This thesis describes a new approach for developing large-scale object- oriented software systems, called Object Management Systems (OMS). The OMS development methodology consists of four stages: Domain Customization, System Architecture, Application Development, and System Test. The methodology is demonstrated by implementing the SmartAHS simulation framework, a Customized Object Model. SmartAHS is used to capture different Automated Highway System (AHS) designs and benchmark scenarios and to generate performance metrics through micro-simulation of the designs. The California PATH Program has proposed a hierarchical control architecture that yields up to a four-fold increase in transportation capacity while enhancing safety. This report demonstrates the use of SmartAHS by implementing elements of the PATH automation architecture. The resultant OMS Application is called SmartPATH.