Common practices in fire hazard assessment for underground transport stations

•Many building constructions do not comply with prescriptive fire safety codes.•Timeline approach is commonly applied in performance-based design.•Evacuation simulations of an underground transport station were carried out.•Available Safe Egress Time and Required Safe Egress Time were estimated.•Problems with applying timeline analysis raised earlier were further demonstrated.

Timeline approach is commonly applied in performance-based design for many big construction projects with difficulties to comply with the prescriptive fire safety codes. Both the Available Safe Egress Time (ASET) and the Required Safe Egress Time (RSET) are estimated and then compared. The common practice will be discussed in this paper and illustrated by referring to an example underground transport station. Fire scenarios with different fire sizes were identified with ASET predicted by fire simulations. Evacuation simulations were carried out to predict RSET. However, the results will be entirely different under a bigger fire, or in buildings with higher occupant loading. The associated problems in this approach commonly adopted in performance-based design in crowded areas pointed out earlier are further confirmed.