For new and existing rail network forecasting maintenance intervention is an important aspect of the network’s overall operation, can offer an alternative to “run to failure” strategies and assist greatly with renewal programs. Recent progress implemented in mechanistic formation design is performance-based where the design is developed to achieve a cumulative plastic deformation and or a rail deflection based on a forecasted rail traffic, train loading and speed for a design life. This paper presents an application of the mechanistic formation design to assist in predicting formation performance over the design life and assist rail operator with maintenance forecast typically comprising tamping to maintain rail grade through the design life. This paper presents results for typical embankment heights and at grade conditions for typical heavy haul traffic loading. This can be applied to green field new projects but also to existing networks. The mechanistic formation design uses a Li and Selig Approach incorporating stress distribution estimated using three-dimensional finite element modelling of sleeper, ballast formation and subgrade.