This paper investigates the capacity of weaving bottlenecks in Nanjing, where multiple traffic streams merge or diverge closely, causing significant traffic disruptions. Utilizing trajectory data from 862 vehicles collected through UAV cameras, the study assesses the bottleneck's capacity and performance measures, including traffic flow, speed, and lane occupancy. The analysis employs a combination of the Highway Capacity Manual (HCM) 2010 guidelines and PTV Vissim simulation software. The HCM 2010 framework provides a standardized approach for evaluating traffic flow characteristics and determining the level of service, while Vissim allows for the evaluation of diverse traffic scenarios. The results reveal that the bottleneck operates at Level of Service E (LOS E), characterized by high congestion, reduced speeds, and prolonged travel times. However, introducing ramp metering to the area improves conditions, resulting in a transition to Level of Service D (LOS D). This study emphasizes the potential of ramp metering to enhance bottleneck performance. Nevertheless, future research should explore other strategies, such as intelligent transportation systems and improved public transportation services, to encourage modal shifts and reduce private vehicle usage. By addressing these challenges, cities like Nanjing can mitigate traffic congestion and create more efficient and sustainable transportation systems. The findings provide valuable insights for urban planners and policymakers seeking evidence-based solutions to optimize traffic flow and mobility in busy cities. By adopting the HCM 2010 guidelines and simulation tools like Vissim, this study contributes to the development of efficient traffic management strategies, ultimately fostering more livable and accessible urban environments.