Exploring novel surrogate safety indicators measuring conflict riskiness and severity: a case study in Sacramento,...

Determining appropriate traffic conflict indicators is essential for accurately conducting road safety evaluations. However, existing studies often fail to comprehensively address key factors such as the presence or absence of collision courses, the riskiness before and after the conflict point, and the mobility of the conflict point when selecting conflict riskiness indicators. Moreover, current conflict severity indicators are based on fully inelastic collision theory, which lacks sufficient modeling accuracy. This study delves into the characterization of collision and crossing courses in both angle and straight-line conflicts, providing a comprehensive analysis of the risks faced by road users both before reaching a conflict point and after one has passed it. Based on this analysis, a new combination scheme of conflict riskiness indicators is proposed. A two-dimensional, six-degrees-of-freedom potential collision model is then developed based on the theory of partially elastic collisions, and a new indicator, Extended Delta-E, is introduced. Finally, correlation analysis based on crash and conflict data is performed to compare the proposed indicators with traditional riskiness and severity indicators, evaluating their accuracy in road safety evaluation. The results demonstrate that the conflict rates and severity rates derived from the proposed indicators exhibit the strongest correlation with actual crash rates and crash severity rates, respectively, compared to other indicators. The conflict riskiness and severity indicators proposed in this study offer a more nuanced characterization of conflict events, and can serve as highly accurate alternative measures for crash-based road safety evaluations.