The faults with default

Any computer model is merely a representation of reality that involves a combination of the model’s representation of current theory, user’s knowledge, and engineering judgment. When employing sophisticated simulation tools, the user is required to provide input data to the model, select between embedded data-sets, select between scenario or behavioral settings, and/or rely on hardwired data. Depending on the model, the user is frequently tasked with providing information on occupant response (movement and behavior) that allows the simulation tool to operate and results to be generated. This requires a significant amount of expertise on the part of the model user and during model development. Critically, it requires an understanding of the implications of using and employing this data. This paper discusses model defaults, their use, and the consequences of their use on engineering results. A default setting is an initial setting provided by a developer that enables the model to be used without the modification of model settings and/or the provision of new data. Defaults are often provided as shortcuts to configuring an evacuation model because they allow the user to run the model and familiarize themselves with the model’s functionality without understanding all of the model’s capabilities. In reality, the vast majority of software programs (including engineering models) require defaults to prevent the model from initially being difficult to use and to provide some guidance on parameter selections. This is reasonable and expected. However, in scientific or engineering models, the selection (and the associated description) of the default settings can have a significant impact on the results produced. This is particularly the case in a relatively immature field(s) such as egress modeling and human behavior in fire. There are both positive and negative aspects of providing defaults in current evacuation models. Default values or parameters can prove useful in the simulation of certain (basic) scenarios that are commonplace and/or similar to those from which the default data/understanding was collected 1,2 , especially given the lack of an overarching theory. Conversely, the use of default values or parameters can provide the user with ready-made input that may not be relevant to the scenario being modeled and/or provide a ready-made scenario that precludes the user from understanding the input and the results produced

Simulating a building as a people movement system

Egress models are being used more frequently to simulate people movement; i.e., how people enter, use, and leave a building. However, little has been written on the different phases of people movement over the lifecycle of the building that can be examined and how these models may achieve this. In addition, little has been written on how these phases interact. This interaction may be due to these different phases occurring simultaneously or when an individual's experience in one phase (e.g., entering a building) influences another (e.g., route selection when leaving). This paper presents six modes in which an egress model can be applied: Naı¨ve, Operational, Predictive, Engineered, Real-Time, and Interactive. The paper describes what is needed to enable these application modes, in terms of data, expertise, and model functionality and the benefits that these modes provide. These modes should appear in the same model enabling a comprehensive and integrated representation of people movement, and the factors that influence it, to be produced

Questioning the linear relationship between doorway width and achievable flow rate

This paper challenges the currently assumed linear relationship between doorway width and achievable flow. The current view is seen as a simplification that may lead to anoverly optimistic view of the achievable flowrates. Analyzed data are presented in order to demonstrate the impact that the actual use of the doorway and its design can have upon the flow rate generated. These data are then supported by the use of numerical simulations to demonstrate the impact that this overestimation can have upon the design process. It is contended that the specific flow rate assumed for a doorway should take into consideration not only its width, but also the design of the doorway (i.e., the opening and closing mechanism) and how evacuees behave in response to it. The issues raised have implications for the governing codes/regulations, engineering guidance and on the development of future computational egress models

A decision model for pre-evacuation time prediction based on fuzzy logic theory

Efficient evacuation is crucial for reducing deaths and injuries caused by disastrous events such as earthquakes. Notably, pre-evacuation time constitutes a large proportion of the total evacuation time; whether and when to initiate the evacuation largely determines the outcome of the evacuation in an emergency. Despite considerable efforts made to elaborate the pre-evacuation process, the evacuees’ vague and imprecise cognitive evaluation on the environment in pre-evacuation decision-making process is underrepresented in these studies. This study aims to enrich behavioral knowledge in the evacuation process during earthquakes and to explore modeling methods for characterization of the pre-evacuation process. As such, we conducted detailed analysis of real earthquake evacuation records to gain some insight into evacuees’ behavioral features. The extracted information from the records, together with the empirical knowledge formed the basis of building a fuzzy logic based decision-making model. The proposed model allowed the prediction of investigating/evacuating decision time with the consideration of individual heterogeneity and changes of cues. The validity of this model was validated against real-case data with reasonable agreement in average pre-evacuation time. A further parametric study was conducted to investigate the influence of features of physical signals and those of instructions on the investigating/evacuating decisions