A federal study of drug and alcohol crash risk finds drivers who have been drinking are much more likely to crash than drivers who have consumed pot.

The study also found, after adjusting for demographic factors like age, gender and race, as well as alcohol use, marijuana users were not at a greater risk to crash than sober drivers.

The National Highway Traffic Safety Administration (NHTSA) conducted the study in Virginia Beach, Virginia. It compared more than 3,095 drivers in the area who were involved in crashes, and twice as many controls (6,190) who were not.

The findings diverge from several studies on marijuana and driving, but the NHTSA believes this new study is the most comprehensive.

“We believe this to be the largest, the most closely controlled study of its kind that’s been conducted in the United States,” said Gordon Trowbridge, a spokesman for NHTSA.