Calculation Method for Traffic Capacity of Short-Distance Continuous Merging Areas of Expressways in Mountainous Urban

In mountainous urban areas, road construction is often severely constrained by topographical conditions, leading to the frequent occurrence of short-distance continuous merging areas along expressways. Accurately calculating the capacity of such merging areas is critical for effective traffic management. However, existing studies mainly focus on capacity calculation for single merging areas, with limited attention given to short-distance continuous merging areas in mountainous urban contexts. This study proposes a specific capacity calculation model for short-distance continuous merging areas in mountainous urban. First, the definition of short-distance continuous merging areas is provided. Subsequently, drones were used to collect empirical data in short-distance continuous merging areas. The geometric and traffic flow characteristics of short-distance continuous merging areas were descriptively analyzed. Furthermore, the relationship between capacity and key factors was investigated, and a capacity calculation model was established based on these factors. The proposed model is validated using VISSIM simulation. The results show that (1) shorter merging point spacing tends to intensify traffic flow turbulence within continuous merging areas, (2) the capacity of short-distance continuous merging areas is primarily influenced by merging point spacing and merging ratios, and (3) the proposed calculation method demonstrates high accuracy, with a maximum absolute error of 2.77%. This study provides a methodological framework for calculating the capacity of short-distance continuous merging areas in mountainous urban contexts, providing a foundation for targeted traffic control strategies and informed interchange planning.