California Democratic Assemblywoman Norma Torres is crafting legislation making it illegal for any driver to be under the influence of any drug, marijuana or prescription drugs included. The move is meant to offset the increasing number of drivers who are high on medical marijuana when the commit traffic infractions or are involved in vehicle crashes.

Colorado has had medical marijuana for more than a decade and since that time the number of ‘high’ drivers has caused a slight surge in the number of vehicle crashes. This connection is tenuous, but enough to urge lawmakers to pursue legal recourse before the issue gets out of hand.

Q: How does marijuana’s effect on drivers compare to alcohol?

A: Although the symptoms for THC intoxication are similar to alcohol intoxication, the effects on drivers are very different. According to a study by researchers from Yale University, alcohol-impaired drivers struggle with complex tasks like merging onto a crowded highway, but can generally perform automatic functions like turning on the car. Marijuana users, however, can better handle complex situations than simple tasks like following the curve of a road.

Users of alcohol and marijuana also differ in their perceptions of their own impairment. Alcohol users tend to underestimate their level of impairment and drive faster and more recklessly. By contrast, marijuana users tend to overestimate their impairment and don’t display as many obvious impairment symptoms.