Railway transportation plays a vital role in modern societies. Due to increasing demands for transportation of passengers and goods, higher speed trains with heavier axle loads are introduced to the railway system, and it is expected to continue in the future. Therefore, track geometry bears huge static and dynamic forces that accelerate degradation process. As a result, railway track should be inspected regularly to detect geometry faults and to plan for maintenance actions in advance. Track geometry inspection has a profound impact on railway track availability and maintenance cost. Although there have been improvements in safety performance and maintenance planning of railway tracks, still infrastructure managers expect a more effective maintenance planning and scheduling regime. This thesis proposes a simulation-based model for optimization of track geometry inspection intervals. To simulate the track geometry evolution a linear model is used to model track geometry degradation in a maintenance cycle. It is assumed that the parameters of degradation model are random variables following lognormal distribution. Using the proposed model, the track geometry behaviour is simulated under different inspection intervals. Later, different inspection intervals are compared with respect to the cost function and the optimal range of inspection intervals is obtained.