Subjective Fatigue and Performance Variation Correlation During Simulated Driving Tasks

Abstract

During prolonged driving tasks, fatigue increases and driving performance becomes impaired. To investigate variation of driver fatigue and driving performance, 14 driving simulator test subjects were asked to complete a questionnaire designed to subjectively quantify fatigue levels. Driver fatigue was estimated in several aspects such as ability to drive safely, drowsiness, and physical fatigue symptoms. Quantitative driving performance was evaluated by measuring steering wheel, lateral position, and speed control parameters. The results showed significant increase in subjective driver fatigue and driving performance impairment following simulated driving sessions. Based on questionnaire scores, a driver fatigue indicator was developed. Analysis of this indicator revealed that subjective fatigue increased rapidly during the first 45 minute session, and more gradually during the remaining two sessions. Short breaks between sessions resulted in temporary fatigue recovery. Increased standard deviations for steering wheel rate, lateral velocity, and average speed indicated similar quantitative driving performance impairment. Comparison of subjective scores with standard deviation of acceleration indicates a possible relationship between the increased subjective fatigue and impaired driving performance.