Cannabis Legalization and Traffic Safety

Washington legalized recreational cannabis with Initiative 502 in late 2012. One of the potential consequences of legalization is increased access to cannabis and the potential for an increase in cannabis-impaired driving, which remains illegal. Working with the Washington Traffic Safety Commission, researchers affiliated with the WSICJ are engaged in several projects in this area.

Cannabis and Driving Behavior

Examining data from the Washington State Fatality Analysis Reporting System (WAFARS), researchers examined the degree to which positive blood test results for cannabis were related to risky driving behavior. Early results showed that cannabis consumption was a risk factor for speeding, but not necessarily other driver errors. Importantly, the results also suggested that alcohol was a much larger risk factor for poor driving behavior. Subsequent research indicated that there was considerable covariate imbalance when comparing individuals who tested positive for cannabis (specifically, Delta-9-THC) and those who did not. Propensity score matching was applied to create comparable groups and a small-sample of traffic crash narrative reports were qualitatively coded and examined. These results further support the claim that cannabis is a risk factor for driver error. Ongoing research is focused on the specific effect of legalization on cannabis-impaired driving. Project staff: Youngki Woo, Dale Willits, and Mary Stohr.

Cannabis and Driver Culpability in Fatal Crashes

While prior research conducted by researchers affiliated with the institute demonstrates that cannabis is a potential risk factor for risky driving behavior, this research could not demonstrate that a driver who had consumed alcohol was responsible for the crash directly. We are currently undertaking a qualitative analysis of crash reports with the goal of establishing the extent to which each driver was not at fault, partially at fault, or completely at fault for each accident and will compare drivers who test positive for cannabis to those who do not. Project staff: Dale Willits and Samantha Bill.

Procedural Justice and Police Traffic Stops

Working with the Washington Traffic Safety Commission and three municipal police agencies in the state, this project examined procedural justice in the context of traffic stops. Data were drawn from officer surveys (completed after each stop), citizen surveys (mailed out after a stop), and body-worn camera footage using third-party coders. Results from this project will be available in the near future. Project staff: Dale Willits, David Makin, Rachael Brooks, Wendy Koslicki, and Samantha Bill.