The transportation community has long used two distinct simulator types without any formal integration between them. First, are microscopic Traffic Simulation (TS) models, which simulate the movement of individual vehicles based on car-following and lane-changing models, and which have been used to evaluate the operational efficiency of transportation networks. Second, are Driving Simulators (DS), which have been used to examine individual human subjects within a virtual environment. The current research develops a prototype human-in-the-loop transportation simulation modeling framework by integrating these heterogeneous simulation platforms, whose specifications are often in direct opposition. To illustrate the feasibility of the approach, a prototype simulator is developed by integrating a commercial state-of-the-art traffic simulation model with a Driving Simulator custom-developed by the present research team. The prototype system allows the human driver to control (i.e. drive) a subject vehicle in the virtual traffic simulation environment. At the same time, the background traffic that the human driver sees and drives amongst is that resulting from the macroscopic TS, which now intelligently responds to the actions made by the human driver. This capacity helps to broaden the range of applications to which either type of simulators is applicable. As a pilot application for the present study, the prototype integrated simulator is used in conjunction with a fuel consumption and tailpipe emissions model for a small group of subject drivers. In this study, several human subjects are asked to drive a simulated real-world course twice, once each in two levels of traffic congestion. The paper concludes by suggesting possible refinements to the developed prototype, including a real-time networking capacity that will allow multiple human participants to simultaneously interact within our integrated environment. Such a feature is prevalent in entertainment gaming environments, but absent, to date, in research-minded, vehicle simulation and training applications.