population density compounds the problem because transit agencies must manage large numbers of evacuees who congregate at transit stations, bus stops, or other preestablished assembly points for transport out of the affected area. On the other hand, in urban areas where transit service and ridership are limited, the use of transit in an emergency evacuation is also likely to be limited and focused on those populations served by the system (e.g., lower-income groups, immigrants). The spatial concentration of transit-dependent populations in an urban area is a factor as well. Regular transit service may not provide adequate service for these populations in an emergency, so that more drivers and equipment must be shifted to these locations for an evacuation.
Transit has a unique role to play in the evacuation of transit-dependent and vulnerable populations—frequently termed special-needs populations—who may lack access to a private vehicle and may also need assistance in evacuating. Vulnerable populations include those with disabilities, the elderly, the medically homebound, and poor or immigrant populations who are dependent on transit for transport. The way special-needs populations are defined varies among urban areas: some definitions are limited to those who need medical attention (but not hospitalization) in an emergency, while others include anyone who may lack access to a private vehicle (e.g., transit commuters, tourists) or who chooses not to use such a vehicle during an emergency. These differences in how urban areas characterize special-needs populations can either limit or expand the potential role of transit in meeting the needs of these populations in an emergency evacuation. Moreover, matching transit services with those needs is a major challenge because the different populations to be served vary greatly in both the type of transport and the assistance they require in an emergency evacuation (e.g., those who are ambulatory and can access fixed-route transit versus many elderly people and those with disabilities who require specially trained operators and accessible equipment). Transit agencies are likely to be hard pressed to accommodate those who need special assistance because these services are often contracted out to smaller paratransit operators or demand-responsive service providers. In an emergency evacuation, these specialized providers often face competing demands for their services1 and