First, the scale of the incident matters. The larger and more catastrophic the incident, the greater are the surge capacity requirements not only of the transit system but also of the transportation system in general in an emergency evacuation. In the event of a catastrophic emergency, is evacuation of a large portion of a major metropolitan area a realistic goal? What role can transit reasonably play in such a situation?
Second, the type of incident is important. Events that occur with some regularity, such as hurricanes—even though there is uncertainty about their trajectory and intensity—are easier to plan for than unexpected events, such as the terrorist attacks of September 11, 2001. In the case of the former events, affected areas typically have evacuation plans in place, including predesignated evacuation routes and destinations, as well as considerable experience with handling incidents that has resulted in plan modifications. In areas that face a multitude of different threats, emergency managers are focused on procedures and flexible plans that can be modified once the type of incident and its extent become clear. This capability requires sophisticated coordination and communications in which transit agencies must be a partner.
Third, the role transit can play in an emergency evacuation depends on its size relative to the UA, the mutual-aid agreements it has forged with other providers, and the representation of its key staff in the incident command structure. In addition, transit’s response depends on the time of an incident (e.g., during or after peak hours); the day of the week; the duration of the event; and, of course, whether the system itself is compromised. For example, surge capacity needs are probably greatest if the incident occurs during the morning or afternoon peak. However, personnel and equipment are at their maximum capacity during these times. During off-peak hours, such as midday, it takes time to recall people and equipment in the event of an emergency requiring evacuation. Similarly, an event that simply requires shifting service away from a particular area or even conducting a partial evacuation places far less demand on the system than one that requires a large-scale evacuation, multiple trips to take customers and the carless out of the area, and potential diversion of some equipment to help support emergency responders.
Finally, transit can play a unique role in the evacuation of special-needs populations, ranging from those who simply lack access to a private vehicle to those who may need special assistance (e.g., the disabled, the elderly). The difficulty lies in identifying these populations and their specific trans-