Transportation in Minnesota is overseen by the Minnesota Department of Transportation (MnDOT for short and used in the local news media). Principal transportation corridors radiate from the Minneapolis–St. Paul metropolitan area and Duluth. The major Interstate highways are Interstate 35 (I-35), I-90, and I-94, with I-35 and I-94 passing through the Minneapolis–St. Paul metropolitan area, and I-90 traveling east-west along the southern edge of the state.[110] In 2006, a constitutional amendment was passed that required sales and use taxes on motor vehicles to fund transportation, with at least 40% dedicated to public transit.[111] There are nearly two dozen rail corridors in Minnesota, most of which go through Minneapolis–St. Paul or Duluth.[112] There is water transportation along the Mississippi River system and from the ports of Lake Superior.[113]