Public conveyance such as a bus is a major contributor to socio - economic development of any geography. The international market for passenger bus needed to be made viable in terms of passenger comfort, minimum operational costs of the fleet by reduced fuel consumption through light weighting and yet robust enough to meet stringent safety requirements. Optimized design of bus body superstructure plays vital role in overall performance and safety, which necessitates to evaluate bus structure accurately during initial phase of design.This paper presents a robust methodology in numerical simulation for enhancing the structural characteristics of a bus body with simultaneous reduction in the weight by multi-material optimization while supplemented with sensitivity and robustness analysis. This approach ensures significant reduction in vehicle curb weight with promising design stiffness.Firstly, the finite element analysis model of the original bus was created and validated by experiments. Target design space of the bus is identified and modelled considering available packaging constraint. Bending and torsional stiffness, fundamental frequency and design stress are constraints in topology optimization. Functional and manufacturing parameter constraints in terms of dimension of selective tubular section and side - symmetricity of bus structure are defined. The critical zones identified in perspective of rollover were defined for higher stiffness to account for safety at this stage itself. Subgroups for design variable are strategically divided for faster and optimal result solutions. The optimal design with enhanced mechanical response of superstructure is achieved, satisfying all constraints with significant reduced weight.