Last week’s article was about the increase in crashes in states that legalized recreational use of marijuana compared with similar states that didn’t. This article will take it a bit further and show that research by the Insurance Institute for Highway Safety (IIHS) shows that some drivers don’t view using marijuana as risky for driving as imbibing alcohol, and those attitudes appear to extend to cannabis users who drive with children, a new study of Washington state drivers shows.

Drivers in the weekend roadside surveys were more likely to test positive for marijuana than alcohol, and almost none of the drivers traveling with a child were alcohol-positive, which is good news. However, drivers were about equally likely to be marijuana-positive whether or not a child was present. These are the main findings of a new study by the Pacific Institute for Research and Evaluation, the Washington Traffic Safety Commission and IIHS. Drivers surveyed after retail marijuana sales began were more likely to test positive for marijuana than before, primarily due to a large increase in marijuana-positive drivers during the daytime. Drivers who tested positive for the drug were less likely to agree that marijuana impairs driving.

The latest study examines how more permissive attitudes about marijuana use and driving might affect child passenger safety.

About nine percent of the 2,056 drivers age 21 and older in the sample were driving with a child. While almost none of the drivers with child passengers tested positive for any amount of alcohol, 14 percent tested positive for cannabis.

The presence of THC or its metabolites in oral fluid or blood generally indicates recent use of marijuana, but it doesn’t necessarily indicate impairment because the chemicals can be detected in the body for hours or, in the case of some frequent users, days.

When queried about their attitudes on marijuana and driving, the majority of drivers said they consider marijuana use “very likely” to impair driving. This was especially the case among drivers traveling with a child. The percent of THC-positive drivers was significantly lower among those who perceived the risk as “very likely” than other drivers. Among this group, nine percent traveling with a child tested positive for THC, compared with 14 percent of drivers without kids in the car.

“The fact that few weekend drivers with children were alcohol-impaired is good news,” says David Harkey, IIHS-HLDI president. “What’s concerning, though, is that some drivers may be under the influence of marijuana and traveling with kids in the car. This points to the need to examine driving situations that put children at risk, especially given the trend toward legalizing marijuana.”

The most recent national roadside survey of drivers found that 13 percent of nighttime, weekend drivers and nine percent of daytime (Friday) drivers tested positive for marijuana in blood or saliva during 2013-14, according to the IIHS “Status Report.” Combining marijuana with alcohol or other drugs may make driving worse than using marijuana alone.