An analysis of evacuation travel paths on stair landings by means of conditional probabilities

• Occupants׳ movement on stair landings during an evacuation drill is analysed.
• Two factors are investigated: crowding and occupants׳ interactions.
• Under the observed conditions, floors are emptied from the top to the bottom.

This paper analyses data on occupants׳ movement on stair landings collected during an evacuation drill performed in a six-storey office building in the United States. A total of 215 occupant travel path trajectories were filmed and time on the stair landings and egress behaviours were analysed. Data were analysed using a probabilistic approach, i.e., the probability of different occupant travel paths were calculated in relation to two different factors: (1) crowding on the landings, and (2) the type of interactions between occupants (e.g., merging flows, deference/overtaking behaviours, etc.). Results showed that a higher number of occupants on stair landings caused an increase in the probability for (1) longer travel paths and (2) usage of the outer boundaries on the stair/landing connections. This paper highlights that data and modelling assumptions should be used after a careful evaluation of their field of applicability. In the case of a low occupant load and non-homogenous merging streams (a higher number of people entering the landing from the stairs than the door), floors tend to be emptied from the top to the bottom.