ABSTRCT : The Gerede - Ankara and Ankara Peripheral Motorway (GAAPM) is about 270 Km long portion of the Turkish Motorway (TM)., The TM is presently being constructed and having a planned total lenght of 3600 Km. It connects the Trans European Motorway (TEM) to the neighboring countries. Iran, Iraq, and Syria.. The GAAPM has. numereous structures, such as major viaducts and bridges.,, overpasses .and underpasses, high cuts, and embankments, and large culverts.. The Gerede - Ankara, section has four 3.75 meter lanes in each direction whereas Peripheral Motorway is designed as five 3.75 meter lanes in each direction. Both have a ten meter wide median, between carriageways.In order to define, the design, parameters a detailed surface and subsurface geotechnical investigations and. a complete testing program are performed.In this respect a 25000 scale regional, 5000 scale vicinty and 10ÖG scale site engineering geological mapping are carried, out. Numerous boreholes, test, pits, and. trenches .are opened,. Both in situ and laboratory tests are executed.Geophysical surveys are also used as supplementary investigation work.Some of the main lithologies,, encountered, along the alignment are nietadetritics, Permo-Triassic limestones, metavolcanics, tectonosedimentary deposits, ophiolites, mainly extrusive igneous rocks, marine sedimentary rocks, lake deposits, alluvium, eoUuviuni, and talus. Their engineering characteristics are briefly given, in the text. Gravity faults are more common than reverse .and thrust faults along the. GAAPM. The motorway design is higjy dependable on large faults especially the ones oblique `to the. motorway. The. other structural features, such as foldings.,, unconfomities,beddings, and joints are widespread along the alignment .and their detailed identification obviously provides valuable information to select appropriate,design parameters.The- GAAPM crosses several perennial streams, dam reservoirs» and swamps. Their extents and bedrock configurations ,are identified, to be able to execute a. proper design. Shallow groundwater plains, soft marshy grounds» seeps» springs, .and shallow artesian and leaky aquifers, `are some of the common hydrogeological features, along the .alignment. It is well-known that- they do have great influence on ground stability. Hence hydrogeological investigation has formed, one of the main part of the geotechnical studies along the route.