Nearly 20 percent of drivers involved in fatal crashes in 2009 tested positive for drugs.  The report from the National Highway Traffic Safety Administration highlights the role drugs might play in automobile fatalities.  Many drugs–legal and illegal–impair judgment and reaction time, thus increasing the likelihood of an accident.

Tests checked for both prescription and illegal drugs, including cocaine, methamphetamine, marijuana, LSD, heroin and more. Common drugs such as aspirin, alcohol and nicotine were excluded from testing.

The role of drugs in these crashes is not clear, though. Some drugs take months to leave the body, so it is unclear whether or not drivers were impaired at the time of the accident.

The number may vary, as only three in five drivers killed in an auto accident were tested and drug testing methods vary by state. Winter driving is especially dangerous, so make sure you’re drug and alcohol free when you get behind the wheel.