Effect of Different Vehicle Speeds on Mental Fatigue in Healthy Drivers

The objective of this study was to assess the effect of different driving speeds on autonomic nervous activities in healthy drivers on highway by using power spectral analysis of heart rate variability (HRV). A total of 30 healthy male drivers were randomly divided into three groups: A (with speed of 40 km/h), B (with speed of 80 km/h) and C (with speed of 120 km/h). All drivers were required to be well rested before the experiments. All subjects of three groups were required to drive the car on A20 highway for 2 hours. Heart rate signals were collected throughout the experiment and blood pressure was measured and compared before and after the experiment. Subjective evaluation to a questionnaire was obtained after the driving task in three groups. After the driving task, low frequency (LF) component, high frequency (HF) component and their ratio LF/HF of HRV in normalized units (NU) were calculated and compared between both groups and between the beginning and the end of the task. Finally, it was found that different vehicle speeds induced different parasympathetic nerve activity change level. In fact, sympathovagal balance changes were induced by different parasympathetic nerve activities.