Future lunar science and exploration missions will involve the use of pressurized rovers for long duration lunar surface missions. Designs for pressurized rovers are being studied by NASA and the industry. This paper presents some results of work currently underway on the development of a rover simulator in the context of a new pressurized rover concept. A motion base simulator will play a vital role in generating rover vehicle design and performance requirements. A simulator based on a modular simulation (MODSIM) architecture, has been under study and development since 1991. The MODSIM approach will provide benefits of flexibility of modification, low cost, phased scheduling and ease of supportability when compared with more traditional simulator architectures. A lunar rover simulator based on MODSIM will help rover vehicle engineers to be productive through all phases of simulator development. Although MODSIM is being applied to rovers here, it can just as easily be used to simulate other vehicles without additional expenditure on hardware.