Estimation of traffic conflict risk for merging vehicles on highway merge section

This study proposed a methodology for estimating rear-end conflict risk of vehicles on freeway merge sections as a probabilistic measure. The methodology consisted of two major components. The first part estimated the merging probability of a vehicle, given its position on a merge lane. Detailed vehicle trajectory data from the Next Generation Simulation program were used to find the underlying probability density function of the merging decision. The second part derived the probabilistic risk of a merging vehicle conflicting with vehicles around it as a function of a surrogate safety measure, namely, modified time-to-collision. These two parts were combined, and an index was proposed to describe the conflict risk of each merging vehicle at each time step. With aggregation of the conflict risk over time and space, a risk map for describing the level of conflict risk could be created. A case study demonstrated the implementation of the proposed method for traffic conflict analysis in detail. The result of this study can be used to evaluate the safety level of merge sections and develop real-time traffic control strategies to reduce conflicts associated with merging traffic.