TIME SERIES VARIATIONS OF TRAFFIC ACCIDENT RISKS ON INTERCITY EXPRESSWAYS CONSIDERING TRAFFIC STATES

Abstract

In recent years, it has been reported that the traffic capacity of expressways has been declining over the years. In the previous study, it has been pointed out that the characteristics of drivers behavior have been shifted from high-speed and short-headway distance to reduced-speed and widen-headway in the last decade. If this difference of driving behavior was caused by the change of drivers attitude to traffic safety, such changes in driving behavior may also contribute to enhance traffic safety. To prove this hypothesis, in this study, we analyzed the time series variations of traffic accident risks for 13 years at 9 sections of intercity expressways explicitly considering the traffic condition of the entire section. In addition, the relationship between the time series variations of traffic capacity and the traffic accident risk is analyzed. As a result, it is revealed that the traffic accident risk significantly increase especially in the critical traffic state and jam flow state in multiple sections for rear-end collision, whereas for sidewipe and road facility collisions the traffic accident risk significantly increase especially in the free flow state. Also, it is confirmed that the correlation between time series variations of traffic capacity and accident risk shows negative value in multiple sections, implying that the less traffic capacity becomes, the more often traffic accidents occur. These facts suggest that the countermeasures preventing distracted driving and drawing drivers attention at bottlenecks are essential for enhancing traffic safety as well as increasing traffic capacity.