Two expanded approaches to the assessment of the physiological correlates of vigilance behaviour are proposed: heart rate within the context of cardiovascular function, and short-epoch analysis of the spontaneous EEG (electroencephalogram). Driver arousal during open-highway driving serves as the example. Steady decline in heart rate (hr) has been observed during extended driving periods, and has been interpreted as a manifestation of declining driver arousal. An experiment was conducted in which impedance cardiographic measurements were obtained on a male subject during a three-hour drive. Of interest was a hemodynamic pattern that occurred during periods of greatest driver attentiveness: the first 20 minutes of the trip and again during the first 30 minutes of the return trip. This pattern was characterized by hr and hr30 (30-sec. Period) values at or below the three-hour average and stroke volume values one to two standard deviation units above the average. Cerebrocortical electrical activity patterns similar to those at sleep onset have been reported for drivers whose performance deteriorates with time. An automated EEG scanning approach could be devised to provide short-epoch (ten to 20 sec.) Analysis for excessive theta activity, a characteristic of drowsiness. Such a device could be used to identify road variables and highway information systems that reduce drowsiness. For the covering abstract of the conference see IRRD 268805.
Abstract