In this chapter, salient performance aspects of the human in the context of a person-machine control system, the motor vehicle, will be summarized. The driver-vehicle system configuration is ubiquitous. Practically all readers of this chapter are also participants in such a system; yet many questions, as will be seen, remain to be answered in modeling the behavior of the human component alone. Recent publications (IVHS 1992; TRB 1993) in support of Intelligent Transportation Systems (ITS) have identified study of "Plain Old Driving" (POD) as a fundamental research topic in ITS. For the purposes of a transportation engineer interested in developing a molecular model of traffic flow in which the human in the vehicle or an individual human-vehicle comprises a unit of analysis, some important performance characteristics can be identified to aid in the formulation, even if a comprehensive transfer function for the driver has not yet been formulated.
