 Four miles east of the Interstates, US 12/US 18 becomes a two lane surface road again and passes through Cambridge, where US 12 splits southeast at the Jefferson County line.US 18 crosses WIS 89 and WIS 26 in Jefferson and passes through Sullivan.Entering Waukesha County, Wisconsin, US 18 passes north of Dousman at WIS 67, south of the Kettle Moraine State Forest - Lapham Peak Unit and north of Wales at WIS 83.