When calculating the required cumulative width of emergency egress points for a permanent venue, what specific factor, besides total occupancy and exit factor, must be rigorously accounted for to ensure effective evacuation time, particularly for large crowds?

Beyond total occupancy and exit factor, the specific factor that must be rigorously accounted for is the effective flow capacity per unit of clear egress width. This concept recognizes that the physically measured width of an egress path does not always translate directly into a proportionally equivalent capacity for unimpeded flow, particularly for large crowds. Effective flow capacity per unit of clear egress width refers to the actual number of people or the rate at which individuals can simultaneously and efficiently pass through a given width of an exit opening or corridor. This is critical because human bodies have dimensions that require a certain amount of space for movement, and in high-density situations, factors such as body sway, personal space requirements, and friction between individuals can reduce the usable width. For example, a 72-inch wide corridor, while physically twice the width of a 36-inch wide one, may not effectively allow for double the flow capacity because the efficiency of movement for multiple parallel streams of people decreases when they are in very close proximity. Therefore, the calculation must ensure that the cumulative width provides sufficient independent and unimpeded pathways to maintain the required evacuation flow rate and prevent bottlenecks or congestion, factoring in the realistic dynamic behavior of a dense crowd rather than just static dimensions.