In India the traffic consists of different categories of fast and slow moving vehicles. Due to the heterogeneous nature of the traffic, the existing methods of signal settings and performance assessment can not be suitably adopted. Because of the complexities inherent to the system, computer simulation is by far the best tool for dealing with such a system. In this study an effort is made to develop a simulation model for pretimed signal settings processing mixed traffic for medium to large cities with Madras as the case study.