Sound Transit 3, abbreviated as ST3, was a ballot measure during the November 2016 elections in Seattle, Washington, proposing an expansion of the regional public transit system. The measure was proposed by Sound Transit, which was established by a similar initiative passed in 1996 and expanded by the Sound Transit 2 vote in 2008, who have operated regional transit systems in the Seattle metropolitan area since 1999. On November 8, 2016, Sound Transit 3 was approved by over 54 percent of voters in the Puget Sound region; voters in Pierce County rejected the measure, but the measure passed in King and Snohomish counties, and had an overall majority.