In this paper we have described the development of a system level vehicle architecture simulation model for self-propelled off highway vehicle. Model based systems simulation approach has been deployed for this project. Detailed requirement analysis is performed to derive system/sub-system level requirements. Top-down vehicle decomposition has been carried out for identifying different systems/sub-systems and rightly scoping the model. Functional interface analysis has been performed in order to understand interfaces and energy flows between systems/sub-systems. It helps identify vehicle interactions with externals like operator and environment. Using inputs from the system engineering tools, a complex system level model is developed. The model consists of operator model, controller models, environment interactions and various vehicle systems. The model is modular enough to adapt easily for architectural evaluation at various phases of product development. Model has been parameterized to ease automated evaluations. The model is modular enough to adapt easily for architectural evaluation. The full vehicle model is correlated against test data for various field operations. Model has further been used for driving architectural design decisions, system optimization and energy analysis.