This study was concerned with qualifying and quantifying one aspect of a man-machine system. The man-machine system consisted of the driver-automobile complex; and the subject of interest of this system was the longitudinal control of the automobile by the human under the restraint that the driven automobile is confined to one traffic lane under dense traffic conditions. Analysis of Barbosa's decision point model of car following revealed that it left many aspects of the car-following problem unexplained. In justifying the decision point model, the phase plane technique was used to study the acceleration velocity trajectory generated by a driver closely following a lead vehicle. Utilization of the phase plane representation definitely established the existence of the action point. Results from a velocity threshold experiment yielded the driver's threshold velocity for different values of headway and presentation time. In applying psychophysical techniques to the velocity threshold data it was shown to be applicable. This law then served as the basis for the derivation of two general velocity threshold equations which interrelate the relative velocity threshold, headway, and presentation time. Correlation of the velocity threshold curves with the driver's phase plane trajectory was accomplished. This correlation made possible the proposal of the perception-decision- action process which is the basis of the action point model. A stability analysis of the phase plane limit cycle yielded the criteria for stability as well as an indication of the technique the driver uses to maintain stability. An estimate of the driver's velocity sampling time was also made. Lastly, the action point model was described in detail.
Abstract