of the South Blair Street turn, and US 51 crosses US 151 further northeast. Madison to Fond du Lac At a cloverleaf interchange with I-39/I-90/I-94, a section of freeway begins and continues along US 151 northeast through commercial zones into residential areas. A highway bypass was constructed north and west of Sun Prairie, but so much commercial and residential development subsequently happened to the north and west of the bypass that the route essentially divides Sun Prairie in half. The route now has four interchanges with highways and streets in Sun Prairie. After Sun Prairie, US 151 passes through farmland, heading toward Columbus. The highway bypasses the city via a partial beltline to the north and east, completely clearing the city. WIS 16 and WIS 60 crosses under US 151 about midway along the Columbus bypass. US 151 becomes an expressway with level intersections after the interchange with WIS 73 at the end of the bypass portion. The route becomes a freeway at Beaver Dam, bypassing the city to the southeast. The route follows the edge of residential zones of the city before passing an industrial area at the northeastern end of the bypass. Within this freeway section exists a level railroad crossing near CTH-E (East Burnett Street). US 151 crosses at-grade intersections after the interchange with CTH-A northeast of Beaver Dam and encounters one more freeway section at Waupun, bypassing the city to the east. The Waupun bypass also includes a level railroad crossing halfway between the CTH-M and WIS 26 interchanges. The four-lane expressway of US 151 continues east, bypassing Fond du Lac to the south and east. This expressway provides a mixture of at-grade intersections and grade-separated interchanges at I-41/US& 41 and WIS 23. WisDOT currently is studying upgrades to two sections of US 151. The first study would preserve the Fond du Lac Bypass from I-41 to WIS 23, with the ultimate goal being freeway conversion. The second study is examining freeway upgrades to the route from WIS 73 in Columbus to WIS 49 in Waupun. Fond du Lac to Manitowoc The multi-lane section of US 151 ends after turning north away from Fond du Lac and the route follows the east shore of Lake Winnebago for about half the length of the shoreline. US 151 then turns east at the intersection with WIS 55 and follows two-lane surface roads and briefly running concurrently with WIS