Planning with Large Agent-Networks against Catastrophes (PLAN C)
PLAN C is an innovative tool for emergency managers, urban planners and public health officials to prepare and evaluate Pareto-optimal plans to respond to urban catastrophic situations.
PLAN C uses a powerful large-scale computational multi-agent based disaster simulation framework involving thousands of agents. It has been able to simulate the complex dynamics of emergency responses in different urban catastrophic scenarios (e.g., chemical agent, bomb explosion, food poisoning, small pox). It can devise plans that optimize multiple objective functions (e.g., number of casualties, economic impact, time to recovery, etc.) in terms of their Pareto frontier in a high-dimensional space; for this purpose, it uses an evolutionary genetic search algorithm. It is designed to be easy to use and parametrize by relatively unsophisticated users. The technology can be easily transferred to any urban setting, to multiple computer platforms, and to different modes (offline or online) of planning.
An effective response simulation to catastrophes in an urban environment requires modeling the actions of a large number of actors, each endowed with their own skills, objectives, behaviors and resources, to be able to coordinate their efforts in order to mitigate the outcome of a disaster. This modeling and simulation effort aims to build a flexible, adaptable and general model, combining expertise from both public health and computational sciences, to improve preparedness and response capabilities of a city. Typically, training drills in the field and tabletop exercises are used to inform policy-makers to prepare responders for catastrophes of large magnitude. Usage of computer modeling simulation enables close to optimal design of such exercises to maximize their effectiveness across multiple dimensions. With the powerful computational reasoning and analysis technologies that have been implemented and developed in Plan C’s models, it is now possible to go beyond table-top exercises to help policy makers to consider, simulate and analyze the effect of a wide range of parameters, in several concomitant catastrophes.
Our effort in this direction has resulted in a system with the following combination of features:
- A large number of computational actors/agents, comprising five different classes: Person, Hospital, On-Site Responder, Ambulance and Catastrophe;
- A flexible number of parameters for describing the computational agents’ behavior and interaction, the time course of the disease, environmental factors, etc., which enable the user, e.g., an emergency manager, to modify adaptively to diverse urban scenarios;
- Several communication channels for information (health / resource levels, hospital operation mode, etc.) exchange among similar and differing computational agents;
- Modeling people as selfish and bounded rational beings, with stochastic personality traits emulating panic or contrarian behavior;
- Realistic models of medical / responder units and catastrophe chemical agent effects (disease prognosis and dosage response), validated by medical, sociological and legal experts from the NYU CCPR;
- Integration of real urban infrastructure constraints (streets, subways, hospitals, etc), via publicly available Geographic Information System data of a city such as New York City;
- Computer software for parallel and distributed concurrent computing on large-scale clusters of workstations, using the integration between ProActive and RePast.
- Integration of medical, legal, public safety, and social professionals’ perspectives in the model design and development.
The earliest scenario investigated by Plan C was the 1998 food poisoning of a gathering of over 8000 people at a priest's coronation in Minas Gerais, Brazil leading to 16 fatalities. Multi-agent modeling was explored for this problem by allowing simplistic hospital and person agents to interact on a two-dimensional integer grid. As various complex, counter-intuitive and unanticipated behaviors emerged in the simulation of an extremely parameter sensitive system, it could immediately validate its potential use in agent-simulation-based analysis of catastrophes.
For the second scenario, Plan C examined an attack with the nerve gas agent Sarin in Manhattan to further evaluate these tools and techniques. Its choice was based on the literature available about a similar attack that occurred in Matsumoto in 1994 and later, in Tokyo in 1995. Several important emergency response issues were addressed by repeated simulation: namely, when to proceed to a hospital, when to discharge a person from the hospital, number of on-site treatment units necessary, the importance of public awareness and law enforcement, the role of responder size and activation time, and the diffusion of information about hospitals and capacities.
From a more theoretical and computer science perspective, we also studied the source of complexity of the emergent dynamics generated by the model in different catastrophic scenarios.
As part of our research effort, we also continue to work on a novel optimization tool that, when used in combination with the model, can help in deciding how to select better plans. As soon as our rigorous modeling, simulation and analysis approach matures, our next step is to go beyond the simple simulation and analysis of a response plan in order to directly search for “optimal” plans that can efficiently manage a crisis. A large scale emergency plan naturally involves multiple objectives: minimize the number of casualties (affected people), fatalities (mortalities), the average ill-health of the total population, average waiting time at the hospitals, etc., and maximize the average time taken by a person to die (so as to increase the chance for external help to arrive), utilization of resources at different locations (so that no one location runs out of critical resources), etc. There are also tangible economic, legal and ethical issues in disaster management, which stipulate many different classes of objective functions. NYU’s Plan C models provide as their output the individual traces of all its agents and statistical information about the time-course of the global behavior. In this context, planning can be seen as the problem of adjusting the controllable parameters in the interaction between different classes of agents (hospitals, persons, on-site responders, ambulances, etc.) and available resources, in order to moderate the negative consequences of a catastrophic event. The emergency response planning problem is formulated by Plan C as a multi-objective optimization problem where the input parameters of the model are the decision variables and the criteria for plan evaluation are the output objectives of the system. Multi-objective evolutionary algorithms have been explored to effectively tackle this problem, in order that suitable Pareto optimal plans can be generated automatically.
Sarin Release in Port Authority Bus Terminal, New York City