Managing Pedestrians During Evacuation of Metropolitan Areas > Table of Contents

4  Identification of Variables and Concepts

4.1    Evacuation Context and Management

Using the information from the literature review and the interviews, concepts and practices that would be useful in planning and managing metropolitan evacuations were delineated. Once the various contextual elements of a metropolitan evacuation are established, the planning effort can focus on the combination of response elements that are bested suited to structural and situational aspects of the specific event and the area affected by it. Basic variables that combine to affect the evacuation process, and which form the basis for planning and managing a no-notice urban evacuation, include the following:

The context for the evacuation varies in terms of:

• Characteristics and geographic scope of the threat to personal safety,
• Location and number of evacuees,
• Configuration and capacity of evacuation routes and mass transit systems,

Evacuation management variables include:

• Strategic intent of evacuation implementation (e.g., minimize vehicle traffic; maximize evacuees going north, etc.).
• Primary evacuation instructions as formulated by the authorities. 
• Available options for communicating instructions to evacuees.

The conversations with practitioners and subject matter experts emphasized the distinction between what is managed as an emergency evacuation (primary goal of getting people moved quickly and directly away from a danger area) and an unusually heavily and simultaneous surge of commuters outside of normal rush hour periods. Although the latter situation is by definition unexpected and creates special demands on transportation, public safety, and emergency response personnel, it does not require intervention in destination choices.

As a starting point, it is easiest to think about an evacuation situation in terms of a best case situation.  For example, one in which the scope of the impacted area is relative small, the impact moment is past and believed to be over, the weather is mild, it is daytime, transportation modes and routes are similar to normal circumstances, and the transportation and public safety agencies are prepared to work together effectively.

In order to conceptualize approaches for managing large numbers of people leaving the impact area on foot as part of the evacuation plan of a metropolitan area, it is necessary to start by assuming the best case situation.  As any transportation or public safety official knows, real events and exercise scenarios introduce variables into this basic scenario that necessitate adaptations to the best-case situation to use as a stating point.  Based on observations from the practitioner interviews, case studies of evacuations by disaster researchers, and some degree of logical thinking, such variables are outlined below.  There obviously can be multiple combinations variables related to the type of event, characteristic and current conditions of the area, transportation and routing alternatives, whether evacuees are leaving home or going home, and the degree of preparedness and cooperation among the agencies involved in facilitating the evacuation. 

While the following sets of variables are not necessarily exhaustive, they are introduced here to provide an idea of variables related to planning and implementing an evacuation involving a large number of pedestrians.  In Chapter 5, several conceptual approaches for managing or accommodating evacuees other than those who are driving or riding in a private vehicle are presented.  For simplicity’s sake, these are predicated on the existence of the basic, stripped down scenario of a completed impact in a downtown district that is mostly office buildings, during good weather conditions, and in a city with mass transit options.

The base scenario can be affected by variations in the impact situation, the operating principles of the response and management agencies, the characteristics of the population that will be evacuating, and the array of routes and transportation modes that can be safely used for the evacuation. Following are sets of variables for each of these aspects, for the purposes of developing planning assumptions for a particular urban location. 

4.1.1   Variables in the Event Situation and Volume of Evacuees

The characteristic of the threat to personal safety is one of the following.  This determines the degree of urgency for evacuation, and whether evacuation direction must be controlled.

1. Impact period is over and effects are localized at point of initial impact.
2. Impact period is over, but secondary effects are spreading away from initial point of impact.
3. There is uncertainty about whether impact phase over.
4. There is no specific impact, but there is concern for safety due to indeterminate threat.

Origin of the anticipated evacuation stream is characterized by one of the following, which determines the number of people emerging simultaneously onto the street:

1. Origin is restricted to one place of work.
2. Origin extends across multiple places of work in the same area.
3. Origin is mainly residential in nature, so evacuees leaving home.

4.1.2   Evacuation Management Assumptions and Strategies

Primary belief of officials (e.g., law enforcement) directing and managing an urban evacuation that involves large numbers of people on foot as well as in vehicles can make a difference.  Expectations about evacuation or social behavior may affect what type of actions officials take toward pedestrian evacuees.

1. Pedestrian Evacuees must be told what to do so they don’t engage in counterproductive actions that further endanger themselves and others. Or,
2. Pedestrian Evacuees want information on what to do, at least initially, because they will be uncertain or confused by not knowing what has happened and delay departure. Or, 
3. Pedestrian Evacuees can figure things out given adequate information on the circumstances; agency officials will focus on responding to problems as they occur.

The priority evacuation strategy as established by authorities might be one or more of the following.  This is the basis for the type of information and instructions given and how public safety and transportation personnel are deployed.

1. Get people to move away as quickly as possible, even a short distance.
2. Get people to move a certain minimum distance away from the impact or threat.
3. Get people to move in a certain general direction to avoid a moving threat.
4. Get people to go along a specific route and avoid other routes.
5. Get people to shelter in place rather than evacuate.

4.2    Multi-Disciplinary Panel Discussion

 

 

A list of considerations such as in the previous section was provided to a multidisciplinary panel that was formed to discuss pedestrian evacuation as a concept and as an evacuation scenario. The panel participants included eight practitioners and subject matter experts representing expertise in fire fighting and incident command, evacuation planning, public safety and law enforcement, traffic operations, modeling of pedestrian movement, and social science research on evacuation and disaster response. Many of the participants were from agencies located in the Washington, D.C., metropolitan area, and were particularly sensitive to past experience and special issues related to evacuation in that area. The panel discussed a large number of topics and identified gaps in knowledge and areas in which concepts from one discipline could be transferred to another. A major recurring theme was that best practice for managing pedestrian evacuees lies with the application of best practice in overall emergency preparedness and response. The following points were discussed in detail.

4.2.1   Ability to Adapt General Response Concepts to Specific Events

From the perspective of most of the panel, pedestrian evacuees are considered to be one element that may or may not emerge in conjunction with an emergency event. When engaging in “all hazards” planning, the basic approach is to have all relevant agencies understand the overall concept of operations for an integrated interagency response operation. It is not possible to plan for specific configurations of the event and the city characteristics, so it is critical that agency personnel be able to adapt management and response concepts to be appropriate to particular situations and to know what to expect of each other.

4.2.2   City Characteristics and Planning for Pedestrians in Emergencies

The panel participants identified a few characteristics of a city that probably increase the importance of being prepared to manage pedestrians in an evacuation. These include the extent to which commuters to the downtown area use mass transit, the proximity of transit options to office complexes, and the extent of tourism. These are the factors that are associated with the presence of larger numbers of people unfamiliar with facilities and routes.

4.2.3   Facilitation of Decision Making by Pedestrian Evacuees  

Safety is the highest priority when managing pedestrian evacuees. Pedestrian evacuees can make good decisions related to evacuation, even in no-notice events. To assist pedestrians in making choices that are consistent with smart and safe behavior while evacuating, responders and emergency managers must strive to provide consistent and clear information, enabling evacuees to make decisions about the best evacuation mode and route for them.

4.2.4   Multi-Jurisdictional Planning

The history of city growth and residential patterns in the U.S. means that the major metropolitan areas include many jurisdictions, including both local and state jurisdictions and multi-agency planning bodies. If evacuation routes leading out of the central downtown area cross jurisdictional boundaries, planning and practicing for handing off functions to counterpart agencies in the adjoining jurisdiction is crucial. For example, if evacuees not using a private vehicle use mass transit in an evacuation that takes them away from their normal destination, they may not know how to transfer over to the connecting transit system. Coordination between different transit agencies can keep evacuees from becoming stranded at the end of the line of their initial transit ride.

4.2.5   Elaboration of the Role of the Transportation Agency

Transportation agencies have begun to play much more active roles in emergency planning and response. In cities where Intelligent Transportation System (ITS) assets are well developed, the traffic operations personnel will have some of the best information and broadest overview about traffic and pedestrian flow. Transit operations personnel have the best knowledge of the location of transit facilities and assets, and the authority to deploy them. Transportation officials should be considered key players in emergency planning and response, and not simply as a support agency that responds to requests from the emergency manager during the course of an incident or response operation.