UCL CENTRE FOR ADVANCED SPATIAL ANALYSIS
Agent Based Modelling in Second Life: Pedestrian Evacuation Model
 UCL logo
 
 
 

 

Agent Based Modelling in Second Life: Pedestrian Evacuation Model

Andrew Crooks, Andrew Hudson-Smith and Joel Dearden

Introduction

The last model we developed in Second Life was a pedestrian evacuation model. This is a much more accurate simulation of real life than the previous two models and the rules that govern the agents are a lot more complicated.

The model was designed and developed by Joel Dearden based on ideas from Dr Andrew Crooks and Dr Andrew Hudson-Smith.

Basic Concept Model

We started out by building a much simpler model to investigate how pedestrian behaviour could be simulated in Second Life. The agents in this model represent people wandering around a room and this forms the idea for the initial part of the final model where pedestrians wander around a room until the fire alarm goes off.

Wandering Agents Model

 

 



Movie of wandering agents

Evacuation Model Detail

The final version of the model simulates a pedestrian evacuation in response to a fire alarm, from the time before the alarm is triggered when people are moving around a building but not trying to exit, through the fire alarm being triggered and then to the end of the evacuation when the building is finally empty. It supports multiple floor layouts and simulates pedestrian movement down a staircase.

The model runs at about 1/30th of real-time due to constraints of the Second Life scripting environment and physics engine. The main problem being that if the pedestrian's moved any faster than they currently do the physics engine in Second Life (Havok) tends to miss collisions and so the pedestrians start walking through walls and other barriers.

Layouts

We have provided three pre-defined floor layouts in the model. Each of these is described on a separate page along with screen shots and a movie of a model run using that layout:

It is easy to create new layouts or modify existing ones either in the pre-defined scripts or by just dragging walls around in Second Life.

Model Components

Each of the parts that make up the model are shown below and are flexible enough to allow most building layouts to be re-created:

Controller
Builder
Exit
Exit Sign
Floor
Furniture
Wall
Pedestrian
Line-of-sight (LOS) ray
Predicted Movement Volume (PMV)
Staircase PMV
Staircase Steps
Staircase Dummy
Staircase Entry
Staircase Start
Staircase End

PedTrace System

To help validate the model we linked it to a custom built web application called PedTrace running on a web server outside Second Life via HTTP messages. The web server records the position and speed of each pedestrian every second of the model. PedTrace uses this data to generate movement trace images and two graphs: a time-to-exit graph and an average walking speed graph.

PedTrace provides a webpage overview of the current model run (shown below).

Technical Details

A PDF document containing details about how the model was implemented is available to download:

Source Code

The Linden Scripts for this model are covered by the GNU GENERAL PUBLIC LICENSE and are available to download below.

The Visual C# source code for the PedTrace web service has also been released under the GNU GENERAL PUBLIC LICENSE and is available to download below. You might need some knowledge of C# and ASP.NET to make this work.

If you prefer to get up and running more quickly we have a vending machine on nature island here that will give you a complete working copy of the model when you click on it.