Paper Title
Evaluation of Drivers’ Stress Using Heart Rate Variability in the Mountainous Road Driving: In the Case of Overtaking and Passing a Vehicle

Abstract
It is widely known that stress can have a profound effect on driving performance and road traffic accident. Particularly driving a vehicle in the curved mountainous two-way two-lane road is relatively different from those on expressways or multi-lane roads. To evaluate the drivers' stress due to the driving environment context, for this study we used Twenty-five participants', psychological states while overtaking and passing vehicles on the actual road test displayed in the form of changes in heart rate variability. The collected test data include the participants' heart rate and vehicle speed variation when overtaking different types of vehicles on a straight road driving and passing vehicles proceeding in the opposite direction in different positions on right-turning horizontal curved road sections. Then using a linear interpolation method and formula, the result shows that the stress increment due to overtaking small car raised by 25% and when overtaking large vehicle increased by 17.85% above the normal baseline. However, overtaking large vehicle took high overtaking speed, and riskier than overtaking a small car. Also, passing a vehicle on the curve generated different level of stress based on the position which passing vehicle had been done. Accordingly, the stress level varied between 10.4% and 25.46% and driving on the beginning of the curve had more possibility of a road traffic accident existence. Keywords - Heart Rate, Heart Rate Variation, Overtaking, Passing, Stress, Vehicle