This report documents a series of experiments designed to identify the dynamic behavior of drivers controlling headway behind a lead vehicle. The experiments were performed on both a test track and the open highway. Time series were recorded during relatively periods of vehicle following. The main recorded variables included headway distance to the lead vehicle, following vehicle velocity, and driver throttle activity. FFT (Fast Fourier Transform) analysis procedures were used to identify transfer functions of driver/vehicle response to changes in headway distance with respect to the lead vehicle. Transfer function analysis allowed the identification of driver gain and time delay in manual headway control. The results showed that manual headway control is a low bandwidth process carried out with average, continuous control time delays on the order of seconds. Phase margins showed the headway control process tends to be under damped (i.e. somewhat oscillatory) with bandwidths on the order one-third of a radian per second (0.05 Hz). This identification of the coupling dynamics of manual headway control will be useful in setting desirable automatic headway control (Intelligent Cruise Control) system characteristics. (Author/publisher)
Abstract