A study of patients in a shock-trauma unit who had been in traffic accidents revealed that 15 percent of those who had been driving a car or motorcycle had been smoking marijuana, and another 17 percent had both THC and alcohol in their blood. In Memphis, Tennessee, researchers found that, of 150 reckless drivers who were tested for drugs at the arrest scene, 33 percent showed signs of marijuana use, and 12 percent tested positive for both marijuana and cocaine.
