“For the first time, drivers killed in crashes are more likely to be high than drunk. A new report finds that 43 percent of drivers tested in fatal crashes in 2015 had used* a legal or illegal drug — eclipsing the 37 percent who tested above the legal limit for alcohol. The data comes as part of a complicated portrait of drug use, as an opioid epidemic persists and marijuana laws are increasingly relaxed.” That’s 80% combined; 4 of every 5 fatal crashes involved drugs or alcohol.**
One can only assume the other 20% were because of texting while driving.
*THC stays in your body a long time, so very possible that some of these drivers were not high at the time of the accident. Drivers who tested positive for marijuana accounted for ~5000 deaths in 2015.
**Someone could have both alcohol and drugs in their system, so this combined number is probably misleading.