Crashes are up by as much as six percent in Colorado, Nevada, Oregon and Washington, compared with neighboring states that have not yet legalized marijuana for recreational use, according to research from the Insurance Institute for Highway Safety (IIHS) and Highway Loss Data Institute (HLDI).
Colorado and Washington were the first states to legalize recreational marijuana for adults 21 and older with voter approval in November 2012. Retail sales began in January 2014 in Colorado and in July 2014 in Washington. Oregon voters approved legalized recreational marijuana in November 2014, and sales started in October 2015. Nevada voters approved recreational marijuana in November 2016, and retail sales began in July 2017.