EXODUS MODEL BRIEFLY EXPLAINED

EXODUS comprises five core interacting submodels, the Occupant, Movement, Behaviour, Toxicity and Hazard submodels (see below). The software, written in C++ using Object Oriented techniques, comprises a set of rules or heuristics which define the function of each submodel. Using these rules, EXODUS tracks the trajectory of all individuals as they make their way out of the enclosure or are overcome by the fire hazards such as heat and toxic gases.

The spatial and temporal dimensions within EXODUS are spanned by a two-dimensional spatial grid and a simulation clock (SC).  The spatial grid maps out the geometry of the structure, locating exits, internal compartments, obstacles, etc.  Geometries with multiple floors can be made up of multiple grids connected by staircases, with each floor being allocated a separate window. The structure layout can be specified using either a DXF file produced by a CAD package, or the interactive tools provided, and may then be stored in a geometry library for later use.  The grid is made up of nodes and arcs with each node representing a small region of space and each arc representing the distance between each node. Individuals travel from node to node along the arcs. The escape strategy (Behaviour submodel) chosen by each individual is a product of their interactions with the enclosure, other occupants and any fire hazards present.
 

Movement Submodel

Controls the physical movement of individual occupants from their current position to the most suitable neighbouring location, or supervises the waiting period if one does not exist. The movement may involve such behaviour as overtaking, side stepping, or other evasive actions.

Behaviour Submodel

Determines an individual's response to the current prevailing situation on the basis of their personal attributes.  The submodel passes this decision on to the movement submodel. The behaviour submodel functions on two levels, global and local. The local behaviour determines an individual’s response to their local situation, while the global behaviour represents the overall strategy employed by the individual. This may include such behaviour as, exit via the nearest serviceable exit or most familiar exit.

Occupant Submodel

Describes an individual as a collection of defining attributes and variables such as gender, age, max running speed, max walking speed, response time, agility, etc. Some of the attributes are fixed throughout the simulation while others are dynamic, changing as a result of inputs from other submodels.

Hazard Submodel

Controls the atmospheric and physical environment.  It distributes pre-determined fire hazards such as heat, smoke and toxic products throughout the atmosphere and controls the opening and closing of exits.

Toxicity Submodel

Determines the effects on an individual exposed to toxic products distributed by the hazard submodel.  These effects are communicated to the behaviour submodel which, in turn, feeds through to the movement of the individual.

VALIDATION

Validation of computer models should not be considered as a “once and forget” task. It should be delt with in a systematic and graduated approach that involves,
(i) component testing,
(ii) functional validation,
(iii) qualitative validation and
(iv) quantitative validation.

Viewed in this manner, validation is considered an on-going activity and an integral part of the life cycle of the software. While the first three components of the validation protocol pose little or no significant problems, the task of quantitative validation poses a number of challenges, the most significant being a shortage of suitable experimental data.

The EXODUS suite of evacuation models has and is undergoing this process of validation.  The quantitative validation is based on predictions made using EXODUS for several full-scale evacuation experiments.  Several documents have been produced describing the validation process used with EXODUS.  These publications can be found on our publications pages.  Amongst other publications, Interested readers should view papers 106, 111 and 112.

CAPABILITIES

EXODUS software capabilities include:

Ability to simulate both evacuation and normal pedestrian dynamics scenarios.

Can simulate the interaction of many thousands of people

• Examples include:

- 25,000 people in 110 storey high-rise building
- 125,000 people in city square

SHORT RUNTIMES: Example runtime performance

• 1,000 people in 2,500 m2 enclosure, 15 sec using 1.9GHz, 1Gb PC
• 8,200 people in 110 storey building, 25 min using 3.6 GHz, 3Gb PC

Ability to distinguish emergency exits from normal exits

Can assign exit usage according to occupant familiarity.

Simulates occupant interaction with signage.

Ability to specify both internal and external exits.

Itinerary function enabling allocation of tasks to individuals

Determines time spent in congestion for each occupant.

Census nodes/lines/regions allows collection of flow statistics at any arbitrary point
or region within the structure.

Link to SMARTFIRE CFD fire simulation output files

Reads CFAST history files

Toxicity calculations determined using FED models.

• Occupant interaction to:
  - Convective and radiative heat
  - Toxic gases
  - Irritant gases

Occupant interaction with smoke (low visibility) including crawl capability.

vrEXODUS post-processing Virtual Reality animation tool

askEXODUS is a tool designed to assist in the analysis of large
data output files produced from multiple runs

Interactive run-time 2D graphics allows occupant interrogation.

Run-time 2D graphics can display:

- individual occupants,
- population densities,
- smoke and temperature distribution.

Batch Mode allows rapid execution of multiple runs.

SPECIFICATION/REQUIREMENTS/PROCEDURES

MS WINDOWS including XP and VISTA

• minimum recommended requirement: Pentium II 300 MHz, 128MB RAM

UPGRADE PATHS AVAILABLE

GRAPHICAL INTERFACE ALLOWS USER TO MONITOR PROGRESS OF EVACUATION

VIRTUAL REALITY PLAY BACK CAPABILITY PROVIDED WITH vrEXODUS (LEVEL 2 SOFTWARE ONLY)

BATCH MODE OPERATION ALLOWS RAPID PROCESSING OF PRODUCTION RUNS

INTUITIVE USER INTERFACE

GEOMETRY EDITOR AND LIBRARY
Allows the user to construct the enclosure. Several methods are available
(a) the enclosure can be manually constructed using the interactive tools provided,
(b) imported from a DXF file,
(c) loaded from a library case.
Procedure also automatically identifies maximum travel distance.

POPULATION EDITOR AND LIBRARY
Generates the group of occupants to be used in the analysis. As in the Geometry mode, interactive tools are provided to assist with population definition. Entire populations or subgroups of people can also be stored and recalled from a user-defined library.

SCENARIO EDITOR
Control scenario specifics such as exit capabilities, exit potentials, fire hazards etc. Fire hazards (heat, smoke and toxic gases) can be defined using CFAST generated history files or SMARTFIRE simulation files. The evolution of the fire scenario can be depicted in Simulation Mode through the contouring graphic option.

FIRE HAZARD EDITOR AND LIBRARY
Provides choice of two FED toxicity models. Manually created fire atmosphere data (e.g. derived from either experimental data or fire models) can be edited.

SIMULATION MODE
Allows simulation to be run in either interactive or batch mode. In interactive mode, two-dimensional animated graphics are generated as the software is running. This allows the user to observe the evacuation as it takes place. In this mode the simulation can be replayed, paused and a shuttle facility is provided to allow the user to step through the simulation a time step at a time. It is possible to view simulation in individual person mode (so that each person is displayed) or in population density mode, where a dynamic colour map of the population density is displayed. The graphics are interactive allowing the user to interrogate occupants and events. A range of scenario specific data (both input and output data) can be saved into spreadsheet-style output files for later interrogation.

OTHER FEATURES
To aid in the interpretation of the results produced by EXODUS several data analysis tools have been developed. These are intended to be used once a simulation has been completed and enable large data output files to be searched and specific data selectively and efficiently extracted (askEXODUS). In addition, a post-processor virtual-reality graphics environment has been developed (vrEXODUS), providing an animated three-dimensional representation of the evacuation.