The development of a computer simulation model to approximate the interactions of those traffic elements present at a signalized intersection is presented. The simulation model is designed as a tool for the engineer or analyst to predict the behavior of a signalized intersection under different operational conditions. GASP IV is the simulation language used in this study. This language is FORTRAN based and can be easily implemented on the computing systems of different manufacturers. By varying different parameters (logo, geometrics, movement percentages, traffic signal information, volumes, phasing, etc.) while holding others constant, the impact of design changes were studied. Both exclusive and no exclusive left-turn phase signal operation were investigated and the simulation output indicates reasonable results. The engineer could use this simulation model in the integral part of making traffic operation decisions.