Generally, maximum egress travel path is considered to arrive at the number of stairways in a building. However, queuing time(tq) in front of exit stairway doors in each floor is more critical as it is greater than the time taken for horizontal distance (exit travel path) movement on a floor(td). So why do we not consider tq for the number of stairways required.

Or, put in another way - why is travel distance not added to queuing time in egress calculations.

Hi Ajit:

It looks like you may be working on some egress mathematical modeling concepts. I really do not know how to answer your question, but here is my thoughts that may spirit a good discussion.

The prescriptive requirements of NFPA 101 are from empirical modeling. Knowledge derived from investigation, observation, experimentation, or experience, as opposed to theoretical knowledge based on logical or mathematical assumptions.

Respectively,

Milt Werner