Evaluation of Drivers’ Speed Behavior on Mountainous Rural Highways

In developing countries, the crash risk on mountainous rural highways is higher than on non-mountainous rural highways due to their complex geometric design. Thus, the consistency of geometric characteristics with drivers’ behavior plays a remarkable role in reducing crashes in these areas. In this study, two substandard mountainous rural highways of Iran were selected to measure local design consistency based on continuous speed data collected by smartphone technology. The idea of employing critical elements was introduced to evaluate local design consistency. The critical element is an individual element with a higher CCR (curvature change rate) value compared to the CCR values of their adjacent elements. An individual element was defined as a curve or a group of curves with similar CCR values, and short tangents between each two curves. The efficiency of this concept was evaluated base on statistical hypothesis test and determining spearman rank coefficient between a popular design consistency indictor and expected rural highway crashes. The null hypothesis was rejected for all of the critical elements and it was confirmed that drivers reduce their speed when they face the critical element. Finally, several concepts related to design consistency on mountainous rural highways were elaborated according to operating speed profiles.