Traffic searches by highway patrols in Colorado and Washington dropped by nearly half after the two states legalized marijuana in 2012. That also reduced the racial disparities in the stops, according to a new analysis of police data, but not by much. Blacks and Hispanics are still searched at higher rates than whites.

Highway stops have long been a tool in the war on drugs, and remain a charged issue amid a furious national debate about police treatment of minorities. Last week, protests erupted over the acquittal of a Minnesota police officer who shot to death Philando Castile after pulling him over for a broken tail light.