Optimal Roof–Ground Bidirectional Evacuation Strategies for Three-Story Kindergartens: Experimental Measurement and Simulation-Based Analysis

Under fire conditions, kindergartens typically adopt a fully descending evacuation strategy. However, this approach has certain limitations in roof–courtyard bidirectional evacuation scenarios. Therefore, this study conducted an efficiency analysis of bidirectional evacuation strategies for three-story kindergartens. First, the ascending evacuation velocities of children were collected and used as fundamental input parameters for the simulations. Subsequently, MassMotion software was used to model and compare multiple roof–courtyard bidirectional evacuation strategies. The results indicated that under localized fire scenarios occurring on each floor, the optimal strategies were 3G, 2B, and 1A, respectively. Under overall evacuation conditions, Strategy 3G also achieved the best performance, improving total evacuation efficiency by 8.25% compared with the fully downward strategy and demonstrating strong tail-end clearance capability. This study quantified children’s ascending evacuation velocities and proposed a new bidirectional evacuation strategy tailored for three-story kindergartens, providing methodological guidance and practical insights for safe evacuation design in kindergarten buildings.