A new study shows the number of Washington state drivers involved in deadly crashes who tested positive for THC has doubled.

According to research by AAA between 2008 and 2012, an estimated eight percent of Washington drivers involved in fatal crashes were positive for THC. That rate now is more than double since marijuana became legal in Washington.

In the five years before legislation, an average of 56 Washington drivers involved in fatal crashes each year were THC positive. In the five years after legislation, that average jumped to 130.