Abstract Manager

As Canadian LRT systems expand and vehicles are specified for higher crush loads, interior layout becomes a safety critical design choice. In this operating regime, small geometric constraints can trigger queue spillback and sharply increase evacuation time. Recent Canadian sourcing and specification negotiations have highlighted a recurring challenge: comfort driven seating rules, such as minimum transverse seating ratios, can unintentionally force interior arrangements that degrade emergency egress performance at the very loads the vehicle is required to carry.

This paper evaluates three Light Rail Vehicle seating layouts commonly considered in procurement: a baseline hybrid layout with transverse end seating pods, a longitudinal layout with sidewall seating and a continuous aisle, and a modified hybrid layout intended to retain transverse seating while improving circulation. Two load cases are assessed using project defined values: 145 passengers and an AW2 maximum of 195 passengers. The method combines an auditable bottleneck capacity model with Monte Carlo simulation (N = 1000 trials) to quantify both typical performance and tail risk using the 95th percentile evacuation time.

Results show a non linear density penalty for hybrid layouts at AW2 loading. Localized end pod constrictions reduce effective aisle width and increase merging friction, producing mean evacuation times near 310 s and a 95th percentile near 351 s. The longitudinal layout maintains a wider continuous aisle and clears the vehicle in about 114 s mean and 129 s at the 95th percentile for the same AW2 load. The paper introduces an “Egress Elasticity” metric to measure how quickly evacuation time increases as load approaches AW2, enabling clearer comparison of layout robustness. Lessons learned are translated into procurement ready recommendations, including performance based interior requirements such as maximum evacuation time at AW2, geometry based minimum aisle constraints at pinch points, and a structured waiver pathway when seating ratio targets conflict with quantified evacuation safety.