EVALUATION OF SURFACE UNEVENNESS CONSIDERING MENTAL FATIGUE BASED ON HEART RATE VARIABILITY ANALYSIS

Functional evaluation of road surfaces has traditionally been based on the safety and comfort of traveling vehicles. However, the influence of road surface condition to unconscious mental fatigue while driving is also significant for drivers. This study examines a new evaluation method of surface unevenness based on heart rate variability analysis in terms of “passive fatigue” that is defined as mental fatigue caused by road surface condition. For this purpose we conduct a driving experiment by use of a sophisticated driving simulator to diagnose the passive fatigue induced by repeated traveling over specific surface conditions. The frequency analysis of heart rate variability signals measured by pulse waves is employed to monitor the behavior of high frequency (HF) and low frequency (LF) components of the signals, which reflects mental stress of humans. According to the result a multiple regression model of the International Roughness Index (IRI) on the HF and LF/HF contributes to evaluate surface unevenness considering the passive fatigue. This study also suggests an IRI value of 5.2mm/m as an acceptable level for highways in respect of the passive fatigue