The Question
Stairways are one of the main evacuation routes in multi-story buildings, especially when elevators cannot be used. As more people enter a stairway, movement becomes increasingly affected by limited space and interaction between occupants.
This project asked a simple question: how does stairway performance begin to change as demand increases? I focused on identifying the early signs of congestion rather than only studying conditions after severe crowding had already developed.
My Approach
Observe a Real Stairway
Conduct a pilot study at the Fresno State library and record stairway travel under lower- and higher-flow conditions.
Compare Travel Times
Review how long occupants took to move through the stairway as the number of users increased.
Benchmark the Results
Compare the pilot observations with published stairway evacuation data, including research from NIST.
Prepare for Simulation
Use the observations and literature review as a starting point for future BIM-based evacuation models in Pathfinder.
Pilot Observation Study
The pilot study compared two stairway usage conditions at the Fresno State library. During lower-flow periods, the observed flow rate was approximately 1.07 people per minute, with an average travel time of 21.68 seconds.
During the higher-flow condition, the flow rate increased to about 5.32 people per minute, while the average travel time rose to 23.57 seconds. The change was not dramatic, but it suggested that movement was already becoming less efficient as demand increased.
An Early Sign of Congestion
The stairway did not need to appear fully crowded before its performance began to change. Reduced movement freedom and greater variation in travel time appeared before severe congestion.
What the Data Suggested
Travel Time Increased
Occupants generally took longer to move through the stairway during the higher-flow observation period.
Movement Became Less Consistent
Travel times varied more as stairway use increased, suggesting that occupants had less freedom to move naturally.
Performance Changed Gradually
The stairway did not suddenly fail at one exact point. Efficiency began to decrease as demand moved closer to the available capacity.
Demand Matters More Than Occupant Count Alone
Stairway performance depends on how occupant demand compares with available width, geometry, movement speed, and capacity.
Study Data
The charts compare the distribution of observed travel times during lower- and higher-use periods. The higher-flow condition showed a shift toward longer travel times and greater variability.
Because this was a small pilot study, I treated the results as an early indication rather than a final conclusion. The observations helped identify patterns that could be studied more closely with a larger dataset and controlled simulation.
Connecting Observation and Simulation
Real-world observation shows how people behave in an existing stairway, but it is difficult to test emergency conditions or very high occupant loads in a real building. Simulation provides a way to explore those scenarios without placing people at risk.
The next step would be to model building geometry in BIM and import it into Pathfinder. That would allow different occupant loads, movement speeds, stair configurations, and blocked-exit scenarios to be compared under controlled conditions.
What I Learned
One of my biggest takeaways was that congestion is not always a sudden event. A stairway can begin losing efficiency before the crowd looks severe, which makes early changes in travel time and movement consistency important.
This project also helped me understand the value of combining field observations, published research, and simulation. Each method has limits on its own, but together they can provide a clearer picture of how a building system may perform during an evacuation.