Minimum Tunnel-length Criterion for Installation of Disaster Prevention and Rescue Areas in Railway Tunnels

Disaster prevention and rescue areas in railway tunnels are essential facilities that support passenger evacuation and rescue operations in the event of a fire. However, the current “Technical Standards for Railway Facilities” mandate uniform installation regardless of tunnel scale or operational characteristics, resulting in cost inefficiency. Accordingly, this study aims to establish a rational installation criterion by conducting passenger evacuation simulations and fire analysis, considering tunnel cross-section, passenger composition, longitudinal gradient, and external temperature as key variables. The results indicate that large-section tunnels exhibit approximately 1.15% longer evacuation distances than medium-section tunnels, while evacuation distance decreases by about 5 m per 1‰ increase in longitudinal gradient. Moreover, moderate-temperature conditions yielded 3–4% longer evacuation distances than winter conditions, and the inclusion of vulnerable passengers reduced evacuation performance to approximately 63% of that of general passengers. Under the most adverse scenario, the minimum available evacuation distances were 523 m for medium-section tunnels and 529 m for large-section tunnels, corresponding to critical tunnel lengths of 1,046 m and 1,058 m, respectively. The results establish 1 km as the minimum tunnel length requiring installation of a disaster prevention and rescue area, improving passenger safety while reducing inefficiencies associated with unnecessary fire-safety facility installation.