The four-lane motorway (Dunedin Southern Motorway) runs through Dunedin's southern suburbs until the interchange with SH 87 at Mosgiel. SH 1 then heads southwest across the Taieri Plains. The area between the Taieri and Waipori Rivers is flood-prone, and the highway crosses this on a major embankment known colloquially as the "flood-free highway". SH 1 continues through gentle hill country and along the shore of Lake Waihola, then crosses the Tokomairiro Plains into Milton. South of Milton is a major junction with SH 8 at Clarksville Junction. SH 1 continues to cross rolling hill country to reach Balclutha.