The phone rings and a mother answers. She is stunned by what the voice on the other end says. “Your son was in a car accident. The driver was another teen who was high and drunk. She crashed her car into a lake and your son was trapped inside and drowned.” Colleen Sheehey-Church, the current National President of MADD received that call in 2005. Since that time drugged driving has progressively increased and now 1 in every 3 people killed in a car crashes tested positive for drugs.
Drunk driving is just as dangerous as drugged driving but much easier to detect by law enforcement. While alcohol impairment standards are built on years of research, the science behind drug impairment standards is still not definite. For example, alcohol and pot behave very differently in the body. The concentration of alcohol in the body is pretty uniform; if it's 0.08% in your blood, it's similar in the brain. You're at your drunkest when your blood alcohol concentration, or BAC, is highest.
But pot's chief mind-altering component, THC, acts differently. A blood test could find THC in the brain but not in the blood. States have tried to set limits. In Colorado, for example, the legal limit is five nanograms of THC per milliliter of blood. But the AAA Foundation for Traffic Safety says legal limits for marijuana and driving are "arbitrary and unsupported by science." That makes it difficult to compare collision data.
Pot is not the only drug that can impair drivers. The drug tests in the FARS data also included other drugs tested for by individual states, and went beyond illicit substances to include prescription and over-the-counter drugs that can cause impairment, none of which come with evidence-based standards for measuring their effects on drivers. When drugs or drink are the cause of a wreck, then under Virginia law the at fault driver's insurer may have to pay punitive damages beyond the money to compensate the family of a person killed in an accident.