Traffic Conflict and Risk Analysis of Small-Spacing Interchange Interweaving Sections on Expressways Using Joint Simulation

Affected by the limited interchange spacing, the operational risk of vehicles in expressway small-spacing interchanges (SSIs) is more complex compared to other interchanges. In this study, UAV measurements were integrated with joint simulation data to explore the risk characteristics of SSIs with the help of traffic conflict theory. Seven traffic flow parameters, including mainline traffic volume, were selected to evaluate their impact on traffic conflicts. The distribution of four traffic conflict indicators, such as time to collision (TTC), was analyzed, and their severity was categorized using cumulative frequency analysis and minibatch K-means clustering. By varying the spacing, the study scrutinized trends in traffic conflicts, emphasizing the influence of various traffic flow parameters, distinctions in conflict indicators, and the ratio of severe conflicts to total conflicts. Additionally, an analysis of the spatial distribution of severe conflicts was conducted. The results suggested that traffic conflicts in SSIs are influenced by multiple factors, with mainline and entry traffic volumes being the most significant. Heavy vehicle proportions and entry ramp speeds had notable effects under certain spacing conditions. Considerable variations were observed in conflict indicators across different spacings, with maximum conflict speed being the most affected by spacing, while TTC was the least. As spacing increased, the proportion of severe conflicts decreased, with severe TTC dropping from 18% to 10%. High-density conflict zones were identified near merging points in the second and third lanes. With larger spacing, the conflict zone range narrowed while the density of conflict points intensified.