Traditional studies of cascading failures in urban road networks mainly focus on the road segment failures, often neglecting the bottleneck effect of intersections on traffic flow. This study proposes a cascading failure model that considers the coupling between road segments and intersection turning movements. An urban road network model was constructed using Python, and a single-segment attack strategy was applied to simulate cascading failures under emergency conditions. Using average system travel time, network efficiency, and Origin-Destination (OD) demand loss as urban road network vulnerability assessment indicators, we compare the changes under different cascading failure models in the event of failures on different road segments. The results show that after considering the intersection turning movements, the propagation range of cascading failures significantly expands, the average system travel time increases, network efficiency decreases, and OD demand loss increases. If only the cascading failure process of road segments is considered, ignoring intersection effects may substantially underestimate the impact of disruptions on network performance. Therefore, accounting for intersection turning movements in cascading failure modeling more accurately captures the propagation characteristics of traffic flows, enhances the precision of vulnerability assessments, and provides theoretical support for urban road network vulnerability analysis and traffic emergency management.