There is always variability in the length, spacing and orientation of discontinuities. Hence, in practice it may be preferable to use software such as STEPSIM for a probabilistic estimate for these equivalent shear strength parameters by considering the variability of parameters such as discontinuity persistency and strength. The “step-path” concept was initially conceptualised by Dr Barry McMahon in 1979 during his pit slope design work for  Bougainville  in Papua New Guinea (PNG).  The STPSIM  software  was  coded  in  1981  to  run  on  mainframe computers. Several minor code modifications were made during the 1980’s. STPSIM was transported to the Ok Tedi Mine in 1991 and adapted to run on personal computers. During the final pit slope optimisation study at Ok Tedi in 1997-99, the STPSIM software was extensively modified and rewritten as STEPSIM4. Baczynski (N.R.P. Baczynski, 2000. STEPSIM4 “Step Path” method for slope risks. In GeoEng 2000, Melbourne, Australia.) described the latest version of this software, STEPSIM4, which envisages a potential rupture path through a rock slope as a series of adjacent cells. Within the LOP Project, provision of services to perform a STEPSIM4-Revised software rewrite has been completed. For more information see the reference below: