The routes for a proposed Freeway and associated minor roads have been investigated to assess the nature of the materials which will be met in cuttings. In particular it has been required to delineate the portions which can be excavated by dozing or ripping, as distinct from those requiring drilling and blasting, and to assess angles for cuttings to ensure their permanent stability. The work has included detailed geological mapping of natural outcrops and existing cuttings, diamond drilling, seismic refraction traverses and resistivity measurements. Precambrian rocks including shale, sandstones, quartzite, schist and gneiss occur along the routes. They are weakened to varying degrees by structural weaknesses, principally jointing, and by chemical and mechanical weathering. The relationships between rock mass weaknesses that could aid material behaviour during excavation, and confer stability in cuttings, are discussed. Assessments of excavation methods required and suggestions for cutting angles are given in tables, which also list the factual data from which the assessments are made. Exploration of the Crafers-Stirling section of the proposed SE Freeway included geological mapping, seismic and resistivity surveys, and drilling of three diamond holes. The rocks encountered along the route are mainly Aldgate Sandstone, with minor areas of Barossa Complex schist and gneiss.