A Study of the Combined Effects of Extended Driving and Heat Stress on Driver Arousal and Performance

Abstract

An experiment was conducted on the highway to identify the effects of hot, humid environments on driver performance, subjective state, and various physiological responses believed to reflect arousal or stress. Each driver drove a standard-sized American passenger car over a 360-mile (600 km) route, once under comfortable conditions and once under heat stress.

Under heat stress, the drivers had a systematically higher heart rate, greater heart rate variability, less energy in the higher frequency EEG bands, and produced fewer 17-hydroxycorticosteriods than they did in the comfortable driving environment. They rated themselves more alert early in the trip when in the hot environment but significantly less alert near the trip’s end; they also rated themselves as notably more fatigued during the second half of the trip when in the hot environment. Finally, their performance was systematically poorer in the hot environment as reflected by a greater number of relatively large steering adjustments, the commission of a greater number of technical errors, and an increased tendency to inadvertently drift out of the appropriate lane of traffic.